title: Multifidus innervation and muscle assessment post-spinal surgery.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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.
  
  
  RESULTS
  Mean CSA across all lumbar multifidus muscles was 4.29 cm(2) in the MISS group, 2.26 cm(2) for OSS (p = 0.08). At the instrumented levels, mean CSA was 4.21 cm(2) for MISS and 2.03 cm(2) for OSS (p = 0.12). At non-instrumented adjacent levels, mean CSA was 4.46 cm(2) in the MISS group, 2.87 cm(2) 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).
  
  
  CONCLUSIONS
  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.
authors: Department of Trauma and Orthopedic Surgery, Adelaide and Meath Hospital, Tallaght, Dublin 24, Ireland, derekcawley@hotmail.com.
authors: Derek T
authors: DT
authors: Cawley
authors: Michael
authors: M
authors: Alexander
authors: Seamus
authors: S
authors: Morris
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D004576:Electromyography; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008161:Lumbosacral Region / Q000294:innervation* / Q000601:surgery; D008297:Male; D008875:Middle Aged; D019060:Minimally Invasive Surgical Procedures / Q000379:methods*; D064170:Paraspinal Muscles / Q000294:innervation*; D011183:Postoperative Complications; D016103:Spinal Fractures / Q000601:surgery*
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