title: Hypertrophic changes of the teres minor muscle in rotator cuff tears: quantitative evaluation by magnetic resonance imaging.
abstract: BACKGROUND
  Few reports have assessed the teres minor (TM) muscle in rotator cuff tears. This study aimed to quantitatively analyze the morphologic changes of the TM muscle in patients with or without rotator cuff tears by magnetic resonance imaging (MRI).
  
  
  METHODS
  This retrospective study consisted of 279 subjects classified on the basis of interpretations of conventional MRI observations into 6 groups: no cuff tear; partial-thickness supraspinatus (SSP) tear; full-thickness SSP tear; SSP and subscapularis tears; SSP and infraspinatus (ISP) tears; and SSP, ISP, and subscapularis tears. With use of ImageJ software (National Institutes of Health, Bethesda, MD, USA) for oblique sagittal MRI, we measured the areas of ISP, TM, and anatomic external rotation (ISP + TM) muscles on the most lateral side in which the scapular spine was in contact with the scapular body. The occupational ratios of the TM muscle area to the anatomic external rotation muscle area were calculated. Ratios above the maximum of the 95% confidence intervals of the occupational ratio in the no-tear group were defined as hypertrophy of the TM muscle.
  
  
  RESULTS
  Occupational ratios of the TM muscle in the no-tear group followed a normal distribution, and ratios >0.288 were defined as hypertrophic. Hypertrophic changes of the TM muscle were confirmed in rotator cuff tears involving the ISP tendon. A negative correlation was found between the occupational ratios of TM and ISP (P < .001).
  
  
  CONCLUSIONS
  The TM muscle appeared hypertrophic in rotator cuff tears involving the ISP, and the progression of ISP muscle atrophy seemed to induce the development of this compensatory hypertrophy.
authors.affiliation: Department of Orthopaedic Surgery, Kumamoto Social Insurance General Hospital, Yatsushiro, Kumamoto, Japan. Electronic address: kikukawakenshi@yahoo.co.jp.
authors.forename: Kenshi
authors.initials: K
authors.lastname: Kikukawa
authors.affiliation: Department of Advanced Joint Reconstructive Surgery, Kumamoto University Hospital, Kumamoto University, Kumamoto, Japan.
authors.forename: Junji
authors.initials: J
authors.lastname: Ide
authors.affiliation: Negotiation Conflict Resolution and Administration, Graduate School of Social and Cultural Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Kikuchi
authors.affiliation: Department of Orthopaedic Surgery, Kumamoto Social Insurance General Hospital, Yatsushiro, Kumamoto, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Morita
authors.affiliation: Department of Orthopaedic Surgery, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Mizuta
authors.affiliation: Department of Orthopaedic Surgery, Kumamoto Social Insurance General Hospital, Yatsushiro, Kumamoto, Japan.
authors.forename: Hiroomi
authors.initials: H
authors.lastname: Ogata
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D018450:Disease Progression; D005260:Female; D006801:Humans; D006984:Hypertrophy; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000473:pathology*; D009133:Muscular Atrophy / Q000473:pathology; D012189:Retrospective Studies; D017006:Rotator Cuff / Q000473:pathology*; D000070636:Rotator Cuff Injuries; D013708:Tendon Injuries / Q000473:pathology*; D014481:United States; D055815:Young Adult
keywords: MRI evaluation; Teres minor muscle; atrophy; hypertrophic change; infraspinatus muscle; rotator cuff tear