Limb Salvage

Limb-sparing procedures have become possible because of advances in imaging, reconstructive surgery, microsurgery, and cancer treatment. Improved methods of resuscitation and time-sensitive transport have decreased ischemia time. Optimal skin and soft tissue closure with pedicle flaps and microvascular free flaps allows the surgeon to meet the initial goal of critical limb length and the later goal of skin durability for long-term socket use. Whether it is tumor, trauma, or congenital malformation, the decision to attempt salvage with reconstruction or amputation remains difficult. The best decision is one formed by the consensus of the experienced trauma, oncology, and rehabilitation specialists. Upper and lower limb characteristics are different and must be kept in mind when considering limb salvage or amputation. The upper limb is non–weight-bearing. It remains functional with significant sensory impairment, which is different from the lower limb. An upper limb that preserves only assistive function is still often more functional than one with a prosthetic replacement.

Injury scores were developed for severe trauma-related limb injuries, to help determine which vascular injury patients would benefit from primary amputation versus an attempt at limb salvage. Their validity has been questioned. The mangled extremity syndrome is defined as significant injury to at least three of the four tissue groups (skin/soft tissue, nerve, vessel and bone).²⁴ The mangled extremity scoring systems have been shown to be poor predictors of amputation or salvage with regard to functional outcome.^18,39,48 Ly et al.³⁷ concluded that the available injury severity scores are not predictive of functional recovery of patients who undergo reconstruction surgery. Bosse et al.,⁶ using the Sickness Impact Profile, presented evidence that the functional outcomes from limb salvage and reconstruction after severe trauma were the same at 2 years for those who underwent amputation. Finally, in this salvage-versus-amputation equation, no significant long-term psychological outcome advantage has been reported for limb salvage surgery compared with amputation.⁴⁵ Consequently, objective measures have not functionally supported the natural desires of the patient and the tendency of the trauma team to make all attempts at salvaging the limb.

In severe limb trauma that includes defects from burns and tumor resection, the appropriate soft tissue restoration is an essential component of the overall treatment. This is common both to limb salvage and amputation, especially when critical lengths are being preserved. It requires a vascularized flap that can protect the neurovascular and musculotendonous structures (Box 12-3). The pedicle flap is one where a local muscle inclusive of the overlying skin is moved over with it own blood supply to fill a large defect. A microvascular free flap is one in which the donor tissue is taken from a different site and the microvasculature of the donor tissue is anastomosed to the available vessels in the site of the defect. The feasibility of limb salvage is determined partly by the ability to reconstruct the soft tissue defect. In the upper limb, few pedicle flap options are available to repair significant defects. The recent advancement of microvascular reconstruction techniques and free flaps from sites like the rectus abdominus have promoted the option of limb salvage and preserved limb length.

Once it has been decided that amputation is more appropriate than limb salvage, the team must plan the most distal level possible, based on principles of wound healing and functional prosthetic fitting. Skin flaps now afford closures that were not historically possible. The skin closure must be without tension and should be done so that nonadherent, strategically placed, mobile scars are produced. It is the artful surgeon who crafts the distal residual limb with the appropriate muscle padding, rather than producing a bony atrophic limb or one with excessive preservation of soft, redundant tissue that makes it difficult to fit the prosthetic socket. Stable distal muscle padding can be accomplished through myodesis, in which the deep layers are sutured directly to the periosteum. It can also be accomplished by myoplasty, in which the superficial antagonistic muscles are sutured together and to the deeper muscle layers. These techniques typically produce muscle padding with sufficient balance and tension.

Although these are the conventional surgical techniques to address the residual muscle tissue, myoplasty presents a challenge downstream when attempting to localize an optimal myoelectrode placement, because the muscles that are sutured together tend to contract simultaneously. The ideal distal muscle stabilization occurs with tenodesis. If the muscle is preserved with its tendon, the tendon can be sutured to the periosteum.

Neuroma formation is the normal and expected consequence of nerve division. Nerves should be gently withdrawn from the wound, sharply divided, and allowed to retract under cover of soft tissue. The goal is to locate the ends of incised nerves away from areas of external contact such as the socket interface, so the cicatrix will remain asymptomatic.

For those with malignant tumors, 70% to 85% are treated by limb salvage without compromising the oncologic result.⁵⁰ The goal of this type of surgery is to preserve function, prevent tumor recurrence, and enable the rapid administration of chemotherapy or radiation therapy. In the tumors of the hand, ray resection is done. In the wrist, multiple options are available such as an endoprosthesis implant or an allograft or vascularized bone transplant (e.g., fibula). For the elbow an endoprosthetic reconstruction is the best possible option. The humerus is similar to the wrist in that an endoprosthesis, or an allograft, or a vascularized bone transplant can be used. For tumors of the scapula or proximal humerus, a forequarter amputation or flail arm is prevented by reconstruction with a combination of an endoprosthesis and allograft. These types of reconstruction would not be possible without major improvements in radiography, chemotherapy, radiotherapy, and staging.⁵⁰

The complication rate is much higher after limb salvage than after amputation in the oncology population. These complications can be divided into early and late. The earliest complications include infection, wound necrosis, and neurapraxia. The late complications include aseptic loosening, prosthetic fracture and dislocation, and graft nonunion.⁴ Consequently additional surgery is often necessary. Advancements in resection techniques, radiation, and chemotherapy have improved both functional limb survival and life expectancy. Serletti et al.,⁴⁵ using the Enneking Outcome Measurement Scale, reported the functional outcome as “excellent” or “good” in greater than 70% of the patients who had reconstruction after resection of limb sarcomas. The Enneking Outcome Measurement Scale is an outcome tool that assesses seven characteristics of upper limb use: ROM, stability, deformity, pain level, strength, functional activity, and emotional acceptance. Limb salvage has cosmetic advantages, but whether the quality of life of these patients is superior to that of those who undergo amputation is unclear.

