3. Adult Reconstruction (Hip & Knee) MCQs

Current recommendations are for a lifetime restriction of load bearing and avoidance of impact activities following total elbow arthroplasty (TEA). TEA is a very effective procedure in reducing pain or reconstructing previously unreconstructable fractures. However, its usage must be tempered with the limitations of currently available prostheses. Aggressive triceps strengthening must be delayed following TEA to allow healing of the triceps attachment, regardless of the surgical approach. Wrist and hand mobilization should begin immediately postoperatively to prevent stiffness. Pronation and supination should not stress a humeral ulnar arthroplasty.

Factor V Leiden is a disease caused by an abnormality of factor V in which a single amino acid substitution of glutamine for arginine in the protein C cleavage region leads to decreased inactivation of factor V and thus a greater tendency to form clots. More than half of all individuals with Factor V Leiden will develop deep venous thrombosis in the presence of a single additional risk factor such as long bone fracture or total joint arthroplasty.

DISCUSSION: This complication is best addressed with either a single-stage or two-stage total knee arthroplasty. A recent report suggests that a single-stage arthroplasty can be effective, although many surgeons would perform a two-stage procedure with an articulating or static spacer. Arthroscopic would be non-effective, especially given 4 weeks of symptoms. Resection arthroplasty without a spacer would leave an unstable and poorly functioning extremity. Knee fusion should be used as a salvage procedure.

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 anterior cruciate ligament (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 aids the orthopaedic surgeon in determining the correction of the varus deformity and assessing the lateral compartment. An 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 with other age groups, but survivorship is lower for UKA than for TKA. No studies to date have shown any differences in survivorship between fixed-bearing and mobile-bearing UKAs. The complication that is unique to mobile-bearing UKA is bearing spinout, which occurs in less than 1% of mobile-bearing UKA procedures. In vivo and in vitro polyethylene wear in mobile-bearing UKA are low. Arthritis may progress faster in patients with mobile-bearing UKAs than in those with fixed-bearing UKAs.

Activity levels do not affect cobalt and chromium ion levels, which are the bulk of serum ion levels. The majority of ions are produced in the run-in period in the first several years. A gradual reduction in ion levels occurs thereafter. The kidneys are responsible for the bulk of clearance from the serum, and to date there is no relationship of cancer to ion levels in the serum.

In the design of tibial and femoral components, a compromise must be made between contact stresses and constraint. Increased conformity increases constraint, limits motion, and potentially increases stress on the knee-cement interface. By increasing conformity, the surface area over which force is applied is increased, resulting in decreased peak contact stresses and decreased component wear rates.

Protection of the superior laryngeal nerve is critical in a professional singer. The nerve is easily injured with retraction when using vertical extension of common anterior surgical approaches to gain exposure to the C2-3 level. McAfee and associates reported on 17 patients with C1-2 and C2-3 pathology. They used a modified submandibular approach as an anterior retropharyngeal exposure with modification of the superior extension of the Smith-Robinson technique that allows visualization of the superior laryngeal nerve and surrounding structures. No incidences of superior laryngeal nerve injury were recorded. The transoral approach should be avoided because of the high rate of infection and limited exposure.

Studies show that degenerative arthritis of the spine associated with a hip arthrodesis can be decreased with conversion to a total hip arthroplasty. The pain associated with degenerative arthritis of the knee usually persists after arthrodesis take-down procedures and often requires total knee arthroplasty. Pain in the contralateral hip is not resolved by converting the arthrodesis. Improving range of motion of the hip and correcting a limb-length discrepancy are not good indications for take-down procedures.

In select patients with thoracolumbar idiopathic scoliosis, an anterior approach with a single rod and interbody cages may be indicated. Thoracic hyperkyphosis (>40 degrees ) is a risk factor for pseudoarthrosis in patients treated with this method.In a prospective study, Sweet et al found anterior instrumented fusions using a single solid rod had good radiographic and clinical outcomes. In their treatment group they found common risk factors for pseudarthrosis were smoking, weight >70 kg, and T5-T12 hyperkyphosis of > 40 degrees. They recommend consideration should be given to alternate techniques in larger adolescents (>70 kg) with thoracic hyperkyphosis (>40 degrees ). The average coronal correction of thoracic curves was from 55 degrees to 29 degrees (47%). The average correction of thoracolumbar/lumbar curves was from 50 degrees to 15 degrees (70%). Neither of these variables were associated with pseudoarthrosis. In the sagittal plane, lordosis was maintained in thoracolumbar/lumbar fusions at -58 degrees (T12-sacrum). Improved maintenance of lumbar lordosis is considered one of the advantages of an anterior approach.In an additional study from the same group at Wash U, Hurford et al designed a study to compare the results of anterior DUAL-rod instrumentation with their previous experience using single-rod constructs. They found the two technique were comparable in the amount of radiographic deformity correction obtained. However, they report the absence of any pseudarthroses in the 60 patients with dual-rod is a distinct advantage over the single rod technique.

