title: Glenohumeral contact pressure in a simulated active compression test using cadaveric shoulders.
abstract: BACKGROUND
  The active compression test has been described to detect superior labrum anterior and posterior (SLAP) lesions. Some have speculated that contact between the lesser tuberosity and the superior glenoid in the testing position causes a positive test. This study evaluated the location of peak glenohumeral contact pressures during a simulated active compression test in a cadaveric model with and without SLAP lesions.
  
  
  METHODS
  Six specimens were tested. A pressure sensor was used to record glenohumeral contact, and a motion analysis system was used to measure humeral head translation. Contact pressures and translations were measured during serial deltoid and biceps loads. These were repeated for small and large SLAP lesions.
  
  
  RESULTS
  There was a notable shift in the location of peak contact pressure from the anterior-inferior glenoid to the anterior-superior glenoid with increasing deltoid load. Deltoid loading translated the humeral head posteriorly relative to the glenoid. Conversely, biceps loads countered the pull of the deltoid only when the biceps load was greater than the deltoid load. The SLAP tears did not significantly alter the degree of humeral head translation or location of the contact pressures.
  
  
  CONCLUSIONS
  In the active compression test, the posterior capsule is taut and the anterior capsule is lax, which permits the deltoid to translate the humeral head posteriorly. This shift in the peak contact pressure to the superior glenoid may elicit a positive active compression test.
  
  
  METHODS
  Basic Science Study, Biomechanics, Cadaver Model.
authors.affiliation: Orthopaedic Biomechanics Laboratory, Veterans Administration Long Beach Healthcare System, Long Beach, CA, USA.
authors.forename: Tony
authors.initials: T
authors.lastname: Lin
authors.forename: Pooya
authors.initials: P
authors.lastname: Javidan
authors.forename: Michelle H
authors.initials: MH
authors.lastname: McGarry
authors.forename: Guillem
authors.initials: G
authors.lastname: Gonzalez-Lomas
authors.forename: Orr
authors.initials: O
authors.lastname: Limpisvasti
authors.forename: Thay Q
authors.initials: TQ
authors.lastname: Lee
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D002102:Cadaver; D057645:Deltoid Muscle / Q000502:physiology / Q000503:physiopathology; D006801:Humans; D058430:Humeral Head / Q000502:physiology / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000502:physiology / Q000503:physiopathology; D011312:Pressure; D000070599:Shoulder Injuries; D012785:Shoulder Joint / Q000502:physiology* / Q000503:physiopathology*