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.