Optimization of bone-block positioning in the Bristow-Latarjet procedure: a biomechanical study.

BACKGROUND: In the Bristow-Latarjet procedure, optimal positioning of the coracoid bone-block on the anterior aspect of the glenoid (standing or lying on the glenoid rim) remains debated. A biomechanical study assessed the effect of the position of the bone-block with its attached conjoint tendon on anterior and inferior stabilization of the humeral head.

MATERIALS AND METHODS: The Bristow-Latarjet procedure was performed on 8 fresh cadaveric shoulders. The bone-block size was systematically at 2.5×1×1 cm. Anterior translation of the humeral head was stress induced under 30-N traction, in maximum external rotation at 0° and at 90° abduction: respectively, adduction and external rotation (ADER), and abduction and external rotation (ABER). Under radiological control, displacement of the center of the humeral head was compared with the glenoid surface at the 3, 4 and 5 o'clock (medial, antero-inferior and inferior) positions for the 2 bone-block positionings.

RESULTS: The lying position at 4 o'clock substantially decreased anterior and inferior displacement of the humeral head respectively in ADER and ABER; and in ABER it also tended to decrease anterior translation, but not significantly. The standing bone-block position did not affect translation.

CONCLUSIONS: Positioning the bone-block so that it lies on the anterior aspect of the glenoid in the middle of the antero-inferior quarter of the rim at 4 o'clock can decrease anterior displacement of the humeral head and inferior glenohumeral translation, especially in ADER for anterior displacement and in ABER for inferior displacement.

STUDY DESIGN: Laboratory study.