title: Biomechanical analysis of the modified Bristow procedure for anterior shoulder instability: is the bone block necessary?
abstract: BACKGROUND
  Anterior shoulder instability with bone loss can be treated successfully with the modified Bristow procedure. Opinions vary regarding the role of the soft-tissue sling created by the conjoined tendon after transfer. Therefore, the aim of this study was to determine the effect of the modified Bristow procedure and conjoined tendon transfer on glenohumeral translation and kinematics after creating anterior instability.
  
  
  METHODS
  Eight cadaveric shoulders were tested with a custom shoulder testing system. Range-of-motion, translation, and kinematic testing was performed in 60° of glenohumeral abduction in the scapular and coronal planes under the following conditions: intact joint, Bankart lesion with 20% glenoid bone loss, modified Bristow procedure, and soft tissue-only conjoined tendon transfer.
  
  
  RESULTS
  A Bankart lesion with 20% bone loss resulted in significantly increased external rotation and translation compared with the intact condition (P < .05), as well as an anterior shift of the humeral head apex at all points of external rotation. Both the modified Bristow procedure and soft-tissue Bristow procedure maintained the increase in external rotation but resulted in significantly decreased translation (P < .05). There was no difference in translation between the 2 reconstructions.
  
  
  CONCLUSIONS
  The increase in external rotation suggests that the modified Bristow procedure does not initially restrict joint motion. Translational stability can be restored in a 20% bone loss model without a bone block, suggesting the importance of the soft-tissue sling.
authors.affiliation: Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
authors.forename: Curtis J
authors.initials: CJ
authors.lastname: Kephart
authors.affiliation: Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
authors.forename: Michael H
authors.initials: MH
authors.lastname: Abdulian
authors.affiliation: Orthopaedic Biomechanics Laboratory, Long Beach VA Healthcare System, Long Beach, CA, USA.
authors.forename: Michelle H
authors.initials: MH
authors.lastname: McGarry
authors.affiliation: Department of Orthopaedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.
authors.forename: James E
authors.initials: JE
authors.lastname: Tibone
authors.affiliation: Orthopaedic Biomechanics Laboratory, Long Beach VA Healthcare System, Long Beach, CA, USA; Department of Orthopaedic Surgery, University of California, Irvine, CA, USA. Electronic address: tqlee@med.va.gov.
authors.forename: Thay Q
authors.initials: TQ
authors.lastname: Lee
mesh_terms: D001696:Biomechanical Phenomena; D001862:Bone Resorption / Q000503:physiopathology / Q000601:surgery*; D016025:Bone Transplantation; D002102:Cadaver; D005260:Female; D006801:Humans; D058430:Humeral Head / Q000503:physiopathology; D007593:Joint Instability / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D012783:Shoulder Dislocation / Q000503:physiopathology / Q000601:surgery*; D012785:Shoulder Joint / Q000503:physiopathology / Q000601:surgery*; D013709:Tendon Transfer; D013710:Tendons / Q000601:surgery
keywords: Shoulder; anterior instability; conjoined tendon; glenoid bone loss; modified Bristow