One-year follow-up of 20 patients undergoing the Latarjet procedure : a biomechanical study during an apprehension-relocation test measured with radiostereometry.

Aims: The Latarjet procedure is the treatment of choice for patients who have recurrent anterior shoulder instability with glenoid bone loss. However, the stabilizing effect of the Latarjet procedure in patients is sparsely described. The aim of this study was to evaluate the glenohumeral joint (GHJ) kinematics during an apprehension-relocation test in patients with anterior shoulder instability before and after their Latarjet procedure, and in comparison with their contralateral healthy shoulder.

Methods: A total of 20 patients scheduled for the Latarjet procedure were enrolled. The patients were examined preoperatively with bilateral radiostereometric analysis (RSA) and one year after surgery on the operated shoulder with an apprehension-relocation test. Bone models were obtained from CT scans and aligned with the RSA images. The GHJ kinematics was evaluated with two methods: the humeral head centre location relative to the glenoid centre, and the GHJ contact point relative to the glenoid centre.

Results: No difference in GHJ kinematics was found between the healthy and the postoperative GHJ. Compared with the preoperative injured shoulder, the postoperative mean (95% CI) humeral head centre was 0.8 mm (0.1 to 1.4) more superior and 0.7 mm (-0.1. to 1.4) more posterior during the apprehension test, and 0.5 mm (0.0 to 1.1) more posterior during the relocation test. The postoperative contact point was posterior to the coracoid bone block and 0.9 mm (-0.2 to 2.0) more posterior than in the preoperative injured shoulder during the apprehension test. The articulating area of the coracoid bone block was decreased by 63.9% (75.5 to 114.6) one year after surgery.

Conclusion: The Latarjet procedure restored the humeral head centre location posterior and superior, and the contact point posterior, to the coracoid bone block. This suggests that the stabilizing effect of the GHJ following the Latarjet procedure is primarily due to the conjoined tendon rather than the coracoid bone block itself.