3. Adult Reconstruction (Hip & Knee) MCQs

Dynamic patellofemoral joint contact measurements on cadaveric knees with simulated increased Q angle demonstrated that forces shifted to the lateral facet. The lateral shift in the patella was most pronounced from 40 to 90 degrees of flexion. At lower degrees of flexion, the lateral shift was significantly less. At higher degrees of flexion, the continued shift of the patella was not as pronounced.

Hemophilia A is inherited in an X-linked recessive fashion.linked recessive disorders occur when a mutation occurs on the X chromosome that causes the phenotype to be expressed in males and in females who are homozygous for the gene mutation. These disorders are much more common in males since they only have one X chromosome. Other X-linked recessive disorders include: Duchenne muscular dystrophy, Becker's muscular dystrophy, Hunter's syndrome, and spondyloepiphyseal dysplasia (SED) tarda.Vanderhave et al. reviewed the orthopaedic consideration in patients with hemophilia. Amongst other things, they discuss arthroplasty in patients with this condition. While they are at higher risk for stiffness and acute hemarthrosis following total knee arthroplasty, ~90-95% of patients have good or excellent results.Illustration A shows how hemophilia is inherited through a punnett square. Illustration B shows how a weak clotting mechanism causes increased bleeding in patients with hemophilia.Incorrect Answers:

The most appropriate treatment is arthroscopic capsular release, loose body removal, and osteophyte decompression. The patient has moderate osteoarthritis of the dominant elbow, with mechanical symptoms suggestive of loose osteochondral body formation. Because the patient has failed to respond to the typical nonsurgical therapeutic options, it is unlikely that further oral medication will be helpful, and job modification may not be practical at this stage. Soft-tissue arthroplasty may be reasonable to consider when less invasive methods, such as arthroscopy, fail. Isolated radial head arthroplasty would not sufficiently address the symptoms. Total elbow arthroplasty is indicated in cases of more advanced disease in older patients with lower physical demands.

DISCUSSION: A patient with medial compartment arthritis and a correctable varus deformity with no clinical or examination findings of knee instability most likely has an intact ACL. The pattern of medial compartment osteoarthritis most commonly associated with an intact ACL is that of anteromedial osteoarthritis. An incompetent ACL is commonly associated with a fixed varus deformity and radiographic signs of posteromedial wear. An incompetent ACL is a relative contraindication to a mobile-bearing UKA. When evaluating patients for a mobile-bearing UKA, a stress radiograph will allow the orthopaedic surgeon to determine the correction of the varus deformity and assess the lateral compartment. Inability to fully correct the deformity or narrowing of the lateral compartment with valgus stress should influence the surgeon against UKA. Joint registries across the world have shown decreased survivorship associated with TKA and UKA in men compared to other age groups, but survivorship is lower for UKA than TKA. No studies to date have shown differences in survivorship between fixed- or mobile-bearing UKAs. The complication that is unique to mobile-bearing UKA is bearing spinout, and this occurs in fewer than 1% of mobile-bearing UKA procedures. In vivo and in vitro polyethylene wear in mobile-bearing UKA is low. Arthritis progression may be faster for mobile-bearing UKAs than fixed-bearing UKAs.

DISCUSSION: Anatomic positioning of the acetabular component has been shown to be the optimal position for reconstruction of the acetabulum in total hip arthroplasty for DDH. The use of medialized component positioning has been shown to be successful at maximizing the host bone coverage and minimizing the use of bone graft to structurally support the acetabular component. A small acetabular component can be used successfully as long as the femoral head is also reduced in size to maintain the thickness of the acetabular polyethylene. High and lateral positioning for the acetabular reconstruction will result in an increase in the joint reaction forces. In addition, a high and lateral placement will not provide adequate bone to stabilize the reconstruction. REFERENCES: Numair J, Joshi AB, Murphy JC, Porter ML, Hardinge K: Total hip arthroplasty for congenital dysplasia or dislocation of the hip: Survivorship analysis and long-term results. J Bone Joint Surg Am 1997;79:1352-1360. Dorr LD, Tawakkol S, Moorthy M, Long W, Wan Z: Medial protrusio technique for placement of a porous-coated, hemispherical acetabular component without cement in a total hip arthroplasty in patients who have acetabular dysplasia. J Bone Joint Surg Am 1999;81:83-92. Jasty M, Anderson MJ, Harris WH: Total hip replacement for developmental dysplasia of the hip. Clin Orthop 1995;311:40-45.

DISCUSSION: The radiographs show substantial valgus malalignment of the femoral component, with lateral mechanical axis deviation. Clinically, by examination she displays instability and stiffness as a result. Revision knee replacement is appropriate and should consist of total revision to stemmed femoral and tibial components with a varus-valgus constrained insert, given the likely attenuation of the medial collateral ligament. Open debridement with ligament balancing and polyethylene exchange do not address the underlying cause and are inappropriate. Distal femoral osteotomy is not useful in the setting of previous total knee replacement. Nonsurgical treatment with an unloader brace would be ineffective in correcting the alignment.

DISCUSSION: An acetabular reinforcement cage is required infrequently except when there is pelvic discontinuity in which there is no posterior column support of the acetabular cup. A larger cup inserted with cement and morselized bone graft is an effective technique for contained cavitary and anterior wall defects. Zone 1 osteolysis and a medial wall defect are essentially the same as a contained cavitary defect and can be reconstructed using cementless cups.

