Selection of Amputation Level

The quality and type of amputation performed greatly affects the overall outcome for the patient. When determining amputation level, all the factors affecting the patient’s function must be considered. These factors include not only tissue viability, but also prosthetic options, gait dynamics, cosmesis, and the biomechanics of the residual limb. The objective of preoperative evaluation is to determine the level at which healing will occur and maximal function will be restored after removal of all compromised or infected tissue. Preservation of tissue is balanced with restoration of function, as higher amputations result in increased morbidity and decreased rehabilitation potential. Prediction of healing requires careful evaluation of surgical technique, postoperative care, nutritional status, and arterial circulation—particularly tissue perfusion.

The earliest attempts to judge the appropriate level of amputation focused on the presence of palpable pulses, angiographic findings, skin color and temperature, character and location of pain, and most notably, the presence of incisional skin bleeding at the time of surgery. Various diagnostic methods exist to help determine the level at which healing will occur. These include Doppler pressure measurements, pulse volume recordings, photoplethysmographic pressures, laser Doppler blood flow studies, xenon-133 skin blood flow studies, arterial angiography, and transcutaneous oxygen determinations (see Chapter 57). However, these tests have not been more consistently reliable than clinical judgment in predicting wound healing at a given level.^5,25 Most surgeons use a combination of objective data and assessment of the appearance of the tissues at the time of surgery, particularly bleeding, to decide on the site of amputation.

Several other factors that influence the patient’s prosthetic function need to be considered when determining amputation level. For example, Chopart and Lisfranc amputations might allow some ambulation for short distances without a device, but they have a short forefoot lever arm, and they are difficult to fit with an adequate prosthesis biomechanically. They also have a high rate of equinovarus deformity. Alternatively, higher levels of amputation, such as a Syme’s or transtibial amputation, allow for better gait with a prosthesis and superior performance in more demanding activities. Cosmesis is also an important consideration. Ankle and knee disarticulations have the advantage of long lever arms for prosthesis control and end weight-bearing, but the prostheses have a considerably poorer appearance than that of transtibial or transfemoral prostheses. This can be a determining factor for some patients.

Amputations are classified into three categories: closed, open, and guillotine. Closed amputation is the most commonly used technique for amputations necessitated by arterial disease. For this procedure, an incision is made through presumably healthy tissues, and skin flaps are shaped for primary (sutured) closure. In contrast, open amputations are performed only in instances of severe trauma or overwhelming infection. This type of intervention allows for appropriate drainage and observation of the wound. Finally, guillotine amputation is an open procedure in which all the tissues are cut at the same level by a circular incision. This type of amputation eventually requires a closed amputation performed at a higher level. Guillotine amputation is rarely necessary today and is reserved for extremely ill patients who require quick control of a rapidly spreading infection such as gas gangrene.

Functional Rehabilitation

There are often a few days or even weeks from the time a decision is made to do an amputation until it actually occurs. This time can be used to initiate a functional rehabilitation program before the amputation. It is easier to stretch out a tight or contracted joint using the entire limb length before the amputation, than it is after surgery when the limb is shortened and tender. Preoperative rehabilitation should emphasize ROM, conditioning remaining limb segments, increasing endurance, improving transfers, and training the patient in one-legged gait with an assistive device. This can reduce or even eliminate the need for inpatient rehabilitation after the amputation.

Pain Control

Good perioperative pain control is essential for the patient facing limb loss. Beyond patient comfort, adequate pain control minimizes the patient’s stress, and allows the patient to participate more fully in a rehabilitation program. Uncontrolled pain can result in the development of central nervous system–mediated pain and chronic pain,⁶⁰ as well as impair postoperative healing and immune functions.^8,22

The mainstay of perioperative pain control treatment is opioid therapy. Oral opiates are usually sufficient, but there should be no hesitation to use more aggressive pain control measures including transdermal, subcutaneous, intramuscular, or intravenous routes. A scheduled dose of a long-acting agent in conjunction with an immediate-release analgesic is recommended so that the patient has consistent pain relief. A sufficient dose of analgesia just before therapies often helps the patient fully participate. Caution, however, should be used in the geriatric population given the risk of delirium in these individuals, and opiate use should be streamlined in these instances.

Patient-controlled analgesia systems are useful for patients having severe pain in the perioperative period. They provide a continuous infusion of analgesic, with the ability of the patient to use a supplemental dose as needed. Patient-controlled analgesia provides excellent analgesia and can reduce some of the patient’s stress or fear related to pain. Continuous regional nerve blocks and epidural anesthesia can also be used for perioperative pain control,⁵⁸ although typically these cannot be continued in the post–acute care setting.

Psychological Support

Psychological assessment and support for the patient facing limb loss should be a high priority. Assessment of the patient’s expectations and goals is important. Frequently, patients fear that they will never be able to walk again after amputation and might not expect to be able to accomplish more demanding occupational or recreational tasks. These perceptions are often unfounded because most amputees can do very well functionally. As noted above, several studies indicate that greater than 80% of amputees at all levels will be able to successfully walk with a prosthesis,^40,63,72 and this is consistent with our experience. Each patient’s specific long-term goals should be identified before surgery, and a comprehensive rehabilitation program should be outlined to achieve these goals. Patients feel empowered and reassured when higher functions (such as sports) are recognized as legitimate goals, and the rehabilitation team helps them achieve these goals.

Describing the rehabilitation process in detail to patients and educating them about prostheses can help to allay their fear of the unknown. Providing educational literature and website addresses can be a valuable and calming service to patients and their families (Box 13-1). Some programs use a peer counseling program in which patients who are successful prosthesis users visit patients with new amputees on request. Finally, it is important to discuss phantom limb sensation and phantom limb pain with patients before surgery. Phantom limb sensation is the temporary nonpainful feeling that the amputated limb is still present. This feeling typically fades away over a period of weeks. Phantom pain is the usually temporary pain that can occur in a limb after its amputation, especially in a patient with a long history of preamputation limb pain. All patients need to be told to expect these sensations in the missing limb after surgery and to realize that they are normal.

Wound Care

Wound healing is dependent on adequate tissue perfusion, good wound care, and adequate nutrition. Care for primary surgical wounds is straightforward. The limb should be washed on a daily basis either with normal saline or simple soap and water; antiseptic agents such as iodine solutions or hydrogen peroxide inhibit wound healing and should be avoided unless there are signs of infection. Dressings should be kept clean and changed daily.

After traumatic amputations there are often large open wounds that could have been contaminated in the trauma, and additional coverage procedures such as flaps and grafts might have been performed. These wounds require close observation and meticulous wound care. They often cause a delay in the fitting of the initial lower limb prosthesis. Wounds do not need to be completely healed for the fitting of the prosthesis, but the viability of flaps and grafts needs to be established and monitored carefully.

In patients with vascular compromise, wound margin necrosis can develop. The limb should be monitored closely in these cases, kept clean, and protected from any trauma that could cause a dehiscence in such a fragile wound. Once the nonviable tissue is clearly demarcated, debridement can be considered. Adjuvant therapies such as negative pressure wound therapy and hyperbaric oxygen treatment are available options that have possible benefit but warrant further investigation to determine their efficacy with this population.^43,91,98

Good nutrition must be encouraged and supported with supplements when necessary. Eneroth³⁰ found that when supplementary nutrition was given to malnourished patients, twice as many adequately nourished patients healed their residual limb wound when compared with controls.

Edema Control

Reducing postsurgical edema is important to promote wound healing, minimize postoperative pain, and shape the limb for prosthetic fitting. Postsurgical edema stretches a surgical wound, which stretches nerve endings and causes pain. Edema puts tension on the wound, compromising healing. Swelling gives a bulbous shape to the residual limb, which interferes with prosthetic fitting and can slow the patient’s functional recovery. An effective compressive dressing can minimize these problems.

Several different edema control systems are available. The most commonly used treatment is elastic wraps on the residual limb (e.g., Ace bandages). Although elastic wraps can provide effective compression, they are high-maintenance items that must be properly applied and changed about every 4 to 6 hours to maintain consistent compression.⁶¹ This can be difficult and time-consuming for a patient, or even the health care team, to accomplish. Elastic wraps that are improperly applied or displaced in the normal course of regular movement can turn into tourniquets, causing pressure wounds and even limb ischemia. Consequently the use of elastic wrapping is not recommended.

The use of elastic socks or elastic stockinette provides a better alternative than elastic wraps. Elastic stockinette (e.g., Compressigrip and Tubigrip) can be applied in multiple layers to give graded and increasing compression toward the end of the residual limb (Figure 13-1). It is inexpensive and easily applied. Premanufactured residual limb shrinkers can also be used. For transfemoral amputees, a residual limb shrinker with a waist belt must be used, because otherwise the dressing tends to slide off the conical-shaped residual limb. The waist belt should be attached to the elastic dressing at the side of the limb. If the attachment is worn in front, the shrinker will slide off during sitting.

FIGURE 13-1 Use of elastic stockinette for edema control. (A) Place just over half of the length on the limb and twist a half turn. (B) Pull second half over leg to provide two layers of compression.

Prosthetic elastomeric liners can also be used as compression socks for edema reduction in amputees.^49,51 They can provide compression and also lend some degree of protection to the residual limb. Because of their suction fit, they can be used on the transfemoral amputee without a waist belt. When using any elastic dressing, bony prominences should be closely monitored because pressure can concentrate at protruding bony areas and lead to skin breakdown.

Rigid dressings provide additional benefits over soft dressings alone for transtibial amputees (Figure 13-2). Rigid dressings help protect the residual limb from any inadvertent trauma, such as a fall.³¹ They provide good compression to minimize edema, and the cast can be conformed to minimize pressure over bony prominences. Partial weight-bearing can also be started through the rigid dressing to help desensitize the limb and build tolerance to pressure.

FIGURE 13-2 Rigid dressings for transtibial amputee. (A) Rigid dressing. (B) Rigid removable dressing.

A nonremovable rigid dressing is a cast that is applied over the fully extended residual limb up to the midthigh (see Figure 13-2, A). This type of cast is helpful in preventing knee flexion contractures and can be used as an immediate postoperative prostheses (as discussed below). A nonremovable cast does not allow for wound inspection except at cast changes. It also does not allow patients to massage their residual limbs, an important part of the desensitization program.

A removable rigid dressing (RRD)^104,105 is a custom-made cast that covers the residual limb up to the knee (see Figure 13-2, B). It is held in place with either elastic stockinette or a thigh cuff. As the limb shrinks, socks, shrinker socks, and elastic stockinette are added underneath the RRD to keep it snug. The RRD allows for frequent wound inspection and massage of the residual limb. It also helps to teach patients how to adjust sock ply, a necessary skill for using most types of prostheses. A suggested protocol is to start with a rigid nonremovable dressing applied immediately after surgery. After the first 3 to 6 days, the cast should be changed to an RRD, which should be used until most of the edema is resolved and the wound is well healed. If more than 12 to 18 ply of sock is required to keep the RRD snug, a new RRD is recommended.

Functional Rehabilitation

Early rehabilitation management is critical in the postoperative period. Hopefully the rehabilitation team has been involved already, but if not, consultation with physiatry and involvement of physical therapy and occupational therapy should begin as soon as possible. Therapy staff work on a variety of areas such as self-care, bed mobility, transfers, wheelchair skills, ambulation, and patient and family teaching. Amputee rehabilitation principles include proper positioning, initiation of ROM, early mobilization, and evaluation for durable medical equipment and adaptive devices.

Patients should be educated in proper positioning. Prevention of hip and knee contractures is critical in this period. Patients should not have pillows placed under the knee because this can lead to knee flexion contracture. To prevent hip abduction contractures, pillows should not be placed between the legs. Dangling the residual limb over the side of the bed or wheelchair should be avoided. A knee extension board (Figure 13-3) can be fitted underneath the wheelchair or chair to promote knee extension and help prevent dependent edema. Wheelchair-elevating leg rests are generally less effective and more expensive than these boards. If knee flexion contractures are of great concern, a knee immobilizer while the patient is in bed can be used to maintain knee extension. Patients should be instructed to lie prone several times a day for 10 to 15 minutes at a time to prevent hip flexion contractures. Individuals who cannot tolerate prone positioning can lie supine on a mat while performing hip extension exercises of their affected limb.

