Identification of the optimal intercondylar starting point for retrograde femoral nailing: an anatomic study.

BACKGROUND: Retrograde nailing of femoral shaft fractures is an effective and increasingly more popular method of fracture fixation. However, concern remains regarding the effect of the intercondylar entry-portal location on knee function.
METHODS: The optimal entry-portal location was identified in cadaver femurs. Approximating the clinical intraoperative situation, a threaded guidewire was inserted into each of 26 distal femur specimens and positioned in the center of the femoral shaft as determined by anteroposterior and lateral fluoroscopic imaging. Each guidewire was then overdrilled with a 12-mm cannulated drill bit. All entry-portal locations were recorded relative to the posterior cruciate ligament attachment and the intercondylar groove and mapped relative to the known patellofemoral contact area.
RESULTS: The starting holes averaged 6.21 mm anterior to the posterior cruciate ligament attachment and 2.67 mm medial to the intercondylar groove. Overall, 100% of starting portals were located in safe areas relative to the patellofemoral contact area.
CONCLUSION: In the vast majority of femurs, the optimal entry portal for retrograde femoral nailing (in line with the long axis of the femur) is located in the expected safe position, anterior to the posterior cruciate ligament insertion and slightly medial to center of the intercondylar groove. However, because of anatomic variability, the ideal starting position occasionally may be located in a patellofemoral contact area. Potential compromise of the patellofemoral contact area by the retrograde nail entry portal can and should be recognized before nailing, allowing the surgeon the option of altering the surgical technique.