Posterior fusion of the lumbosacral spine. Evaluation of the operative results and the factors influencing them.

The operative results of 79 patients subjected to posterior fusion of the lumbosacral spine were evaluated on the basis of a follow-up examination performed on average 5.4 years after operation. A method of evaluation was developed which measured the patients' subjective improvement and working capacity. The method proved appropriate for clinical use and gave a more correct picture of the operative result than methods relying on the patients' own opinion or the radiographic assessment as the only criterion. Sixty per cent of the patients were subjectively improved, 40 per cent had returned to their previous or a corresponding occupation and 24 per cent had a good operative result, assessed by the method applied. A statistical analysis was performed in order to find the factors influencing the operative results. Age over 40 years, heavy or moderately heavy preoperative work and over 6 months' preoperative disability had a statistically significant, unfavourable effect on the results. In the case of labourers in heavy occupations, working capacity was seldom restored to a degree sufficient for return to their previous work. The operative technique proved reliable with 91 per cent successful fusions, assessed from functional radiographs. Successful fusion did not imply a good operative result, although it did so more often than non-fusion. On the basis of this study, operative fusion of the lumbosacral spine seems to be of relatively little value in the treatment of patients suffering from low back pain, and factors other than purely medical or surgical have a considerable influence on the operative results.