title: Denervation and atrophy of paraspinal muscles after open lumbar interbody fusion is associated with clinical outcome--electromyographic and CT-volumetric investigation of 30 patients.
abstract: BACKGROUND
  Different studies have shown that atrophy of paraspinal muscles arises after open dorsal lumbar fusion, and the reasons for this atrophy are still not yet fully clarified. This prospective study investigates the extent of atrophy of the lumbar paraspinal muscles after open lumbar interbody fusion, its possible causes, and their association with clinical outcome measures.
  
  
  METHODS
  Thirty consecutive patients were prospectively included (13 male, 17 female, median age 60.5 years, range 33-80 years). Mono or bisegmental, posterior lumbar interbody fusion and instrumentation was performed applying a conventional, open lumbar midline approach. Clinical outcome was assessed by the Short Form (36) Health Survey (SF-36) questionnaire and visual analogue scale. Needle electromyography of paraspinal muscles was performed preoperatively, at 6 and 12 months. Serum values of creatine kinase, lactate dehydrogenase and myoglobin were determined preoperatively, at day 2 after surgery and at discharge. Paraspinal muscle volume was determined by volumetric analysis of thin-slice computed tomography scans preoperatively and 1 year after surgery.
  
  
  RESULTS
  There was a significant increase of electromyographic denervation activity (p =0.024) and reduced recruitment of motor units (p = 0.001) after 1 year. Laboratory studies showed a significant increase of CK (p < 0.001) and myoglobin (p < 0.001) serum levels at day 2 after surgery. The paraspinal muscle volume decreased from 67.8 to 60.4 % (p < 0.001) after 1 year. Correlation analyses revealed a significant negative correlation between denervation and muscle volume (K = -0.219, p = 0.002). Paraspinal muscle volume is significantly correlated with physical outcome (K = 0.169, p = 0.020), mental outcome (K = 0.214, p = 0.003), and pain (K = 0.382, p < 0.001) after 1 year.
  
  
  CONCLUSIONS
  Atrophy of paraspinal muscles after open, posterior lumbar interbody fusion seems to be associated with denervation, as well as direct muscle trauma during surgery. While muscle atrophy is also correlated with a worse clinical outcome, it seems to be a determining factor for successful lumbar spine surgery.
authors.affiliation: Department of Neurosurgery, Jena University Hospital - Friedrich Schiller University Jena, Erlanger Allee 101, 07747, Jena, Germany, albrecht.waschke@med.uni-jena.de.
authors.forename: Albrecht
authors.initials: A
authors.lastname: Waschke
authors.forename: Christin
authors.initials: C
authors.lastname: Hartmann
authors.forename: Jan
authors.initials: J
authors.lastname: Walter
authors.forename: Pedro
authors.initials: P
authors.lastname: Dünisch
authors.forename: Falko
authors.initials: F
authors.lastname: Wahnschaff
authors.forename: Rolf
authors.initials: R
authors.lastname: Kalff
authors.forename: Christian
authors.initials: C
authors.lastname: Ewald
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003714:Denervation / Q000379:methods; D004576:Electromyography; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D009133:Muscular Atrophy / Q000209:etiology* / Q000503:physiopathology; D064170:Paraspinal Muscles / Q000294:innervation* / Q000503:physiopathology / Q000601:surgery*; D011446:Prospective Studies; D013123:Spinal Fusion / Q000009:adverse effects* / Q000379:methods; D016896:Treatment Outcome