3. Adult Reconstruction (Hip & Knee) MCQs

The imaging shows significant osteolysis and raises concern for pelvic discontinuity and acetabular implant failure. The surgical treatment consists of acetabular reconstruction. In this patient, concern exists for discontinuity based on the substantial amount of bone loss and nonsupportive anterior and posterior columns. This scenario requires complex acetabular revision using a custom triflange device, distraction with a jumbo acetabular component, or placement of a porous metal cup/cage construct with augmentation.

This patient presents with HO 4 months after undergoing THA. Symptomatic HO may complicate nearly 7% of primary THA cases. Improvement in pain is expected within 6 months, and most patients will not need surgical treatment. Surgical excision may be warranted for symptomatic patients after full maturation of the HO, usually 6 to 18 months after the surgery. Patients can be followed with repeated serum alkaline phosphatase levels, which are elevated initially and should return to normal upon maturation of the HO. Alternatively, a bone scan can show decreased activity after the HO has matured. Twenty-five milligrams of indomethacin 3 times daily for 6 weeks or 1 dose of irradiation at 700 to 800 Gy is effective in the prevention of HO but not for the treatment of established HO.

Revision of a failed patellar component can be difficult because of bone loss and damage to the extensor mechanism. Several authors have advised against reinsertion of a patellar component if the residual patellar thickness is 10 mm or less. Leaving an unresurfaced bony remnant in place at the time of revision or reimplantation surgery has been shown to be a reasonable option; however, the results are of a lower quality when compared with revision surgery where the patellar component can be retained or revised.

Postoperative management of total elbow arthroplasty patients is directed to avoidance of complications commonly associated with this procedure. Following total elbow arthroplasty, 24 hours of perioperative antibiotics should be given, consistent with other arthroplasty procedures. Because of the relatively thin soft-tissue envelope surrounding the elbow, particularly in patients with rheumatoid arthritis, consideration must be given to the surrounding soft tissues postoperatively. The surgical wound should be given several days of quiescence prior to initiation of motion to minimize wound healing complications. Splinting at 60 to 90 degrees allows tension to be removed from the soft tissues. Immediate motion places these tissues under immediate stress; immobilization of the elbow for 6 to 8 weeks until the triceps has healed would result in significant stiffness. Splinting should not be used more than 10 days to avoid stiffness of the elbow.

THA has proven to be durable and reliable for pain relief and improvement of function in patients with end-stage arthritis. Appropriate bearing selection is critical to minimize wear and hip complications. Ametal-on-metal articulation is associated with excellent wear rates in vitro. Because it offers a low wear rate with large femoral heads, it is an attractive bearing choice for THA. However, local soft-tissue reactions, pseudotumors, and potential systemic reactions—including renal failure, cardiomyopathy, carcinogenesis, and potential teratogenesis after the possible transfer of metal ions across the placental barrier—make metal-on-metal bearings less desirable and relatively contraindicated for younger women of child-bearing age.The work-up of a painful metal-on-metal hip arthroplasty necessitates a systematic approach. Several algorithms have been proposed. Routine laboratory studies including the erythrocyte sedimentation rate, C-reactive protein (CRP) level, and serum cobalt and chromium ion levels should be obtained for all patients with pain. Advanced imaging, including MRI with MARS, should be performed to evaluate for the presence of fluid collections, pseudotumors, and abductor mechanism destruction. Infection can coexist with metal-on-metal reactions, so when indicated (if the CRP level is elevated), a hip arthrocentesis should be obtained. However, in this setting, a manual cell count and differential should be obtained because an automated cell counter may provide falsely elevated cell counts. The results of revision surgery for a failed metal-on-metal hip prosthesis can be variable. The amount of local tissue destruction and the integrity of the hip abductor mechanism can greatly influence outcomes. Instability is the most common complication following a revision of failed metal-on-metal hip replacements.

Some authors have reported the incidence of lateral femoral cutaneous nerve neuropraxia following hip arthroplasty with the direct anterior approach to be near 80%, though resolution of sensory deficits is typically observed over time.

Precoating of the femoral stem with PMMA results in increased bonding of the stem to the cement mantle. However, this has not been shown to result in superior survivorship compared with nonprecoated stems of similar design.

