Percutaneous hamstring lengthening in cerebral palsy and the risk of neurovascular transection

Percutaneous hamstring lengthening is increasingly popular due to its simplicity, fast recovery rate, and low morbidity. Neurovascular anatomy changes due to knee flexion contracture and the precise proximity of peroneal nerve and Biceps femoris tendon are not well established. This study examined (1) the coronal distance between the peroneal nerve and lateral hamstring tendon ("PLD"), and (2) the distance between the popliteal vessels and medial hamstring tendons ("VMD") to determine the safe distance for percutaneous hamstring lengthening.

This prospective study recruited cerebral palsy patients aged under 15 who needed hamstring lengthening. Ultrasonography was performed after the patients were anesthetized. PLDs and VMDs at popliteal angles (PAs) of 40°, 60°, and 80° knee flexions were collected.

Sixteen patients (32 knees) were enrolled. The mean minimum PLDs at PAs of 40°, 60°, and 80° were 3.5, 4.1, and 3.1 mm, respectively. The peroneal nerve physically touched the lateral hamstring tendon in 5/32 knees (15.6%). The mean minimum VMDs at PAs of 40°, 60°, and 80° were 19, 18.3, and 16.4 mm, respectively. One spastic diplegic patient had a minimum VMD < 3 mm on both sides. Changing the PAs demonstrated no statistical significance for both PLD and VMD (P value = 0.105 and 0.779, respectively).

Percutaneous medial hamstring lengthening should be done with caution. We recommend open biceps femoris surgery, with preoperative ultrasonography (to check the PLD) or peroneal nerve palpation to reduce the risk of peroneal nerve transection.