Native femoral sulcus as a guide for the position of the femoral component in primary total knee arthroplasty: a prospective comparative study of 420 knees.

A prospective randomized study was conducted to evaluate the effects of using the native femoral sulcus as a guide for the positioning of the femoral component in primary total knee arthroplasty (TKA), especially for patellar tracking. Between 2000 and 2002, 420 cases of primary TKA were collected. All the TKAs were performed with the same approach. The cases were randomly separated into two groups. In group 1 (consisting of 202 knees), the femoral insertion of the posterior cruciate ligament and the midline of the lateral-medial femoral condyles were used as a guide for the midline position of the femoral component; while in group 2 (consisting of 218 knees), the native femoral sulcus was used as the guide for the femoral component. Intraoperatively, no thumb technique was used to check the patellar tracking. In group 1, 16 knees (7.9%) received lateral retinacular releases, while none received lateral retinacular release in group 2 (P<0.0001). The average (range) follow-up period was 40 (30-56) months. In postoperative radiographic evaluation, two knees (1%) of lateral tilting of the patella were noted in group 1; while two knees (0.91%) of lateral tilting of the patella were noted in group 2 (P=0.751). In conclusion, native femoral sulcus could be a very effective and simple guide for the medial-lateral position of the femoral component, especially for patellar tracking. The prostheses used in this series were all Nexgen LPS-FLEX PCL Substituting (Zimmer, Warsaw) prostheses.