The radiographs show well-fixed components of a posterior cruciate-retaining total knee replacement. The relative position of the femoral component is anteriorly subluxated relative to the tibial component. The AP radiograph shows that the articular space is markedly asymmetric, indicating either failure or fracture of the polyethylene or subluxation of the femur relative to the tibia. The patient’s symptoms suggest a failure of the posterior cruciate ligament that is consistent with the radiographic findings; therefore, the treatment of choice is revision to a posterior cruciate-substituting implant.

S. aureus is the most common organism cultured in early (fewer than 4 weeks postoperative) periprosthetic infections. Methicillin-resistant S. aureus is becoming a more common pathogen in certain patient populations. Beta-hemolytic Streptococcus and some gram-negative infections can also be found in early postoperative infections. S. epidermidis, S. viridans, and P. acnes are more commonly found in late (more than 4 weeks postoperative) infections.

Neurologic injury after shoulder replacement is relatively uncommon. The presumed mechanism of injury is traction on the plexus that occurs during the surgery. A neurologic injury after total shoulder arthroplasty usually does not interfere with the long-term outcome of the arthroplasty itself; it is best managed by protective measures with passive range of motion of the involved extremity.

DISCUSSIONFigure 58 reveals a posttraumatic valgus deformity. Correction of valgus with lateral soft-tissue release places tension on the peroneal nerve, resulting in an increased risk for nerve palsy. Figures 59a (lateral view) and 59b (Merchant view) illustrate juvenile rheumatoid arthritis with tibiofibular fusion and lateral patellar dislocation. Chronic patellar dislocation is associated with contracture of the lateral retinacular soft tissues and increased risk for patellar subluxation or dislocation after TKA. Extensor mechanism realignment, possibly including tibial tubercle osteotomy and/or proximal soft-tissue realignment, may be required during TKA to centralize the extensor mechanism. Figures 60a (anteroposterior [AP] view) and 60b (lateral view) reveal a fused knee in full extension.TKA after fusion is associated with multiple complications including skin necrosis, infection, and instability. The skin is contracted because of limited knee motion and has multiple scars (Figure 60c). Mobilization of the skin during and after knee arthroplasty can place excess tension on the soft tissues, resulting in skin necrosis and infection. Treatment consisting of prompt debridement and soft-tissue coverage, usually with medial gastrocnemius muscle transposition, is required. Figure 61 shows a knee with prior tibial tubercle fixation and marked patella infera. Shortening of the patellar ligament is associated with restricted knee motion. This may necessitate more extensile exposure using tibial tubercle osteotomy or rectus snip during TKA to obtain adequate surgical exposure. The inferior position of the patella can cause impingement between the patellar component and tibial insert, resulting in anterior knee pain. Restoring a more normal position of the patella may necessitate distal positioning of the femoral component as well as tibial tubercle osteotomy with proximal recession of the osteotomized tibial tubercle. Figures 62a (AP view of the distal femur) and 62b (AP view of the proximal femur) show a posttraumatic deformity with a large retained intramedullary rod. There is a varus distal femoral deformity that is not severe enough to necessitate extra-articular corrective osteotomy. However, intramedullary hardware precludes use of conventional intramedullary instrumentation, so computer navigation or patient-specific cutting guides will be necessary to orient the bone cuts and avoid implant malalignment.

DISCUSSION: Patients with ankylosing spondylitis (AS) are likely to have achieved significant pain relief and improvement in function following total knee arthroplasty (TKA). These patients, however, are also likely to experience a higher incidence of complications, particularly stiffness and heterotopic ossification (HO). In one series, the incidence of HO following TKA in patients with AS was 20%. REFERENCES: Parvizi J, Duffy GP, Trousdale RT: Total knee arthroplasty in patients with ankylosing spondylitis. J Bone Joint Surg Am 2001;83:1312-1316. Fintersbush A, Amir D, Vatashki E, et al: Joint surgery in severe ankylosing spondylitis. Acta Orthop Scand 1988;59:491-496.

DISCUSSION: Rheumatoid arthritis is an inflammatory arthritis that usually involves multiple joints. Radiologic findings of periarticular erosion, osteopenia, and minimal osteophyte formation favor rheumatoid arthritis over osteoarthritis. Pigmented villonodular synovitis and Charcot arthropathy are more often considered monoarticular diseases. There are no radiographic findings of Paget’s disease. REFERENCE: Dutkowsky J: Miscellaneous non traumatic disorders, in Crenshaw A (ed): Campbell’s Operative Orthopaedics. St Louis, MO, Mosby, 1992, pp 2007-2012.

