title: A longitudinal MRI study of muscle atrophy during lower leg immobilization following ankle fracture.
abstract: OBJECTIVE
  To investigate MRI biomarkers of muscle atrophy during cast immobilization of the lower leg.
  
  
  METHODS
  Eighteen patients (8 male, 10 female), who had one lower leg immobilized in a cast, underwent 3.0 Tesla (T) MR imaging 5, 8, 15, 29, and 43 days after casting. Measurements were made on both lower legs of total muscle volume. Cross-sectional area (CSA), fractional water content, and T(2) were measured in tibialis anterior (TA), gastrocnemius medialis (GM) and lateralis (GL) and soleus (SOL). Fiber pennation angle was measured in GM.
  
  
  RESULTS
  Total muscle volume decreased by 17% (P < 0.001) over the 6 weeks of immobilization. The greatest loss in CSA (mean[SD]) was seen in GM (-23.3(8.7)%), followed by SOL (-19.0(9.8)%), GL (-17.1(6.5)%), and TA (-10.7(5.9)%). Significant reductions of CSA were also detectable in the contra-lateral leg. T(2) increased in all muscles: TA 27.0(2.5) ms to 29.6(2.8) ms (P < 0.001), GM 34.6(2.9) ms to 39.8(5.4) ms (P < 0.001) and SOL 34.4 (2.9) ms to 44.9(5.9) ms (P < 0.001). Small reductions were found in fractional water content. Pennation angle decreased in the cast leg (P < 0.001).
  
  
  CONCLUSIONS
  Quantitative MR imaging can detect and monitor progressive biochemical and biophysical changes in muscle during immobilization.
authors: Musculoskeletal Research Programme, University of Aberdeen, Aberdeen, Scotland, United Kingdom.
authors: Maria
authors: M
authors: Psatha
authors: Zhiqing
authors: Z
authors: Wu
authors: Fiona M
authors: FM
authors: Gammie
authors: Aivaras
authors: A
authors: Ratkevicius
authors: Henning
authors: H
authors: Wackerhage
authors: Jennifer H
authors: JH
authors: Lee
authors: Thomas W
authors: TW
authors: Redpath
authors: Fiona J
authors: FJ
authors: Gilbert
authors: George P
authors: GP
authors: Ashcroft
authors: Judith R
authors: JR
authors: Meakin
authors: Richard M
authors: RM
authors: Aspden
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D016512:Ankle Injuries / Q000473:pathology* / Q000628:therapy*; D002370:Casts, Surgical; D005260:Female; D050723:Fractures, Bone / Q000473:pathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D007866:Leg / Q000473:pathology*; D008137:Longitudinal Studies; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009133:Muscular Atrophy / Q000473:pathology*