Back muscle injury after posterior lumbar spine surgery - A histologic and enzymatic analysis

Study Design. Back muscle injury after posterior lumbar surgery was studied by muscle histology and serum creatine phosphokinase MM isoenzyme activity. Objective. To investigate intraoperative factors influencing the magnitude of back muscle injury after posterior lumbar surgery. Summary of Background Data. The authors previously have reported iatrogenic back muscle injury in an animal model and in humans. Serious injury of the back muscle has been shown by short-term and long-term follow-up evaluation. Methods. The retraction pressure was monitored, and the retraction pressure-time products were calculated in 24 patients. Early histologic changes of multifidus muscle, which were taken at completion of surgery, and serum creatine phosphokinase MM isoenzyme activity changes were examined. Results. The magnitude of back muscle injury was significant as the pressure-time product increased. Creatine phosphokinase MM isoenzyme activity increased after surgery and reached a plateau 1 days after surgery, followed by recovery to the normal value 1 week after surgery. Creatine phosphokinase MM isoenzyme activity tended to be high in cases with multilevel exposure and with high pressure-time product. Conclusions. Back muscle injury occurs in all patients who underwent posterior lumbar surgery, and these injuries are related to the retraction pressure, time, and extent of exposure.