Introduction

The treatment of disabling hip pain as a result of degenerative joint disease in the young patient has many surgical options, the least palatable of which has traditionally been total hip arthroplasty (THA). The innate desire of the orthopedic surgeon to preserve the native hip joint in this population has led to the successful development of a variety of procedures, such as hip arthroscopy, surgical dislocation, and hip resurfacing. At the same time, the evolving technology and long-term success of THA have engendered increased confidence in the durability of this procedure and led to expanded indications.

Although indicating a young patient for THA is always disheartening, the good news is that patients can usually expect excellent pain relief and a high level of performance in a reproducible and predictable manner. Long-term results are tempered by wear-induced failures, which are a function of the increased number of loading cycles as a result of increased activity levels (Table 35-1) and increased life expectancies (Table 35-2). This data shows that there is a higher risk of failure in a younger patient during the subsequent 15 years after THA.

Table 35–2 15-Year Survival of Patients with Total Hip Arthroplasties

From Berry DJ, Harmsen WS, Cabanela ME, Morrey BF. Twenty-five-year survivorship of two thousand consecutive primary Charnley total hip replacements: factors affecting survivorship of acetabular and femoral components. J Bone Joint Surg Am. 2002;84-A:171–177.

Sir John Charnley articulated this problem well: “The challenge comes when patients between 45 and 50 years of age are to be considered for the operation, because then every advance in technical detail must be used if there is to be a reasonable chance of 20 or more years of trouble free activity.”

This chapter will discuss the inherent challenges involved when performing a THA in a young patient.

Informed consent

The process of obtaining informed consent from a young patient is, not unexpectedly, detailed and laborious. Multiple family members are frequently involved. Many questions will be asked, and tensions will usually be high. Quite often, the discussion is focused on the different alternative bearings and fixation options that are currently available. At the present time, the greatest challenge may be offering a balanced view of the risks and benefits of hip resurfacing. A detailed comparison of hip resurfacing with THA is beyond the scope of this chapter.

Indications

Although young age was a relative contraindication during earlier days, the current indications for THA in young patients do not differ significantly from those of older patients. From 1969 to 1971, of the 2000 consecutive patients who underwent THA at the Mayo Clinic, only 187 (9.3%) were less than 50 years old. In the United Kingdom, this figure was even less than 1% (93 out of 10,469). According to a survey by Mancuso and colleagues in 1996, only 17% of surgeons were willing to perform a THA in young patients. However, with increased success, predictability, and experience with THA, the indications have been broadening. Although pain remains the primary indication for surgery, disability and reduced function associated with a painful and stiff hip are increasingly seen as indications for THA. The diagnosis pattern of the young arthritic hip is usually secondary arthritis caused by dysplasia, avascular necrosis, impingement, epiphysiolysis/Perthes disease, slipped capital femoral epiph-ysis, inflammatory conditions, or trauma.

History and physical examination

The patient history determines the source of the patient’s symptoms, with the understanding that a wide spectrum of musculoskeletal and nonmusculoskeletal diseases can present with a chief complaint of hip pain. Detailed questioning is performed to clarify the character, location, duration, and severity of the symptoms; the resultant functional disability; and the realistic expectations of the patient. Concurrent spine pathology, ipsilateral knee disease, and a history of inflammatory arthritis should be investigated. A history of childhood or adolescent hip disease, previous hip surgery, hip trauma, risk factors for avascular necrosis, and current medical problems and medications should also be determined.

The physical examination includes the patient’s general condition and body habitus. In general, large, muscular males are more likely to have difficulty with exposure than are obese patients. The posture and gait pattern are observed. Hip abductor function is assessed with the use of the Trendelenburg test and side-lying abduction strength testing. Functional and real limb-length discrepancy should be distinguished and quantified. While assessing the range of motion, it is important to steady the pelvis to appreciate the endpoint and the forced motion of the pelvis through the hip. The impingement test is a very useful and sensitive test for any intra-articular pathology, and the McCarthy test can indicate labral pathology. It is also important is to evaluate the previous surgical interventions as well as the current neurovascular status of the limb.

