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

Purpose of the study The main objective of this work was to determine the i mpact 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 recalled for assessment patients who had undergone surgery for stenosis of the lumbar spine and who had a posterolateral lumbar or lumbosacral arth odesis in addition to the spinal decompression. Among a total of 98 operate d patients, 31 had arthrodesis without instrumentation. These 31 patients w ere matched for age, sex, smoking habits, and extent of the fusion with 31 other patients who had an instrumented arthrodesis. Radiological and clinic al assessment obtained preoperatively and at 6, 12, and 24 months postopera tively were available for all 62 patients. Results Our two groups of patients were similar for comorbidity, number of arthodes is levels, fusion zone, extent and site of associated radicular release, lu mbar lordosis, slope of the sacrum, global spinal mobility, and angular ant eroposterior intersegmentary mobility of the different levels of the fusion zone, and interertebral sliding (site, degree, type, ante- or retrolisthes is). At last follow-up, rate of malunion was the same in the two groups (35 p. 100). Statistical analysis demonstrated three factors significantly ass ociated with malunion: anteroposterior intersegmentary mobility, and especi ally angular mobility and disk height. Disk height was not however signific ant if it was associated with intersegmentary hypermobility. Other paramete rs studied, and notably use of ostheosynthesis material or not, preoperativ e 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 g lobally minimally mobile spine) the series demonstrated that the use of ost eosynthesis material does not significantly increase the rate of fusion of posterolateral arthrodesis and that the mobility of the spinal segment invo lved is probably a more important predictive factor for the quality of the fusion.