Effect of hamstring and psoas lengthening on pelvic tilt in patients with spastic diplegic cerebral palsy

The purpose of this study was to evaluate the effects of hamstring lengthen ings and psoas recessions over the brim of the pelvis (OTB) on pelvic funct ion in the gait of patients with spastic cerebral palsy. Seventy-three pati ents were divided into four groups based on surgical intervention: medial h amstrings (n = 37), medial and lateral hamstrings (n = 12), medial hamstrin gs with psoas OTB (n = 9), and medial and lateral hamstrings with psoas OTB (n = 15). Three-dimensional gait analysis was completed both before and si milar to 1 year after surgery. When pelvic position in gait was normal or p osterior of normal preoperatively, there was a significant increase in pelv ic tilt (p < 0.05) when medial and lateral hamstrings were lengthened, irre spective of simultaneous psoas OTB surgery. Medial hamstrings alone, with o r without simultaneous psoas OTB, did not result in a significant change in pelvic position, irrespective of preoperative pelvic position. The only su rgical combination that caused a reduction in excessive preoperative anteri or pelvic tilt was medial and lateral hamstrings with psoas OTB, a 4 degree s change of limited clinical significance. Tn general, psoas and medial ham string surgery have minimal effect on the pelvic position during gait. Medi al and lateral hamstring lengthening will increase pelvic tilt if preoperat ive pelvic position is normal or slightly posteriorly tilted. The results o f this study suggest that the fundamental determinants of pelvic position d uring gait postoperatively are the extent of hamstring surgery (medial only vs. both medial and lateral hamstring lengthening) and the preoperative po sition of the pelvis.