Intraoperative force measurements during correction of scoliosis

Intraoperative forces applied to the spine were measured during the routine application of Harrington instrumentation for correction of scoliosis. This was accomplished by instrumenting the outrigger and distractor with strain gauges. Measurements were obtained in 16 patients undergoing their first operative procedure for scoliosis. Outrigger forces employed by two surgeons unapprised of the force data were not significantly different. Outrigger forces were significantly different for adolescent and adult groups of idiopathic scoliotics. Unusually low initial outrigger forces appeared to correlate with lower final correction obtained. In addition, in several cases transient distractor forces were observed that exceeded average levels at which bone failure is postulated to occur.