title: Serial changes in trunk muscle performance after posterior lumbar surgery.
abstract: METHODS
  Serial changes in trunk muscle performance were prospectively studied in 20 patients who underwent posterior lumbar surgery.
  
  
  OBJECTIVE
  To evaluate the influence of back muscle injury on postoperative trunk muscle performance and low back pain, to clarify the significance of minimization of back muscle injury during surgery.
  
  
  BACKGROUND
  The current investigators have reported examination of iatrogenic back muscle injury in an animal model and in humans. However, definite impairment caused by such back muscle injury has not been clarified.
  
  
  METHODS
  The patients were divided into a short-retraction-time group (< 80 minutes; n = 12) and a long-retraction-time group (> or = 80 minutes; n = 8). Before surgery and 3 and 6 months after surgery, the degree of back muscle injury was estimated by magnetic resonance imaging, and trunk muscle strength was measured. In addition, the incidence and severity of low back pain were serially analyzed.
  
  
  RESULTS
  Back muscle injury was directly related to the muscle retraction time during surgery. The damage to the multifidus muscle was more severe, and the recovery of extensor muscle strength was delayed in the long-retraction-time group. In addition, the incidence of postoperative low back pain was significantly higher in the long-retraction-time group.
  
  
  CONCLUSIONS
  Postoperative trunk muscle performance is dependent on the muscle retraction time. Thus, it is beneficial to shorten the retraction time to minimize back muscle injury and subsequent postoperative low back pain.
authors.affiliation: Department of Orthopaedic Surgery, Toyama Medical and Pharmaceutical University, Japan.
authors.forename: R
authors.initials: R
authors.lastname: Gejo
authors.forename: H
authors.initials: H
authors.lastname: Matsui
authors.forename: Y
authors.initials: Y
authors.lastname: Kawaguchi
authors.forename: H
authors.initials: H
authors.lastname: Ishihara
authors.forename: H
authors.initials: H
authors.lastname: Tsuji
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007405:Intervertebral Disc Displacement / Q000503:physiopathology / Q000601:surgery*; D007537:Isometric Contraction / Q000502:physiology; D007796:Laminectomy; D017116:Low Back Pain / Q000503:physiopathology; D008159:Lumbar Vertebrae / Q000503:physiopathology / Q000601:surgery*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000293:injuries / Q000503:physiopathology*; D011446:Prospective Studies; D013997:Time Factors