The Effect of Knee Flexion Angle on the Neurovascular Safety of All-Inside Lateral Meniscus Repair: A Cadaveric Study.

Purpose: To evaluate if different knee flexion angles can modify the neurovascular injury risk during lateral meniscus repair.

Methods: Twenty cadaveric knees were studied. An all-inside suture device (FasT-Fix; Smith & Nephew, Andover, MA) was placed at the posterior horn and at the medial and lateral limits of the popliteal hiatus. The minimal distances between the device and the popliteal artery and peroneal nerve were measured with the knee at 90°, 45°, and 0° of flexion through a limited posterolateral arthrotomy.

Results: The distance between the device when inserted at the lateral edge of the popliteal hiatus and the peroneal nerve decreased from a median of 26 mm (interquartile range [IQR], 3.5 mm; range, 19 to 29 mm) at 90° to 21.5 mm (IQR, 4.5 mm; range, 14 to 25 mm) at 45° and 15.5 mm (IQR, 6.5 mm; range, 4 to 20 mm) at 0° (significant differences, P < .001). The distance between the device when inserted at the medial edge of the popliteal hiatus and the peroneal nerve decreased from 16 mm (IQR, 3.3 mm; range, 9 to 21 mm) at 90° to 12 mm (IQR, 4.3 mm; range, 9 to 16 mm) at 45° and 7 mm (IQR, 4.0; range, 4 to 15 mm) at 0° (significant differences, P < .001). The distance between the device when inserted at the medial edge of the popliteal hiatus and the popliteal artery decreased from 21 mm (IQR, 5.0 mm; range, 11 to 27 mm) at 90° to 19 mm (IQR, 5.0 mm; range, 10 to 23 mm) at 45° and 16 mm (IQR, 7.5 mm; range, 10 to 23 mm) at 0° (significant differences, P < .001). The distance between the device when inserted 5 mm lateral to the posterior root of the lateral meniscus and the popliteal artery decreased from 13 mm (IQR, 4.3 mm; range, 7 to 27 mm) at 90° to 10.5 mm (IQR, 4.3 mm; range, 4 to 19 mm) at 45° and 5.5 mm (IQR, 4.0 mm; range, 0 to 14 mm) at 0° (significant differences, P < .001).

Conclusions: The risk of injury to the popliteal artery or to the peroneal nerve during all-inside repair of the posterior half of the lateral meniscus is lower at 90° of flexion and increases with knee extension to 45° and 0°.

Clinical Relevance: All-inside meniscal repair of the lateral meniscus is safer with the knee at 90° of flexion.