Application and results of the AO internal fixation system in nontraumatic indications.

The AO internal skeletal fixation system (ISFS) permits posterior spine fixation to be restricted to the vertebrae immediately adjacent to the lesion and allows manipulation of each instrumented vertebra in three planes. In a prospective study to assess the value of this fixation for adult spinal disorders, 68 patients were reviewed. The device was used in spondylolisthesis, postlaminectomy instability, post-traumatic kyphosis, degenerative scoliosis, spinal stenosis, tumors, and infections. A total of 322 transpedicular screws have been inserted without neurologic complication. Satisfactory results were achieved in 88% of the patients, and only four pseudarthroses (6%) occurred. The ISFS provides rigid stabilization to enhance bone graft consolidation and to allow rapid postoperative mobilization in a light external orthosis.