Reimplantation of traumatically amputated limbs is now possible, especially in children, because of the potential for successful neurologic recovery.³⁰ Effective treatment of the patient and the ischemic, detached body part requires appropriate early cooling and prompt reimplantation within the initial 12-hour window. Predictors of successful reimplantation include adequate preservation, contraction of the muscle in the amputated limb after stimulation, the level of injury, and no tobacco use. The best predictor of success is the serum potassium level in the amputated segment. If the serum potassium level is higher than 6.5 mmol/L, reimplantation should be avoided.⁵¹

Reimplantation is indicated in levels from the distal forearm to the fingers. The more proximal to the wrist, the greater the amount of ischemic muscle mass and the more complex the metabolic and surgical demands. Approximately 85% of replanted parts remain viable. Sensory recovery with two-point discrimination occurs in 50% of adults.³⁵ The functional results are more promising in children, but the viability rate is lower because of the technically demanding microvascular surgery. Major limb reimplantation entails significant metabolic disturbance and risk. It requires scrupulous medical management. Reimplantation is contraindicated in those with crushed and mangled limbs and those with atherosclerosis. Because nerves transected in the proximal arm must regenerate over a considerable length, only limited motor return is typically seen in the forearm and hand. Useful function of the wrist and hand is unusual and limited at best. Function can often be improved by converting these patients to transradial prosthetic wearers. Unfortunately it means performing a transradial amputation after successful transhumeral reimplantation. This is known as segmental reimplantation, in which portions of compromised limbs are salvaged that would otherwise have been discarded.

During the past 10 years, collaboration between hand surgeons and immunologists has led to successes in hand transplantation. Recent advances learned from clinical organ transplant immunosuppression known as composite tissue allograft (CTA) have permitted hand transplantation to progress beyond the first one done in the United States in 1997. CTA is the term used to describe transplantation of multiple tissues (skin, muscle, bone, cartilage, nerve, tendon, blood vessels) as a functional unit. In addition to the usual problems of identifying an organ donor, selecting a donor for a hand transplant must involve additional and careful emphasis on matching skin color, skin tone, gender, ethnicity and race, and the size of the hand. After a hand has been lost, much time can pass before a donor is found. Representation of the hand in the individual’s brain is lost because of cortical reorganization during this time. Researchers have learned through functional magnetic resonance imaging that after transplantation, amputation-induced cortical reorganization is reversed to reestablish the hand “image.”⁵ During transplantation the surgeon repairs the tissues in the following order: bone fixation, tendon repair, artery repair, nerve repair, and vein repair. The surgery can last from 12 to 16 hours, almost double that of heart and liver transplants. Immunosuppression after CTA is composed of two elements: treating the patient with monoclonal antibodies on the day of transplant, followed by a donor bone marrow infusion several days later. Typical postoperative complications include vessel thrombosis, infections, and rejection. Rejection can appear as a spotty, patchy, or blotchy rash. It could appear anywhere on the transplant and is usually painless. As rejection appears first in the skin, the clinical team and patients are encouraged to carefully watch for the signs. Unlike internal organ transplants, where rejection is difficult to detect early, it is relatively easy to monitor in the hand, allowing for early biopsy and treatment. Recovery is relatively slow, requiring an extensive program of occupational therapy. As of this printing the longest reported patient follow-up has been 43 months. This patient, a paramedic instructor, is now reportedly able to start intravenous lines and perform endotracheal intubation.

Amputation

Hand function is vital in our competitive and industrialized society. There are many techniques for reconstruction of the hand. It is much better to have a painless hand with some grasp function and sensation preserved than to have a prosthesis. The most important part of the hand is the opposable thumb. The goal is to preserve as much of the sensate thumb as possible. Phalangization (Figure 12-3) of the metacarpals is a reconstructive technique in which the web space is deepened between the digits to provide more mobile digits. This works well for the thumb especially if the first metacarpal is adjusted to create opposition to the thumb. Pollicization (Figure 12-4) is the process of moving a finger with its nerve and blood supply to the site of the amputated thumb. This allows fine and gross grasp through opposition. A prosthesis for a hand amputation is inferior to the functional outcomes achieved with reconstructed hands.⁹ In reconstructing the hand, three issues should be considered: (1) preservation of sensitivity to the grasping surface; (2) the consequences of scarring; and (3) cosmetic acceptability.

FIGURE 12-3 Phalangization of the metacarpals is a reconstructive technique in which the web space is deepened between the digits, providing more mobile digits. (A) Amputated thumb. (B) Web space deepened. (C) Final web space deepened to provide more mobility.

FIGURE 12-4 Pollicization is the process of moving a finger with its nerve and blood supply to the site of the amputated thumb. (A) Amputated thumb including metacarpal. (B) Index finger to be moved. (C) Final index finger in the thumb’s place.

Wrist disarticulation involves removal of the radius and ulna to the styloid processes, because there is no benefit to retaining the carpal bones. It retains the distal radial-ulnar joint, preserving more forearm rotation. The prosthetic attachment to the bulbous end is enhanced if the distal radial flare is retained for suspension. Burkhalter et al.¹⁰ indicate that it is important that the radial and ulnar styloids be resected slightly to minimize the discomfort the amputee will experience in active supination and pronation within the prosthetic socket. Tenodesis of the major forearm muscles stabilizes these groups and improves functional outcome, including myoelectric performance. Pronation and supination, as well as full elbow motion, are preserved with wrist disarticulation. Some will argue that (1) the wrist disarticulation creates a complicated prosthetic situation with difficult socket fabrication; (2) conventional wrist units are too long and cannot be used; and (3) it is harder to fit with a myoelectric prosthesis because there is no room to conceal the electronics and power supply.