DISCUSSION: In a survivorship study of 9,200 total knee arthroplasties, Rand and Ilstrup identified four independent variables associated with a significantly lower risk of failure: primary total knee arthroplasty, diagnosis of rheumatoid arthritis, age of 60 years or older, and use of a condylar prosthesis with a metal-backed tibial component. Other clinical studies report the use of a posterior stabilized prosthesis to be comparable to a total condylar prosthesis with retained posterior cruciate ligament.

These radiographs are dominated by the subsidence of the femoral component. There is also evidence of polyethylene wear and femoral osteolysis in the region of the greater trochanter. There is no evidence of proximal (calcar) stress shielding, and there is a thick distal pedestal. Engh and associates defined two major signs of osseointegration - the absence of radiolucent lines around the porous-surfaced portion of the implant and new bone bridging the gap between the endosteal surface and the porous portion of the implant. Implant migration indicates failure of ingrowth. Osteolysis is a periprosthetic loss of bone secondary to particulate debris and it is often clinically silent unless it is accompanied by pathologic fracture. It is often globular. Acetabular loosening is based on radiolucent lines and implant migration. The current radiographs demonstrate subsidence of the stem with pedestal formation.

According to two studies looking at patients with a cobalt-chrome metal-on-metal lumbar disk arthroplasty, serum ion levels in these patients were similar to values measured in patients with total hip arthroplasty metal-on-metal prostheses.

The MRI findings show highly increased signal through the entire femoral head and neck on STIR imaging, diagnostic of transient osteoporosis of the femoral head. This disease entity can be seen in middle-aged men, and should be treated nonsurgically. The natural history is that of self-resolution.

Any inflammatory disease, including crystalline arthropathy, is a contraindication for patellofemoral arthroplasty. Patellar tilt and dysplasia frequently occur in the setting of patellofemoral arthritis and do not constitute a contraindication to this procedure. Severe crepitus is common and frequently addressed with patellofemoral arthroplasty.

The radiograph reveals primary osteoarthritis of the elbow; therefore, ulnohumeral arthroplasty is the preferred procedure. Patients with severely limited preoperative elbow extension of more than 60 degrees and flexion of less than 100 degrees are at risk for ulnar nerve dysfunction postoperatively and should undergo a concomitant ulnar nerve decompression. Nonsurgical methods are unlikely to improve his chronic condition. Elbow arthroplasty is contraindicated for patients in this age group and with this diagnosis.

One possible reason for improved efficacy of LMWHs is the relative improved bioavailability compared with that of unfractionated heparin. This is, in part, the result of a more predictable dose response and a longer half-life. There is no alteration of venous flow, and the rate of bleeding complications is the same or slightly higher than that of other prophylactic agents.

The patient’s symptoms at follow-up—pain, swelling, and difficulty descending stairs—suggest knee flexion instability. Considering his history, an incompetent PCL must be considered. Revision of the knee to a posterior stabilized or nonlinked constrained condylar implant (depending on the condition of the ligaments) likely is needed to address his symptoms. The difference in extension stability and flexion stability makes polyethylene exchange a poor option. A constrained rotating hinge design is not necessary. Repeat use of a PCL-retaining insert is not recommended. Tibial and femoral revision both are required. Correction of excessive slope will be attained with tibial revision, femoral component revision is required to convert to a PCL-substituting design.

Patellar clunk syndrome is associated with certain types of posterior stabilized knee arthroplasties. Arthroscopic resection of the band of inflammatory tissue inferior to the patellar component is effective in treating this condition. Arthroscopic lavage of infected knee arthroplasties is not associated with an acceptable success rate.

This 86-year-old woman has poor bone quality and osteoarthritis of the left hip. Her lateral radiograph confirms Dorr type C bone quality. A hybrid left THA with a cemented femoral stem is the treatment of choice.

This patient has severe, uncorrectable varus deformity and pain from end-stage osteoarthritis secondary to prior adolescent tibia vara. Although he is young to consider arthroplasty, this option is likely to give him the most functional limb compared with arthrodesis with a long antegrade nail. During arthroplasty surgery, his knee will likely require extensive medial release to achieve anatomic limb alignment. Standard components in total knee arthroplasty likely would result in lateral instability, so this option is not the best answer. The best choice is total knee arthroplasty with a constrained device, which adds constraint to the knee to provide balance.

Patellar clunk syndrome is caused by the development of a fibrous nodule on the posterior aspect of the quadriceps tendon at its insertion into the patella. It causes a painful catching sensation when the extensor mechanism traverses over the trochlear notch as the knee extends from 45° of flexion to 30° from full extension. It characteristically occurs in posterior stabilized total knee arthroplasties and appears to be related to femoral component design. The syndrome can usually be prevented by excising the residual synovial fold just proximal to the patella. Flexion gap instability can also cause a painful total knee arthroplasty but is less common in posterior stabilized implants. Femoral component malrotation can cause pain attributable to a flexion gap imbalance or patellar tracking problems. Polyethylene wear would be unlikely after just 1 year. Patellar clunk syndrome can usually be addressed successfully with arthroscopic synovectomy.

Very large corrections of tibial deformity can be achieved at or just below the tibial tubercle. This level of osteotomy maintains the relationship between the tubercle and the rest of the joint, does not alter patellofemoral mechanics, and avoids complicating possible future conversion to total knee arthroplasty. High tibial osteotomy is contraindicated for large corrections because of excessive elevation of the tibial tubercle and overhang of the lateral plateau. Correction in the tibial diaphysis creates a zig-zag pattern in the tibia by correcting below the deformity and risks nonunion in cortical bone. There is no evidence that the femur is deformed; therefore, femoral osteotomy is not indicated.