Review Question - QID 220005

Failure to recognize the presence of a hypoplastic lateral femoral condyle during total knee arthroplasty (TKA) of a valgus knee can lead to internal rotation of the femoral component, ultimately causing lateral patellar maltracking (Answer 2).

Patellar maltracking is a common complication after total knee arthroplasty (TKA). Patellar tracking is optimized by minimizing the Q-angle (lateralize the femoral and tibial components, medialize the patellar component), and by avoiding internal rotation of the femoral and tibial components. The femoral rotational alignment is regarded as a main factor that affects postoperative patellar maltracking, which was the main cause of revision TKA in the past, and external femoral rotation is considered effective in decreasing the risk of patellar maltracking.

Favorito et al. review the challenges and techniques for performing total knee arthroplasty (TKA) in patients with valgus knee deformities. They describe unrecognized deficiency of the lateral femoral condyle can lead to internal rotation of the femoral component, creating abnormal patellofemoral alignment, an increased Q-angle, and abnormal patellar tracking. The authors emphasize the importance of careful preoperative planning and intraoperative assessment to obtain a stable and well-functioning knee replacement in these complex cases.

Putman et al. review common patellar complications that can occur after total knee arthroplasty (TKA), such as fractures, instability, and implant-related issues. Risk factors for patellar complications include valgus, obesity, lateral retinacular release, and a thin patella. With regard to patellar instability, they describe the internal rotation of the femoral and tibial implants as a risk factor.

Figure A is an AP radiograph demonstrating severe valgus osteoarthritis of the knee.

Incorrect answers:
Answer 1: Kinematic alignment (KA) and mechanical alignment (MA) are both strategies to achieve a balanced knee, with the latter being the more traditional approach. Some authors have associated KA with patellar maltracking while others have refuted this association. Regardless of alignment strategy, surgeons must practice the fundamentals (minimize Q-angle and establish appropriate femoral rotation) to prevent patellar maltracking.
Answer 3: Raising the joint line has been implicated in mid-flexion instability. It is not, however, a contributor to patellar maltracking.
Answer 4: Excessive external rotation of the femoral component would contribute to good patellar tracking, but may also cause medial flexion looseness.
Answer 5: Extension of the femoral component is associated with notching of the femur.