Glenoid and coracoid dimensions and their implications in the latarjet operation: a dry bone study

Abstract

Background: The coracoid process is widely used as a graft in patients with recurrent anterior shoulder instability with significant glenoid bone defects. However, no local studies have determined the coracoid dimensions and correlated them to the glenoid dimensions.
Objective: To measure the widest anteroposterior (AP) diameter of the glenoid cavity, the length, width and thickness of the coracoid process, compare these with other populations, determine the amount of coverage the thickness and width of the coracoid process can afford in case of bony glenoid deficiency and the adequacy of the coracoid process to safely accommodate fixation screws used in the Latarjet and congruent-arc Latarjet procedures.
Methods: The dimensions were measured using digital vernier callipers on dried scapulae that were not deformed. The ratio between coracoid thickness and width to the glenoid AP diameter was determined as the percentage cover that particular dimension can provide to the deficient glenoid.
Results: A total of 26 scapulae were obtained. Average AP diameter and height of the glenoid was 25.1mm and 36.2mm respectively. Average coracoid length, width and thickness was 22.3mm, 13.3mm and 7.7mm respectively. There was no significant difference between the right and left sides in all the dimensions. The average coverage provided by the coracoid thickness (Latarjet procedure) was 30% with coracoid width providing average coverage of 50% (congruent-arc Latarjet procedure). The coracoid width could safely accommodate the 3.5mm and 4.5mm screws while coracoid thickness offered a very thin margin round the screws.
Conclusion: The coracoid process can cover glenoid defects of between 30% and 50% and while it may safely accommodate the 3.5mm and 4.5mm screws if oriented for the classic Latarjet operation, care is needed especially if the congruent-arc Latarjet is planned as coracoid thickness may not be adequate to accommodate the fixation screws.

Keywords: Coracoid process, Glenoid, Latarjet, Congruent-arc Latarjet