3. Adult Reconstruction (Hip & Knee) MCQs

The incidence of lateral femoral cutaneous nerve injury is much higher than that of other complications after anterior-approach total hip replacement. This injury is usually clinically inconsequential, presenting as thigh numbness.

The radiograph shows a metal-on-metal hip resurfacing arthroplasty. The acetabular component is malpositioned in excessive abduction, which may explain the clunking symptoms and be allowing the joint to subluxate. The best option is to convert this failed surface replacement to a conventional total hip arthroplasty.

There are a number of possible causes of groin pain after total hip replacement, but 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 scan 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 is indicated. Fluoroscopic-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.

There are a number of possible causes of groin pain after total hip replacement, but 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 scan 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 is indicated. Fluoroscopic-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.

Increasing the diameter of the femoral head when the diameter of the femoral neck remains the same increases the range of motion to impingement and hip stability. Femoral heads with neck skirts impinge early and have less range of motion.

A high level of acetabular inclination over the Lewinnek safe zone of 50 degrees has been associated with high levels of chrome and cobalt ions. This may be related to the fact that wear may be increased by the uncoverage of the implant.

Diabetes mellitus and high blood glucose levels have been shown to increase risk for perioperative complications and symptomatic pulmonary embolism in patients undergoing arthroplasty. Other risk factors include a body mass index higher than 30 and bilateral knee arthroplasty. Neither coronary artery disease, previous knee surgery, nor female gender has been shown to increase risk.

A Vancouver type B-2 periprosthetic fracture pattern (between the lesser trochanter and the tip of the femoral component) frequently compromises stem fixation. This patient’s stem fixation status was not stable because the stem was inserted only 3 weeks before the fracture occurred. The most effective treatment for Vancouver type B-2 fractures is revision with a long stem to achieve distal diaphyseal fixation, along with fixation of the fracture using cables or wires with or without strut graft based on the quality and quantity of the bone stock.

The patient has an approximate 1-cm increase in leg length and a 1-cm increase in offset (Figure 83b). A transischial line intersecting the lesser trochanters shows a 1.14-cm difference in leg length. The lateral distance from the pubic midline to the medial femoral neck shows a difference in lateral offset of 1.1 cm. This has resulted in pelvic obliquity and an apparent leg length discrepancy in addition to a true leg length discrepancy.

Well-fixed components in the presence of minimal osteolysis and a worn acetabular polyethylene liner in a symptomatic patient should be treated with liner and ball head exchange. Revision of either or both of the well-fixed and otherwise well-functioning components is unnecessary and introduces the possibility for additional complications. Observation is a suboptimal choice considering that significant wear is seen and the patient is symptomatic.

Patients with ankylosing spondylitis experience pain relief and improved function after total knee replacement, but a number of studies have shown an increased risk for knee stiffness and heterotopic ossification in this subgroup. Patients should be advised that their underlying condition could make them more likely to experience this complication.

The particles isolated from the knee are larger and less reactive. Wear in a total knee replacement prosthesis differs from that in a total hip replacement. Wear is the result of pitting and delamination; there are not submicron wear debris particles as one would find in the hip. Because of this patient’s age and medical risks, polyethylene exchange is the best decision. The components appear to be well-fixed, and progressive valgus deformity is caused by asymmetric polyethylene wear.

The particles isolated from the knee are larger and less reactive. Wear in a total knee replacement prosthesis differs from that in a total hip replacement. Wear is the result of pitting and delamination; there are not submicron wear debris particles as one would find in the hip. Because of this patient’s age and medical risks, polyethylene exchange is the best decision. The components appear to be well-fixed, and progressive valgus deformity is caused by asymmetric polyethylene wear.

In this scenario, suspicion for a periprosthetic joint infection is high. The synovial fluid WBC count is elevated and the synovial fluid culture result may be a false negative. The AAOS Clinical Practice Guideline, The Diagnosis of Periprosthetic Joint Infections of the Hip and Knee, recommends strongly against the use of gram stain and strongly in favor of multiple culture and frozen sections to aid in the diagnosis of infection. Considering the chronicity of the infection, removal of both components is indicated.

In this scenario, suspicion for a periprosthetic joint infection is high. The synovial fluid WBC count is elevated and the synovial fluid culture result may be a false negative. The AAOS Clinical Practice Guideline, The Diagnosis of Periprosthetic Joint Infections of the Hip and Knee, recommends strongly against the use of gram stain and strongly in favor of multiple culture and frozen sections to aid in the diagnosis of infection. Considering the chronicity of the infection, removal of both components is indicated, which is the first stage of a two-stage exchange (resection arthroplasty with placement of an antibiotic spacer).

The recognized treatment for a proximal periprosthetic fracture is to first identify the extent and then optimize the correction. Several studies indicate that proximal cerclage wiring is adequate to create“barrel hoop” stability of the proximal femur. Braided cables offer superior stability compared to twisted wires or Luque wires. Finally, the appropriate postoperative treatment is protected weight bearing for 6 weeks, with periodic radiographs taken at 2-week intervals. Other options such as cementing the femoral stem and using a revision arthroplasty device are indicated for unstable fractures.

The situation described here is consistent with a successful treatment for deep infection. If the patient’s knee aspiration reveals no organisms and the CRP and ESR trend toward normal, the patient is a candidate for a second-stage revision knee arthroplasty. A 2-week antibiotic holiday is necessary to obtain accurate culture results either with aspiration or soft-tissue specimens at the time of second-stage revision TKA. There is no evidence that waiting for up to 6 months provides a lower recurrence rate, and there may be long-term problems with a spacer left in place for 6 months, such as breakage, instability, or loosening.

The use of modular femoral stems and acetabular implants have increased the number of head, neck, and liner designs, but the features of recent designs can cause intra-articular prosthetic impingement within the arc of motion required to perform daily activities. Impingement may lead to limited motion, increased wear, osteolysis, and subluxation or dislocation. Minimizing impingement involves avoiding skirted heads, matching the femoral head with an appropriate acetabular implant, maximizing the head-to-neck ratio and, when possible, using a chamfered acetabular liner and a trapezoidal, rather than circular, neck cross-section.

Drainage from a knee after arthroplasty can be ominous; here, a previous incision was made for an osteotomy, possibly compromising wound healing. At 2 weeks, persistent wound drainage is not expected and warrants urgent attention with surgical debridement, cultures, and a baseline check of inflammatory laboratory data. Intravenous antibiotics can be started while awaiting cultures, but oral or intravenous antibiotics alone are not sufficient and a vacuum drain is not indicated in this situation.

The ESR is a sensitive serologic indicator of inflammation; however, it is less specific for infection. Other noninfectious conditions may cause an elevated ESR. The CRP is a specific indicator of infection, which may be transiently elevated after uncomplicated total hip arthroplasty, but usually returns to a normal range within 1 to 2 weeks of surgery. If both the ESR and CRP are elevated, there is a high likelihood that a painful hip replacement is infected, and joint aspiration is indicated.