Transradial amputation involves the myodesis of the forearm muscles and equal volar and dorsal skin flaps for closure. It is extremely functional, with forearm rotation and strength that is proportional to the length retained. The shorter the transradial amputation, the more the elbow and humerus are needed for suspension. Preserving the elbow joint is paramount because of the functional outcome possible with prosthetic enhancement. If the amputation must be very proximal, then an ulna 1.5 to 2 inches long is still adequate to preserve the elbow joint. To fit this very short residual limb with a prosthesis, it might be helpful to detach the biceps and reattach it to the ulna.³⁶

A couple of special situations arise with transradial amputations. One is when the forearm bone is considerably longer than the other and the longer bone can be covered with an adequate soft tissue envelope. Rather than decrease prosthetic function by shortening the longer bone, it may be preferable to create a one-bone forearm. Another is the Krukenberg amputation (Figure 12-5), which transforms the residual ulna and radius into digits that have significant forceful prehension and retained ability to manipulate because of preserved sensation. This is an option for patients who have at least 4 inches of residual limb, those with bilateral amputation, and those with limited prosthetic facilities. It can be fitted with conventional as well as myoelectric prostheses.

FIGURE 12-5 The Krukenberg amputation transforms the residual ulna and radius into digits that have significant forceful prehension and retained ability to manipulate because of preserved sensation.

Elbow disarticulation allows the transfer of humeral rotation to the prosthesis through the myodesis of the biceps and triceps, and it preserves a stronger lever. Although the skin flaps are approximately equal, the posterior muscle flap remains longer than the anterior muscle flap, to wrap around and cushion the end of the humerus. The ultimate position of the scar is not critical with modern total-contact sockets, but beware of the vulnerable skin over the medial epicondyle. The full humeral length precludes the use of a myoelectric elbow. Elbow disarticulation causes some prosthetic fitting challenges because the outside “elbow” hinge creates a bulky limb that is longer and asymmetric compared with the opposite limb. Disarticulation is the level of choice for juvenile amputees. The high incidence of residual limb revision because of bony overgrowth is avoided, and humeral growth is preserved. It remains controversial who is a good candidate for elbow disarticulation, but modern prosthetic fabrication techniques can overcome the socket and cosmetic difficulties.^12,14

Transhumeral amputations are performed at or proximal to the supracondylar level. The humerus is sectioned at least 3 cm from the joint to allow for fit of the prosthetic elbow mechanism. Transhumeral amputations should be performed with minimal periosteal stripping to prevent the occurrence of bony spurs. Rough edges should be removed, but beveling of the bone is unnecessary. All possible length should be preserved to transmit glenohumeral motions through the prosthesis. To help preserve humeral length, at times it should be considered whether free-flap coverage and skin graft coverage are possible alternatives to allow primary closure. The anterior and posterior fascias over the flexor and extensor muscle groups are sutured together to cover the end of the humerus. Biceps and triceps myoplasty preserves strength for prosthetic control and myoelectric signals. Myodesis is rarely needed.³⁸ Performing a more proximal amputation at the level of the surgical neck, which is the site of insertion of the pectoralis major, results in the same function as if a shoulder disarticulation had been done. This is because independent motion of the humerus is no longer possible. However, because the terminal device is controlled by active shoulder girdle motion, the humeral head should be preserved when amputation has to be done proximally.

Amputations through the glenohumeral and scapulothoracic articulations, shoulder disarticulation and forequarter amputation, respectively, are rare, and both result in loss of normal shoulder contour. Advances in vascular surgery have made reestablishment of blood flow to severely traumatized limbs effective, but reimplantation of a limb amputated through the shoulder girdle is seldom feasible. The cosmetic deformity of both of these amputations is significant. When possible, retention of the scapula is far less disfiguring and of psychological benefit to the patient. Personal concerns of having standard clothing fit supersede more complex concerns of functional restoration. In shoulder disarticulation, the rotator cuff tendons should be sutured together over the glenoid wing. The deltoid is attached to the inferior glenoid and lateral scapular border to fill the subacromial space. In forequarter amputation, the pectoralis major, latissimus dorsi, and trapezius are sutured together to form additional padding and contour over the chest wall. During forequarter amputation, osteotomy of the clavicle should be performed at the lateral margin of the sternocleidomastoid insertion to preserve contour of the neck.

Preamputation

The team approach to amputee rehabilitation begins in the preamputation phase whenever possible. The surgical team joins forces with the rehabilitation team to educate and counsel each other and the patient. It is important to include family members and other supporting individuals in the counseling. A plan of the surgery must be made that takes into account an understanding of the healing potential and the most realistic and optimal functional prosthetic restoration. This is based on the information flow between the rehabilitation team and the surgical team. Important discussions need to be held with the patient about the planned surgical outcome and postsurgical period. This should include a discussion about the different types of pain that might occur, the prevention of possible complications, and a preview of potential functional outcome. It is important to acknowledge the loss and mitigate the fear with education. A powerful intervention is to have a trained amputee volunteer, a “peer visitor,” who has successfully gone through a similar limb loss and can give support to the patient throughout the recovery process.

Acute Postamputation

This phase begins with an understanding that the decision to amputate is emotionally powerful for the patient, family, and clinical team. Amputation is not a failure but rather reconstructive surgery that creates improved functional possibilities and resumption of one’s life. The focus of the immediate postamputation period is to control pain and edema, promote wound healing, prevent contractures, initiate remobilization, and continue the supportive counseling and education (Box 12-4). This must be individualized to meet the needs of each patient. Surgical site infection needs to be seriously considered when pain, drainage, and edema are increasing despite the reasonable control measures instituted. The earlier an infection is eradicated, the earlier the time-sensitive prosthetic phase can begin. The goal for rehabilitation is for patients to acquire the skills and equipment needed to achieve prosthetic acceptance and holistic reintegration back into their own lives. It is imperative that the prosthesis be introduced at the earliest possible time after amputation.

