Surgical Outcomes of Instrumented and Uninstrumented Arthrodesis for Lumbar Spinal Stenosis: A Comparative...

Lumbar spinal stenosis (LSS) is a prevalent degenerative condition that severely impairs mobility and quality of life in older adults. Decompressive surgery, often combined with spinal arthrodesis, remains the cornerstone of treatment. However, the role of instrumentation, particularly the use of interbody cages, remains debated. Instrumented arthrodesis may enhance fusion and segmental stability but is associated with higher morbidity, while uninstrumented techniques are less invasive but may compromise long-term fusion. This study compared clinical, radiographic, and surgical outcomes of three approaches: decompression with instrumented arthrodesis using interbody cages, decompression with instrumented arthrodesis without cages, and decompression with uninstrumented arthrodesis.

In this prospective comparative study, 74 patients with LSS underwent one of the three procedures at a spine-specialized center and had ≥24 months of follow-up. Patients were stratified into Group 1 (n = 30), instrumented arthrodesis with interbody cages; Group 2 (n = 20), instrumented arthrodesis without cages; and Group 3 (n = 24), uninstrumented arthrodesis. Clinical outcomes were assessed using the Oswestry Disability Index (ODI), Roland-Morris Disability Questionnaire (RMDQ), Short Form-36 (SF-36), and Visual Analog Scale (VAS) for lumbar and radicular pain. Radiographic assessments included sagittal balance, lumbar lordosis, and fusion, which were carried out by two independent radiologists. Statistical analyses were performed using chi-square tests, paired and unpaired t-tests, Pearson correlations, and logistic regression.

All groups showed significant improvement in ODI, RMDQ, SF-36, and VAS scores (p < 0.001). Postoperative sagittal balance improved significantly in Groups 2 and 3 (p = 0.001), whereas changes in lumbar lordosis were not significant (p = 0.663). Fusion rates were highest in Group 2 (95%) and lowest in Group 3 (75%; p = 0.018). Complications were most frequent in Group 3 (20.8%), largely incidental durotomies and wound infections. Reoperations were most common in Group 1 (23%), predominantly due to adjacent segment disease and implant failure.

Despite comparable functional improvements, the three strategies demonstrated distinct radiographic and surgical profiles. Instrumented arthrodesis without cages achieved superior fusion and sagittal correction with fewer complications, whereas uninstrumented arthrodesis, though effective for symptom relief, carried higher intraoperative complication rates. Cage-assisted fusion did not improve clinical or radiographic outcomes and was associated with more reoperations, particularly due to adjacent segment disease. These findings support tailoring instrumentation to patient comorbidities, stability requirements, and the need for anterior column support.

All three surgical techniques improved function and pain in LSS patients. Instrumented arthrodesis without interbody cages provided the most favorable balance between fusion success and complication risk. Cages should be reserved for selected patients requiring sagittal realignment or foraminal restoration. Given the increased reoperation burden associated with instrumentation, surgical planning should be individualized, prioritizing stability, complication avoidance, and patient-specific risk factors, such as bone quality and comorbidities.