Journal of Bone & Joint Surgery - American Volume:
Letters to The Editor
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To The Editor:
The otherwise excellent article, “Comparison of the Vastus-Splitting and Median Parapatellar Approaches for Primary Total Knee Arthroplasty: A Prospective, Randomized Study. Surgical Technique” (2007;89 Suppl 2 Part 1:80-92), by Kelly et al., was marred by an error in the legend to Figure 1. The axial radiograph of the knee was mislabeled as “a Merchant radiograph of the patella.”
The shape and appearance of the dista part of the femur on the radiograph demonstrates that it is really a Settegast view. This technique requires the knee to be acutely flexed well beyond 90°, drawing the patella, which might otherwise be severely subluxated laterally at the trochlear level, into the intercondylar space to articulate with the distal, or weight-bearing, surface of the femoral condyles.
Conversely, the “Merchant” axial view radiograph is exposed with both knees flexed no more than 45°, showing the patella's true relationship to the trochlea1,2.
This may seem to be a minor point, but if the surgeon is not aware that the patella is subluxated laterally prior to surgery, he or she may not take sufficient measures to correct that subluxation during surgery. Many postoperative patellofemoral complications can be avoided if the surgeon is aware of this problem before surgery.
Disclosure: The author did not receive any outside funding or grants in support of his research for or preparation of this work. Neither he nor a member of his immediate family received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the author, or a member of his immediate family, is affiliated or associated.