FIGURE 13-3 Knee extension board to prevent flexion contracture in transtibial amputee.

ROM and strengthening exercises of the affected limb are important adjuncts to positioning. Muscles that oppose the common sites of contracture must be strengthened, especially knee and hip extensors. Other important muscles groups that should be strengthened include the hip adductors and abductors. Because patients are increasingly reliant on their arms to assist with mobility, arm strengthening and conditioning are needed. Specific exercises include strengthening of the wrist, elbow extensors, and scapular stabilizers. This training prepares patients to properly execute transfers and to correctly use crutches or a walker. Initiation of aerobic exercise is needed to increase endurance and cardiovascular fitness, but given the high incidence of concomitant cardiovascular disease in individuals with a vascular etiology of amputation, adherence to cardiac precautions is important.

Early mobilization facilitates early functional improvements. Usually the first activities include bed mobility, transfers, and mobilization to a chair or wheelchair. As the patient progresses, the activities should increasingly focus on standing and balance exercises in the parallel bars, and hopping. The use of a walker or crutches is the next step in mobilization.

Early partial weight-bearing can begin in the first few days if there are no wound complications. For transtibial amputees with rigid dressings, limited weight-bearing can be performed through their cast using a strap across their wheelchair (Figure 13-4). When the patient is up in the parallel bars, weight-bearing can be done via a tire jack or adjustable footstool. Immediate postoperative prostheses can also be used for early weight-bearing as described below. Inspection after weight-bearing is important in monitoring wound tolerance of pressure. This is especially important in individuals with amputation from vascular disease or patients with impaired sensation.

FIGURE 13-4 Partial weight-bearing with rigid dressing through strap on wheelchair armrests.

Evaluation for appropriate adaptive equipment and durable medical equipment is important. Adaptive devices such as reachers, long handles, sponges, shoehorns, dressing sticks, and sock aids can be issued as needed to assist with activities of daily living. Long-handled mirrors can also be helpful to allow patients to monitor the status of their residual limb easily. Because sitting in a wheelchair makes the amputee’s center of gravity higher and more posterior, rear wheels should be set posterior to the chair back and antitippers should be placed, to minimize the risk of tipping backwards and sustaining a head injury. This is particularly important for transfemoral and bilateral amputees.

A plan for ongoing rehabilitation services needs to be made during the early postoperative period. Younger patients with unilateral amputations can usually be discharged home as crutch ambulators with ongoing outpatient rehabilitation. Older and marginally functioning patients and multilimb amputees usually need acute inpatient rehabilitation before they can safely return home. These patients can generally be admitted to a rehabilitation unit between postoperative days 3 through 7, after any drains are removed, pain is under control with oral medications, and they have the endurance to participate in a comprehensive rehabilitation program. The acute postoperative period prepares the patient for a safe return home with the temporary assistance of a wheelchair, walker, crutches, or with an early fitted prosthesis.

Patients need to be followed up closely for the first 12 to 18 months. Early on, the key issues remain wound healing, edema control, psychological adjustment, and pain control. Prosthetic fitting and prosthetic gait training can usually be started within 3 to 6 weeks of surgery, and patients are usually able to ambulate independently (perhaps with an assistive device) within 1 month of starting therapy with their prosthesis. The residual limb continues to shrink during the first 6 to 8 months. This requires constant monitoring to ensure an adequate fit of the device by both the patient and the rehabilitation team. After shrinkage abates in 6 to 8 months, the patient can then be fitted with a new, definitive prosthesis (or at least a new socket).

Most amputees need a full year to completely adjust to their limb loss. Regular physician visits during this time are needed. Follow-up should be done, if possible, in multidisciplinary amputee clinics by a physiatrist, prosthetist, nurse, and preferably, a physical therapist. A multidisciplinary clinic also gives amputees the opportunity to visit with others being seen in the clinic. This provides a peer support or “milieu therapy” that is very beneficial.

Pain Management

Identifying the etiology of postoperative limb pain is important for successful control of the pain. Because of nerve fiber damage and ongoing stimulation of the nerves in the residual limb, a generalized residual limb pain is initially expected secondary to the surgical incision and postoperative edema. Ectopic activity at the cut end of nerves is expected and can be due to unstable sodium channels or the uncovering of new pathologic receptors.^6,7 Ephaptic transmission, which is the stimulation of afferent fibers (nociceptors) by efferent neurons (motor or sympathetic), can also contribute to limb pain.^48,77 This acute pain responds well to intravenous or intramuscular opiates. It subsides fairly rapidly, and the parenteral opiates can usually be discontinued within 2 to 3 days. Scheduled doses of oral opiates with rescue medications as needed should be continued beyond this period and weaned slowly so that the patient continues to receive adequate pain control.

Desensitization techniques should be added to the treatment plan within a few days of surgery. Patients should be instructed to start massaging and tapping their residual limb, which can be performed through any soft dressing. This gentle stimulation can help to reduce residual limb pain by closing the pain gate,⁶⁰ and gives patients a technique for controlling their pain independently. Self-massage also forces patients to attend to their amputation; this can help with their new body image and psychological adjustment to limb loss.

When generalized residual limb pain does not subside as expected, the patient should be reevaluated. Wound infection and abscess must be excluded, and reevaluation of the arterial system needs to be considered. Patients with peripheral vascular disease, diabetes, or both can have continued limb ischemia that is a form of claudication. This claudication can be constant or intermittent, resulting from activity. Patients with residual limb ischemia often exhibit poor skin color, and the residual limb pain is frequently dependent on the limb’s position. Over the course of weeks, ischemic pain often resolves as the swelling goes down, the circulation remodels with the decreased distal tissue load, and the limb heals. Sometimes reamputation to a higher level is required if the wound fails to heal, tissue necrosis progresses, or ischemic pain persists. During the interim, the patient needs to continue to receive adequate analgesia, although giving adequate pain relief without excessively sedating the patient can be difficult. When ischemic limb pain does not quickly subside, the patient, the family, and the entire rehabilitation team need to be made aware of the plan to wait and see whether the residual limb is salvageable or reamputation is necessary.

Even after the immediate postoperative period and residual limb healing, the incidence of pain is high in patients with amputation, with 68% reporting residual limb pain and 80% reporting phantom pain.³² The most common types of sensory problems reported include phantom pain, phantom sensation, and residual limb pain. The differential diagnoses for pain in an amputated lower limb are diverse, and treatment options differ significantly based on the etiology of pain. Consequently the source and mechanism of the pain must be investigated and identified so that an optimal treatment plan can be implemented.

Prosthesis use is a common cause of residual limb pain in individuals with amputation. In these instances, pain tends to be worse with prosthetic use and during ambulation. Usually there is skin irritation that correlates with the area of the prosthesis causing the pain. Multiple factors can contribute to prosthetic pain including socket fit, suspension, alignment, and gait pathology. Consideration must be given to all of these areas when there are complaints of pain in the residual limb during prosthetic use. As an example, Table 13-1 lists some of the common causes of distal tibial pain, a very common site for prosthesis-related pain in transtibial amputees. Addressing the prosthetic etiology typically results in pain reduction.

Table 13-1 Prosthetic Adjustments for Distal Tibial Pain in the Transtibial Amputee

Phantom limb sensation and pain are likely maintained by afferent, central, and efferent (sympathetic) dysfunction.⁵⁴ Phantom limb sensation and pain are neuropathic perceptions in a portion of the limb that was amputated. Most amputees experience some degree of phantom limb sensation and pain, but the natural history is for these feelings to diminish both in frequency and intensity over the first few weeks to months after the amputation.²⁹ These sensations are highly variable in character. Phantom limb sensations are frequently described as numbness, tingling, pins and needles, or itching. Some amputees report the sensation of the phantom limb becoming shorter, known as telescoping. Patients can also complain that the missing limb feels like it is moving or is in a cramped or awkward position. It is important to explain that these are normal sensations that will likely diminish with time. Sometimes patients do not consider the sensation to be painful, but uncomfortable or “bothersome.” These sensations can be severe enough to interfere with sleep, impair patients’ functioning, or significantly reduce their quality of life. At this point the phantom limb sensation should be treated as neuropathic pain. The character of phantom limb pain is often described as sharp, burning, stabbing, tingling, shooting, electric, or cramping. Patients frequently perceive the same type of pain that they had before the amputation. For example, they might feel like they still have a painful foot ulcer.

Residual limb pain, previously referred to as stump pain, is another manifestation of central sensitization. Preliminary work in the area suggests that it is a form of allodynia (i.e., pain evoked by previously innocuous stimuli) or a spontaneous pain of peripheral neuropathic origin, central neuropathic origin, or both. Spontaneous residual limb pain is usually described as aching, burning, or throbbing, whereas evoked pain can be electrical or shooting (which can easily be confused with a clinically significant neuroma).⁹⁵ The pain is localized in the residual limb and can be associated with phantom limb pain. Edhe et al.²⁹ reported residual limb pain to be as common as phantom limb pain in lower limb amputees, and often more distressing.

The first line of treatment for bothersome phantom limb sensation, phantom limb pain, and residual limb pain is desensitization techniques. Massaging, tapping, slapping, wrapping, and friction rubbing of the residual limb often diminish such sensations. Patients frequently find that their phantom limb pain diminishes with the stimulation of using a prosthesis. Anecdotally, many patients find that for a phantom itch, scratching the remaining leg in the same spot is helpful. For cramped or malpositioned limb sensations, hypnosis can be helpful.^27,65,88 Under hypnosis, the patient might be able to alleviate a cramped phantom hand or move an awkwardly phantom positioned limb to a more comfortable position.

If desensitization techniques are insufficient and these pains are significantly interfering with quality of life, pharmacologic treatment should be considered. Unfortunately, the literature is not robust with regards to demonstrating efficacy of any particular agent in treating phantom pain.⁶⁹ However, the two primary categories of medicines generally used in clinical practice to treat chronic phantom limb phenomenon are antidepressants and anticonvulsants. Antidepressants have several advantages in addition to pain control. They can also treat depression, which is a common problem in new amputees. They generally have anxiolytic effects and, some being sedative, can improve sleep. They are convenient because they are usually taken just once per day, and they are generally less expensive than the newer antiseizure medications. Analgesic antidepressants apparently need to have both noradrenergic and serotonergic receptor activity to effectively treat neuropathic pain,³³ which explains why the selective serotonin reuptake inhibitors do not help with the treatment of phantom limb pain. Tricyclic antidepressants have the most anecdotal and empirical support for treating pain, but they also have undesirable anticholinergic side effects.^52,82 Some antidepressants have both serotonergic and noradrenergic activity without the anticholinergic activity (serotonin and norepinephrine reuptake inhibitors [SNRIs]), and might help in treating neuropathic pain. Mirtazapine is an SNRI that can be useful for the treatment of phantom limb pain because it has no anticholinergic side effects, and it enhances sleep (night is often when phantom limb pain is most problematic). It is an effective antidepressant and an anxiolytic, although weight gain can be a significant side effect.⁸⁵ Venlafaxine and the newer agent duloxetine are also SNRI-type agents that might have some value for the treatment of neuropathic pain.

A number of anticonvulsants have been used to treat neuropathic pain syndromes.⁶ At present, gabapentin is probably the most widely prescribed neuropathic pain medicine in the United States. Despite its name, gabapentin’s mechanism of action is unknown. Nevertheless, gabapentin has demonstrated efficacy with neuropathic pain, has minimal side effects, and has been shown in a small study to have efficacy in phantom pain.^10,45 However, it usually requires frequent dosing (generally three to four times a day). Traditional anticonvulsants such as carbamazepine and phenytoin are membrane stabilizing agents (sodium channel blockers) that have the widest historical use for the treatment of neuropathic pain syndromes.^21,69 However, they have a high incidence of significant side effects. Other anticonvulsants that are being used to treat neuropathic pain include oxcarbazepine, topiramate, levetiracetam, and pregabalin, but few or no data exist yet concerning their efficacy. Anticonvulsants can also be used in combination with antidepressants or with each other to maximize relief from phantom limb pain. This must be done in a thoughtful fashion that uses complementary mechanisms.

