Spinal canal and dural sac morphometry as demonstrated by CT scan analysis in patients undergoing chemonucleolysis for the treatment of herniated lumbar discs was analyzed in an attempt to develop a method of predicting positive or negative follow-up clinical results. The morphometry of the canal and dural sac at the intervertebral disc level was defined by reviewing normal levels of CT scans. Levels with herniated discs were then analyzed for comparison of treatment results between successful and unsuccessful procedures. The concept of spinal reserve capacity was evaluated. Significant differences between canal morphometric parameters of patients with treatment success or failure were then identified. The concept of spinal reserve capacity may be applicable in spinal stenosis, but we were unable to delineate any predictive value in the evaluation of patients with herniated lumbar discs undergoing chemonucleolysis.