Study design: Serial changes in trunk muscle performance were prospectively studied in 20 patients who underwent posterior lumbar surgery.
Objective: To evaluate the influence of back muscle injury on postoperative trunk muscle performance and low back pain, to clarify the significance of minimization of back muscle injury during surgery.
Summary of background data: The current investigators have reported examination of iatrogenic back muscle injury in an animal model and in humans. However, definite impairment caused by such back muscle injury has not been clarified.
Methods: The patients were divided into a short-retraction-time group (< 80 minutes; n = 12) and a long-retraction-time group (> or = 80 minutes; n = 8). Before surgery and 3 and 6 months after surgery, the degree of back muscle injury was estimated by magnetic resonance imaging, and trunk muscle strength was measured. In addition, the incidence and severity of low back pain were serially analyzed.
Results: Back muscle injury was directly related to the muscle retraction time during surgery. The damage to the multifidus muscle was more severe, and the recovery of extensor muscle strength was delayed in the long-retraction-time group. In addition, the incidence of postoperative low back pain was significantly higher in the long-retraction-time group.
Conclusions: Postoperative trunk muscle performance is dependent on the muscle retraction time. Thus, it is beneficial to shorten the retraction time to minimize back muscle injury and subsequent postoperative low back pain.