Imaging and diagnostic studies

We prefer to routinely obtain five radiographs for preoperative evaluation:

It is important to obtain the anteroposterior view of the pelvis with the hips internally rotated about 10 degrees to 15 degrees to calculate the offset accurately. Specific parameters to be assessed include the lateral center-edge angle, the anterior center-edge angle, the acetabular inclination and version, the sphericity of the femoral head, the head–neck offset, the alignment and morphology of the proximal femur, and the height of the greater trochanter. Adjunctive imaging studies are sometimes needed to evaluate and define the cause of symptoms; these include computed tomography scanning and magnetic resonance imaging. Sometimes a scanogram may be needed if the limb-length discrepancy is the result of extra-articular causes distally in the extremity (e.g., healed fractures in the distal femur or tibia).

Preoperative templating

Because these patients are usually healthy, the most important issue is usually preoperative planning. Careful consideration must be given to proximal femoral and acetabular deformities to ensure the availability of modular implants. Preoperative radiographs are important when planning the type and the size of the prosthesis and when making decisions about the position and orientation of the components with the aim of restoring the biomechanics of the hip in terms of the center of rotation, the offset, and the limb length. In addition, the distance from the top of the lesser trochanter to the center of the femoral head is also measured, and every attempt is made to match this length with that of the normal side during surgery. It is crucial to consider the effect of magnification during these measurements.

The next step is to template the implants. In cases of unilateral hip disease, the goal is to match the opposite leg in terms of limb length and offset. Thus, the templating should be performed on the normal side, provided that the socket would reproduce the normal hip center. A template is made of the acetabulum for the approximate component size and position and to find out its effect on the center of rotation. The acetabular template is placed just lateral to the lateral edge of the teardrop at an angle of 40 degrees to 45 degrees. Ideally, the cup should be completely covered by bone, and it should span the distance between the teardrop and the superolateral margin of the acetabulum. In most cases, this will restore the anatomic center of rotation. Templating of the femoral canal is performed to determine the type and size of the component to be selected, its position relative to the lesser trochanter, the level of the neck osteotomy, and the selection of the head length to reproduce both leg length and femoral offset. The component size that best accomplishes this is chosen. All of the preoperative sizes for which templates have been made should be noted and correlated with the operative findings.

Anesthesia and surgical technique

We prefer hypotensive regional anesthesia in the form of a single spinal shot. Regional anesthesia has shown advantages with respect to blood loss, deep vein thrombosis, postoperative pain management, and rehabilitation. We usually supplement the anesthesia with 1000 IU of intravenous heparin during femoral preparation to minimize the risk of deep vein thrombosis.

Patient positioning and its assessment before patient preparation and draping are crucial. The relative position of the knees and feet with symmetric flexion of the hips and knees can provide an idea about the starting leg-length relationship. Usually the superior side when the patient is in the lateral position would appear to be slightly shorter because of the adduction. Moreover, correct patient positioning is extremely important if external acetabular guides are used.

The choice of approach and the implant used are subjective and often geographic. Most surgeons in North America prefer cementless fixation, whereas cemented fixation is still popular in Europe. We use a posterolateral approach with the patient in a lateral position. We prefer a tapered wedge, a proximally hydroxyapatite (HA)-coated non-cemented femoral stem, and an HA-coated non-cemented acetabular cup. The choice of bearing surface is often discussed at length with the patient; in our practice, it is most often ceramic on highly cross-linked polyethylene or metal on metal. Ceramic-on-ceramic articulations have fallen out of favor in our practice as a result of their tendency to squeak.

We prepare the acetabulum first; some surgeons who use computer navigation prefer to prepare the femur first to have an idea of the femoral anteversion and to then adjust the combined anteversion on the acetabular side. In many cases, 1 mm to 2 mm of acetabular over-reaming is necessary to compensate for the hard bone associated with younger, healthier patients. This technique is helpful for avoiding acetabular insertional rim fractures and the incomplete seating of the component.

Uncemented femoral preparation is also critical for the young patient, because it can be complicated by fracture, subsidence, or leg-length discrepancy. We use a burr to open up the posterolateral neck and to remove the overhanging trochanteric bone. This not only avoids varus position and calcar fracture, but it also prevents tip contact with the posterior femoral cortex. “Touch, feel, and pitch” change are learned skills of broaching that come with experience. Once again, we recommend overbroaching to ensure the proper fit and seating of the tapered wedge component. The use of selective distal broaching may be necessary if the diaphyseal fit is too tight.

