A Biomechanical Evaluation of Bicortical Metal Screw Fixation Versus Absorbable Interference Screw Fixation After Coracoid Transfer for Anterior Shoulder Instability

PurposeThe purpose was to evaluate the load to failure of 2 coracoid fixation techniques after transfer of the coracoid to the anterior glenoid neck.MethodsTen cadavers (mean age, 87 years; range, 74 to 96 years) underwent the Bristow conjoined tendon tenodesis technique as described by Boileau et al. (bioabsorbable interference screw fixation of a coracoid bone plug) in 1 shoulder and the Latarjet-Patte coracoid transfer popularized by Walch (fixation with 2 screws through a larger piece of the coracoid) in the opposite shoulder. The force on the conjoined tendon required to pull the coracoid off of the anterior glenoid was recorded, along with the mode of construct failure.ResultsThe median ultimate failure load was 110 N (range, 35 to 170 N) in the interference screw group and 202 N (range, 95 to 300 N) in the bicortical screw group (P = .002). The mode of failure of the interference screw technique was complete avulsion of the bone plug from the socket in 6 cases (60%) and fracture of the bone plug in 4 (40%). The mode of failure of the bone block technique was a vertical fracture through both screw holes in 7 cases (70%), a horizontal fracture through the distal screw hole in 2 (20%), and an intratendinous rupture of the conjoined tendon in 1 (10%).ConclusionsFixation of a coracoid bone block to the anterior glenoid neck with 2 bicortical metal screws is stronger than fixation of a coracoid bone plug with an absorbable interference screw.Clinical RelevanceThese data may influence surgeons' decisions regarding coracoid fixation as well as postoperative rehabilitation after coracoid transfer.