The team has a responsibility to explain and give visualization of the postamputation treatment phases, from the early postoperative phase through rehabilitation and community reentry. Each team member (including the surgeon, physiatrist, prosthetist, and rehabilitation therapists) has specific duties related to physical, educational, and psychological support through these phases. An amputee peer visitor, preferably someone who has been formally trained, is a team member who has a distinct vantage point because of real-life experience. The Amputee Coalition of America (ACA), which is the national nonprofit limb loss advocacy group in the United States, can serve as a comprehensive source of information to persons with limb loss and their professional team. This includes locating ACA-trained peer visitors and regional support groups.

Pain control requires an early, aggressive approach that considers the multiple potential pain generators in the postsurgical period. The patient-controlled analgesia systems are often the first-line treatment by the surgical team. This is transitioned to regularly scheduled long- and short-acting oral narcotic medications. It is imperative to maintain consistent pain control. Loss of adequate pain control is painful for the patient and disrupts the timely pursuit of the rehabilitation program. The escalation of the doses of opiates needs to be avoided, if possible, by addressing other pain generators. Understanding the characteristics of postsurgical residual limb pain and phantom pain allows the clinical team to choose pain interventions wisely. Residual limb pain is located in the remaining limb and generated from the soft tissue and musculoskeletal components. Phantom limb pain is pain in the absent limb and is considered neuropathic.¹⁷ The nonsteroidal antiinflammatory drugs and nonopiate pain relievers are helpful, and these can diminish the need for higher doses of opiates. Opiates administered at safe doses are often ineffective against phantom pain. Careful attention should be given to the description, timing, and quality of the pain complaint to tease out the central neuropathic pain component inclusive of painful phantom sensations versus peripheral nerve–generated pain. Peripheral nerve pain is more intense at night, and it is characterized as burning, stabbing, and buzzing. Phantom sensations occur in greater than 70% of amputees and do not have to be treated unless painful and disruptive. The use of medications known for controlling neuropathic pain and sensations, such as some anticonvulsants and antidepressants, can also diminish the need for opiates.

The new amputee should be taught how to change the dressings and self-administer the desensitization techniques. Desensitization techniques help to eliminate the hypersensitivity to touch. They include compression, tapping, massage, and application of different textures. These techniques are performed for 20 to 30 minutes three times per day as tolerated by the skin and scar.²² The use of modalities such as transcutaneous nerve stimulation, heat, and cold are also useful adjuvants for pain and diminish opiate need. Ramachandran and Rogers-Ramachandran⁴³ have reduced phantom pain using mirrors to visually trick the brain. Because the loss of a limb is emotionally “painful,” the team should address and acknowledge this. It should be kept in mind that from the individual’s psychological standpoint, it might be more socially acceptable to express the psychological pain in terms of generalized pain complaints. It is important to address the psychological pain early, through grief counseling, peer visitation, and education.

Edema control begins once the last suture or staple is placed by the surgeon. If there is no contraindication and the surgeon has the appropriate training, an immediate postoperative rigid dressing (IPORD) can be placed in the operating room. This is a special cast placed on the residual limb by the surgeon or certified professional. The control of edema leads to earlier wound healing and improved pain control through the reduction of pain mediators in the accumulated “third-spaced fluid.” Typically additional shrinkage of the residual limb occurs after the initial IPORD placement, necessitating its early replacement. The rigid dressing can be removed in 5 to 7 days and replaced with a fresh cast. The attachment of joints and a terminal device to this rigid dressing creates an immediate postoperative prosthesis that can allow early functional use of the residual limb. The IPORD is the preferred treatment approach for the transradial amputation, and if healing progresses without issue, the second cast can be replaced with the first prosthesis.¹⁹

Traumatic upper limb loss is often accompanied by large tissue defects, burns, and wound contamination from complex infections. These make immediate postoperative techniques impossible. In these cases, once drains and negative pressure dressings are discontinued, a soft compressive dressing can be placed to control edema and initiate shaping of the residual limb.

The ideal residual limb shape is cylindrical. The dressing should be placed and replaced by a trained clinician. It should extend beyond the proximal joint to maximize suspension and improve edema control. Those not placed correctly can create problems with distal edema accumulation, skin breakdown, and abnormal shaping (such as a dumbbell shape). The healing surgical and trauma sites frequently have patches of sensory impairment and should be monitored by the team. This is especially the case in properly using the compressive dressings to prevent pressure sores. Once the skin has closed, dressings are replaced with “shrinkers,” a silicone liner, or both. Edema control is a lifelong daily management issue for most amputees.

The control of pain and residual limb edema allows for early functional remobilization of the residual limb, which in turn helps prevent contracture formation. Contractures are not fully reversible, and it is critical to begin remobilization as early as possible. Techniques for prevention of elbow flexion and shoulder adduction contractures should be reinforced with the patient and team. This can be difficult in the setting of uncontrolled pain, burns, and other complex trauma factors such as fractures, brain or spinal cord injuries, spasticity, and systemic illness.

The formation of heterotopic bone impairing joint function and ROM should be considered in these complex trauma cases and can be diagnosed with the help of laboratory testing and triple-phase bone scan. The treatment of heterotopic ossification beyond trying to maintain ROM is limited, and surgical intervention is not feasible until the heterotopic bone matures at approximately 12 to 18 months after injury.²³ Proper limb positioning and frequent monitoring of joint mobility are necessary. Any loss of ROM in a joint of the residual limb can have significant effects on functional use of the prosthesis. The loss of ROM needs to be investigated and aggressively managed to maximize range.