For the assessment of limb-length discrepancy, we prefer the method described by Ranawat and colleagues. This technique involves the use of the posterior approach. After the initial dissection and release of the short external rotators, the inferior capsule is incised at the 6-o’clock position to expose the posteroinferior lip of the acetabulum. A -inch Steinmann pin is inserted into the posterior infracotyloid groove (Figure 35-1, A through C); this represents the bony groove inferior to the posteroinferior lip of the acetabulum. The pin is placed initially at an angle of approximately 60 degrees until it touches the ischium, and it is then made vertical and allowed to slide along the bone into the infracotyloid groove. The pin is kept vertical and viewed end-on from above, and then a mark is made on the greater trochanter before hip dislocation (see Figure 35-1, B). The hip is then dislocated. The center of the femoral head is marked with electrocautery, and the distance between the center and the lesser trochanter is noted and compared with the calculation made during the preoperative planning (Figure 35-2, A). The neck resection is now completed in accordance with preoperative templating.

Figure 35–1 The Ranawat and colleagues method of intraoperative assessment of limb-length discrepancy. A, A schematic representation of the placement of the Steinmann pin in the posterior infracotyloid groove in a bone model. B, During surgery and before the hip is dislocated, the pin is initially placed at an angle of approximately 60 degrees until it touches the ischium. It is then made vertical and allowed to slide along the bone into the infracotyloid groove. With the pin kept vertical and viewed end-on from above, a mark is made on the greater trochanter before the hip is dislocated. C, After the trial reduction, the Steinmann pin is reinserted, with the pin and the leg kept in the same position. The difference in the leg length is measured by noting whether the point on the trochanter has moved up or down, which indicates shortening or lengthening, respectively.

Figure 35–2 A, The center of the femoral head is marked with electrocautery before neck osteotomy, and the distance between the center and the lesser trochanter is noted. B, After the placement of the trial implants, the distance from the center of the head to the lesser trochanter is again reassessed and correlated with the preoperative plan. A symmetric relationship among the head, the greater trochanter, and the lesser trochanter usually implies satisfactory implant positioning.

After bone preparation and the placement of the trial implants, the offset and the distance from the center of the head to the lesser trochanter are assessed (see Figure 35-2, B). After reduction, the component position is assessed with the use of the combined anteversion test (Figure 35-3, A and B). This test measures the angle of internal rotation required for the femoral head to be coplanar with the face of the acetabulum with 10 degrees of flexion and 10 degrees of adduction. Normally, the angle is between 35 degrees and 45 degrees of internal rotation for women and between 25 degrees and 35 degrees for men.

Figure 35–3 After trial reduction, the component position is assessed with the use of the combined anteversion test. This test measures A, the amount of internal rotation required for the femoral head to be B, coplanar with the face of the acetabulum, with about 10 degrees of flexion and 10 degrees of adduction at the hip.

Assuming that the components are in the proper position, attention is turned to the soft-tissue envelope. The tightness of the tensor fascia lata is assessed by direct palpation and the Ober test. The tightness of the anterior capsule is evaluated by keeping the patient’s leg in full extension and externally rotating the hip. The posterior border of the greater trochanter should be within one fingerbreadth of the ischial tuberosity without impinging. The “shuck test” can be used to determine overall laxity. In general, more than half of the femoral head should not disengage from the liner with direct axial traction. The “dropkick test” is a maneuver with which the hip is held in extension while the knee is concomitantly flexed to 90 degrees. If the extremity has been overlengthened, the extensor mechanism becomes excessively taut; this may manifest as a passive swing of the knee into extension as the leg is released.

It should be emphasized that all of these soft-tissue tension tests are subjective and depend on the muscle relaxation at that point in the operation, the amount of effective force applied to distract the joint, the muscularity and habitus of the patient, and the extent of soft-tissue release that occurred during surgery. Moreover, because these tests provide an assessment of stability, they may sometimes encourage increased neck lengths, which leads to potential limb lengthening. Thus, these tests should be used in conjunction with each other along with the preoperative template to determine the appropriate construct. After an adequate soft-tissue balance is achieved around the hip, the Steinmann pin is reinserted, with the pin and the patient’s leg kept in the same position (see Figure 35-1, C). The difference in the leg length is measured by noting whether the point on the trochanter has moved up or down, which is indicative of shortening or lengthening, respectively. If lengthening of the limb (especially of more than 2 cm) is anticipated, the sciatic nerve must be palpated to determine whether it is excessively taut before the length that has been gained is accepted.

