Traction injury to the sciatic nerve can occur during hamstring lengthening. The aim of this study was to monitor the influence of hamstring lengthening on conduction in the sciatic nerve using evoked electromyography (EMG).

Ten children with spastic cerebral palsy underwent bilateral distal hamstring lengthening. Before lengthening, the evoked potential was recorded with the patient prone. During lengthening, it was recorded with the knee flexed to 90°, 60° and 30°, and at the end of lengthening with the hip and knee extended.

In all patients, the amplitude of the evoked EMG gradually decreased with increasing lengthening. The mean decrease with the knee flexed to 60° was 34% (10 to 77), and to 30°, 86% (52 to 98) compared with the pre-lengthening amplitude. On hip extension at the end of the lengthening procedure, the EMG returned to the pre-lengthening level.

Monitoring of the evoked EMG potential of the sciatic nerve during and after hamstring lengthening, may be helpful in preventing traction injury.

Purpose: To investigate sciatic nerve conduction during hamstring lengthening.

Conclusion: Sciatic nerve traction is caused during hamstring lengthening.

Summary of method, results, and discussion: Ten children with spastic cerebral palsy underwent distal hamstring lengthening, average popliteal angel before surgery was 80 degrees.

Methods: The tendon of the semitendinosus was elongated by sliding lengthening. The gracilis tendon was cut and the tendons of the biceps and semimembranosus were elongated by dividing the aponeurosis. Thereafter to elongate the hamstring the hip and knee were flexed to 90 degrees and the knee slowly extended with continuous evoked EMG monitoring. Bipolar nerve stimulation placed near the sciatic nerve consisted of the delivering of rectangular impulses of amplitude 0.8-1.2 ma for 100 US duration. The EMG recordings were performed from the tibialis anterior muscle.

Results: In all patients motor potential amplitude gradually decreased during extension of knee (hamstring lengthening). The average decrease of the amplitude at popliteal angle of 60 degrees was 37 percent (16-75) and at 30 degrees 83 percent (36-98). The elongation was stopped at 30° of popliteal angle. On extending the hip and knee motor potential amplitude returned to normal. Discussion: Elongation of hamstring muscle is associated with traction on the f sciatic nerve as appears by decrease in sciatic nerve motor potential amplitude. To avoid nerve injury no excessive hamstring lengthening should be done and no nerve traction should be allowed at postoperative immobilization.

We have had experience of an 18-month-old boy with a cardiomyopathy who died a few minutes after removal of his cast with a saw, apparently from a malignant cardiac arrhythmia triggered by anxiety. We therefore examined the anxiety reaction to this method of removal of a plaster cast in 20 healthy children; ten were provided with hearing protectors and ten were not. The level of anxiety was assessed by measuring the heart rate, a known physiological indicator of anxiety, before, during and five minutes after removal of the cast. The noise level was also measured. The results showed a mean increase in heart rate during the procedure of 27.9 beats per minute (bpm) (26.9%) in the children with no hearing protectors and 10.4 bpm (11.1%) in children who used hearing protectors (p < 0.001). Five minutes after the procedure the heart rate had returned to the baseline rate in all patients.

We recommend that hearing protectors should be used in children undergoing removal of a plaster cast to decrease the anxiety reaction. If possible, clinicians should avoid the use of a saw for this purpose in children with a cardiomyopathy.