Effect of anatomic bone grafting in post-traumatic recurrent anterior shoulder instability on glenoid morphology.

BACKGROUND: Shoulder stability primarily depends on concavity compression, which relies on the concave shape of the glenoid not mere glenoid width. This study analyzed the effect of anatomic glenoid reconstruction surgery on concavity morphology.
METHODS: Thirty-one consecutive patients with recurrent anterior shoulder instability and glenoid bone loss underwent surgical stabilization using the J-bone graft. Twenty patients were available for preoperative, postoperative, and 1-year follow-up computed tomography scans. On standardized axial images, the change over time of the glenoid concavity extent, depth, version, and step-formation was measured and compared with the unaffected side.
RESULTS: The mean preoperative concavity extent was 82.3% and increased (P < .001) after surgery to 113.1% before decreasing (P < .001) to 99.2% at follow-up concordant to the contralateral side (P = .75). The mean concavity depth was 56.6% preoperatively, increased to 226.4% postoperatively (P < .001), and diminished to 149.2% at follow-up (P < .001). Affected glenoids showed an average loss of -6.0° of retroversion preoperatively, with an increase to +5.6° postoperatively (P < .001) and a decrease to +0.2° at follow-up (P < .001). The average step-formation on the articular surface after graft insertion diminished significantly, from 2.3 mm postoperatively to 0.3 mm at follow-up (P < .001).
CONCLUSION: Anatomic glenoid reconstruction surgery using the J-bone graft provides temporary overcorrection of the glenoid concavity extent, depth, and version, with subsequent normalization due to physiologic remodeling processes.