Pain management and rehabilitation

Changes in pain management have probably had the greatest impact on patients’ recovery after THA. Improved pain control means that patients are more satisfied and comfortable and thus more willing to participate in physical therapy. We prefer a multimodal approach that emphasizes patient education and preemptive analgesia and that avoids the use of parenteral narcotics. This approach is designed to limit the patient’s sensitization to pain and thus reduces the overall analgesic requirement. At our institution, patients receive 400 mg of celecoxib, 20 mg of extended-release oxycodone, 40 mg of pantoprazole, and 5 mg of warfarin in the preoperative holding area.

A local periarticular injection has been shown to have a significant effect on the reduction of immediate postoperative pain. We perform two such injections: 1) one before the final reduction in the anterior capsule, the iliopsoas tendon, and the insertion site; and 2) one after the final reduction in the abductors, the fascia lata, the gluteus maximus and its insertion, the posterior capsule, the short external rotators, and the synovium (Table 35-3).

Table 35–3 Ranawat Orthopedic Center Cocktail

A clonidine transdermal patch is applied in the operating department (100 μg/24 hours). No steroid is given to diabetic, immunocompromised, elderly, or revision patients. Vancomycin is used if the patient is allergic to penicillin.

From Parvataneni HK, Ranawat AS, Ranawat CS. The use of local periarticular injections in the management of postoperative pain after total hip and knee replacement: a multimodal approach. Instr Course Lect. 2007;56:125–131.

Postoperatively, the patients are managed with around-the-clock pain medications, which consist of a combination of acetaminophen, celecoxib, ketorolac, and oral narcotics. The use of a parenteral narcotic is discouraged. The anticoagulation consists of warfarin with a therapeutic international normalized ratio level of 1.5 to 2, along with in-bed exercises, foot pumps, and rapid mobilization. A routine Doppler scan is performed on the second postoperative day; if it is negative, the patient is put on aspirin for the next 6 weeks, depending on individual medical comorbidities. In-bed exercises are begun the same day, and patients are mobilized to ambulate on the first postoperative day, with weight bearing as tolerated; these patients are usually discharged by postoperative day 3. They start with a walker and then graduate to two crutches, then one crutch, and then a cane. The patients are instructed to walk every day, gradually increasing their distance to a goal of 1 mile. Most of these patients can walk without support, pain, or limp at 4 to 6 weeks.

Complications

Apart from the general complications of THA, young, active patients are more prone to dislocation, periprosthetic fracture, implant breakage, wear, osteolysis, and aseptic loosening. In a study by Kerboull and colleagues, the mean wear rate was 0.12 ± 0.21 mm per year; a wear rate of more than 0.1 mm per year was found to be predictive of implant loosening. A high level of participation in sports is associated with at least a two-fold increase in the polyethylene wear rate after 10 years. Implant loosening and instability may be the most common indications for reoperation.

Sports and total hip arthroplasty

Preoperative athletic activity is an important factor to consider when recommending athletic activity after THA. Patients who have achieved high levels of skill in athletics have the best chance of safely resuming these activities; patients who have not participated in specific sports or recreational activities are less likely to achieve high skill levels after THA. Moreover, the latter group may have an increased risk of injury while participating in a new activity after THA.

Participation in sports after a THA is a subjective question. Surgeons have a duty to educate their patients regarding the risk of athletic activity after THA. The most significant risk is accelerated wear, but loosening and traumatic complications may also occur.

Generally, high-contact, high-impact activities are discouraged after THA. Current recommendations are shown in Table 35-4. Improving function is an increasing indication for THA, and we believe that athletic activity is important to many of our patients. We prefer to educate our patients regarding the risks associated with athletic activity rather than to directly discourage the practice. Some patients accept this risk, whereas others choose to avoid sports.