Some success has been reported with topical anesthetic agents such as various analgesic balms, sprays, and patches. Capsaicin, a substance P inhibitor, has been anecdotally reported to be effective for phantom limb pain and residual limb pain.⁵¹ Lidocaine cream, ointment, and patches have also been used with some success.

Other nonpharmacologic modalities exist for the treatment of phantom limb pain such as stress-relaxation techniques and biofeedback.^37,50,87,88 Transcutaneous electrical nerve stimulation has also been shown to give temporary pain relief.^35,56 Mirror therapy, while primarily used with upper limb amputations, has been attempted in patients with lower limb loss,^16,19 with some success.

If these measures are unsuccessful or inadequate, then a judicious use of opioids can significantly improve the amputee’s quality of life. Care must be taken in prescription with consideration to addiction, tolerance, and side effects.

Neuromas are bundles of nerve endings that form after a nerve is cut, as is done during an amputation. They can produce sharp, focal pain under pressure or upon palpation (i.e., Tinel’s sign).²² If a neuroma is superficial, then a small, tender mass can be palpated. It can cause significant pain and can preclude use of a prosthesis. Initially, prosthetic socket adjustments are used to relieve pressure over a neuroma. If this is unsuccessful, neuropathic pain medication, intralesional steroid and anesthetic injection, or neuroma ablation with phenol, alcohol or cryoablation can provide pain relief. However, literature demonstrating efficacy in patients with amputation remains severely limited. Ultrasound-guided phenol instillation has been shown in a small case series to provide some benefit in the treatment of neuroma pain.⁴⁴ Radiofrequency ablation has also had some success in case reports for both neuroma and phantom limb–related pain.^76,103

If these interventions are all ineffective, the neuroma can be surgically excised and the nerve endings buried deep in the soft tissue to protect them from mechanical pressures. Surgical resection has been found to be up to 80% successful.^12,42

While the causal relationship between amputation and phantom limb pain or residual limb pain is obvious, other conditions can also cause pain in a phantom limb. In trauma, referred pain can be generated down the leg by a proximal nerve injury, plexopathy, radiculopathy, or occult fractures, even if the leg has been amputated. Referred leg pain from spinal stenosis or arthritis at the knee or hip can also be mistaken for phantom limb pain. These alternative diagnoses must be considered and clearly require different treatment plans.

Psychological Adjustment

The emotional impact of limb loss is devastating and is frequently underestimated by the rehabilitation team. Grieving over the loss of one’s limb is necessary, and a brief exogenous (reactive) depression is expected. Amputees are at high risk of developing more severe psychological problems. The incidence of persistent clinical depression is estimated to be 21% to 35% for people with limb loss.^20,83 Risk factors for depression include low income, comorbid conditions, and the presence of phantom and back pain.²⁰ Posttraumatic stress disorder is a recognized complication after traumatic amputation, but frequently goes untreated. Nontraumatic amputees can also develop anxiety disorders from the stress related to limb loss.

The rehabilitation team should assist patients with their psychological adjustment by giving encouragement about prognosis, providing educational materials, and incorporating the patient’s specific goals into the rehabilitation plan. Team members can also reassure their patients by emphasizing gains made in therapy. They should also initiate discussions about prosthetic options with patients early on and impress upon patients that their input in the decision-making process is necessary. This not only educates patients and optimizes their prosthetic prescriptions, but it also helps to empower them and give them a sense of control.

Peer counseling and amputee support groups are another important emotional support mechanism. The opportunity to talk to persons who have been through a similar amputation, and to see how well they are doing, can be very valuable to the patient. The Amputee Coalition of America (see Box 13-1) has a national peer network that provides peer counselor training sessions and lists amputee support groups by region.

The physician should regularly monitor the patient’s emotional adjustment to amputation by assessing mood, appetite, weight changes, quality of sleep, and the occurrence of nightmares. Any correlation between the patient’s perceived stress level and pain should be explored. Sometimes adjustment issues will not become problematic until shock and denial wear off and time passes. Because studies have shown that the incidence of depression in younger amputees increases with time,³⁸ continued monitoring by the rehabilitation team is necessary. The whole team must be involved in monitoring the patient’s emotional state, and not just the physician. In most cases the therapists and prosthetists will spend much more time with the patient and might have better insight regarding a patient’s emotional status.

Each patient should be encouraged to have an evaluation by an experienced psychologist. This evaluation should include an assessment of mood, pain, other stressors, coping skills, past psychological problems, alcohol and drug use, body image issues, and sexuality. When clinical depression, anxiety disorders, or adjustment disorders are identified, a comprehensive treatment plan should be initiated, with cognitive-behavioral psychotherapy and pharmacotherapy as needed.

Skin Problems

Problems with skin are frequent in patients with amputation. It has been reported that 63% of patients experienced a skin problem in the past month in one questionnaire.⁶¹ Adequate treatment requires proper identification of etiology and type of skin issue.

Verrucose Hyperplasia

Verrucose hyperplasia (also termed verrucous hyperplasia) is the development of a wart-like lesion on the end of the residual limb (Figure 13-5). Cracks in the skin and even infection can occur in severe cases. Verrucose hyperplasia is most common in the transtibial amputee, but can occur with other levels of amputation. This dysplastic skin condition is thought to be due to choking effect on the residual limb. It is hypothesized that if the prosthesis fits tightly around the limb (circumferentially) and there is a lack of distal pressure, then vascular congestion can occur that somehow leads to verrucose hyperplasia. The pathophysiology of the condition remains unknown. Adjusting the prosthesis to create adequate distal pressure usually resolves the verrucose hyperplasia within a few weeks or months. Adjustments such as simply adding an end pad to the socket can be sufficient; otherwise a new total contact socket is recommended.

FIGURE 13-5 Severe verrucose hyperplasia.

Epidermoid Cysts

Epidermoid cysts occur when sebaceous glands are plugged. These cysts are firm, round, mobile, subcutaneous nodules of variable size that are most commonly found in the popliteal fossa of transtibial amputees and the upper thigh of transfemoral amputees (Figure 13-6). They can be quite tender and can become inflamed by the pressure of the prosthesis. Sometimes bleeding into the cyst makes them appear dark. Ruptured epidermoid cysts have a purulent or serosanguineous discharge. Treatment with topical or oral antifungal and/or antibacterial agents has been recommended.⁵² Treatment should also include minimizing pressure over the cysts by adjusting the prosthesis and ensuring an optimal fit. Sometimes larger inflamed cysts require incision and drainage. However, recurrences are frequent because incision and draining does not remove the keratin-producing lining of the cyst. A more definitive treatment consists of surgical excision, but even this intervention cannot completely eliminate the possibility of recurrence.

FIGURE 13-6 Epidermoid cysts. (A) Early cyst.(Courtesy James Leonard, MD.) (B) Epidermoid cyst with hemorrhage.

Other Complications

Joint contractures are frequent complications during the rehabilitation of people with limb loss. Initial treatment consists of a stretching program both in therapy and at home. For knee contractures, extension devices like knee immobilizers can provide relief. For hip flexion contractures, prone lying on a daily basis is helpful. Ultrasound heating can also be an effective therapy when combined with aggressive stretching, provided the patient’s vasculature is adequate for vigorous heating. For transtibial patients who are expected to ambulate, the knee flexion contracture is initially accommodated in the prosthetic alignment. Once the patient is ambulating adequately, flexion is gradually taken out of the socket. This causes an extension stretch when the patient walks, and progressively reduces the contracture. In severe cases that do not respond to the above treatment, surgical release can be considered.

Bony growths at the end of the amputated bone are called bone spurs. They occur frequently and are usually asymptomatic. Similarly, heterotopic ossification (HO) is a spontaneous development of bone in soft tissue, usually occurring after traumatic amputations. The incidence of HO with traumatic amputation has been reported to be as high as 63% in recent armed conflicts.⁷³ If a bone spur or HO protrudes distally and is not covered by adequate soft tissue, it can become painful and cause skin breakdown. Accommodating the spur or HO with a relief and/or padding in the socket might solve the problem. If this fails, surgical excision might be required.

Timing of Prosthetic Fitting

Prosthetic sponsorship must be considered as soon as possible, even before the patient is ready to be fitted with an artificial limb. Many insurers require preapproval before the patient can be fitted with a prosthesis. Such authorization can sometimes take weeks (or even months) to obtain and cause detrimental delays in the rehabilitation of the amputee. Starting the required paperwork as soon as possible can minimize these delays. Some providers also have copayment restrictions in coverage that affect prosthetic prescription (preferred providers, component limitations, even a restriction of one prosthesis per lifetime). These restrictions need to be determined, considered, and discussed with the patient when designing a treatment plan.

Determining when to fit the lower limb amputee with a prosthesis and what kind of prosthesis to use are issues open to considerable debate. One option for transtibial amputees is to use an immediate postoperative prosthesis (IPOP). IPOPs traditionally have been thigh-high casts with a pylon and foot attached (Figure 13-7, A). Prefabricated devices are also now available (Figure 13-7, B and C). These devices allow for earlier bipedal ambulation. Although many claims have been made for the advantages of IPOPs over soft dressing management (including improved psychological acceptance, reduction in pain, accelerated rehabilitation times, reduced revision rates, and time to healing), these claims have rarely been evaluated with controlled studies.⁸⁹ A review of 10 controlled studies yielded only two proven claims for the IPOP: (1) that rigid plaster casts result in accelerated rehabilitation times and significantly less edema compared with soft dressings; and (2) that prefabricated pneumatic prostheses were found to have significantly fewer postsurgical complications and fewer higher level revisions compared with soft gauze dressings. Only limited weight-bearing can take place with an IPOP, and patient compliance is important for such success.⁸⁹ Although weight-bearing is limited through IPOPs, patients clearly have greater stability in standing and walking with the bipedal support. Some studies have shown an increase in wound dehiscence and infection with these devices.¹⁸ Frequently the residual limb is too tender and painful to allow early weight-bearing to take full advantage of these devices. With the nonremovable IPOPs, patients are unable to inspect or massage their residual limbs, which can interfere with desensitization and emotional adjustment to their amputation.

FIGURE 13-7 Immediate postoperative prostheses (IPOPs) for transtibial amputees. (A) Custom-made, full-length cast IPOP. (Courtesy Prosthetic Research Study.) (B and C) Prefabricated adjustable socket IPOPs.

(B courtesy Flo-Tech O&P Systems; C courtesy Airlimb Inc.)

Another option is early fitting of a custom prosthesis, which requires a delay of 3 to 6 weeks until much of the surgical swelling has resolved and the wound has started to heal. Ideally the limb has also become cylindrically shaped (i.e., the circumference of the distal residual limb is equal to or less than the proximal size). It is preferable that the wound has also attained some integrity (although it need not be completely healed and sutures or staples do not need to be removed). Because most of the postsurgical pain has subsided by the time of early prosthetic fitting, patients are better able to tolerate weight-bearing. Much of the postoperative edema is gone, so the residual limb has a better shape for fitting with a prosthesis. A custom device is used so there is a more intimate and secure fit with the prosthesis, and full weight-bearing is allowed. However, the patient has only one leg for any support until the prosthesis is made, and is less stable for transfers and gait as compared with using an IPOP.

The most conservative option is to wait until the wound on the residual limb is completely healed and surgical edema has resolved before the patient is fitted with a custom prosthesis. This generally takes 3 to 6 months with dysvascular amputees. Although this approach can minimize wound problems related to early weight-bearing, there is a higher risk of complications such as joint contracture, deconditioning, pressure ulcers, and an unnecessarily long delay in returning to functional ambulation.

After 6 to 9 months, when the residual limb volume stabilizes, a new prosthesis, or at least a new socket, is recommended. At this point, different componentry can be considered. If a new prosthesis is made, the preparatory prosthesis can serve as a backup prosthesis.

All amputees will require prosthetic gait training from an experienced physical therapist. The therapist initially trains the patient to independently don and doff the prosthesis, monitor skin tolerance, and adjust sock ply fitting as the residual limb shrinks. The training maximizes the patient’s function. The level of performance will vary with each patient, but community ambulation and the negotiation of stairs and curbs are goals for most patients. A floor-to-sit transfer should also be a goal for most patients and is frequently overlooked. Therapy does not need to stop with this level of performance. For more active amputees, continuing to work in therapy on vocational activities, running, bike riding, or other sports present more advanced therapeutic goals.

