Functional and radiological outcome of modified spinous process osteotomy (MSPO) technique in decompressive surgery for lumbar canal stenosis

Introduction: The Modified Spinous Process Osteotomy (MSPO) surgery is done for degenerative spinal canal stenosis which gives adequate exposure and avoid iatrogenic instability and long segment fusion following conventional laminectomy. The objective of this article is to evaluate clinical and radiological results of the MSPO. Materials and Methods: Total 20 patients (13 male and 7 female) were included and studied prospectively with multilevel degenerative lumbar canal stenosis that were operated for posterior decompression by MSPO and laminectomy after detailed clinical and radiological work up. Regular follow up was done at 6 weeks 3 months and 1 year, clinical assessment for leg pain and back pain done by VAS, functional measurement of disability by Oswestry Disability Index (ODI) done. Dynamic view X-ray of lumbar spine taken and compared to the preoperative X-ray. CT scan was taken at 1 year post op to assess the union of spinous process. Results: All patients were followed up for 3 years. All patients recovered completely from thigh and leg pain and no patients had neurological deterioration. VAS for LBA and leg pain improved significantly along with significant improvement in ODI. The overall results were good to excellent in 93% of the patients, fair in 7% and no poor outcome. All patients were satisfied with the outcome at the last follow-up. The osteotomised spinous process eventually united with the retained laminar bridge in all patients. Conclusion: A less invasive and less techniquelly demanding MSPO technique provides better exposure and visualization, retaining median structures with least disturbance of kinematics of the lumbar spine. This procedure gives advantages for early ambulation and normalisation of patient's lifestyle and early return to work.