There is considerable debate among spine surgeons regarding whether fusion should be used to augment decompressive surgery in patients with symptomatic lumbar spinal stenosis involving Grade I degenerativespondylolisthesis. The authors prospectively evaluated the outcomes of patients treated between 2000 and 2002 at two institutions to determine whether fusion improves functional outcome1 year after surgery.

Patients ranged in age from 50 to 81 years. They presented with degenerativeGrade I (3- to 14-mm) spondylolisthesis and lumbarstenosis without gross instability (< 3 mm of motion at the level of subluxation). Those in whom previous surgery had been performed at the level of subluxation were excluded. Each patient completed Oswestry Disability Index (ODI) and Short Form-36 (SF-36) questionnaires preoperatively and at 6 to 12 months postoperatively. Some patients underwent decompression alone (20 cases), whereas others underwent decompression and posterolateral instrumentation-assisted fusion (14 cases), at the treating surgeon's discretion. Baseline demographic data, radiographic features, and ODI and SF-36 scores were similar in both groups. The 1-year fusion rate was 93%. Both forms of surgery independently improved outcome compared with baseline status, based on ODI and SF-36 physical component summary (PCS) results (p < 0.001). Decompression combined with fusion led to an improvement in ODI scores of 27.5 points, whereas decompression alone was associated with a 13.6-point increase (p = 0.02). Analysis of the SF-36 PCS data also demonstrated a significant intergroup difference (p = 0.003).

Surgery substantially improved 1-year outcomes based on established outcomes instruments in patients with Grade I spondylolisthesis and stenosis. Fusion was associated with greater functional improvement.