Object: The aim of this study was to determine the extent of muscle injury caused by continuous or intermittent muscle retraction during macro- and microdiscectomy in lumbar disc surgery. Pain scores, serum creatine phosphokinase (CPK) levels, and histological findings obtained in muscle specimens were compared.
Methods: Sixty patients who underwent surgery for a one-level disc herniation during a 1-year period (January 2004-January 2005) and who had similar demographic characteristics were randomly assigned to one of four groups, each consisting of 15 patients: Group A, microdiscectomy in which the retractor was never released; Group B, microdiscectomy in which the retractor was released every 15 minutes; Group C, macrodiscectomy in which the retractor was never released; and Group D, macrodiscectomy in which the retractor was released every 15 minutes. Muscle biopsy samples were acquired in each group, and biochemical studies were conducted to determine serum CPK levels. The duration of muscle retraction was 15 minutes followed by 3 minutes of relaxation in Groups B and D. In all groups, muscle degeneration and elevation in serum CPK levels were observed immediately after surgery. The overall results, however, were different. The decline of serum CPK levels started 1 week after surgery. The smallest degree of muscle injury (reflected by the lowest serum CPK level) was observed in Group B. When the pre- and postoperative CPK values were compared in all groups, the patients in Groups B and D reported the least amount of back pain (p < 0.001). No significant differences in serum CPK levels were observed between Groups A and C or between Groups B and D. The extent of back pain was evaluated using a visual analog scale, and the consumption of analgesics was also assessed. The groups exhibited significantly different responses: the lowest analgesic consumption and the lowest pain scores were demonstrated in Groups B and D.
Conclusions: In this prospective randomized clinical trial, the authors determined that muscle injury during lumbar disc surgery was closely related to muscle retraction and relaxation times whereas the size of the paravertebral skin incision had no effect on postoperative back pain and disability. There was no significant difference among the groups in terms of back pain during the long-term follow-up period (18-19 months).