1589. How does minimally invasive lumbar decompression surgery impact lumbar muscle health?

Authors: Sohrab Virk; Avani Vaishnav, MBBS; Steven McAnany, MD; Todd Albert, MD; Sravisht Iyer, MD; Catherine Himo Gang, MD; Sheeraz Qureshi, MD, MBA (New York, NY)

Introduction: One of the benefits of minimally invasive spine (MIS) surgery is the muscle sparing nature of the approach. There has been little evidence quantifying the amount that paralumbar muscle changes during minimally invasive spine surgery. The goal of this study was to quantify the change in muscle health before and after MIS lumbar decompression surgery. Methods: We analyzed magnetic resonance imaging (MRI) to quantify muscle health using validated measures of cross sectional area using the lumbar indentation value (LIV) and lumbar muscle fatty atrophy using the Goutallier classification. T2 axial slices from the disc space at the operative level were analyzed. We graded fatty atrophy on a 0-4 scale and the LIV was calculated using standard techniques of measuring the distance between the tip of a spinous process and a line tangential to the muscular fascia. We also compared the average pre and post-operative Goutallier classifications and LIV’s using a student’s t-test. Results: A total of 19 patients had pre and post-operative MRI scans for lumbar radiculopathy. There were 21 disc spaces involved in these operations. The average age was 59.8+/-15.6 years old and there were 10 men and 9 women. The average gap between post-operative MRI and the primary surgery was 21.5+/-0.3 weeks. We found that the average pre-operative LIV was 15.7+/-7.2mm and the average post-operative LIV was 13.1+/-6.3mm which was not statistically difference (p = 0.22). The correlation between pre and post-operative LIV was significant (r^2 = 0.91, p = 0.96) and did indicate a proportionate decrease in LIV of 16.9% before and after surgery. Conclusion: Our findings demonstrate the minimal changes in fat atrophy after MIS lumbar decompression surgery. There is evidence of a decrease in muscle cross sectional area of paralumbar muscle after MIS decompressive surgeries as measured by LIV.