title: Differences in muscle activities during shoulder elevation in patients with symptomatic and asymptomatic rotator cuff tears: analysis by positron emission tomography.
abstract: BACKGROUND
  Differences in muscle activity patterns between patients with symptomatic and asymptomatic full-thickness rotator cuff tears have not yet been fully clarified. The purpose of this study was to investigate the muscle activity pattern by use of positron emission tomography (PET) in patients with symptomatic and asymptomatic rotator cuff tears.
  
  
  METHODS
  Ten shoulders of 9 patients with full-thickness rotator cuff tears were divided into 2 groups by a numerical pain rating scale (0-10), symptomatic (≥2) and asymptomatic (0 or 1), with 5 shoulders each. Scaption exercise of bilateral arms (200 repetitions in 10 minutes) with a weight of 0.25 kg each was performed before and after injection of fluorodeoxyglucose. After PET examination, the standardized uptake value of each muscle was calculated to quantify its activity and compared between the two groups.
  
  
  RESULTS
  The activity of the anterior and middle deltoid was significantly decreased in the symptomatic group compared with the asymptomatic group (anterior deltoid, P = .02; middle deltoid, P = .03). In contrast, the activity of the superior trapezius was significantly increased in the symptomatic group compared with the asymptomatic group (P = .02).
  
  
  CONCLUSIONS
  In patients with a symptomatic tear, the deltoid activity was decreased and the trapezius activity was increased. It is likely that they might have moved the painful glenohumeral joint less and instead moved the painless scapulothoracic joint more during the prescribed exercise. We conclude that patients with painful rotator cuff tears use the parascapular muscles more than those without pain do during arm elevation.
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Nobuhisa
authors.initials: N
authors.lastname: Shinozaki
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan. Electronic address: sanohirotaka@med.tohoku.ac.jp.
authors.forename: Hirotaka
authors.initials: H
authors.lastname: Sano
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Rei
authors.initials: R
authors.lastname: Omi
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Koshi N
authors.initials: KN
authors.lastname: Kishimoto
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Yamamoto
authors.affiliation: Division of Cyclotron Nuclear Medicine, Cyclotron and Radioisotope Center, Tohoku University, Sendai, Japan.
authors.forename: Manabu
authors.initials: M
authors.lastname: Tashiro
authors.affiliation: Department of Orthopaedic Surgery, Tohoku University School of Medicine, Sendai, Japan.
authors.forename: Eiji
authors.initials: E
authors.lastname: Itoi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D018771:Arthralgia / Q000175:diagnosis / Q000209:etiology; D057645:Deltoid Muscle / Q000503:physiopathology*; D015444:Exercise; D005260:Female; D006801:Humans; D022125:Lacerations / Q000150:complications / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010147:Pain Measurement; D049268:Positron-Emission Tomography; D011187:Posture; D016059:Range of Motion, Articular / Q000502:physiology; D017006:Rotator Cuff / Q000000981:diagnostic imaging / Q000473:pathology; D000070636:Rotator Cuff Injuries; D012782:Shoulder / Q000000981:diagnostic imaging / Q000503:physiopathology*; D013708:Tendon Injuries / Q000000981:diagnostic imaging / Q000503:physiopathology*
keywords: Shoulder pain; arm elevation; asymptomatic rotator cuff tear; muscle activity; positron emission tomography