Preprosthetic training begins with the early postsurgical therapy visit and continues until prosthetic fitting is completed. Prosthetic fabrication and fitting ideally should be completed within 4 to 8 weeks after surgery. Early prosthetic fitting is important, because prosthetic acceptance declines if fitting is delayed beyond the third postoperative month.²⁰ Preprosthetic training is critical to maintain motivation and create an easier transition to prosthetic use. Amputation results in a loss of body symmetry. This imbalance results in shoulder elevation and scapula rotation on the affected side, as well as loss of neutral positioning of the residual limb. Close attention must be paid to the individual’s awkward or compensatory body motions when approaching an object. The rebalancing begins with observing and correcting static postures in the mirror. The mirror remains an important tool in conscious recognition and correction of the abnormal positioning. The amputee is encouraged to use muscle memory to relearn correct postural and limb positioning control.²² As remobilization progresses, emphasis is placed on recognizing the abnormal postures and positioning that occur with basic activities of daily living (ADLs).

ADLs are mastered with one hand and, when appropriate, with the use of adaptive equipment. The amputee progresses from independence with basic hygiene to the advanced homemaking tasks. Hand dominance is retrained when necessary, especially with handwriting and keyboarding. Repetitive tasks can be used for strengthening. These tasks include fine motor exercises with nuts and bolts or tweezers, as well as gross motor exercises with equipment and mirrors. Proprioceptive neuromuscular facilitation is a particularly effective approach that enables the therapist to work in diagonal planes, vary the amount of resistance, and concentrate on specific areas of weakness. Isometric exercises are effective in creating muscle bulk for stabilization of the arm in the socket of the prosthesis. The stability of the prosthesis depends on both the bulk of the stabilizing musculature and the amputee’s ability to voluntarily vary residual limb configuration. Because balance is often disrupted in a new amputee, the goals should include strengthening of the trunk, core, and lower limbs using isometric exercise and aerobic training. Depending on level of loss, the upper limb amputee should begin to practice several motions that will be needed to control the prosthesis (Box 12-5).

Orientation to the planned prosthesis, premyoelectric testing and training, and defining the amputees’ prosthetic expectations are all important tasks for the team during this period. If a myoelectric prosthesis is being considered, early site testing and training are needed. An emphasis is placed on using specific residual limb muscles efficiently. Electrode site identification is handled by the specially trained occupational therapist to identify the best placement of the electrodes. The occupational therapist needs to work closely with the physician and prosthetist in the design of the socket and optimal electrode site placement. With the use of biofeedback equipment, motor training is done to increase muscle activity at specific sites. These muscles include the elbow flexors used for closing the terminal devices (TD), and extensors used for opening and for supination. Once isolated movements are mastered, proportional control of the muscle is learned. This is necessary for controlling the speed and force of the prosthetic movements. The new amputee needs to have an orientation to prosthetic component terminology.

During this time the major components of the prosthesis should be identified, such as the figure-of-eight harness, cable, elbow unit or elbow hinge, wrist unit, terminal device, and hook or hand. It is also important during this time to explore or reexplore the expectations of the person with a new limb loss. The new amputee’s initial personal vision of what function the prosthesis will restore is often significantly unrealistic. It is helpful to reinforce the supportive roles the prosthesis will play in cosmesis, gross task and object stabilization, push, and assistive function. Supportive education by the trained peer visitor, therapists, prosthetist, and physician helps to fine tune a realistic vision of what each type of prosthesis has to offer from a functional standpoint.

Introduction to Upper Limb Prosthetic Systems

Each prosthesis is unique and customized to the individual. While two prostheses might be alike or very similar, there is no such thing as a “normal” or “standard” prosthesis (especially in the world of upper limb prosthetics). There are four categories of upper limb prosthetic systems: the passive system, the body-powered system, the externally powered system, and the hybrid system. Selecting among these can be difficult. Each patient’s functional and vocational goals, geographic location, anticipated environmental exposures, access to prosthetists for maintenance, and financial resources all need to be considered (Box 12-6).

A passive system is primarily cosmetic but also functions as a stabilizer. A passive system is fabricated if the patient does not have enough strength or movement to control a prosthesis, or wears a prosthesis only for cosmesis. Sometimes young children initially use passive upper limb prostheses for balance and for crawling. A body-powered system prosthesis uses the patient’s own residual limb or body strength and ROM to control the prosthesis. This includes powering the basic functions of terminal device opening and closing, elbow movement, and shoulder joint mobilization. An externally powered system uses an outside power source such as a battery to operate the prosthesis. A hybrid system uses the patient’s own muscle strength and joint movement, as well as an external supply for power. An example of a hybrid system is one in which there is a body-powered elbow joint but an externally powered terminal device.

The field of prosthetics has a unique vocabulary that is not part of the everyday practice of medicine (Box 12-7).

Socket and Suspension Choices

The socket has to have a snug and intimate fit around the residual limb. Although an upper limb prosthesis is not end-bearing or weight-bearing, it still needs an intimate, secure fit for proper control of the unit. A prosthetic socket can be fabricated from many different materials. The most commonly used are flexible, durable, and lightweight, such as a carbon graphite material or plastic. Upper limb sockets are typically double walled with a second lamination pulled over the first to provide cosmesis and function. They can also contain an inner flexible thermoplastic liner to allow for growth (as in the case of a child) and other fluctuations in size. It is critical that the socket is comfortable and does not irritate or injure the residual limb. During fabrication the prosthetist attends to the proper distribution of pressures around bony prominences, such as the olecranon and distal portion of residual bone. Computer-aided design (CAD system) and computer-aided manufacturing (CAM system) have reduced fabrication time, but whether such techniques are actually improvements over the skilled hands of a seasoned limb maker is debated widely in the field. There is never a single shape for a socket because of the differences in anatomy from user to user. This customization allows for socket designs to adapt to shapes that are the result of congenital or surgical issues. For example, a Kruckenberg socket is designed to internally use the unique radial and ulnar branches to pinch grip for the suspension formed from the Kruckenberg procedure.

