Proper entry point for femoral intramedullary guide in total knee arthroplasty.

Postoperative tibiofemoral alignment of the lower extremity is one of the most important factors that will assure a successful long-term outcome of a total knee arthroplasty. In this regard, most surgeons prefer to use an intramedullary guide than an extramedullary one for the femoral cut. However the entry point for the guiding rod is crucial for an appropriate femoral cut and femoral component positioning. The ideal entry point of the guiding rod should be the central axis of the distal femur in both coronal (anterior view) and sagittal planes (lateral view).The authors studied the proper entry point for the femoral intramedullary guiding rod in total knee arthroplasty by using the top of the femoral intercondylar notch as the referenced point.A series of radiographs for twenty-nine femurs from thirty-one cadavers, both anterior-posterior and lateral views, were evaluated in this study.75.8 percent of the entry points in the coronal plane were at least 1 mm medial to the top ofthefemoral intercondylar notch. 82.7 percent of the entry points in the sagittal plane were superior to the top of the femoral intercondylar notch more than 10 mm. The proper entry point at the distal femur should be 1.5 +/- 2.01 mm medial and 12 +/- 2.72 mm superior to the top of the femoral intercondylar notch.The result of this study could be useful for surgeons who prefer intramedullary guide system in total knee arthroplasty.