The present study compared the computed tomography (CT) scan muscle area/muscle density and isokinetic trunk strength of a group of spinal surgery patients (35 males and 11 females) 3 months postoperatively. Analyses showed trunk strength means to be below 50% of gender-specific "normal" values obtained by evaluating a normative sample. Extensor strength was more significantly affected than flexors. Single-cut CT scans performed at the time of isokinetic trunk strength assessment demonstrated psoas and erector spinae atrophy through a significant decrease in muscle density, with only a trend towards decreased cross-sectional area. Findings also indicated that there was a significant correlation between increased mechanical trunk strength performance and greater muscle density on CT scan. Strength was significantly lower for the male patients undergoing spinal fusion compared with those undergoing disc excision. However, no significant difference was found in strength measures between: males with high versus low pain level and working versus nonworking males at the time of evaluation.