Object: Muscle injury is inevitable during surgical exposure of the spine and is quantified by the release of creatine phosphokinase (CPK). No studies have been conducted on different spinal approaches and nonspinal surgery with regard to muscle injury. The present prospective cohort study was conducted to evaluate the results of postoperative serum CPK as an indicator of muscle injury in relation to various spinal and nonspinal procedures.
Methods: The authors analyzed data in 322 consecutive patients who had undergone 257 spinal and 65 nonspinal procedures. Primary procedures were performed in 264 patients and revision surgeries in 58. Spinal procedures were subdivided according to the degree of surgical invasiveness as follows: minimally invasive (microendoscopic lumbar discectomy, unilateral transflaval discectomy, and minithoracotomy), average invasiveness (bilateral lumbar discectomy, laminectomy, and anterior cervical discectomy), and extensive surgery (instrumented single or multilevel spondylodesis of the entire spinal column). Spinal localization, number of spinal levels involved, surgical approach, duration of surgery, and body mass index (BMI) were recorded. Creatine phosphokinase was measured before surgery and 1 day after surgery, and the CPK ratio (that is, the difference within one patient) was used as the outcome measure.
Results: There was a significant dose-response relationship between the CPK ratio and the degree of surgical invasiveness; extensively invasive surgery had the highest CPK ratio and minimally invasive surgery had the lowest. Thoracolumbar surgery had a significantly higher CPK ratio compared with those for cervical and nonspinal surgery. There was a slightly negative relationship between the number of spinal segments involved and the CPK ratio. The CPK ratio in revision surgery was significantly higher than in primary surgery. Posterior surgical approaches had a higher CPK ratio, and the ratios for unilateral compared with bilateral approaches were not significantly different. The duration of surgery and preoperative serum level of CPK significantly influenced postoperative CPK. There was also a significant association between CPK ratio and nonspinal surgery. Age, sex, and BMI were not significant factors.
Conclusions: Data in this study have shown a dose-response relationship between CPK and the extent of surgical invasiveness. Thoracolumbar surgery, posterior approaches, duration of surgery, revision surgery, and preoperative value of CPK were significant influencing factors for the CPK ratio. The clinical significance of the results in the present study is not known.