The Safe Zone for Femoral Cross-Pin Fixation –An Anatomical Study

Abstract

Femoral cross-pin fixation in anterior cruciate ligament (ACL) reconstruction has a potential for neurovascular injury, thus a "safe zone" must be defined for safe pin passage with this technique. In this anatomic study, femoral-sided, arthroscopic-assisted ACL reconstruction using the TransFix system (Arthrex, Naples, Fla) was performed on five fresh extended thigh and lower leg cadavers. Using a goniometer, five cross-pin guidewires were sequentially drilled at 0 degrees, -20 degrees, -40 degrees, +20 degrees, and +40 degrees, using the parallel to floor line as 0 degrees. Negative was defined as starting the pin more posteriorly, and positive was defined as starting the pin more anteriorly. Distance from the pin to the peroneal nerve, saphenous nerve, and femoral artery was measured after pin placement, and measurements were averaged. The peroneal nerve was at minimal risk with average distance to the guide pin of 1.87, 2.13, 2.45, 2.74, and 3.05 cm at -40 degrees, -20 degrees, 0 degrees, +20 degrees, and +40 degrees, respectively. The saphenous nerve was an average distance of 2.19, 1.98, 1.41, 1.42, and 1.29 at -40 degrees, -20 degrees, 0 degrees, +20 degrees, and +40 degrees, respectively. The femoral artery was an average distance of 1.81, 1.51, 0.78, 0.46, and 0.08 cm at -40 degrees, -20 degrees, 0 degrees, +20 degrees, and +40 degrees, respectively. Based on this anatomical study, the absolute neurovascular safe zone during cross-pin guidewire placement is from +20 degrees (0 degrees parallel to floor line) and -40 degrees (lowering guide more posterior).