A histologie study of lumbar pseudarthrosis

Biopsy specimens were obtained from 35 consecutive patients undergoing pseudarthrosis repair after failed posterior spinal fusions. Biopsy specimens were obtained when possible from the fusion mass, from areas of motion, and from the lumbar facet remnant where identifiable. Tissue found between adjacent bony segments was noted to contain predominantly fibrous tissue often accompanied by signs of local fibrocartilaginous metaplasia. In addition, small fragments of impacted bone, sometimes seen to be undergoing active resorption, also were noted frequently in these areas. The bone adjacent to the areas of motion was sclerotic and poorly organized, containing a mixture of woven and lamellar bone. Interestingly, multiple microtrabecular fracture with appositional new bone formation was a frequently seen feature. All facet joint biopsies were noted to have evidence of degenerative disease. Both cartilage fissuring and significant chondrocyte cloning were noted. Subchondral bony sclerosis was also a consistent feature.