Abstract:

Spinous process fixation (SPF) has gained attention as a less invasive option for lumbar fusion surgery. Minimally invasive techniques are of interest in an elderly population due to decreased surgical time and post-operative complications. Clinical outcomes and fusion rates have not been determined in a large cohort. Our objective was to describe significant predictors of visual analog scale (VAS), length of stay, blood loss, fusion rates, and complication rates for patients treated for degenerative lumbar spondolysis with ISP fixation with and without supplemental instrumentation. Charts were assessed for post-operative VAS vs. pre-operative VAS at: 1-3, >3-6, and >6-12 months. To control confounding variables, VAS scores were modeled as a repeated-measures linear-mixed-model. In a sub-cohort CT images were assessed for interspinous and interbody (IB) fusion. The images were reviewed by an independent radiologist to evaluate fusion status. Eighty-six SPF patients (91 levels, mean age 67 years) were identified. After determining the model, age and sex remained predictors of VAS. Adjusting for age and sex, patients saw a decrease of 3.6 VAS points from baseline to three months (95% CI: 2.9-4.4, p< 0.0001) that was maintained over the six to 12 month follow-up period. A sub-cohort of 50 patients with CT scans were identified and assessed for ISP and IB fusion at a mean of 181 days postoperatively. Ninety-four percent of levels demonstrated ISP fusion. Sixty-one percent of solid ISP fusion patients also had an interbody cage, but this did not impact fusion rates. Eighty-six percent of these levels showed solid IB fusion (BSF-3). Of the four pseudoarthrosed levels, two had pedicle screw fixation, and two were IB and ISP fixation. Only two patients went on to re-exploration and explantation due to pain secondary to spinous process and/or lamina fracture. This elderly cohort treated with SPF demonstrated significant improvement in VAS with reliable fusion rates.

Authors:

Amir Vokshoor, MD, Neurosurgeon, Providence Saint John’s Health Center, Chief of Spine Section, Santa Monica, CA, Sanjay Khurana MD, Orthopedic Spine Surgeon, Saint John’s Health Center, Santa Monica, CA, Dean Wilson, PA-C, Physician Assistant, West Hills Hospital, West Hills, CA, Peter Filsinger MD, Radiologist, Kaiser Permanente Health Center, Woodland Hills, CA

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