Advances in custom fitting techniques and suspension devices have led to the use of such suspension devices as the “seal-in” liner. This is a system that incorporates a membrane lip placed circumferentially around the distal aspect of the liner to cause a plunger-type negative pressure for suspension. There is also a pin system in which the roll-on gel liner incorporates a jagged edged pin that locks into a female receptacle in the socket. Such advances in suspension have reduced restriction on elbow flexion, pronation, and supination. The application of roll-on liner suspensions for upper limb prostheses provides not only improved suspension, but more comfort as well. Conventional transradial self-suspending sockets rely on pressure above the elbow to hold the prosthesis in place, which can lead to discomfort and reduced ROM. With the roll-on suspension design, the liner provides the suspension, while the gel protects the skin from pressure and friction. This is different from conventional skin fit suction socket designs that use one-way air valves or external sleeves for suspension and require a stable limb volume to maintain suction.

The shorter the residual limb or the heavier the anticipated workload, the more it is necessary to anchor the prosthesis proximally with single or polycentric hinges, as well as shoulder harness systems. Single pivot hinges do not allow for any pronation or supination and are not recommended for those with bilateral transradial amputations. Flexible hinges allow for some pronation and supination and can replace the single pivot hinges for those with bilateral transradial amputations. Flexible hinges are also recommended for children.

A very heavy duty user needs a traditional socket with single pivot hinges. A self-suspending socket might not be enough support for the heavy duty upper limb amputee, regardless of the suspension system used. This amputee might need to wear a traditional transradial socket (“screwdriver” design in cross section to enhance supination and pronation control) with single pivot elbow hinges that stabilize rotation.

With a figure-of-eight harness for control and suspension, the harness not only operates the terminal device but also functions to keep the socket correctly positioned. There are four main components to the harness; the axilla loop, the anterior support strap, the control attachment strap, and the crosspoint (Figure 12-6). While wearing a prosthesis with this harness the amputee is able to open and control the terminal device with shoulder forward flexion.

FIGURE 12-6 Components of the figure-of-eight harness: axilla loop, anterior support strap, control attachment strap, and crosspoint.

Power

If amputees are given training on both the myoelectric and the body-powered prostheses, they will self-select their primary choice. It is not uncommon for the amputee to prefer myoelectric for one activity and body powered for another, which then drives what TD is selected.²⁴ Body-powered prostheses use forces generated by body movements transmitted through cables to operate joints and terminal devices. An example is forward flexing the shoulder to provide tension on the control cable of the prosthesis, resulting in opening the terminal device. Relaxing the shoulder forward flexion results in return of the terminal device to the static closed position. An alternative movement for opening the terminal device is biscapular abduction, which is commonly used when operating the terminal device close to the body. Body-powered prostheses are more durable, give higher sensory feedback, and are less expensive and lighter than myoelectric prostheses.

Externally powered prostheses use muscle contractions or manual switches to activate the prosthesis. Electrical activity from select residual muscles is detected by surface electrodes used to control electric motors. Prostheses powered by electric motors can provide more proximal function and greater grip strength, along with improved cosmesis. They can also be heavy and expensive. Patient-controlled batteries and motors are used to operate these prostheses. Currently available designs generally have less sensory feedback and require more maintenance than do body-powered prostheses.

Externally powered prostheses require a control system. The two types of commonly available control systems are myoelectric and switch control. A myoelectrically controlled prosthesis uses muscle contractions as a signal to activate the prosthesis. It functions by using surface electrodes to detect electrical activity from select residual limb muscles to control electric motors. Different types of myoelectric control systems exist. The two-site/two-function (dual-site) system has separate electrodes for paired prosthetic activity, such as flexion/extension or pronation/supination. This control system is more physiologic and easier to control.

When limited control sites (muscles) in a residual limb are available to control all the desired features of the prosthesis, a one-site/two-function (single-site) system can be used. This device uses a single electrode to control both functions of a paired activity such as flexion and extension. The patient uses muscle contractions of different strengths to differentiate between flexion and extension. For example, a strong contraction opens the device, and a weak contraction closes it. When multiple powered components on a single prosthesis must be controlled, sequential or multistate controllers can be used, allowing the same electrode pair to control several by a brief cocontraction of the muscle or by a switch used to cycle between control-mode functions.²⁷

Switch-controlled, externally powered prostheses use small switches to operate the electric motors. These switches typically are enclosed inside the socket or incorporated into the suspension harness of the prosthesis, such as the “nudge,” which is operated by the chin depressing the switch on the anterior chest strap. A switch can be activated by the movement of a remnant digit or part of a bony prominence against the switch or by a pull on a suspension harness. This can be a suitable option when myoelectric control is otherwise not feasible.⁴⁰ A hybrid system is one that incorporates both power options.

Level-Specific Upper Limb Amputation Prostheses

Partial hand prostheses are not commonly used. Amputation distal to the wrist is one of the most common upper limb deficiencies, but is difficult to treat successfully with a prosthesis. Poor results are due to functional limitations of prosthetic technology, discomfort at the prosthetic interface, unsatisfactory appearance, and absence of tactile sensation.¹¹ With the advancement of new technologies, the availability of new prostheses has created additional challenges for the prosthetist. Many patients with limb deficiencies distal to the wrist have declined prosthetic intervention in the past, and most limbs makers have limited experience with partial hand amputations. Partial hand amputation can involve various levels of longitudinal and transverse loss that dictate different treatment options. The person with a partial hand deficiency has four prosthetic options: (1) no prosthetic intervention, (2) a passive prosthesis, (3) a body-powered prosthesis, and (4) multiple task-specific prostheses. Individuals with passive prostheses actively use their prostheses as frequently as do individuals with functional prostheses.²¹ Even though passive prostheses do not offer active grasp and release, they can be used to stabilize objects, to push against items, and to perform other functional tasks. This type of prosthesis usually incorporates a secure socket that is stabilized about the residual limb by means of a total contact suction fit. Body-powered prostheses for partial hand deficiencies can be divided into two categories: cable-driven and wrist- or finger-driven devices. Adequate functional grasp from both system types is limited. Task-specific prostheses are available for both vocational and avocational activities. These prostheses are usually highly customized to effectively meet the functional needs of the individual.