Results and outcomes

The results of THA in the young patient require careful evaluation. The factors to be considered are the length of follow up, the definition of failure (e.g., any revision, aseptic loosening, septic revision, radiographic loosening), the method of obtaining fixation, the underlying diagnosis, and the bearing surface. Diagnosis (e.g., osteoarthritis as compared with rheumatoid arthritis, avascular necrosis as compared with osteoarthritis), male sex, accelerated wear, and varus position of the femur have been linked to the decreased survival of the prosthesis. According to the National Institute for Health and Clinical Excellence, with the use of the most recently available evidence of clinical effectiveness, the best prosthesis (when considering long-term viability as the determinant) should demonstrate a survival rate of more than 90% at 10 years. Although there are not many studies among young patients that fulfill the National Institute for Health and Clinical Excellence criteria, certain trends are evident (Table 35-5).

The results of non-cemented THA will always lag behind those of cemented THA in terms of follow up duration for historic reasons. The long-term results of cemented THA and the mid- to long-term results of uncemented fixation are shown in Table 35-5. Early reports of disappointing clinical results of cemented THA in young patients caused concern and prompted some authors to recommend alternative procedures. Dorr and colleagues found revision rates of 12% at 4.5 years, 33% at 9.2 years, and 67% at 16.2 years. However, recent reports have been more encouraging, with long-term survival rates of 65% to 88% (see Table 35-5). Better survival outcomes have been reported for the femoral stem as compared with the acetabular cup.

Uncemented fixation is growing in popularity, especially for younger patients in most parts of the world. Modern uncemented stems have also shown a good survival rate of 90% to 100% at 10 to 15 years (see Table 35-5). However, the weak link with either type of fixation is the acetabular side: aseptic loosening with cemented components and wear and osteolysis with uncemented modular components. In a study of uncemented THA by McAuley and colleagues, the overall survival rate dipped dramatically from 89% at 10 years to 60% at 15 years. However, if liner exchange was excluded, the survival rate at 15 years was 83.3%. In a report from the Finnish registry about 4661 primary THA cases in young patients who were followed up for 0 years to 22 years, modern uncemented stems and cups fared better than cemented ones in term of aseptic loosening. However, when all revisions were considered (including liner exchange), the survival of uncemented cups was no better than that of all polyethylene (PE) cemented cups. Because of this, alternate options should be considered. Three possible solutions include a reverse hybrid construct, an uncemented cup with improved liner congruence and diminished wear (i.e., a highly cross-linked PE), or a hard-on-hard articulation (Table 35-6).

Table 35–6 Bearing Combinations for Total Hip Arthroplasty Among Young Patients

Metal-on-polyethylene and ceramic-on-polyethylene bearing surfaces may combine some of the advantages of each, but they demonstrate higher wear than metal-on-metal or ceramic-on-ceramic bearing surfaces.

The use of newer combinations (e.g., ceramic-on-metal) requires further research. In preliminary studies, theses combinations have shown lower wear, absence of stripe wear, and lower metal ions.

From Williams S, Schepers A, Isaac G, Hardaker C, Ingham E, van der Jagt D, Breckon A, Fisher J. The 2007 Otto Aufranc Award. Ceramic-on-metal hip arthroplasties: a comparative in vitro and in vivo study. Clin Orthop Relat Res. 2007;465:23-32; Heisel C, Silva M, Schmalzried TP. Bearing surface options for total hip replacement in young patients. Instr Course Lect. 2004;53:49-65; and Fisher J, Jin Z, Tipper J, Stone M, Ingham E. Tribology of alternative bearings. Clin Orthop Relat Res. 2006;453:25-34.

Summary

As disheartening as it is to replace a young person’s hip, both the surgeon and the patient should take solace in the likelihood of excellent pain relief and restoration of function. Uncemented fixation and alternative bearings offer hope for a THA that could last 30 years or more.

Technically, exposure is often more difficult as a result of a more robust musculature, and it usually requires longer incisions. Bone preparation may require over-reaming and over-broaching to optimize fixation and avoid complications.

More research is needed to evaluate the long-term results of THA for the young patient, especially with newer designs and materials. However, our current understanding supports the notion that these patients may experience earlier failure and an increased need for reoperation as compared with older patients.