Infrapatellar Saphenous Nerve Is at Risk During Tibial Nailing: An Anatomic Study

To determine the location and stage of the tibial nailing procedure where infrapatellar saphenous nerve (IPSN) injury may occur. METHODS: Fourteen fresh-frozen right cadaveric knees underwent tibial nailing. Six knees underwent a suprapatellar approach and 8 a medial parapatellar approach. Two proximal medial-to-lateral screws were placed using the aiming guide. The incisions were then closed. After the procedure, medial retinacular and saphenous nerves were dissected under surgical 2.5× loupe magnification from a proximal to distal direction. The branch of the IPSN closest to the locking screws was measured, as was the distance between the IPSN branch and the inferior pole of the patella. RESULTS: Twelve of 14 cadavers had prominent IPSN (main branch from the saphenous proper) with an average of 2.5 sub-branches. The mean (SD) distance from the main branch of the IPSN to the inferior pole of the patella was 40.9 (24.4) mm. Four medial retinacular nerve branches, branching from the femoral nerve and not IPSN, were identified proximal to the patella during the medial parapatellar approach. All were cut after the medial parapatellar arthrotomy. The mean (SD) distance from the IPSN to the nearest locking screw was 10.2 (14.1) mm. Seven of 14 had IPSN injuries, and one had hamstring injury. Two direct screw entrapments occurred, whereas two IPSNs were lacerated by the incision. Suture closure entrapped three nerve branches, and one specimen had injured fibers of the hamstring tendinous insertion. CONCLUSIONS: Injury to the IPSN can occur at different locations and stages of tibial nailing, including approach, proximal locking screw insertion, and closure.