Factors Affecting Prosthetic Prescription

Prostheses are made up of several different components. Many factors determine which components should be used for each individual patient. Residual limb length and strength affect inherent limb stability and can inversely affect the need for added stability in the prosthesis. The quality of the residual limb tissue must be considered in selecting a residual limb interface system. Anatomical stability of joints is a further issue central to selecting socket types and suspension systems. Hand function can be an issue for donning and doffing the prosthesis. Additionally, an amputee’s weight can limit component options, because many components are limited to a body weight of 250 to 300 lb. The desired activities of the amputee are clearly important in component selection; both work and leisure activities must be considered. A prosthesis with low maintenance might be necessary if the user lives in a rural area with poor access to a prosthetist. The relative importance of cosmesis is an issue, because some components have more natural contours than others regardless of any coverings. Good compliance is essential for using some systems such as gel liners, which require daily care for hygiene. Cognitive function is an important factor because cognitively impaired people require the use of simple donning and doffing systems, and family or caregiver support can be necessary for the successful use of a prosthesis. Additionally, financial restrictions are sometimes placed on the availability for individuals to obtain their desired prosthetic components.

In 1994 the federal government attempted to clarify which knee, ankle, and foot components should be used for patients with particular functional abilities or functional levels. The functional level is a measurement of the capacity and potential of the patient to accomplish his/her expected postrehabilitation, daily function. This functional classification was designed to assist the Durable Medical Equipment Regional Committees in determining appropriate reimbursement for prosthetic components.²⁴ It limits patients with lower functional abilities to simpler prosthetic components, while allowing more active people to use more advanced (and expensive) devices. The determination of these levels is for individuals with unilateral lower limb amputations and is at the discretion of the prescribing physician. Items to take into consideration are the patient’s medical history, present medical condition, and functional status, as well as future ambulation goals and expectations. The prescribing physician should keep an open mind regarding the potential or expected functional level, focusing on the patient’s current condition and how it may affect the goals. Documentation of function should be maintained in the patient’s records.

The functional levels (often referred to as the K-modifiers) are listed in Box 13-2. These levels are based on the patient’s potential, not on the current level of function; even deconditioned patients can reach a higher level of function than anticipated with appropriate rehabilitation. Also, the K1 level includes the use of a prosthesis for assisting with transfers. Many low-functioning people with amputations below the knee or lower benefit from the use of a prosthesis. For higher levels of amputation, a prosthesis does not generally assist with transferring; instead, it often gets in the way.

The final determination of prosthetic components should be a team decision involving the physician, the prosthetist, and most importantly, the patient. The real goal is to educate patients and their families about reasonable, available options and their advantages and disadvantages. The decision should then be based primarily on what the patient desires.

Prosthesis Construction

Prosthesis design encompasses socket design, suspension, and construction. The socket, or interface, of a prosthesis is typically custom-made for the user. The socket can be constructed using a cast of the residual limb. The residual limb shape can also be recorded via manual measurements only or by digital measurements that track the outer shape of the limb. This shape is then used to create the socket interface. In most sockets the goal is to achieve total contact with the residual limb. Total contact does not necessarily imply equal pressure distribution. Pressure-tolerant areas can receive higher pressures and pressure sensitive areas can receive lower pressures. Total contact helps decrease edema, increase proprioception, and increase the overall weight-bearing surface. Open-ended, or plug fit, sockets have no distal contact and are no longer used. The exception to this is the individual who has traditionally had one and wants to continue to use this type of socket. With many socket designs, socks are worn over the residual limb to allow for adjustments to fit with small volume changes.

The interface of the residual limb with the socket can either be through a hard interface or a soft interface. Examples of soft interface materials are foam inserts, silicone liners, or other gel materials. Soft interface materials are indicated for most amputees. They provide a cushion for the residual limb and allow for adjustment and comfort if the volume of the residual limb changes. Soft inserts are often necessary for individuals with bilateral limb loss, who cannot transfer weight to a nonprosthetic limb, and individuals with bony or scarred residual limbs. Vascular amputees can also benefit from soft liners because sensitive tissue needs extra cushioning. Individuals with neuropathy, who are unable to know when an extra sock should be added, can benefit as well. The disadvantage of soft inserts is that they are susceptible to wear and tear. They add bulk, and they can also absorb odors. A hard interface, on the other hand, consists of just the socket. These are most commonly used with transfemoral suction suspension, yet they can also be appropriate for other individuals where damage of the liner could occur.

Suspension is the method by which the prosthesis is held onto a person’s residual limb. It can be provided through the anatomic shape of the limb, by a liner, by a sleeve, or with suction. An auxiliary suspension is often used, depending on the individual’s activities. For example, a transfemoral amputee with suction suspension might still wear a belt to provide suspension in activities where suction can be lost or where residual limb volume changes are possible.

The prosthetic socket is connected to the remaining components in two ways: through exoskeletal or endoskeletal construction (Figure 13-8). In the more common endoskeletal construction (see Figure 13-8, B), the socket connects to the remaining components through pipes called pylons. The modularity of these components allows for angular and linear changes in both the sagittal and coronal planes, and makes it easy to adjust the height of the prosthesis if necessary. An important benefit of this modularity includes the ability to use many different components (e.g., adapters and feet). At higher levels (transfemoral and higher) the endoskeletal design is also lighter in weight. Many endoskeletal systems have carbon fiber or titanium pylons, which are even lighter in weight than standard steel components. Endoskeletal pylons also allow the ability to finish the prosthesis with softer, more realistic covers.

FIGURE 13-8 Prosthesis construction. (A) Exoskeletal prosthesis. Strength is provided through the outer lamination. This design is more durable and often prescribed for heavy-duty use. (B) Endoskeletal prosthesis. This design has an inner pylon covered by a soft foam cover. It allows for changes to components and adjustability, and at higher levels it is a lighter prosthesis.

Exoskeletal construction (see Figure 13-8, A) uses a rigid exterior lamination from the socket down and has a lightweight filler inside. This rigid lamination gives the device strength. Since exoskeletal designs do not have a soft foam cosmesis, they are more durable and can be indicated for heavy-duty use and for children. Fewer components are designed for exoskeletal construction, so this construction can limit foot and knee options, as well as long-term adjustability.

A plethora of prosthetic feet are available to prosthetists. Feet can be made out of many different materials including wood, plastic, foam, and carbon fiber. All of the feet can be classified into four different categories: SACH (solid-ankle, cushion-heel), single axis, multiaxis, and dynamic response. Activity, weight, level of amputation, prosthesis construction, and foot size can all influence the choice of prosthetic foot for an amputee. These various choices are discussed in the section on transtibial amputation.

Prosthetic knee selection is also based on patient activity, weight, level of amputation, prosthesis construction, and the strength and ability of the patient to voluntarily control the knee. The five major classifications for the joint design are outside hinges, single axis, weight-activated stance control, polycentric, and manual locking. In addition to the joint design, prosthetic knees are designed to provide resistance to knee flexion through either mechanical friction or fluid friction. This resistance helps to limit heel rise and the rate of knee extension. At higher speeds, the fluid friction provides cadence responsiveness by increasing resistance with increasing speed. Mechanical friction is constant for all speeds.

Additional add-on components designed to provide movement in specific ways can also benefit the amputee, such as shock absorbers for higher impact activities and rotation units for activities such as golf.

Socket Designs

The transtibial socket designs available are intended to provide a means of comfortable weight acceptance of the residual limb during stance on the prosthetic side. These have evolved from plug-fit through patellar tendon–bearing (PTB) and now include total surface–bearing (TSB) and hydrostatic designs. Each of these designs, with the exception of the plug-fit design, is intended to create a total contact environment between the residual limb and the socket. Some of the socket designs also have added features that enable the socket to act as both a weight-acceptance and suspension mechanism.

Patellar Tendon–Bearing

The PTB design focuses on specific weight-bearing areas. Although the socket has total contact with the residual limb, it concentrates force in pressure-tolerant areas and relieves force in pressure-sensitive areas (Figure 13-11). The PTB design gets its name from the amount of force that is borne on the patellar ligament. The socket is designed with an anteriorly directed force, from pressure in the popliteal area, pushing the residual limb onto a “bar” that is created between the distal pole of the patella and the tibial tubercle. Other regions of the residual limb that are used for distribution of forces (pressure-tolerant areas) include the pretibial and gastrocnemius musculature, the medial tibial flare, and the fibular shaft. Pressure-sensitive areas include the patella, hamstring tendons, fibular head, femoral epicondyles, tibial shaft, distal tibia, and distal fibula. An essential part of the PTB design is the alignment of the socket and prosthesis. The PTB design was created to take advantage of normal, or perpendicular, forces on the patellar ligament. This is done by adding initial flexion of the socket to that which is present on the individual’s residual limb. This increased socket flexion loads pressure-tolerant areas of the anterior surface by allowing the patellar ligament to be more parallel with the ground. This provides a surface that is more perpendicular to the ground reaction forces during stance phase. The foot is also aligned medially relative to the socket in order for the individual wearing the prosthesis to experience an external knee varus moment. This moment, in the coronal plane, simulates normal human locomotion and ensures that forces are distributed on the medial tibial flare and the fibular shaft, two of the pressure-tolerant areas on the transtibial limb.

FIGURE 13-11 Pressure-tolerant and pressure-sensitive areas for the patellar tendon–bearing socket.

Suspension

There are several means of suspending transtibial prostheses. Suspension mechanisms can be external to the socket (e.g., a fork strap, cuff, or sleeve), integral with the socket (e.g., supracondylar or supracondylar-suprapatellar suspension), or part of a system in which a locking mechanism is incorporated into a prosthesis containing a pin or other attachment. Although one design may create a more positive seal than another, the better design is that which works best for the particular patient being fit.

Fork Strap With Waist Belt

A fork strap combined with a waist belt is a very simple suspension technique (Figure 13-12). The fork strap, sometimes referred to as a Y-strap, is attached to the medial and lateral aspects of the socket with the junction proximal to the patella. The upper portion of the strap often has some elastic component inherent in its design to permit freedom of knee flexion and extension throughout ambulation and sitting. There is no medial-lateral or anterior-posterior support provided by the fork strap. Its sole purpose is to suspend the prosthesis securely to the waist belt attachment. Because of the bulk and cosmesis of this suspension, it is typically used only when maximum security is required and no other suspension technique is viable (e.g., in obese patients).

FIGURE 13-12 Fork strap and waist belt suspension for a transtibial prosthesis.

The fork strap can be combined with a PTB socket design, thigh-lacer, and joints and rigid sidebars called a joint and corset. This design has the maximum medial-lateral and anterior-posterior stability provided through the rigid sidebars and mechanical stop of the joints, respectively. The joints and corset are required for an unstable knee associated with a traumatic amputation. The joints and corset can also be cinched tightly to provide significant weight-bearing. This can be useful in difficult cases where off-loading of the end of the residual limb is needed to help heal a problematic wound that has failed other measures, or to relieve a hyperpathic residual limb. However, the joints and corset suspension system is very heavy and often not tolerated well by patients

Cuff

Cuff suspension (Figure 13-13) has been used successfully for centuries for individuals with transtibial amputations. Although it is sometimes referred to as a supracondylar cuff or strap, the suspension is provided on the proximal border of the patella and not over the femoral epicondyles. The cuff is attached to the medial and lateral aspects of the socket, over the proximal aspect of the patella, and encircles the distal thigh at a level just proximal to the femoral epicondyles. A prominent patella is required, making this design contraindicated for obese persons or those with excessive thigh musculature. When appropriately applied, the cuff provides an adequate means of suspension between 0 and 60 degrees of knee flexion, and loosens up after 60 degrees of knee flexion to permit comfortable sitting. Similar to the fork strap, the supracondylar cuff provides minimal, if any, medial-lateral or anterior-posterior stability to the knee and has considerable pistoning in the socket. The tightness and width of the circumferential strap can contraindicate the cuff for individuals with vascular compromise.

FIGURE 13-13 Supracondylar cuff suspension for a transtibial prosthesis. Despite the name, the cuff suspends over the patella.

