The common peroneal nerve is most frequently injured in the lithotomy position when the lateral aspect of the knee is compressed against the stirrup, resulting in foot drop and a loss of dorsal extension of the toes. Similarly, the sciatic nerve can be damaged from excessive flexion of the hips, leading to weakness in all muscles below the knee and foot drop. The femoral nerve is vulnerable to injury when trapped under the inguinal ligament due to extreme flexion and abduction of the thighs, which causes a decreased knee jerk, loss of hip flexion, and knee extension.
In addition, the saphenous nerve can be compromised when the medial tibial condyle is compressed by a leg support in the lithotomy position, leading to paresthesia along the medial and anteromedial aspect of the calf. The anterior tibial nerve is at risk when the feet are plantar flexed for extended periods, such as in sitting or prone positions, resulting in foot drop. Lastly, the obturator nerve can be damaged during excessive flexion of the thigh to the groin or during difficult forceps delivery, causing an inability to adduct the leg and diminished sensation along the medial aspect of the thigh.
| Nerve | Mechanism | Deficit |
|---|---|---|
| Common peroneal | Lateral aspect of the knee compressed against the stirrup in lithotomy | Foot drop with loss of dorsal extension of the toes |
| Sciatic | Excessive flexion of the hips | Weakness in all muscles below the knee, foot drop |
| Femoral | Trapped under the inguinal ligament with extreme flexion and abduction of the thighs | Decreased knee jerk, loss of hip flexion and knee extension |
| Saphenous | Medial tibial condyle compressed by a leg support in lithotomy | Paresthesia along the medial and anteromedial calf |
| Anterior tibial | Feet plantar flexed for extended periods, as in sitting or prone positions | Foot drop |
| Obturator | Excessive flexion of the thigh to the groin, or difficult forceps delivery | Inability to adduct the leg, diminished sensation along the medial thigh |
