title: Hypertrophic teres minor restores shoulder strength and range of external rotation in posterosuperior rotator cuff tears.
abstract: BACKGROUND
  In posterosuperior rotator cuff tears (PS-RCT), the progression of infraspinatus (ISP) muscle atrophy seems to induce compensatory hypertrophy of the teres minor (TM) muscles. However, the effect of these changes on shoulder strength and range of external rotation (ER) remains unclear. This study determined the strength and range of ER in patients with PS-RCT with atrophic ISP and hypertrophic TM and compared this with patients with PS-RCT and normal or deficient TM.
  
  
  METHODS
  We investigated 35 patients with PS-RCT and atrophic ISP. TM muscles were classified as hypertrophic (type A) in 17, normal (type B) in 10, or deficient (type C) in 8. The strength ratio of the affected shoulder to the healthy contralateral shoulder was calculated, and the active range of motion was measured for both shoulders.
  
  
  RESULTS
  The strength ratios of ER in types A, B, and C were 60%, 33%, and 7% (P < .01) with the patient's arm at the side and were 60%, 35%, and 5% (P < .001) at 90° abduction, respectively. The average ranges of ER in types A, B, and C were 22.6°, 15.0°, and -12.5° (P < .001) with the patient's arm at the side and were 71.6°, 44.5°, and 21.9° at 90° abduction (P < .01), respectively. The differences between shoulder types in other measures of strength or ER range were not significant.
  
  
  CONCLUSIONS
  In patients with PS-RCT and atrophic ISP, shoulders with compensatory hypertrophy of the TM had greater strength and range of ER than shoulders with normal or atrophic TM.
authors.affiliation: Department of Orthopaedic Surgery, Kumamoto General Hospital, Japan Community Healthcare Organization, 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: Department of Rehabilitation, Kumamoto General Hospital, Japan Community Healthcare Organization, Yatsushiro, Kumamoto, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Terakawa
authors.affiliation: Department of Orthopaedic Surgery, Kumamoto General Hospital, Japan Community Healthcare Organization, Yatsushiro, Kumamoto, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Takada
authors.affiliation: Department of Orthopaedic Surgery, Kumamoto General Hospital, Japan Community Healthcare Organization, Yatsushiro, Kumamoto, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Morita
authors.affiliation: Department of Orthopaedic Surgery, Kumamoto General Hospital, Japan Community Healthcare Organization, Yatsushiro, Kumamoto, Japan.
authors.forename: Kenzo
authors.initials: K
authors.lastname: Hashimoto
authors.affiliation: Department of Orthopaedic Surgery, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Mizuta
mesh_terms: D000222:Adaptation, Physiological; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D006801:Humans; D006984:Hypertrophy; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology*; D009133:Muscular Atrophy / Q000473:pathology; D011446:Prospective Studies; D016059:Range of Motion, Articular / Q000502:physiology; D012399:Rotation; D017006:Rotator Cuff / Q000473:pathology*; D000070636:Rotator Cuff Injuries / Q000503:physiopathology*; D012785:Shoulder Joint / Q000502:physiology*
keywords: Hypertrophy; atrophy; compensatory; infraspinatus; rotator cuff tear; teres minor