Sleeve

Suspension provided by a sleeve (Figure 13-14) is done with elastic and sometimes tacky material. The distal aspect of the sleeve is stretched over the proximal portion of the prosthesis and is held in place by the compression of the sleeve against the outer wall of the prosthesis. The proximal aspect of the sleeve is folded inside out and is reflected down beyond the trim-lines of the socket to facilitate donning. Once the individual has seated the residual limb appropriately inside the socket, the sleeve can be pulled up or rolled up onto the distal thigh to create a bond with the person’s skin and body. These sleeves come in a variety of materials and fabrics including neoprene, latex, silicone, and urethane. Some of these sleeves can provide a vacuum seal inside the socket to provide enhanced suspension via suction. Although most sleeves provide an excellent means of suspension, they are often difficult to don, retain heat, and provide minimal to no stability about the knee. They are relatively inexpensive but require frequent replacement.

FIGURE 13-14 Sleeve suspension for a transtibial prosthesis.

Supracondylar Suspension

Supracondylar suspension (Figure 13-15, A) is designed to use the anatomy as a means of suspension. A compression of medial-lateral dimensions of the prosthesis above the femoral epicondyles differentiates this design from those previously mentioned. A supracondylar wedge, mostly on the medial aspect of the prosthesis, is used to create this suspension. The wedge can be incorporated into the prosthesis in three ways. First, it can be incorporated into a soft insert made from a material such as foam. The foam liner is donned on the limb first, and then the limb and foam liner are inserted into the hard socket. The hard socket keeps the wedge compressed against the medial distal thigh, thereby preventing the prosthesis from falling off.

FIGURE 13-15 Trim-lines for (A) the patellar tendon–supracondylar and (B) the supracondylar-suprapatellar socket suspension designs.

The two other forms of supracondylar suspension are constructed with removable medial wedges or removable medial brims. Removable medial wedges are placed between the outer hard socket and inner socket or limb. The user must push this wedge into place after the limb is inserted into the socket. Removable medial brims are fabricated by creating a medial wall that can be quickly disconnected from the remainder of the socket. This wedge-shaped brim is removed to facilitate donning and is pushed into place once the limb is appropriately seated into the socket. Both of these latter designs are used when a large difference between the measured medial-lateral dimensions of the epicondyles and the area proximal to the epicondyle exists, or when a hard socket fit is desired. With this type of anatomic presentation, it would be very difficult to don supracondylar suspension with the wedge incorporated into the insert.

Supracondylar suspension is a very popular design because it is easily donned and provides good medial-lateral stability. However, problems can arise as a result of a tight lateral grasp, because the iliotibial band does not lend itself to pressure like the medial thigh does. Pressure and skin breakdown over and on the medial epicondyle can occur if insufficient and excessive sock ply, is worn. Supracondylar suspension is contraindicated for obese patients, those with large distal thigh contours that prevent the wedge from grasping above the femoral epicondyles, and those with superficial vascular bypass grafts that run close to the medial femoral condyle.

Gel or Elastomeric Liner Suspension

Suction sock suspension is a very popular design of recent times that provides both suspension and weight distribution through the use of a gel liner and pin-locking mechanism (Figure 13-16). The gel liners that are available, like the sleeves, are fabricated from various materials such as silicone, urethane and mineral oil gel. The liners come in different thicknesses, and some provide more padding in different areas than others. In addition to cushioning and suspension, these liners minimize shear on the limb. Custom-made liners are also available for use with residual limbs that have a complex shape (such as crevices from traumatic amputation) or other skin problems.

FIGURE 13-16 Gel liner and pin-locking suspension mechanism.

Appropriate donning of these gel liners is crucial to the comfort and maintenance of good skin integrity. Most of the liners need to be turned inside out so that the distal end of the inside of the liner is flat when it is applied to the distal residual limb. This is done so that no air becomes trapped between the distal limb and liner creating a negative pressure within the suction liner that can cause erythema and capillary rupture. A well-fitting, appropriately donned gel liner provides a barrier of comfort and creates a suction environment between the limb and liner.

With the gel liner donned on the limb in a suction design, the limb and liner then must be connected to the socket and prosthesis. There are a few methods of providing this connection. The most popular means of joining liner and socket is by means of a pin (stepped or smooth) attached to the distal end of the liner and a locking mechanism built into the distal socket. As the limb and liner are inserted into the socket, the pin engages into the locking mechanism to create this mechanical bond. Most stepped pins create an audible click, which is necessary for some individuals wearing prostheses, while the smooth pin enters the locking mechanism quietly. When the prosthesis has been donned completely and the individual wearing the prosthesis feels that he or she is completely in the socket, the pin should be fully engaged into the locking mechanism, ensuring a total contact fit. This should not occur abruptly, but the limb should gradually work its way into the socket, creating a series of clicks in the stepped pin design. If the limb enters the socket too quickly, sock ply management needs to be addressed. When these pin locks are being used with a hydrostatic design, the wearer is encouraged to engage the pin into the lock and step on and off the prosthesis until the limb becomes fully seated inside the socket. This creates an elongated residual limb and approximates a hydrostatic environment where the bone is less apt to move within the surrounding soft tissue. Another way of elongating this tissue is with the use of a clutch-type mechanism. The pin need only be engaged slightly into the lock, and the user, with the assistance of a key, can twist the locking mechanism to further seat the limb and locking pin into the prosthesis. This procedure also acts to elongate the limb. To remove the prosthesis, a release button is pushed that is built into the side of the prosthesis.

If there are space limitations for the locking mechanism or when engaging the pin proves difficult for the user, suspension can also be achieved with a lanyard at the end of the liner. A lanyard is a cord or strap that is fed through the distal socket and attached to the exterior of the prosthesis. The user can pull the lanyard through the hole while sitting, then tighten it when standing. For some elderly or obese people, the lanyard system proves easier then the pin system.

Gel liner suspension provides an excellent means of suspension, transmits great control of the prosthesis, offers better cushioning of the residual limb, decreases shear forces on the residual limb, and provides a low-profile appearance, as it is inside the socket walls. There are a number of difficulties with liner use that must be considered. They can prove challenging to don and doff. In some cases, individuals have difficulty donning the liners appropriately. The pin can pierce the liner during donning, or the angle at which the pin is canted off of the distal liner can make it difficult to engage the locking mechanism properly. Patients with cylindrical limbs may have issues with rotation in the coronal plane, which can cause internal or external prosthetic rotation. The liners also retain heat, and people often experience excessive sweating when first using gel liners. Fortunately the limb usually accommodates in the first few weeks, and sweating declines. Antiperspirants can be used if needed. Good hygiene is imperative, or skin problems such as rash or infection can occur. If there is concern that a patient might have poor compliance with residual limb and liner care, then gel liners should be avoided. It should also be noted that liner suspension systems are expensive, and the liners require frequent replacement.

Foot-Ankle Assemblies

The number of prosthetic feet available on the market today has grown dramatically since the early 1980s. The introduction of the dynamic response (at that time called “energy storing”) foot started a revolution of prosthetic feet because they could provide users the ability to more easily return to their desired functional ability. The means by which feet are categorized is almost as vast as the number of feet themselves. For the purpose of this text, the feet have been divided into four categories: SACH feet, single-axis feet, multiaxial feet, and dynamic response feet. Because of the advancements in prosthetic component designs, these categories, although differing in their basic descriptions, are not mutually exclusive of each other. Combinations of categories will be described in further detail.

Solid-Ankle, Cushion-Heel Feet

The SACH feet, introduced in 1956 by Foort and Radcliffe, are one of the most basic and widely used feet in prosthetics (Figure 13-17). SACH feet have solid ankles in that there is no articulation within the foot. They attach to the distal aspect of the shank (endoskeletal pylon-ankle adapter or ankle block) in a way that permits no motion. It is important to understand that motion in all planes is arrested. No plantar flexion, dorsiflexion, inversion, eversion or transverse plane motion is allowed during gait. The cushion heel aspect of the foot allows for a simulated plantar flexion during initial contact-loading response by means of compression under loading. This compression lowers the forefoot to the ground and brings the ground reaction force anterior, simulating the function of true plantar flexion. Heel compression also acts to absorb shock during loading response. With correct heel stiffness, shock absorption benefits all of the lower limb, especially the reduction of external knee flexion moment that would be caused by a stiffer heeled foot. External knee flexion moments directly correlate to increased quadriceps activity and decreased stability in individuals with transtibial and transfemoral amputations, respectively. A drawback of SACH feet is that most are designed with keels (the main inner structure of the foot) that are not flexible or are nonresponsive to the typical loads that they will encounter. These keels are usually made of wood or hard plastic. However, these feet are very durable and inexpensive (as compared with other designs). They can vary in heel height and stiffness, and they come in Syme’s varieties. For these reasons, they are still widely used.

FIGURE 13-17 Cutaway of a SACH foot.

Single-Axis Feet

Single-axis feet are named very appropriately because a single mechanical axis runs through the foot from medial to lateral, allowing motion in the sagittal plane. The sagittal plane motion that is observed is mostly plantar flexion; however, some of the single-axis feet permit graded dorsiflexion as well.

The motion of ankle plantar flexion is very important to the stability of ambulation, especially for individuals with lower limb amputations. As the foot begins to plantar flex, the ground reaction force moves forward under the foot. It then moves from posterior to the knee to anterior to the knee, providing for an external knee extension moment. This is good for individuals with transtibial prostheses who can have weak quadriceps, or for individuals with transfemoral amputations who do not have adequate control of the prosthetic knee joint (usually controlled via hip extensor muscles). Ankle plantar flexion can also aid an individual when walking down an incline. The rapid shifting anteriorly of the ground reaction force greatly reduces the external knee flexion moment. This allows an individual to descend the decline without the knee flexing as abruptly as it would with a nonarticulating foot. This allows the prosthetic user to descend ramps directly, rather than having to walk down hills sideways.

Ankle dorsiflexion is also permitted by some single-axis feet. This motion is not as crucial as the aforementioned plantar flexion, but it permits the individuals with lower limb amputations to walk more comfortably. Ankle dorsiflexion is usually permitted in mid to late stance as the ground reaction forces begin to move anteriorly to the ankle. This permits the individual with a lower limb prosthesis to roll over the keel of the foot more readily. If this motion of dorsiflexion were not permitted, the individual would experience an excessive external knee extension moment and would have difficulty progressing into terminal stance and preswing.

The usual method by which the ankle motion in a single-axis foot is permitted is by bumpers that are installed anteriorly and posteriorly to the ankle (Figure 13-18). These bumpers regulate the amount and speed of motion in which the foot can rotate about the mechanical axis. The plantar flexion bumper is posterior to the ankle axis. As the bumper is compressed, the foot is permitted to slowly or quickly rotate about the axis, depending on whether the bumper is firm or soft, respectively. If the bumper is too stiff, the external knee flexion moment will be great and vice versa. The dorsiflexion bumper is mounted anterior to the ankle. As the ground reaction force moves anterior to the ankle, the bumper begins to compress to permit graded ankle dorsiflexion. The speed and degree of this motion can be varied as well with the stiffness of these dorsiflexion bumpers.

FIGURE 13-18 Single-axis foot. The bumpers allow plantar flexion and dorsiflexion movement.

Multiaxial Feet

Multiaxial feet are designed to replicate the actions of the anatomic foot. Multiaxial motion can be obtained either with a foot that has a flexible keel or one that has true mechanical joint axes. A flexible keel foot allows the motion to occur within the keel itself as the ground reaction forces cause deformation of the foot, especially on uneven terrain. This deformation is expected and is an inherent design of the foot. As the foot deforms, it maintains contact with the ground, thereby providing a stable base of support for the individual wearing the prosthesis.

True multiarticular feet are allow motion in all three planes: plantar flexion and dorsiflexion, inversion and eversion, and transverse plane motion. This is accomplished with the aid of adjustable bumpers. These bumpers are relatively durable and are designed to control similar motions to single-axis feet.

Multiaxial feet have now been fabricated with the materials necessary to enhance their energy return as well (Figure 13-19). These multiaxial, dynamic response feet can give an individual the benefits of compensating for uneven ground, absorbing shock, and providing some responsiveness to reduce energy expenditure during ambulation.

