Multifidus innervation and muscle assessment post-spinal surgery
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Assessment of the integrity of the multifidus muscles and corresponding nerve roots, post-open (OSS) versus minimally invasive spinal surgery (MISS) for lumbar spine fractures.
We investigated the first six patients undergoing MISS in our institution and age- and sex-matched them with 6 random patients who previously had OSS. All had a similar lumbar fracture configuration without evidence of spinal cord injury. All were assessed using ultrasound muscle quantification and electromyographic studies at a minimum of 6 months post-operatively. Mean cross-sectional area (CSA) was measured at sequential levels within and adjacent to the operative field. Concentric needle electromyography was performed at instrumented and adjacent non-instrumented levels in each patient.
Mean CSA across all lumbar multifidus muscles was 4.29 cm2 in the MISS group, 2.26 cm2 for OSS (p = 0.08). At the instrumented levels, mean CSA was 4.21 cm2 for MISS and 2.03 cm2 for OSS (p = 0.12). At non-instrumented adjacent levels, mean CSA was 4.46 cm2 in the MISS group, 2.87 cm2 for OSS (p = 0.05).
Electromyography at non-instrumented adjacent levels demonstrated nerve function within normal limits in 5/6 levels in the MISS group compared to 1/6 levels in the OSS (p = 0.03). Instrumented levels demonstrated nerve function within normal limits in 5/12 levels in the MISS group compared with 4/12 in the OSS group, including moderate–severe denervation at 5 levels in the OSS group (p = 0.15).
Posterior instrumented MISS demonstrates a significantly superior preservation of the medial branch of the posterior ramus of the spinal nerve and less muscle atrophy, particularly at adjacent levels when compared to OSS.
KeywordsMinimally invasive Multifidus Spine Surgery Pedicle screw Electromyography Fracture
Medtronic for funding of co-authors to attend conference. The results of this study were presented at Britspine 2012 and Spineweek 2012.
Conflict of interest
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