Wrist disarticulation prostheses are suspended using the patient’s remaining anatomy, specifically the radial and ulnar styloid processes. The benefit of a wrist disarticulation is that it preserves a longer and more powerful lever arm, as well as maximal preservation of forearm pronation and supination. When fitting someone with a wrist disarticulation prosthesis, preserving symmetric limb length becomes an issue. This can be a difficult problem, and wrist units are often not used with wrist disarticulation, to conserve length and preserve symmetry. When not using the wrist unit, compensation is gained through maximizing preserved forearm supination and pronation through the socket. Wrist disarticulation is harder to fit with a myoelectric prosthesis because less space is available in which to conceal the electronics and power supply.

There are a number of traditional transradial socket options (Figure 12-7). Three traditional styles use anatomic suction suspension so that a harness is not needed. This is known as a “self-suspending” system. These three are each designed to be used with a different length of residual limbs and are named the Muenster, the Northwestern, and the TRAC (Transradial Anatomically Contoured) designs. The Muenster-type socket was introduced in the 1960s, and it introduced a fitting technique for a short transradial level amputation that provided more intimate encapsulation of the residual limb. The elbow is set in a preflexed position (usually 35 degrees), and a channel is provided at the antecubital space for the biceps tendon. This allows for unobstructed flexion, and the suspension is achieved through anterior-posterior compression around the olecranon. It is not an optimal design for bilateral amputees because it is donned with a pull sock. This led to additional innovations that included the popular Northwestern socket design. Unlike the Muenster socket, the Northwestern uses medial-lateral compression of the arm above the epicondyles and less restrictive anterior-posterior compression, and is used primarily in those with long residual limbs. The reduced anterior-posterior compression creates a less snug suspension and can lead to problems with electrode contact and increased forces on the distal residual bone.³⁴ The socket is known for its ease of donning and is a popular choice for bilateral amputees. The trim-lines of the transradial socket are dependent on the length of the residual limb; the shorter the limb, the higher the trim-line. The longer the limb, the lower the trim-line, and there is more allowance for pronation-supination. The patient’s ROM will be limited by a transradial prosthesis to approximately 70% of the motion possible without a prosthesis. It might be necessary for the prosthetist to add flexion to the socket so that the end range allows for easy contact with the person’s mouth and face. The TRAC socket incorporates design elements from both the Muenster and Northwestern sockets, but with more aggressive contouring of the limb to maximize load-tolerant areas of the residual limb. Similar to the Muenster, the TRAC retains the encapsulation of the olecranon posteriorly and the generous relief of the biceps anteriorly. The TRAC uses both anterior-posterior and medial-lateral compression for enhanced stability and comfort. The TRAC socket, through detailed anatomic contouring, transfers the load from the distal end of the radius to the more load-tolerant proximal musculature.

An elbow disarticulation socket or a long transhumeral socket (Figure 12-8) includes the residual limb and excludes the acromion, the deltopectoral groove, and the lateral border of the scapula. At this level of amputation, humeral rotation is captured by the intimate fitting at and above the epicondyles, which creates a well-suspended socket. Elbow disarticulation prostheses require the use of outside locking joints located on either side of the humeral epicondyles and external to the socket. This level might add active rotary control but at the expense of additional bulk to the medial-lateral dimension of the socket. When stabilizing the elbow joint with these hinges, the result is excellent weight-bearing and force dispersion. The elbow disarticulation amputation is least desirable because of the cosmetic asymmetry produced when using the prosthesis, including problems with clothing. Few prosthetic elbows are compatible, and amputees typically dislike the appearance. In the bilateral upper limb amputee in whom the transhumeral level is an option, the elbow disarticulation is more desirable in spite of the poor cosmetic appearance of the externally placed elbow. The functional advantages of disarticulation for the bilateral upper limb amputee are in the use of the residual limb for self-care. It is also preferred over the transhumeral level in children because the epiphysis is preserved and bony overgrowth is prevented.

FIGURE 12-8 The transhumeral myoelectronic prosthesis.

With the elbow joint absent, the length of the transhumeral residual limb is a key factor in fitting and successful use of the prosthesis. Prosthetic control varies directly with the length of the humerus. Amputation through the distal third of the humerus provides functional control very similar to an elbow disarticulation. There is the loss of humeral rotary control and epicondylar suspension, which must be provided by the socket design and harnessing. At this level of amputation, control of the prosthesis is by the humerus with additional control from scapular motion. Numerous combinations of body-powered and externally powered components have proved successful. Common examples include using an electric elbow with a body-powered terminal device. Transection of the humerus at least 4 inches above the olecranon allows enough clearance to use all elbow options, including externally powered.

A medium length transhumeral socket has trim-lines up to the acromion, and includes the deltopectoral groove and the lateral border of the scapula. The extra “wings” on this socket are used to stabilize the socket and limit rotation. A short transhumeral socket has trim-lines that include the acromion and acromioclavicular joint. The trim-lines continue medial to the deltopectoral groove and medial to the lateral border of the scapula. These “extended wings” are used to help stabilize the socket and to control rotation.

