[Results of lumbar and lumbosacral fusion: clinical and radiological correlations in 113 cases reviewed at 3.8 years]

Abstract

Purpose of the study: Spinal fusion requires the use of hardware for reduction and stabilization. We present the clinical and radiological behavior of a population of patients with lumbar and lumbosacral spinal fusion.

Materials and methods: Between 1990 and 1992, 113 patients were operated for lumbar and lumbosacral fusion. Mean age of the population was 43 years and mean follow-up was 3.8 years. Most of the fusions were L4-S1 fusions. 56% of the patients had a previous surgery. Thirteen patients in the series were reoperated and analyzed separately. In the majority of the cases, the indication for surgery was back pain with or without leg pain. Diagnoses were: spondylolisthesis, discopathy, scoliosis, and pseudoarthrosis. The spine was fused and reduced using two lordotic rods. Peroperative and postoperative lordosis were calculated on X-rays. Clinical results were analyzed with the Beaujon-Lassale score.

Results: Mean improvement was significantly better for spondylolisthesis than for other pathologies (85.6% versus 77.1%). Returning to work was possible for 85.5% of those with improvement and was not possible for 69.8%. The gain achieved in lordosis at surgery was lost at last follow-up. The lordosis of the construct appeared to protect against the development of discopathies above and below the construct. Discopathis led to a poor score. The rate of non-union was 7.9%, the rate of repeated surgery 6.1% and the rate of hardware removal 23.8%. At last follow-up, improvement was achieved in 45.6% of the 13 patients of the series who had repeat surgery.

Discussion: The results in our series are similar to those reported by others. Lumbar lordosis is an important factor: if lost, more interbody fusions may be subsequently required. Diagnosis of non-union is difficult and reoperation is the only sure manner to prove it by applying distraction-compression manoeuvres on the screws. All non-unions presented were symptomatic; incidence in the series was thus probably higher. Non-union and reoperation with a longer fusion are perhaps correlated with insufficient elasticity in the osteosynthesis. Optimal rod elasticity is a factor which remains to be defined.

Conclusion: Clinical results of lumbar and lumbosacral fusions are not unsatisfactory, but in our series almost one patient out of three had to be reoperated. One of the reasons for so many reoperations is certainly hardware rigidity. Hardware was not removed without testing the fusion as this is the only means of sure diagnosis of non-union. Reoperation should not be considered a failure in this difficult surgery of back pain which requires long-term surgical follow-up.