FIGURE 13-19 Various flexible keel or multiaxial feet: (A) SAFE, (B) K2, (C) Journey, and (D) Trustep. These feet allow plantar flexion and dorsiflexion as well as inversion and eversion. This movement makes them better for walking on uneven terrain.

(Courtesy Otto Bock HealthCare. College Park Industries. All rights reserved.)

Dynamic Response Feet

Dynamic response feet enhance the mobility of the user by using materials that are “energy storing.” Materials in the keel of these feet are required to deflect under load and return to their original shape. This return, while being unloaded, is what propels the foot and leg forward. In doing so, the foot is providing the response to users that lessens their energy expenditure.⁶³ Single-speed, low-activity (often elderly) individuals do not have the ability to load the foot enough to warrant their use.

There are various types of dynamic response feet (Figure 13-20). Some low-profile feet simply have a dynamic keel inside a foot shell providing a smaller spring. Other feet incorporate the pylon and keel as one flexible larger spring. These feet are indicated for variable cadence ambulators and are much better for high-level activities such as running and jumping.

FIGURE 13-20 Various dynamic response feet: (A) Seattle Lite Foot, (B) Carbon Copy Foot, and (C) Modular 3 Flex Foot. These feet are designed to store and release energy and are indicated for variable cadence ambulators.

(B courtesy Ohio Willow Wood Co, Mt. Sterling, OH; C courtesy Ossur International.)

Ankles

As mentioned previously, the feet can be designed to accommodate for motions that have been lost by the absence of the anatomic ankle. Stand-alone ankles have also been designed to replicate these lost motions. Ankle units (Figure 13-21, A) can be added to most solid keel feet (SACH or low-profile dynamic response feet) that can provide the user with multiaxial motion in addition to the functions provided by the foot itself. This addition allows the user to more easily traverse inclines, declines, and uneven terrain. More recent ankle components with adjustable ankles (Figure 13-21, B) can accommodate for shoes with varying heel heights. Actively powered ankle components have also been marketed that provide active dorsiflexion and plantar flexion to accommodate for toe clearance in swing and transitional movements from sit to stand, and aid in stair and ramp ascent and descent (Figure 13-21, C).

FIGURE 13-21 (A) Multiaxial ankle unit, the Endolite Multiflex Ankle with the Endolite Dynamic Response Foot. (Courtesy Endolite.) (B) Adjustable heel height ankle. (C) Externally powered ankle and foot.

(Courtesy Ossur America.)

Pylon Components

Other components are available for absorbing vertical shock or transverse plane motion, or to perform a combination of both (Figure 13-22). Torsion adapters are incorporated into pylons or are stand-alone components. These allow transverse plane rotation that simulates tibial rotation. The stiffness of the devices is adjustable based on the user’s size and activity level. They are particularly useful for people who do a lot of twisting motion (e.g., manual laborers), and for some sports, especially golf.

FIGURE 13-22 Rotation and shock components. (A) Example of a shock absorber pylon incorporated into a foot, Ceterus, and (B) separate, Delta Twist.

(Courtesy Ossur International and Otto Bock HealthCare. All rights reserved.)

Vertical compression units (or vertical shock pylons) are pylon-integrated systems that incorporate vertical compression resistance. They serve as shock absorbers to decrease the impact of initial contact and work much like the shock absorbers of an automobile. Some units combine torsional adaptation with vertical shock absorption. In other designs, the foot is integrated with a vertical shock pylon or tibial rotation capability, or both.

Gait Analysis

Gait patterns for individuals with transtibial amputations vary greatly from person to person. Many factors influence the way amputees walk. Physiologic factors include limb length, knee and hip muscle strength, ROM, and presence of contractures. Socket design, suspension, and foot selection are a few prosthetic factors that can greatly influence the way in which an individual with a transtibial amputation can walk. Patients with amputations must also be trained to condition their bodies and to use their prosthesis appropriately. The timing, quality, and quantity of physical therapy are very important. The clinic team attempts to minimize gait deviations by selecting the most appropriate designs and components for each individual, ensuring optimal alignment of the prosthesis and effectively training the amputee.

Many deviations occur secondary to muscle weakness and prosthetic alignment, and they vary greatly from person to person. Gait deviations based on sound mechanical principles are listed in Table 13-2. These gait deviations are primarily due to an incorrect placement of the foot with relationship to the socket, or vice versa. Other factors in this table include component selection. Although it can be easy to decipher these deviations, it might not be consistent in the gait pattern of the user. For example, an amputee might have had a wonderful gait pattern at one point of rehabilitation, only to present later with a dramatically changed gait pattern. Changes can be due to decreased or increased function by the user, a change in fit, or a change in shoe wear. The wearer might have had a contracture that has been reduced through use of the prosthesis and daily ambulation. This is an example where an increased function can lead to problems with the prosthesis. However, if the alignment of the prosthesis was rectified, the prosthesis would accommodate this improved ROM and greatly improve the gait and overall function of the user.

Table 13-2 Gait Analysis of the Transtibial Amputee

Courtesy Northwestern University Prosthetic-Orthotic Center, Chicago, IL.

Knee Disarticulation and TranscondylarSupracondylar Amputation

The knee disarticulation amputation is a procedure that preserves the femoral condyles, either with or without the patella. This leaves a residual limb that serves as a long lever arm and provides for a stronger residual limb than a transfemoral amputation because the muscular attachments to the condyles are preserved as well. As a result of the long length and weight-bearing properties of a knee disarticulation amputation, the proximal socket trim lines are significantly lower than that of a traditional amputation, often resulting in more comfort and greater ROM in the hip. The bulbous nature of the limb has a poorer cosmesis but can be helpful in using supracondylar suspension of the prosthesis. Variations of knee disarticulation amputations have been described in which the condyles are partially resected to reduce the bulk of the residual limb, but this can interfere with supracondylar suspension. The primary problem with the knee disarticulation is the length at the knee. When a socket and prosthetic knee are added, the functional thigh length is too long. This mandates a poor appearance when sitting because the leg lengths are uneven. In addition, sitting in tight places such as church pews and public transportation is difficult, and kneeling is problematic. For these reasons the knee disarticulation amputation is rarely performed.

Socket Designs

The socket designs for the knee disarticulation limb are highly dependent on the musculature present and the size of the condyles. In designs similar to the transtibial supracondylar suspension, the knee disarticulation socket can be created with an insert to provide both cushioning and suspension. This insert has a thickness of padding, or wedge, incorporated proximal to the femoral epicondyles that provides suspension when donned into a hard socket. As is the case for a Syme’s prosthesis, a door can be cut out of the hard socket to permit donning, and then a strap or elastic webbing can close the door to provide suspension of the prosthesis. If no large discrepancy exists between the femoral epicondyles and the region proximal to them, hard sockets can be used with socks over the residual limbs to facilitate donning through the narrowing distal socket. Gel or foam liners have also been used to suspend the knee disarticulation prosthesis. When donning the hard socket, the liner displaces over the condyles to allow the residual limb to slip past the narrowing socket and then rebounds when the limb is fully seated into the socket.

Individuals with long transfemoral limbs (e.g., transcondylar or supracondylar) have the advantage of a more cylindrical limb. Without the presence of the femoral epicondyles, donning the prosthesis can be easier, and more traditional designs such as pull-in suction sockets can be used. However, these levels might sacrifice the adductor longus insertion and the associated stability that it offers. A gel liner can be used in these levels as well; however, there still might not be room for a locking mechanism. In these cases a lanyard system can be used to provide the mechanical connection between the gel liner and prosthesis.

Component Selection

Knee components are selected for the longer residual limb based on muscular control, limb length and cosmesis. Most individuals with long transfemoral limbs or knee disarticulation limbs have excellent control of their limbs in all planes, and when trained appropriately, can walk with a variety of component designs. The components for knee disarticulation prostheses are chosen to minimize hardware distally, enhancing its aesthetics. Outside (single pivot) hinges (Figure 13-23) are often used in the exoskeletal-style knee disarticulation prosthesis. This offers the best opportunity to equalize femoral segment lengths, but the joints offer no resistance to flexion and extension. Low-profile polycentric joints are very popular for this level of amputation because they provide for a more natural-looking femoral section during sitting. This is because the linkages allow the knee unit to fold under the femoral section. It must be noted, however, that these polycentric knee units also offer increased stability, which might not be necessary for the individual with this residual limb length. Care must be taken to appropriately align the prosthesis to readily permit knee flexion during the preswing and swing phases.

FIGURE 13-23 Sketch of outside hinges for a knee disarticulation–level prosthesis.

Prosthetic Prescription

There are two standard socket designs for transfemoral prostheses: the quadrilateral design and the ischial containment design (Figure 13-24). The quadrilateral socket, described in 1955 by Charles Radcliff,⁷⁴ is designed to allow for muscle function and to provide a seat for the ischium. The quadrilateral socket has four distinct walls with specific biomechanical objectives. The lateral wall supports the femur and provides a surface for the abductor muscles to fire against. The medial wall is in the line of progression and supports the adductor region. The posterior wall is angled away from the medial wall to allow for function of the gluteal tissue, which is critical for knee stability. The anterior wall is contoured to compress the Scarpa’s triangle bounded by the inguinal ligament, the adductor tendon, and the sartorius. There is also relief built into the shape for function of the rectus femoris. Compression of the anterior surface provides the counter force that maintains the ischium on the posterior shelf.

FIGURE 13-24 Sketch demonstrating location of ischium and pelvis for the quadrilateral and ischial containment-style transfemoral sockets.

The ischial containment design was first described as the normal shape–normal alignment socket by Ivan Long in 1975. There are now multiple variations in the socket design for ischial containment sockets.^46,66,84,96 However, the main biomechanical principle of this design is to provide for a bony lock of the ischium in the prosthetic socket. Preventing lateral movement of the socket through containment of the ischium increases medial lateral stability during the stance phase and allows better adduction. This is helpful for all amputees, but is even more important for individuals with shorter residual limbs and for those with mild hip abductor weakness. The ischial containment socket is now the most commonly used design.

Ischial containment sockets are often made with a flexible inner socket and external frame (Figure 13-25). The flexible socket can be made out of a variety of thermoplastic materials. It provides for increased comfort proximally, which is important with the more aggressive ischial containment designs. The frame can be made out of stiffer thermoplastic or laminated materials. Cutouts can be made in the frame posteriorly to provide increased sitting comfort, and along the anterior surface to provide freedom of movement for rectus femoris contraction.

FIGURE 13-25 Flexible inner socket and rigid frame construction for the transfemoral-level prosthesis. This design provides comfort for the more aggressive ischial containment socket designs.

Suspension

Belt Suspension

Belts can be used to suspend a transfemoral prosthesis or provide increased medial-lateral stability. There are three main types of belts: a total elastic suspension belt, a Silesian belt, and a hip joint and pelvic band (Figure 13-26). Total elastic suspension belt belts, because they are elastic, provide less secure suspension and medial-lateral control. They are typically used more for auxiliary suspension and rotational control. The Silesian belt is made of Dacron webbing and can also be used for auxiliary suspension. When this belt is used alone for suspension, the socket is often worn with a sock ply fit. When better medial-lateral control is needed (for a short limb or for someone with mild hip abductor weakness), a Silesian belt should be used. A high lateral wall also increases the effectiveness of the belt in these cases. A hip joint and pelvic band should be worn for severe hip abductor weakness or by active individuals with a very short limb. The metal hip joint connects the socket to a metal pelvic band and leather belt. This provides the maximum medial-lateral stability; however, it also increases bulk and weight.

FIGURE 13-26 Three transfemoral belts: (A) total elastic suspension belt, (B) Silesian belt, and (C) hip joint with pelvic band.

Prosthetic Knees

Knee units can be organized into five classes: outside hinges, single axis, polycentric, weight-activated stance, and locking. The designs vary in the amount of voluntary control required and the amount of inherent stability. Voluntary control refers to the ability of the hip extensors to actively pull the thigh into extension before and during stance phase. Voluntary control stabilizes the prosthetic knee unit. The more voluntary control that is available, the less inherent stability is required, and vice versa. Outside hinges were described in the previous section on knee disarticulation prostheses.

