title: Rotator Cuff Weakness Is Not a Risk Factor for First-Time Anterior Glenohumeral Instability.
abstract: BACKGROUND
  Shoulder instability is a common problem in young athletes and can lead to pain and decreased ability to participate in high-level activities. Little is known about the modifiable risk factors for glenohumeral joint instability.
  
  
  OBJECTIVE
  Isometric shoulder strength at baseline would be a modifiable risk factor associated with subsequent first-time anterior instability events.
  
  
  METHODS
  Cohort study.
  
  
  METHODS
  Study participants were freshmen entering the United States Military Academy in June 2006. All participants completed bilateral isometric strength evaluations with a hand-held dynamometer at baseline upon entry into the study. Variables measured included internal and external rotation at 0° (IR0, ER0) and internal and external rotation at 45° of abduction (IR45, ER45). All subjects were followed for subsequent glenohumeral joint instability events until graduation in May 2010. Independent t tests were used to analyze the data.
  
  
  RESULTS
  Baseline strength data were available for 1316 shoulders with no prior history of instability, of which 26 went on to have an acute first-time anterior shoulder instability event while the individuals were at the academy. There were no significant differences in mean strength between shoulders that did not go on to develop instability (uninjured; n = 1290) and those that did develop anterior instability (injured; n = 26). The mean strength values in pounds of force for uninjured and injured shoulders, respectively, were as follows: IR0 (49.80 vs 49.29; P = .88), ER0 (35.58 vs 33.66; P = .27), IR45 (47.38 vs 46.93; P = .88), and ER45 (40.08 vs 38.98; P = .59).
  
  
  CONCLUSIONS
  No association was found between isometric shoulder strength measures at baseline and subsequent first-time anterior glenohumeral joint instability within the high-risk athletic population studied in this prospective cohort.
authors.affiliation: John A. Feagin Jr Sports Medicine Fellowship, Department of Orthopedic Surgery, Keller Army Hospital, United States Military Academy, West Point, New York, USA.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Roach
authors.affiliation: John A. Feagin Jr Sports Medicine Fellowship, Department of Orthopedic Surgery, Keller Army Hospital, United States Military Academy, West Point, New York, USA.
authors.forename: Kenneth L
authors.initials: KL
authors.lastname: Cameron
authors.affiliation: John A. Feagin Jr Sports Medicine Fellowship, Department of Orthopedic Surgery, Keller Army Hospital, United States Military Academy, West Point, New York, USA.
authors.forename: Richard B
authors.initials: RB
authors.lastname: Westrick
authors.affiliation: John A. Feagin Jr Sports Medicine Fellowship, Department of Orthopedic Surgery, Keller Army Hospital, United States Military Academy, West Point, New York, USA.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Posner
authors.affiliation: John A. Feagin Jr Sports Medicine Fellowship, Department of Orthopedic Surgery, Keller Army Hospital, United States Military Academy, West Point, New York, USA.
authors.forename: Brett D
authors.initials: BD
authors.lastname: Owens
keywords: isometric shoulder strength; risk factor; rotator cuff strength; shoulder instability