DISCUSSION: Metal-on-metal THA was initially introduced in the 1990s, with the proposed advantages of decreased wear and improved stability. However, catastrophic adverse local tissue reactions associated with their use has raised numerous concerns. The work-up of a patient with a prior metal-on-metal total hip arthroplasty involves a thorough history and physical examination; blood analysis, including the erythrocyte sedimentation rate, C-reactive protein, and metal ion levels; and secondary imaging, including ultrasonography, CT, and MRI. In a patient with clinical symptoms, elevated metal ion levels, and a large fluid collection seen on MRI, the most appropriate treatment would be removal of the metal-on-metal bearing. Given the presence of an adverse reaction involving cobalt and chromium, a revision ceramic head may be most appropriate to avoid the potential of trunnion-associated corrosion.

Knee arthrodesis rather than reimplantation should be considered a) following failure of a primary knee prosthetic arthroplasty when the extensor mechanism is insufficient, b) in the immuno-compromised patient, c) in the knee with poor soft tissue coverage, d) when the causative microorganism in the infected prosthetic knee is particularly virulent which may be sensitive to only toxic antimicrobials. It should also be considered in the relatively young patient with high functional demands, whose arthritic process only involves one joint.

DISCUSSION: Groin pain after total hip replacement has a number of possible causes, and an exact diagnosis may remain elusive in some patients. Infection should be ruled out with laboratory studies and, if indicated, diagnostic aspiration of the hip joint. Implant loosening should be evaluated by plain radiograph and bone scan, if indicated. Synovitis resulting from wear debris should be considered in patients with polyethylene liners who experience late-onset symptoms or in any patient with a metal-on-metal bearing. This patient's symptoms are classic for iliopsoas tendonitis. Physical examination usually reveals pain and weakness with resisted hip flexion. A cross-table lateral radiograph and CT show that the anterior edge of the acetabulum protrudes beyond the anterior wall, thereby acting as a source of iliopsoas tendon irritation. In such cases, acetabular component revision and repositioning are indicated. Fluoroscope-guided iliopsoas cortisone injection can help to establish the diagnosis and relieve groin pain. If the acetabular component is well positioned, then iliopsoas tenotomy should be considered.

DISCUSSION: The femoral construct shown in the radiograph has failed to produce ingrowth of the stem. The stem has subsided and rotated. Impingement of the trochanter did not occur until after the stem subsided. There is no evidence of osteolysis or third-body wear debris from the cerclage wire. A larger femoral stem needs to be implanted to achieve rigid fixation.

EXPLANATION: A recent systematic review compared silicone replacement, pyrocarbon replacement, and surface replacement arthroplasty for PIP arthritis. Silicone arthroplasty through a volar approach showed the greatest gains in arc of motion and had the lowest rate of revision surgeries. The rates of revision surgeries from low to high for each type of arthroplasty were 6% for silicone volar, 10% for silicone lateral, 11% for silicone dorsal, 18% for surface replacement dorsal, and 37% for surface replacement volar. Revision surgeries include implant replacement, arthrodesis, explantation, amputation, and other procedures.

Avascular necrosis of the knee is associated with the use of corticosteroids or alcohol 90% of the time. Radiographically evident lesions progress until the necrotic cancellous bone collapses away from the subchondral plate, resulting in the classic crescent sign; earliest sign of mechanical failure of the condyles. Generally seen in a younger age group (less than 50 years old). Of patients with corticosteroid induced AVN of the knee; 81% have systemic lupus erythematosus, 9.5% inflammatory bowel disease, and 9.5% polymyositis.

DISCUSSION: Joint contact pressure is a stress and as such is defined as the load transferred across the joint divided by the contact area between the joint surfaces (the area over which the joint load is distributed). Therefore, any mechanism that decreases the load across the joint (e.g., a walking aid) will decrease the stress. Similarly, any mechanism that increases the area over which the load is distributed (e.g., using a more conforming set of articular surfaces in a knee joint arthroplasty) will also decrease the stress. Other mechanisms that influence joint contact pressure include the elastic modulus of the materials (cartilage in the case of natural joints and polyethylene in joint arthroplasty) and the thickness of the structures through which the joint loads pass.