Knee mechanisms also have friction to provide resistance to excessive knee flexion (heel rise) in swing. Mechanical friction is constant and independent of speed, making it appropriate for single-speed ambulators. Younger individuals tend to walk at variable speeds, while older individuals tend to adopt a single speed for most of their walking. For more active variable cadence ambulators, mechanical friction does not adapt and provide enough resistance as the walking speed is increased or for running. Fluid friction is used to provide friction proportionate to the velocity of movement. The fluid used can be air (pneumatic systems) or liquid (hydraulic systems). Pneumatic systems are lighter and do not need to be sealed, but they can seem “bouncy” for the more aggressive walkers because of the compressibility of air. Both pneumatic and hydraulic systems are more expensive and require more maintenance then mechanical friction units.

Some knee units also include an extension assist (Figure 13-27). An extension assist acts to help limit heel rise (similar to friction), and it also helps to initiate and ensure full extension. The extension assist can be built into the knee or in some cases can be an optional feature. Not all knee units can have an extension assist. They are more common on knees designed for individuals with less voluntary control.

FIGURE 13-27 Polycentric knee.

Weight-Activated Stance-Control Knees

Weight-activated stance-control knees have a braking mechanism that prevents further flexion when weight is applied (Figure 13-28). In this figure the extension assist is external to the knee along the anterior. The braking mechanism is located internally and can be adjusted to be more or less sensitive to the weight required to engage the stance control. These knees have occasionally been referred to as “safety knees,” but because the possibility of knee flexion remains, this is an inappropriate term and should not be used. The braking mechanism of these knees function when weight is applied and the knee is flexed less than approximately 20 degrees. The sensitivity of this adjustment can be set for each individual user, allowing for momentary stability and stumble recovery for those with poor balance. The knee should not be aligned or used in a manner where every step relies on the breaking mechanism to prevent knee flexion, because the wear of the mechanism can cause premature failure and falls.

FIGURE 13-28 Stance-control single-axis knee with extension assist (the wire and springs in front of the knee).

Manual Locking Knees

Manual locking knees (Figure 13-29) are the most stable of the knee designs. These knees have a switch release for sitting and snap into place at full extension. They cannot be flexed again until the switch release is engaged. Manual locking knees compromise gait mechanics because the patient must walk with a straight leg. The leg should be shorter than the contralateral side to allow clearance. This design is only used for those where maximal stability is the main goal: those with significant weakness or instability, some bilateral amputees, and/or those using the prosthesis primarily for transfers.

FIGURE 13-29 Example of a manual locking knee.

Microprocessor-Controlled Knees

New microprocessor-controlled knee systems are also available. One example, the C-leg by Otto Bock (Figure 13-30, A), measures the knee joint angle and the forces in the pylon to determine the phase of the gait cycle and the speed at which the user is ambulating. The microprocessor then adjusts valves to control fluid flow within the hydraulic knee unit. Another computerized knee, the Rheo Knee by Ossur (Figure 13-30, B), is filled with a magnetorheologic fluid that changes flow characteristics when a magnetic field is applied. This knee also uses measured force and position data to determine how to adjust friction for speed or stumbling. Instead of controlling valves, however, the microprocessor controls resistance by adjusting the magnetic field around the fluid. The advantage of computerized knee systems is that they allow knee friction to be varied based on knee angle, forces, speed, and type of activity. When the microprocessor determines that the user is walking faster, it increases friction in swing phase, eliminating excessive knee flexion. If the microprocessor determines that the user has stumbled or is not in a phase of the gait cycle where the knee should bend, it can lock the knee (or increase friction substantially) to allow for recovery and improved stability. These knees can also be set to allow an appropriate friction for easier descent of stairs. As microprocessor computing power evolves, computer-controlled components will continue to allow for a more dynamic responsiveness and make inadvertent flexion of the knee less likely. The primary disadvantages of these microprocessor-controlled knees is that they are very expensive, require robust maintenance, and are not well suited for wet or grimy environments.

FIGURE 13-30 Computer-controlled prosthetic knee joints: (A) the C-leg and (B) the Rheo.

(A, Courtesy Otto Bock HealthCare. All rights reserved. B, Courtesy Ossur International.)

Considerations for Other Component Selection

Prosthetic feet and ankle assemblies are the same as for transtibial amputation. When additional components such as rotators and shock absorbers are used, they should be placed distal to the knee but as proximal as possible to reduce the apparent weight. An additional component available for transfemoral prostheses is a positional rotator, which is added distal to the socket and proximal to the knee. By depressing a button, the lower leg can be rotated, permitting the legs to be crossed and increasing the ease of donning pants and entering and exiting tight spaces such as vehicles. Because it adds length to the proximal segment, however, it cannot be used for the longest residual limbs.

Transfemoral Prosthesis Alignment

Alignment of the transfemoral prosthesis depends on component selection and user strength and ROM. The foot and knee are usually aligned outset with respect to the ischium in the coronal plane. The foot should be further outset (up to approximately the middle of the socket) for those with shorter residual limbs or mild abductor weakness. For those with moderate abductor weakness or for those with a very short limb, however, a Silesian belt or hip joint and pelvic band must be used. In the sagittal plane the socket should be preflexed 5 degrees from vertical beyond the amputee’s hip flexion range. For example, if the amputee has a 5 degrees flexion contracture, the prosthesis should be aligned with 10 degrees of flexion in the socket. This accommodates the loss of knee flexion in late stance at opposite heel contact and allows the user to take a normal sound side step. If this alignment is not made, the prosthetic user might take a short step and, if a flexion contracture is not accommodated, can also result in an unstable knee. For knee alignment with the quadrilateral socket fitting, the trochanter-knee-ankle line is used (Figure 13-31). For this alignment a single-axis knee should fall 6 mm posterior to a line connecting the greater trochanter and ankle. For ischial containment sockets a weight line is typically used. The starting point for alignment is a plumb line from the bisection of the socket at ischial level. Each knee design has a manufacturer-suggested alignment, but generally the knee axis should be posterior to this line. Moving the knee axis further posterior increases the stability. A knee positioned closer to the weight line requires more voluntary control, but allows easier knee flexion in late stance phase and a more normal appearing gait. During dynamic alignment the goal is to have a knee that is stable but easy to control. The foot should progress from heel to toe smoothly, and in the coronal plane, the pelvis should be maintained close to level, and the foot should be flat on the floor. A list of common gait deviations is presented in Table 13-3.

FIGURE 13-31 Trochanter-knee-ankle alignment. For the knee to be stable, the line between the trochanter mark and the ankle must pass in front of the knee axis.

Table 13-3 Common Gait Deviations for the Patient With a Transtibial Amputation

Gait Deviation	Prosthetic Causes	Amputee Causes
Lateral trunk bending: excessive bending occurs laterally away from midline toward prosthetic side	Prosthesis too short Improperly shaped lateral wall fails to support femur Lack of ischial support (high medial wall cause amputee to hold prosthesis away to avoid ramus pressure) Prosthesis aligned in abduction, causing a wide-based gait	Inadequate balance Abduction contracture Residual limb painful Short limb can fail to provide sufficient lever arm for the pelvis. Poor gait habit
Abducted gait: wide-based gait with prosthesis held away from body at all time (stance and swing)	Prosthesis too long Too much abduction built into prosthesis Lack of ischial support (high medial wall can cause amputee to hold prosthesis away to avoid ramus pressure) Improperly shaped lateral wall fails to support femur. Pelvic band can be positioned too far away from the body.	Abduction contracture Poor gait habit
Circumducted gait: the swinging of the prosthesis laterally in a wide arc, returning to vertical for stance phase	Prosthesis too long Too much alignment stability or friction in the knee, making it difficult to bend in swing phase Extension aid too strong	Abduction contracture Lack of confidence for flexing the knee because of muscle weakness or fear of stubbing the toe Poor gait habit
Vaulting	Prosthesis too long Inadequate suspension Excessive knee stability caused by alignment, excessive knee friction, or an excessive extension assist	Poor gait habit Fear of stubbing the toe Residual limb pain
Rotation of the prosthetic foot at heel strike	Heel too firm Too much toe out Loose socket fit Posterior socket tightness	User can extend limb too vigorously at heel strike. Poor muscle control of the limb
Uneven arm swing, with arm on prosthetic side held close to the body	Improperly fitting socket Poor suspension	Poor balance Fear and insecurity accompanied by uneven timing Poor gait habit
Uneven timing, characterized by a short stance phase on the prosthetic side	Improperly fitting socket Weak extension aid or insufficient friction can cause excessive heel rise and result in a longer amount of time spent on the sound side. Knee instability	Weak residual limb User cannot have developed good balance. Fear and insecurity Pain
Uneven heel rise	Knee joint can have insufficient friction. Inadequate extension aid	User can be using more power than necessary to force the knee into flexion.
Terminal swing impact, characterized by rapid forward movement of the shin allowing the knee to reach maximum extension with too much force before heel strike	Insufficient knee friction Knee extension aid can be too strong.	User can deliberately and forcibly extend residual limb to ensure full extension of knee.
Instability of the prosthetic knee, which creates a danger of falling	Knee joint can be aligned anterior to weight line or trochanter-knee-ankle line. Insufficient initial flexion can have been built into the socket. Heel can be too firm, causing the knee to buckle at heel strike. Foot keel can be too soft, allowing knee flexion to occur late in stance.	User can have weak hip extensors. Severe flexion contracture can cause instability.
Medial or lateral whip: these are best observed as the user walks away. A medial whip is present when the heel travels medially on initial flexion at the beginning of swing phase, and a lateral whip exists when the heel moves laterally.	Lateral whips occur from excessive internal rotation of the knee with respect to the socket. Medial whips can result from excessive external rotation of the knee. Socket can fit too tightly, reflecting limb rotation. Excessive valgus in the prosthesis can contribute. Socket can have been donned improperly.	Faulty gait habits can result in whips.
Foot slap: a rapid descent of the anterior of the foot at heel strike	Plantar flexion resistance is too soft (heel too soft).	User can be driving the prosthesis into the ground at heel strike to ensure knee stability.
Drop-off at the end of stance: downward movement of the trunk as the body moves forward over the prosthesis	Inadequate limitation of dorsiflexion of the foot Keel of the foot can be too short or too soft. Socket can have been placed too far anterior with respect to the foot.	None
Long prosthetic step (or short sound side step): the user takes a longer step with the prosthesis than the sound leg.	Insufficient flexion included in the socket	A flexion contracture that cannot be accommodated prosthetically
Excessive trunk extension: during stance phase the user creates excessive, active lumbar lordosis.	Improperly shaped posterior wall causing forward rotation of the pelvis to avoid full weight-bearing on the ischium Insufficient initial flexion built into the socket	Hip flexor tightness Weak hip extensors, substituted for by lumbar erector spinae Weak abdominal muscles Poor gait habit Poor balance
External rotation of the foot at heel off: viewed from posterior, the heel is seen to rotate internally before swing phase.	Insufficient flexion included in the socket	Hip flexor tightness

Courtesy Northwestern University Prosthetic-Orthotic Center, Chicago, IL.

Energy Expenditure

The effect of amputation on the energy cost of ambulation is significant. Typically the cost of ambulation is measured in oxygen consumption. Although various measurement techniques exist, usually the volume of air inhaled and the amount of carbon dioxide exhaled is used to calculate energy expenditure and is subsequently scaled as a function of body mass. The results can be reported as a function of distance or as a rate of oxygen consumption.

With respect to rate of oxygen consumption, individuals with an amputation typically walk slower to keep their rate of oxygen consumption comparable to that of healthy controls. Individuals with or without amputation tend to self-select a comfortable walking speed that provides a comparable rate of oxygen consumption.¹⁰¹ In addition, the relative energy cost, defined as the rate of consumption divided by the maximum aerobic capacity, is comparable for amputations with a traumatic etiology and those with a vascular etiology. the only exception being that transfemoral amputations with a vascular etiology have a higher relative energy cost.¹⁰¹ Some studies have found that younger patients with amputations related to trauma can walk with a higher oxygen consumption rate but at a faster pace than those with older patients with amputation or patients with amputation secondary to vascular problems, but at a slower pace than healthy controls.¹⁰⁰

While the rate of oxygen consumption tends to be similar across individuals, those with amputation incur a larger oxygen cost per distance than a nonamputee walking at the same speed. Individuals with vascular amputations have higher oxygen consumption per distance than those with traumatic amputations.¹⁰¹ Unilateral traumatic transtibial amputees use approximately 25% more energy to walk the same distance as nonamputees. This increases to 63% for traumatic transfemoral amputees. Vascular transtibial and transfemoral amputees use up to 40% and 120% more energy, respectively.^100,102

In addition to oxygen consumption and rate, maximal aerobic capacity influences an individual’s ability to perform with a prosthesis. This capacity decreases with both age and vascular involvement.¹⁰¹ As such, older patients with higher level amputations have less aerobic capacity and are closer to their anaerobic threshold when ambulating.

