title: Magnetic Resonance Imaging Evaluation of the Effects of Surgical Invasiveness on Paravertebral Muscles After Muscle-preserving Interlaminar Decompression (MILD).
abstract: This is a retrospective study.
  
  
  
  The aim of this study was to determine the extent of damage to the paravertebral muscles after muscle-preserving interlaminar decompression (MILD) using magnetic resonance imaging to evaluate changes in the multifidus muscle (MF).
  
  
  
  Short-term surgical outcomes of MILD for lumbar spinal canal stenosis (LSCS) are satisfactory; however, the extent of damage to the paravertebral muscles after MILD remains unclear.
  
  
  
  Thirty-four patients (18 men/16 women; mean age: 72.6 y) who had LSCS treated with MILD were retrospectively investigated. A total of 61 decompressed disk levels [L2/3(5); L3/4(21); L4/5(30); L5/S(5)] and 34 nondecompressed levels (L1/2) were assessed. There was 1 decompressed disk level in 12 cases, 2 in 17 cases, and 3 in 5 cases. Magnetic resonance imaging scans were obtained before surgery and at 3 and 12-18 months after surgery, using the same scanner. The rate of paravertebral muscle atrophy was evaluated to compare the area of the MF in the T2-weighted axial plane (intervertebral disk level) preoperatively and postoperatively, using OsiriX Medical Imaging Software. Changes in muscle signal intensity were also recorded. Statistical analysis was performed using 3-way analysis of variance with the post hoc Fisher PSLD test.
  
  
  
  The rate of MF atrophy was 4.0% at the decompressed levels and 2.1% at the nondecompressed levels. There were no changes of signal intensity in the MF between the preoperative and postoperative periods. In decompressed levels, muscle atrophy and signal intensity were significantly improved from 3 months to 12-18 months after surgery. The number and level of the decompressed disks did not affect the extent of muscle injury.
  
  
  
  The extent of paravertebral muscle injury after MILD is satisfactory. The midline interlaminar approach used in this technique may prevent local denervation and irreversible damage to the paravertebral muscles. These results indicate that MILD is useful to treat LSCS less invasively.
authors.affiliation: *Department of Orthopaedics, Graduate School of Medical Science, Kyoto Prefectural University of Medicine †Department of Orthopaedics, Japanese Red Cross Kyoto Daini Hospital, Kyoto, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tonomura
authors.forename: Yoichiro
authors.initials: Y
authors.lastname: Hatta
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Mikami
authors.forename: Takumi
authors.initials: T
authors.lastname: Ikeda
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Harada
authors.forename: Masateru
authors.initials: M
authors.lastname: Nagae
authors.forename: Hironori
authors.initials: H
authors.lastname: Koike
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Hase
authors.forename: Toshikazu
authors.initials: T
authors.lastname: Kubo
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019299:Decompression, Surgical / Q000379:methods*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D009135:Muscular Diseases / Q000000981:diagnostic imaging / Q000209:etiology; D064170:Paraspinal Muscles / Q000000981:diagnostic imaging / Q000503:physiopathology*; D012189:Retrospective Studies; D013130:Spinal Stenosis / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology* / Q000601:surgery*