Pathomechanism and prevention of further surgery after posterior decompression for lumbar spinal canal stenosis in patients with diffuse idiopathic skeletal hyperostosis

ABSTRACT BACKGROUND CONTEXT Diffuse idiopathic skeletal hyperostosis (DISH) is a risk factor for further surgery after posterior decompression without fusion for patients with lumbar spinal canal stenosis (LSS). However, a strategy to prevent revision surgery has not been described. PURPOSE The aim of this study was to review clinical and imaging findings in LSS patients with DISH extending to the lumbar segment and to propose countermeasures for prevention of revision surgery. STUDY DESIGN A retrospective study PATIENTS SAMPLE A total of 613 consecutive patients with LSS underwent posterior decompression without fusion at our hospital and had a minimum follow-up period of 2 years. We defined patients with DISH bridging to the lumbar segment as L-DISH cases (group D, n=111), and those without as non-L-DISH cases (group N, n=502). OUTCOME MEASURE Demographic data including the rate of revision surgery, neurological examination using Japanese Orthopaedic Association score, radiological studies comprised plain lumbar radiography, CT and high-resolution MRI were assessed. METHODS Clinical features and imaging findings were compared in patients with and without L-DISH. Revision surgery and surgical procedures (conventional laminotomy or lumbar spinous process-splitting (split) laminotomy) were examined in the two groups. No funding was received for this study. RESULTS L-DISH from L2 to L4 was a risk factor for disc degeneration such as a vacuum phenomenon and for further surgical treatment. The rate of revision surgery was higher in group D than in group N (9.0% vs. 4.0%, p=0.026). There was no significant difference in this rate for patients in groups D and N who underwent conventional laminotomy; however, for those who underwent split laminotomy, the rate was significantly higher in group D (16.7% vs. 2.1%, p=0.0006). Furthermore, the rate of revision surgery after split laminotomy at a lower segment adjacent to L-DISH was significantly higher than that after conventional laminotomy (37.5% vs. 7.7%, p=0.037). CONCLUSIONS A negative impact of lumbar spinous process-splitting laminotomy was found, especially with decompression at a lower segment adjacent to L-DISH. In such cases, surgery sparing the osteoligamentous structures at midline, including the spinous process and supra- and inter-spinous ligaments, should be selected.