Recreational activities

People with lower limb loss can enjoy most recreational activities with conventional prostheses, but some components are better suited than others for different activities. High-level activity functions require very secure suspension for safe participation. Suction-type suspension systems are generally preferred. Sports involving running and jumping are best served by high-profile dynamic response feet. For transfemoral amputees, running requires a high-performance variable cadence (hydraulic) knee. Competitive running is a sport where a dedicated prosthetic foot is seen. These feet are custom-made to provide the correct energy return for the individual’s weight and running style. Most designs lack a heel because during short runs, force is only applied to the toes (Figure 13-34). This makes stopping and standing difficult, especially for bilateral amputees. Insurance companies rarely fund these dedicated devices, and cost can make personal purchase prohibitive. Competitive athletes that require dedicated devices like a running foot are often sponsored by companies that supply the componentry.

FIGURE 13-34 Sprinting foot (Cheetah foot).

(Courtesy Ossur International.)

Golf is a very popular sport for many amputees, including dysvascular amputees. The National Amputee Golf Association (see Box 13-1) exists to assist people with this sport and sponsors many events. While golfing can be done with most prostheses, the addition of a tibial rotation unit can be helpful because it allows the necessary tibial rotation to occur during the swing of the golf club.

Racket sports are demanding, and the use of dynamic response feet is recommended. Amputees must decide which type of dynamic response foot works better for them. They can use the multiaxial dynamic response foot that allows medial-lateral motion for aggressive lateral motions, or the high-profile dynamic response foot that is better for running and jumping.

Although most amputees enjoy swimming without the use of a prosthesis, a water leg is useful for the beach or being around water. This can be a prosthesis with water-resistant components or even just a pull-up covering that keeps the prosthesis reasonably dry. Prostheses for use with swimming are also made and include ankles that allow the foot to be plantar flexed for a kicking position. The Leisure Activity Ankle (Figure 13-35) has a design that can be incorporated into modular prostheses. The design permits the ankle to be locked in a neutral or plantar-flexed posture with the turn of a lever. The neutral position is used for limited ambulation, while the plantar-flexed position is designed to be used in water activities such as scuba diving. Because most prosthetic devices are not waterproof, dedicated sockets and attachments are required. Often hollow exoskeletal designs are used, which eliminate most of the metal components. It is also necessary to design a construction that can fill with water and drain easily to limit the effects of buoyancy of the limb. Some swimmers attach a fin directly to the end of their residual limb, eliminating the need for a dedicated prosthesis. All of these components are typically used by recreational swimmers and scuba divers, because competitive swimmers are not allowed to use assistive devices.

FIGURE 13-35 The Leisure Activity Ankle. This unit allows for locking in plantar flexion for swimming. (Courtesy Ortho Enterprises, Abington, Oxfordshire, UK.)

Individuals with a prosthesis sometimes struggle with bike riding because the prosthetic foot is difficult to keep on the pedal, especially for transfemoral amputees. Recreational bikers can either use cages to help keep the foot from sliding off the pedal, or biking shoes with cleats that lock onto the pedal. This creates a safety concern, however, because the lock can be difficult to disengage. Sometimes an old prosthesis can be dedicated to bike riding and aligned in a more advantageous position. Competitive cyclists are usually fitted with extremely rigid feet (to better transfer forces to the pedals) and shoe cleats that are built directly into the bottom of the foot.

Recreational activities should always be kept in mind when determining the functional level of the amputee and the recommended components. Although not all things can be done for all people because of limb length, weight, financial considerations, etc., an effort should be made to recommend a device that allows the amputee to return to as many activities as possible. Additional therapy should also be considered to assist the amputee with sport and leisure activities as needed.

General

Differences between fitting adults and fitting children with prostheses truly exist. Although it is important to involve family members of adults who have had amputations, it is imperative that the family, more specifically the parents, be involved in the decision making and fitting of their child’s prosthesis. These decisions will surround not only the prosthetic intervention, but in many limb anomalies will involve potential surgical intervention. The various limb anomalies and configurations without or after surgery create challenges to the prosthetist. Additionally, the unpredictable growth of the child must be factored into the decision making of the design. In most instances, in pediatric fittings, some type of growth compensation is made (e.g., growth liners, distal end pads and modular fittings).

The etiology behind pediatric amputations is much different than for in the adult populuation. Congenital anomalies are responsible for most pediatric amputations, and most prosthetic fittings are made for children with these anomalies. Acquired amputation from trauma and tumors are less frequent in the pediatric population.

Classifications of Limb Deficiencies

There have been many ways of describing limb deficiencies in the past, but currently there are two main headings for these classifications under the International Organization for Standardization and the International Society for Prosthetics and Orthotics classification of congenital limb deficiency: transverse and longitudinal.⁴⁷ Transverse deficiencies are defined as normal development until the point of the deficiency, beyond which the normal anatomy does not exist. These transverse deficiencies present as guillotine-type amputations, in the fact that no segments distal to the amputation site exist. Most of the causes for these are unknown and are thought to have resulted from vascular disruptions in utero. Transverse deficiency can also result from amniotic band syndrome, where the limb bud is caught in a band that constricts it and prevents normal development. Other regions of the body can experience this banding as well.

Longitudinal deficiencies are defined as the absence of skeletal anatomy within the long axis of a limb and in some cases include normal anatomy distal to the affected bone or bones. As described, the longitudinal deficiencies are a random absence of bony structures. These types of deficiencies are usually of unknown origin and are commonly treated with some type of surgical correction. Longitudinal deficiencies are more common than transverse lower limb amputations and are described below in order of their frequency of occurrence.

Common Lower Limb Deficiencies

Longitudinal Deficiency of the Fibula

Longitudinal deficiency of the fibula is the most common long bone absence³⁹ (Figure 13-36). It is often associated with other anomalies present including a deformed foot (usually with absent lateral ray[s]), valgus angulation at the knee, anterior (kyphoscoliotic) bowing of the tibia, a subcutaneous dimple over the apex of the tibia, ipsilateral femoral shortening, and limited hip internal rotation. The two most common treatments for this anomaly are some form of ankle disarticulation amputation, or lengthening with an external fixator and often subsequent ankle arthrodesis (fusion). There are conflicting opinions regarding the outcome of these two interventions. If the family elects to proceed with the ankle disarticulation, the child can be fitted with a prosthesis shortly thereafter. The more traditional Syme’s amputation for children with fibular deficiencies has proven to be very beneficial. Migration of the heel pad posterior-proximally has sometimes led surgeons to perform Boyd procedures to ensure the centralization of the heel pad. Once fitted with a prosthesis, the child is able to walk with a relatively normal gait. Although there are space limitations for prosthetic feet while the child is very young, the natural occurrence of ipsilateral femoral shortening or the use of an epiphysiodesis can lead to adequate room for most prosthetic foot designs as the child matures. Other factors that can compromise the prosthetic fittings are the lack of ability to end-bear as the child gets larger, and the increased genu valgum resulting from the absence of a lateral stabilizer. This valgus attitude, combined with a long residual limb and an appropriate prosthetic alignment, creates a large bump on the lateral aspect of the prosthesis, compromising cosmesis.

FIGURE 13-36 Amputation level commonly seen for a fibular deficiency.

Longitudinal Deficiency of the Femur (Proximal Femoral Focal Deficiency)

Proximal femoral focal deficiency (PFFD), the second most common congenital deficiency of the lower limb, is a prosthetic, surgical, and rehabilitative challenge. PFFD is a congenital deficiency that can present in a large variety of ways, primarily with a clinical presentation of hip flexion, abduction, and external rotation. Several methods of classifications for femoral malformation or PFFD have been described. Aitken’s method is the most broadly accepted (Figure 13-37).² Aitken classified the PFFD levels according to acetabular and femoral involvement. This classification of A through D is designed with class A being the least involved and class D being the most severely involved. In addition to the femoral and acetabular involvement, the aforementioned longitudinal deficiency of the fibula is present in a large percentage of individuals with PFFD. Because of this severe instability and proximal position of the foot, surgical intervention is often recommended to reshape the acetabulum, disarticulate the foot, fuse the knee, and/or rotate the foot posteriorly. These interventions vary based on clinical setting, geographic location, cultural issues related to body image, and parental wishes.

FIGURE 13-37 The classification levels for proximal femoral focal deficiency.

If no surgical intervention is performed, the prosthesis will be fitted around the involved hip and encompass the affected foot. This “foot-in-foot” prosthesis will require an ankle-foot type of socket and have a prosthetic foot distal to the socket. Many of these first fittings involve a shoe lift because of the lack of space distally, and will later progress into an extension prosthesis with the prosthetic foot distal to the socket. In early fittings, articulated joints can be added to provide a knee joint. This can be accomplished by using outside hinges, as an endoskeletal prosthetic knee will create a femoral length discrepancy. If the femoral length is short enough, there might eventually be space for an endoskeletal knee beneath the foot plate.

Syme’s amputation is commonly performed on the PFFD limb to ablate the foot and provide a bulbous residual end for end-bearing and suspension. This is performed at approximately 1 year of age to prevent the child’s dependence on his or her foot and allow early prosthetic fitting. The same prosthetic designs are used as were used when fitting a child with Syme’s amputation when no surgical intervention was performed. Fitting without and with knee units progresses as the child grows and length permits. Subsequent surgeries are often performed in addition to the Syme’s amputation, including hip reconstruction, knee fusion to create a singular lever arm inside the prosthetic socket, and possibly epiphysiodeses to equalize femoral lengths at full maturity.

The third most common intervention for PFFD is to perform a rotationplasty of the foot 180 degrees (Figure 13-38). This procedure, popularized by Van Nes,⁹⁷ allows children to use their ankle as a knee unit. To ensure success of a rotationplasty, the hip joint and ankle joint integrity must not be compromised. The ankle dorsiflexors will be used as knee flexors, while the ankle plantar flexors will be used as knee extensors. It is critically important for these individuals to maintain ankle strength and ROM for this procedure to be a success. Once again, individuals can be successfully fitted with a prosthesis that has outside hinges. They might also need an endoskeletal knee below the foot complex to provide increased knee flexion to enter tight spaces such as cars.

FIGURE 13-38 Example of the Van Nes rotationplasty technique that is performed on individuals with proximal femoral focal deficiency. This technique uses the ankle to function as the knee.

Acquired Amputations

Training and Treatment Goals

Training for children is, in most cases, playing outside and participating in daily activities. The initial training for children requiring prostheses below the knee is minimal. They will begin with a very abducted gait pattern at first and then progress to a more normal gait as they mature. Children with amputations above the knee, at various PFFD levels or hip disarticulation, require more formalized gait training. All of these children are encouraged to use the prostheses for pull-to-stand activities, which occur anywhere from 8 to 18 months. The children’s progress will be based on their limb lengths, strength, and ROM in their affected limb.

The goal for children with ankle disarticulation and transtibial fittings is to ambulate with a normal gait. Many of these children learn to walk very well and go unnoticed by the general population by the time they reach adolescence. The children with PFFD limbs and prostheses often have to endure poor gait mechanics until their bone growth reaches an acceptable length for surgical intervention. When the timing is appropriate, epiphysiodeses and fusions can be performed to create singular limb segments inside the prosthesis. This affords the child better leverage and control of the prosthesis. Children with transfemoral and hip disarticulation levels are encouraged to achieve as normal a gait as possible. Many of the children with transfemoral amputations from a congenital deficiency, trauma, or tumor can achieve a fairly normal gait pattern. Children with hip disarticulations are not as successful, relying on assistive devices such as canes, crutches, and wheelchairs.

Psychosocial Issues