Classic versus congruent coracoid positioning during the Latarjet procedure: an in vitro biomechanical comparison.

PURPOSE: The purpose of this biomechanical study was to compare the classic Latarjet technique and congruent-arc modification with respect to glenohumeral stability, joint stiffness, translation, and range of motion.

METHODS

Eight cadaveric forequarters were tested on a shoulder simulator that applied loads independently to the conjoint tendon, long head of biceps, rotator cuff, and deltoid. The test conditions included: intact, 30% glenoid defect, and reconstruction of the defect with the classic and congruent Latarjets. The Latarjet techniques were randomly ordered, with the outcome variables being anterior dislocation, glenohumeral translation, rotational range of motion, and joint stiffness.

RESULTS

All 8 specimens dislocated after creation of a 30% glenoid defect. The classic Latarjet stabilized 7 of 8 specimens, whereas the congruent-arc modification stabilized all specimens (8/8). In abduction neutral rotation, there was no difference in joint translation between techniques (P = .613). In abduction external rotation, there was significantly greater anterior humeral head translation after the congruent technique than after the classic (9.9 and 6.5 mm, respectively, P = .013). Rotational range of motion was significantly reduced after classic (-25.8°) and congruent (-22.2°) transfers as compared with the 30% defect (P ≤ .041). Joint stiffness in the abducted, externally rotated position was significantly reduced in the 30% defect as compared with intact (P = .012), congruent (P = .015), and classic (P < .001) conditions. In all abduction positions, the intact was not significantly different from the Latarjet techniques, and the techniques did not significantly differ from each other (P ≥ .102).

CONCLUSIONS

The classic and congruent-arc Latarjet techniques restore shoulder stability and motion in cases of considerable bone loss. The techniques do not substantially differ in rotational range of motion or joint stiffness. The congruent-arc technique, however, does result in significantly greater anterior humeral head translation, as compared with the classic technique, before reaching a stable non-dislocated endpoint.

CLINICAL RELEVANCE: On the basis of this biomechanical model, both the classic and congruent-arc Latarjet techniques can be used to stabilize a shoulder with substantial glenoid bone loss. Further clinical and biomechanical studies are required to determine if particular clinical circumstances exist where 1 technique has an advantage over the other.