Moment arms of the coracobrachialis and short head of biceps following a Latarjet procedure: a modeling study

The Latarjet procedure transfers the coracoid process to the anterior glenoid. This prevents recurrent anterior humeral dislocation but alters the origins of the coracobrachialis (CBR) and short head of the biceps (SHB). The impact of this alteration on the moment arms of these muscles has not been examined. The Newcastle Shoulder Model was updated with 15 healthy cadaveric bone models to create customized shoulder models. The CBR and SHB muscles were attached to the anterior glenoid via an elliptical wrapping object. Muscle moment arms were calculated for abduction, forward flexion, scapular plane elevation, and internal rotation with 20° and 90° of abduction. Statistical comparison of moment arms between native and Latarjet shoulders was performed using spm1D. By transferring the origins of the CBR and SHB to the anterior glenoid, both muscles had extension moment arms during glenohumeral elevation in the coronal, sagittal, and scapular planes. Their average moment arms during abduction (−30.4 ± 3.2 mm for CBR and −29.8 ± 3.0 mm for SHB) and forward flexion (−26.0 ± 3.1 mm for CBR and −26.2 ± 3.2 mm for SHB) suggested that their role after the Latarjet procedure changed compared with their role in the native shoulder (P