The Kouvalchouk procedure vs. distal tibial allograft for treatment of posterior shoulder instability: the deltoid “hammock” effect exists

• Published in: Journal of shoulder and elbow surgery 2024-10, Vol.33 (10), p.e537-e546
• Main Authors: Gao, Ryan, Fleet, Cole T., Jin, Winston, Johnson, James A., Faber, Kenneth J., Athwal, George S.
• Format: Article
• Language: English
• Subjects: dislocation; distal tibial allograft; humeral head translation; instability; Kouvalchouk; Posterior shoulder instability; shoulder
• ISSN: 1058-2746; 1532-6500; 1532-6500
• DOI: 10.1016/j.jse.2024.03.047

In 1993, Kouvalchouk described an acromial bone block with a pedicled deltoid flap for the treatment of posterior shoulder instability. This procedure provides a “double blocking” effect in that the acromial autograft restores posterior glenoid bone loss and the deltoid flap functions as a muscular “hammock” resembling the sling effect of the conjoint in the Latarjet procedure. The primary aim of this study was to compare the Kouvalchouk procedure to distal tibial allograft (DTA) reconstruction for the management of posterior shoulder instability with associated bone loss, while the secondary aim was to evaluate the deltoid hammock effect. Ten upper extremity cadavers were evaluated using a validated shoulder testing apparatus in 0° and 60° of glenohumeral abduction in the scapular plane. Testing was first performed on the normal shoulder state and was followed by the creation of a 20% posterior glenoid defect. Subsequently, the Kouvalchouk and DTA procedures were conducted. Forces of 0N, 5N, 10N, and 15N were applied to the posterior deltoid tendinous insertion on the Kouvalchouk graft along the physiological muscle line-of-action to evaluate the ‘hammock” effect of this procedure. Testing was additionally performed on the Kouvalchouk bone graft with the deltoid muscle sectioned from its bony attachment. For all test states, a posteriorly directed force was applied to the humeral head perpendicular to the direction of the glenoid bone defect, with the associated translation quantified using an optical tracking system. The outcome variable was posterior translation of the humeral head at an applied force magnitude of 30N. The Kouvalchouk procedure with the loaded deltoid flap (10N: P = .039 and 15N: P