Risk of iatrogenic injury to the peroneal nerve during posterolateral femoral tunnel placement in double-bundle anterior cruciate ligament reconstruction.

BACKGROUND: There has been concern for iatrogenic injury to the peroneal nerve with posterolateral femoral tunnel placement in double-bundle anterior cruciate ligament reconstruction.

HYPOTHESIS: The common peroneal nerve and biceps tendon are at increased risk for injury by the guide wire as the knee is brought into increased extension.

STUDY DESIGN: Controlled laboratory study.

METHODS: An anatomical descriptive study was performed on 10 cadaveric knees (ages 49-67 years). After the native anterior cruciate ligament was removed arthroscopically, the posterolateral femoral tunnel starting point was identified using standardized measurements from the articular cartilage rim. With the use of a low-medial accessory portal and one cortical entry point, guide pins were inserted at 120 degrees, 90 degrees, and 70 degrees of knee flexion. The guide pins were kept in situ, and the lateral structures of the knee were dissected. The distance between guide pins and the common peroneal nerve, as well as the relationship to the biceps tendon, were analyzed.

RESULTS: The common peroneal nerve was not directly injured during any guide pin insertion. The mean distance from the guide pin at 120 degrees of flexion was 44.3 mm (range, 36-53 mm), compared with 28.6 mm (range, 25-32 mm) at 90 degrees of flexion and 22.8 mm (range, 20-28 mm) at 70 degrees of flexion. The differences between all 3 groups were statistically significant (P<.0001). Guide pins inserted at 70 degrees of flexion were also noted to pierce the biceps femoris tendon in all cases.

CONCLUSION AND CLINICAL RELEVANCE: During posterolateral femoral tunnel placement, the risk of injury to the common peroneal nerve is minimal but is increased as the knee is placed in less flexion. Guide pin placement at knee flexion of 120 degrees is recommended to ensure safety of the peroneal nerve and the biceps tendon.