title: Does the dynamic sling effect of the Latarjet procedure improve shoulder stability? A biomechanical evaluation.
abstract: BACKGROUND
  Glenohumeral instability with glenoid bone loss is commonly treated with the Latarjet procedure. The procedure involves transfer of the coracoid and conjoint tendon, which is thought to provide a stabilizing sling effect; however, its significance is unknown. This study evaluated the effects of the Latarjet procedure, with and without conjoint tendon loading, on shoulder stability and range of motion (ROM).
  
  
  METHODS
  A custom simulator was used to evaluate anterior shoulder stability and ROM in 8 cadaveric shoulders. Testing conditions included intact, 30% glenoid defect, and Latarjet with and without conjoint loading. Unloaded and 10-N loaded states were tested in adduction and 90° abduction. Outcome variables included dislocation, stiffness (neutral and 60° external rotation), and internal-external rotational ROM.
  
  
  RESULTS
  All 30% defects dislocated in abduction external rotation. The loaded Latarjet prevented dislocation in all specimens, whereas the unloaded Latarjet stabilized 6 of 8 specimens. In abduction external rotation, there were no significant differences in stiffness between loaded and unloaded transfers (P = .176). In adduction, there were no significant differences between the intact and the loaded Latarjet (P ≥ .228); however, in neutral rotation, the unloaded Latarjet (P = .015) and the 30% defects (P = .011) were significantly less stiff. Rotational ROM in abduction was significantly reduced with the loaded Latarjet (P = .014) compared with unloaded Latarjet, and no differences were found in adduction.
  
  
  CONCLUSIONS
  These findings indicate that glenohumeral stability is improved, but not fully restored to intact, with conjoint tendon loading. The results support the existence of the sling effect and its importance in augmenting stability provided by the transferred coracoid.
authors.affiliation: Hand and Upper Limb Centre, St. Joseph's Health Centre, The University of Western Ontario, London, ON, Canada.
authors.forename: Joshua W
authors.initials: JW
authors.lastname: Giles
authors.forename: Harm W
authors.initials: HW
authors.lastname: Boons
authors.forename: Ilia
authors.initials: I
authors.lastname: Elkinson
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Faber
authors.forename: Louis M
authors.initials: LM
authors.lastname: Ferreira
authors.forename: James A
authors.initials: JA
authors.lastname: Johnson
authors.forename: George S
authors.initials: GS
authors.lastname: Athwal
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D006801:Humans; D007593:Joint Instability / Q000503:physiopathology*; D019637:Orthopedic Procedures; D010027:Osteotomy; D016059:Range of Motion, Articular; D012785:Shoulder Joint / Q000503:physiopathology* / Q000601:surgery*; D013709:Tendon Transfer / Q000379:methods*