Amputation at the level of the proximal third of the humerus (proximal to the deltoid insertion) is prosthetically challenging. Control is by scapular motion with assistance from the humerus. At this level there is a reduction in strength and leverage, and cable-powered prosthetic control is severely limited. Body-powered systems require up to 5 inches of total excursion of scapular motion to open the terminal device with the elbow in the fully flexed position.⁷ A transhumeral prosthesis uses two control cables, compared with that of the transradial system where only one cable is used. One of these cables flexes the elbow and operates the terminal device, while the remaining cable is used to lock and unlock the elbow. To fully operate the system, a cycle of movements must take place (Box 12-8). The body motions that typically operate these two cables are shoulder flexion and the simultaneous movement of abduction and slight extension of the shoulder joint. Shoulder flexion is used to apply tension to the cable, causing flexion of the elbow and operating the terminal device. To lock the elbow in flexion, the simultaneous movement of abduction and extension of the shoulder joint (similar to the motion of “elbowing” someone standing behind you) is used. The “figure-of-eight” body harness can be worn with a transhumeral prosthesis. Often additional straps and modifications are made to capture as much excursion as possible, especially with higher level amputations.

The cables are eliminated with myoelectric prostheses, which are also more comfortable, have a more natural appearance, and provide more precise hand functions with much less effort as compared with body-powered prostheses. Suction suspension is possible for the transhumeral level and allows minimal harnessing. This decreases loading in the contralateral axilla, which can reduce deleterious effects on the sound-side brachial plexus and joints, enhance proprioception, and improve myoelectric contact. In some myoelectric prostheses the harness may be totally eliminated. Suction suspension is usually not possible in transhumeral residual limbs with excessively bulbous distal ends, painfully adherent distal scarring, and those with fresh skin grafts. This is also true for bilateral amputees, because they are unable use a “pull sock.”

Shoulder disarticulation (amputation at the glenohumeral joint) involves unique and challenging prosthetic problems. The prosthesis incorporates the greatest number of prosthetic components. There are two commonly used designs for a shoulder disarticulation socket. The complete enclosure shoulder socket encases the shoulder to approximately 5 cm beyond to the middle of the chest. The sockets are difficult to suspend and are often unstable and uncomfortable. The weight of the prosthesis and the ability to dissipate heat (which is important because of the large area of skin covered by plastic) both need to be considered carefully by the rehabilitation team. The second design, the X-frame shoulder socket, seeks to reduce these problems and increase the wearing comfort. The X-frame socket uses very rigid materials to maintain a shape that will lock into the wedge-shaped anatomy of the upper torso to provide a secure anchor for the prosthesis (which increases its stability and function). This shape allows the socket to be much smaller and thinner, as well as cooler and lighter, while maintaining secure suspension. With the use of newer carbon composite lamination techniques, the production of thin, lightweight, but very rigid frames is possible for shoulder prostheses. The weight of the prosthesis is usually between 5 and 8 lb.

Forequarter-level amputations present even more of a challenge to fit with a functional prosthesis. Most control options have been removed with the residual limb. The “nudge” control, which is a force-sensitive resistor operated by the chin, can operate the elbow and hand. For those who choose, a lightweight passive prosthesis anchored from the contralateral limb can be fabricated (Figure 12-9). It functions by creating a cosmetically natural appearance. If no prosthetic is used, a cosmetically sculpted insert should be offered for the shoulder symmetry needed for clothing fit.

FIGURE 12-9 Shoulder disarticulation and forequarter prosthesis, body-powered elbow, and externally powered wrist and hand.

Advantages and disadvantages of myoelectric and body-powered prostheses are summarized in Box 12-9.

Bionic Hands

A newer type of electronic hand has motors and sensors in every digit (Figure 12-13). The hand has two unique features. First, a separate motor is in each finger, which means that each finger is independently driven and can articulate. Second, like the human thumb, the electronic thumb can rotate 90 degrees. Two electrodes sit on the skin and record myoelectric signals. They are used by the computer (which sits in the back of the hand) to do two things: interpret those signals and control the hand. This translates into the wearer being able to generate or use myoelectric signals in the arm to control the grabbing function of the hand. The digits do not move separately, although they appear to do so. When gripping, each finger senses contact with the item being gripped. The motors in the first, second, and third digits stall because of contact with the item being held, and the fourth and fifth digits continue to move until they reach a contact point. This creates the illusion of independent, “natural” movement between the digits. In addition, the first digit of this electronic hand has the capability of being manually positioned to create multiple grip patterns.²⁹

FIGURE 12-13 Bionic hand.

Neuroprostheses

In 2005 the United States began funding over $70 million for the advancement of prosthetic technology through the U.S. Defense Advanced Research Projects Agency. The program has spanned worldwide, with engagement of multiple universities, and engineering and science laboratories to create the most advanced prosthetic arm that simulates the human arm. A human arm is capable of more than 25 degrees of freedom (independent motions)¹⁴ as well as sensory feedback. No prosthetic arm has even remotely achieved this simulation to date. The task is to create a biologically controlled intelligent prosthesis with capacity for sensory feedback. Surgical techniques reroute unused nerves to functional muscles. The technique is called targeted muscle reinnervation (Figure 12-14) and rewires the nerves that no longer have innervation points to the pectoral muscle. Myoelectrodes create the interface with the prosthetic arm. The new prosthetic system has built-in feedback loops that allow the user some sensory feedback. Wireless electrodes have been developed that can be implanted into muscle, and brain electrodes have been developed that can sense nerve impulses. Signal processing algorithms are used. A virtual reality physical and occupation therapy training has been created. The implanted electrodes (both muscle and brain) make the prosthesis easy to wear, by eliminating weight and bulk. To date the implantable electrodes have been successful and are awaiting clinical trials from the Food and Drug Administration. This newer prosthetic technology has been sufficiently successful that manufacturing companies have already been contacted for mass production upon Food and Drug Administration approval. At the time of this writing, at least two amputees are currently using the technology, and by reports, able to play Guitar Hero (a video game that uses an electronic guitar), something no other prosthetic device can control. One of the more interesting features of this research project is the amount of technology that has been deemed “open source,” or free for anyone to access and expand upon. This allows the world to expand upon this work, potentially increasing engineering advancements at much faster paces.²⁸

FIGURE 12-14 Targeted reinnervation.