[Postoperative, appositional ossifications after lumbar laminectomy]

Post-laminectomy segmental hypermobility as well as appositional ossification were suggested by many authors to contribute to the unsatisfactory long-term results of laminectomy. The aim of this study was to find out whether segmental instability, among other factors, influences the degree of appositional ossification following laminectomy.

55 out of 72 patients operated upon by laminectomy or hemilaminectomy for degenerative lumbar spinal stenosis were examined by radiography after an average follow-up period of 5.2 years. Appositional ossification at the site of surgery was evaluated in relation to lumbar instability, the number of segments undergoing laminectomy, and whether simultaneous fusion was done. Instability was determined by measuring angulation and translation using lateral flexion and extension views of the lumbar spine, whereas new-bone formation was best evaluated on antero-posterior radiographs.

94% of the patients had appositional ossification at the site of laminectomy. Patients undergoing simultaneous fusion with laminectomy had a significantly lower amount of appositional ossification compared to patients undergoing laminectomy without segmental fusion. Radiographically measured segmental instability, the number of segments undergoing laminectomy, age, and sex of the patients did not influence the extent of ossification.

Postoperative appositional ossification at the posterior site of resection are seen regularly following laminectomy. The extent of appositional ossification does correlate with lumbar fusions, but does not correlate with the extent of radiographically measured lumbar instability, the number of segments undergoing laminectomy, or the age and sex of the patients.

Simultaneous lumbar fusion with laminectomy is proved to be associated with less appositional ossification. Therefore lumbar fusion should be considered when planning surgery for spinal stenosis.