DISCUSSION: The recognized treatment for a proximal periprosthetic fracture is to first identify the extent and then optimize the correction of the fracture. Several studies indicate that proximal cerclage wiring is adequate to create "barrel hoop" stability of the proximal femur. Braided cables offer superior stability compared with 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.

DISCUSSION: TXA is easy to administer, inexpensive, and safe for virtually all patients. Multiple studies have demonstrated transfusion rates lower than 3% for total knee arthroplasty and lower than 10% for total hip arthroplasty. Regional and hypotensive anesthesia effectively reduce transfusion; however, they cannot be used in as wide a range of patients as can TXA. A reduced transfusion trigger must be considered along with patient symptoms when determining the need for transfusion.

The study describes an example of a cohort study. Cohort studies follow a group of individuals over time and are optimal for studying the incidence, course, and risk factors of a disease. The effects in a cohort study are frequently reported in terms of relative risk (RR). Odds ratios are used to report effects in a case-control study. Incidence and prevalence rates are descriptors of a given characteristic either developed over time (incidence) or at one given time (prevalence). Confidence intervals are used to convey the significance of findings and are often used in lieu of or in conjunction with P values.

This patient is elderly, obese, and nonambulatory and has a chronic quadriceps tendon rupture after infected total knee arthroplasty. Her potential for ambulation after revision total knee arthroplasty is very low. Primary repair of the tendon is unlikely to be successful, even with augmentation. Extensor mechanism allograft could be done but would have a high failure rate in a patient of this size. No sign of infection is seen, based on laboratory studies, so a two-stage procedure is not necessary. The best management, although not optimal, would be treatment in a drop-lock brace. Arthrodesis is also an option, but would have a high complication rate, and in a patient that is nonambulatory, a fused knee would be increasingly difficult with activities of daily living and mobility.

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.

The radiograph shows a posterior wall acetabular fracture-dislocation. Post reduction CT indicates a large comminuted posterior wall fracture with marginal impaction of the articular surface. A comminuted femoral head fracture also is seen extending to the superior weight-bearing surface. Given the marginal impaction of the acetabulum and the considerable comminution of the femoral head (which is likely unreconstructible), this injury would have a high risk of causing posttraumatic arthritis if treated with ORIF of the fractures alone. Considering this fact and the patient’s age, ORIF of the posterior wall and acute total hip arthroplasty would likely have the best functional result and the lowest risk of reoperation. Hemiarthroplasty is inappropriate for this injury considering the acetabular fracture. Skeletal traction currently plays a limited role in the definitive treatment of acetabular fractures.

DISCUSSION: Some authors have reported the incidence of lateral femoral cutaneous nerve neuropraxia following hip arthroplasty with the direct anterior approach to be near 80%, but resolution of the sensory deficits has been observed in most patients over time.

The most likely organism to cause late infection in shoulder arthroplasty is Propionibacterium acnes. This is a slow growing organism that is present in over 50% of chronic infections. Staphylococcus epidermidis is the second most likely organism in this setting, present in 15% of cases. The other three organisms are unlikely to present with this clinical picture.

If wound healing does not occur and deep soft tissues such as the patellar tendon are exposed following TKA, a local rotational flap is the procedure of choice. The procedure should be performed relatively early after the recognition of a soft-tissue wound-healing problem. In the setting of TKA, the gastrocnemius muscle is an excellent source of flaps for wound coverage of the proximal tibia.

Patellar fractures that occur after a total knee arthroplasty are usually stress fractures. Integrity of the extensor mechanism precludes the need for surgical repair or internal fixation, while stability and fixation of the patellar component determine whether revision is indicated. A cylindrical cast and full weight bearing for 6 weeks is recommended for transverse fractures with an intact extensor mechanism and a stable component. A similar fracture, if vertical, may be treated with earlier motion.