Latarjet coracoid transfer vs. distal clavicle autograft for anterior shoulder instability with glenoid bone loss: A biomechanical comparison of two graft reconstructions in various medial to lateral positions

Abstract

While the consensus of optimal positioning of the transferred coracoid, no biomechanical study has established if the position differs for other bone block types. To compare the effect of distal clavicle autograft and coracoid autograft alignment and medialization on glenohumeral stability. Eight Fresh-frozen cadaver shoulders comprised of the scapula and proximal humerus were tested. The cadavers were tested while positioning both grafts, the distal clavicle autograft and coracoid graft, consecutively at 0 mm, 4 mm and 8 mm medially. Each experiment comprised of maximum external rotation and glenohumeral abduction of 60° while applying a constant, 50 N medial compressive force via a pneumatic actuator to the humerus under all conditions. The starting position was determined by the humeral head being seated at its most medial position on the glenoid surface. The conjoint tendon was routed through a split in subscapularis and loaded with a 5N weight using a pulley system for all Latarjet trials to simulate the sling effect. Clavicle grafts at all offsets showed a statistically significant decrease in the stability ratio versus the intact condition. Within the clavicle graft conditions, the 4 mm clavicle offset had a significantly lower stability ratio versus the 0 mm clavicle offset and a significantly higher stability ratio than the 8 mm offset. The clavicle 8 mm offset graft had a significantly lower stability ratio than the 0 mm offset position. The Latarjet graft with 0 mm of medial offset showed no statistically significant difference in stability ratio when normalized at 10 mm of anterior displacement relative to the intact glenoid condition, while the 4 mm and 8 mm medial offset Latarjet conditions had significantly lower stability ratios versus the intact condition. Within the Latarjet graft positions, the stability ratio of the 4 mm medial offset had no statistically significant difference than the 0 mm offset. In shoulders with anterior glenoid bone loss, the Latarjet procedure and transfer of an osteoarticular distal clavicle autograft seem to be biomechanically sound if placed flush with the glenoid. Medialization of 4 mm provides acceptable restoration of shoulder stability when a Latarjet procedure is used but not for a distal clavicle autograft.