A cadaveric morphometric analysis of coracoid process with reference to the Latarjet procedure using the "congruent arc technique".

Abstract

Congruent arc Latarjet procedure involves rotating the coracoid process so that its inferior surface is flush with the glenoid face, owing to their matching radius of curvature (ROC). However, there has been no cadaveric study to actually measure and compare the ROC of coracoid with glenoid, especially in Indian population. 44 shoulders were dissected in 24 cadavers to measure usable length of coracoid process, width, height, ROC of coracoid and glenoid as well as ulnar length (as proxy of cadaver height). Critical coracoid height and length were estimated based on screw sizes of 2.7mm, 3.5mm, 4mm and 4.5mm, and pair concordance between height and length calculated. ROC of coracoid and glenoid were compared to measure extent of congruency. The mean usable length of coracoid process, width and height at mid-point were 21.8mm, 13.7mm and 8.6mm, respectively. Out of the different screw sizes, 2.7mm screws were found safe in 82% shoulders. 24 coracoid-glenoid pairs fulfilled the operational definition (≤ 5mm) of congruency while rest 20 were seemingly incongruent chiefly due to coracoid variations, with mean ROC difference 4.13mm (95% CI 1.51-6.74mm). The ulnar length was significantly smaller in the incongruent ROC group (p = 0.0002). The available length as well as height of the transferred coracoid must be considered when deciding optimum diameter fixation screws in Latarjet procedure. Owing to smaller anatomic dimensions of coracoid in Indian population, 2.7-mm screws provide the safest fixation option. Also, the ROC of coracoid and glenoid does not match in substantial proportion of the cadavers. Pre-operative planning should include a CT-based assessment of glenoid and coracoid dimensions to decide the technique of Latarjet procedure and the optimum diameter fixation screws required.