CLINICAL OUTCOMES AND RADIOLOGICAL INSTABILITY FOLLOWING DECOMPRESSIVE LUMBAR LAMINECTOMY FOR DEGENERATIVE SPINAL STENOSIS - A COMPARISON OF PATIENTS UNDERGOING CONCOMITANT ARTHRODESIS VERSUS DECOMPRESSION ALONE

One hundred twenty-four patients with degenerative lumbar stenosis und erwent decompression with fusion (32 patients) and without fusion (92 patients) during a 30-month period between 1986 and 1988. Patient-repo rted satisfaction at a mean follow-up period of 5.8 years (range 4.6-6 .8 years) revealed a 79% good or fair outcome and a 21% poor outcome ( 26 patients). Seven patients (6%) developed lumbar instability, three patients (2%) developed new stenosis at an adjacent unoperated level, and three patients (2%) developed a new disc herniation between 2 and 5 years after surgery. Progressive postoperative spondylolisthesis occ urred in 31% of patients with normal preoperative alignment (mean 7.8 mm, range 2-20 mm) and in 73% of patients with preoperative subluxatio n (mean 5.1 mm, range 2-13 mm) in whom fusion was nor attained. Radiol ogical progression did not correlate well with patient-reported outcom e. The major conclusions from this study are the following: 1) the maj ority of patients respond well to this surgery, but complication (22%) and late deterioration (10%) rates are not insignificant; 2) radiolog ical instability is common after decompression for degenerative lumbar spinal stenosis, but this correlates poorly with clinical outcome; 3) there are no definitive clinical or radiological factors that preoper atively predict patients at risk for a poor outcome; 4) postoperative radiological instability is more Likely to occur when the following cr iteria are present: preoperative spondylolisthesis, abnormal motion de tected on preoperative dynamic imaging, decompression occuring across a minimally degenerated L-4 or a markedly degenerated L-3 disc; and wh en a radical and extensive decompression greater than one level is pla nned; and 5) the group at greatest risk for a poor outcome consists of those patients with normal preoperative alignment who do not suffer s lippage following surgery.