[Role of osteosynthesis in the consolidation of posterolateral arthrodesis: a comparative study in patients operated for lumbar stenosis].

PURPOSE OF THE STUDY

The main objective of this work was to determine the impact of osteosynthesis for posterolateral arthodesis on bone consolidation. We also tried to isolate factors predictive of nonunion and the effect of nonunion on the final outcome.

MATERIAL AND METHODS

We recaIIed for assessment patients who had undergone surgery for stenosis of the lumbar spine and who had a posterolateral lumbar or lumbosacral arthodesis in addition to the spinal decompression. Among a total of 98 operated patients, 31 had arthrodesis without instrumentation. These 31 patients were matched for age, sex, smoking habits, and extent of the fusion with 31 other patients who had an instrumented arthrodesis. Radiological and clinical assessment obtained preoperatively and at 6, 12, and 24 months postoperatively were available for all 62 patients.

RESULTS

Our two groups of patients were similar for comorbidity, number of arthodesis levels, fusion zone, extent and site of associated radicular release, lumbar lordosis, slope of the sacrum, global spinal mobility, and angular anteroposterior intersegmentary mobility of the different levels of the fusion zone, and interertebral sliding (site, degree, type, ante- or retrolisthesis). At last follow-up, rate of malunion was the same in the two groups (35 p. 100). Statistical analysis demonstrated three factors significantly associated with malunion: anteroposterior intersegmentary mobility, and especially angular mobility and disk height. Disk height was not however significant if it was associated with intersegmentary hypermobility. Other parameters studied, and notably use of ostheosynthesis material or not, preoperative comorbility, presence or not of preoperative intervertebral displacement, and level of the arthrodesis, had no effect.

DISCUSSION

Considering the type of arthrodesis studied (short fusion on a globally minimally mobile spine) the series demonstrated that the use of osteosynthesis material does not significantly increase the rate of fusion of posterolateral arthrodesis and that the mobility of the spinal segment involved is probably a more important predictive factor for the quality of the fusion.