Stabilizing effect of the transferred conjoined tendon on shoulder stability

Abstract

The modified Boytchev procedure, i.e., rerouting of the coracoid process with its attached conjoined tendon (short head of biceps and coracobrachialis) deep to the subscapularis and reattachment to its anatomical location, has been advocated for recurrent anterior glenohumeral instability with controversial clinical outcomes. We aimed to investigate the dynamic contribution of the conjoined tendon in situ or transferred to the glenohumeral articulation in stable and unstable shoulders. Eight cadaveric shoulders were tested with the arm in 90 degrees abduction and 90 degrees external rotation. A constant 1.5 kg anterior translation force was applied to the proximal humerus, combined with 0, 1.5, 3.0 kg of load applied to the conjoined tendon sequentially. Anterior displacement of the humeral head relative to the scapula was recorded before and after an imitation Bankart lesion was created, and after treated with the modified Boytchev procedure for the Bankart lesion. Application of load to the conjoined tendon significantly reduced anterior displacement of the humeral head either with the capsule intact or with Bankart lesion simulated. The most significant decrease of the anterior displacement occurred when the conjoined tendon was transferred beneath the subscapularis. Our findings show that the conjoined tendon per se has a stabilizing effect on stable and unstable shoulders and therefore provide scientific support for the treatment of recurrent shoulder instability using the modified Boytchev procedure.

Open Shoulder Repair of Osseous Glenoid Defects

“…The provided sling effect at the subglenoid level closes the vulnerable gap of the glenoid defect. These results agree with findings of Jiang et al, 22 who found a significant stabilizing effect of the transferred conjoined tendon on shoulder stability. The authors performed anterior translational testing after a rerouting of the osteotomized coracoid process under the subscapularis muscle and consecutive bony reattachment to its anatomic location (Boytchev procedure).…”

Coracoid Process Transfer for Recurrent Instability of the Shoulder

“…Through sequential loading of muscles and tendons in cadaveric specimens, Halder et al tested the effect of the dynamic contribution of the conjoined tendon in inhibiting anteroinferior translation of the humeral head and found that the conjoined tendon had the capability to translate the humeral head superiorly 38 . This finding is similar to those reported by Jiang et al, who also found that the transfer of the conjoined tendon along with the coracoid provided a substantial stabilizing effect on shoulder stability 37 .…”

“…The glenoid index is defined as the ratio of the maximum inferior diameter of the injured glenoid compared with the maximum inferior diameter of the uninjured, contralateral glenoid 16 . Another technique measures the bone loss as the ratio of the inferior width of the injured glenoid to the predicted preinjury width 37 . The preinjury width is determined by multiplying the length from the center of the glenoid to the posterior margin of the glenoid at the 3-o'clock position by 2.…”

A Study of Management of Recurrent Anterior Dislocation Shoulder by Modified Boytchev Procedure

“…The rerouted conjoint tendon increases tension in the subscapularis and reinforces the anterior muscular support and it prevents the superior displacement of the subscapularis and thereby prevents the dislocation. [6][7][8][9][10][11][12][13][14][15] The rerouted conjoint tendon between the head of the humerus and subscapularis, also exerts a pressure effect on the subscapularis tendon, thereby increasing the proprioceptive stimulus in the tendon, which increases the protective reflex to prevent the dislocation. The other advantages of modified Boytchev procedure are, this is an extra articular procedure, with a very low recurrence rate, lower complication rate, lower re-operation rate, less intra operative time, maintains reasonably good range of abduction and external rotation, and the procedure is easy to perform.…”