Obligate Posterosuperior Humeral Head Translation Following the Latarjet Procedure Demonstrates That Its Triple Blocking Effect Is Real

The Latarjet procedure, first described in 19541 and subsequently modified by Patte and Debeyre to enhance the triple blocking effect2, has revolutionized the treatment of anterior instability in shoulders with glenoid and/or humeral bone loss. The procedure has gained in popularity following the landmark study by Burkhart and De Beer3, which raised awareness of the detrimental impact of glenoid bone loss on the success of arthroscopic stabilization. However, the complication profile is certainly more daunting than that following the arthroscopic Bankart procedure, and includes permanent nerve injury, vascular compromise, and hardware failure, all of which can be catastrophic4. Not surprisingly, alternatives to the open and arthroscopic Latarjet procedures, such as open and arthroscopic bone block procedures employing grafts such as distal tibial allograft, have been used to restore stability and minimize surgical risks. Postoperative glenohumeral arthritis can follow any of these intra-articular procedures, although the specific incidence and rate of progression are indeterminate. Postoperative arthritis or capsulorrhaphy arthropathy can occur rapidly from surgical shortcomings or complications, such as prominent or ununited grafts or intra-articular broken or migrated screws and washers. However, arthritis can also arise decades following bone block procedures, as has been reported by Hovelius and colleagues5. The mechanism for late glenohumeral arthritis following the Latarjet procedure is unclear, and is likely confounded by damage to the glenohumeral articular surfaces because of previous surgery or recurrent subluxations and dislocations prior to surgery. Changes in glenohumeral kinematics following the Latarjet procedure may also be a contributing factor to the development of glenohumeral arthritis. Shoulder stabilization surgery aims to restore glenohumeral stability by addressing glenoid bone loss or creating a chock block through labral repair and tensioning or tightening of the associated soft tissues. It follows that the humeral head translates away from the repaired tissue postoperatively, following a path of least resistance. This is referred to as obligate glenohumeral translation, first described by Harryman et al. in 19906, and it occurs when the capsule is asymmetrically tight rather than as the result of capsuloligamentous insufficiency6,7. Kipp et al. employed a cadaveric model of glenoid bone loss in their study to evaluate the glenohumeral joint kinematics before and after coracoid transfer. They found that the humeral head translated anteriorly and inferiorly after the creation of the glenoid defect, and then underwent obligate translation posteriorly and superiorly after the Latarjet procedure. This obligate translation likely results from the Latarjet procedure’s triple blocking2, which consists of the transferred coracoid graft extending the glenoid arc, the attached conjoined tendon providing a dynamic sling during abduction and external rotation, and the coracoacromial ligament reinforcing the capsule8. The study’s findings contradict those of a recent static computed tomography (CT)-based in vivo study that found only nominal posterior glenohumeral translations following Latarjet procedures employing double-button suspensory fixation9. The divergent findings may be explained by the differences in study design (cadaveric versus in vivo), measurements (static axial CT cuts versus radiostereometry), and graft fixation (screws versus double button). One of the novel elements of this study is the use of biplanar radiostereometry to measure subtle humeral head translations. However, the study has all of the limitations inherent in cadaveric biomechanical studies. Additionally, the study employed simulated shoulder rotations and translations that were artificially slow to accommodate the limits of the image-capturing software; 6 seconds elapsed to move the shoulder through 90° of external rotation at 30° or 60° of abduction. Further in vivo study of the Latarjet procedure is needed, also perhaps using biplanar radiography-based motion measurement techniques10–12. Overall, this study should spur further interest in elucidating glenohumeral joint kinematics and mitigating the risk of developing late glenohumeral arthrosis following the Latarjet and other bone block procedures.