Coracoid bone graft volume changes over time after the Bristow procedure: a retrospective case series

The Bristow procedure reportedly achieves good clinical results when used to treat recurrent shoulder instability. This procedure results in an increase in the volume of the coracoid process that contacts the anterior wall of the glenoid, which increases bony support because of an increase in the glenoid surface contact area. However, the timing of this increase in volume and its relationship with the timing of bony union are unknown. The purpose of this study was to clarify the timing of the increase in coracoid process volume and bony union after the Bristow procedure. The study cohort comprised 26 shoulders in 26 patients who underwent the Bristow procedure. The mean age at surgery was 18.4 years, and the mean follow-up duration was 21.8 months. The coracoid bone graft volume was evaluated using three-dimensional computed tomography within the first week after surgery (Time 0), at 3 months, 6 months, and 1 year postoperatively, and at the final follow-up. The primary outcome measure was the volume of the transferred coracoid bone graft measured over time using three-dimensional computed tomography. The mean (± standard deviation) coracoid bone graft volumes were 1.36 ± 0.33 cm 3 at Time 0, 1.39 ± 0.33 cm 3 at 3 months postoperatively, 1.50 ± 0.31 cm 3 at 6 months postoperatively, 1.73 ± 0.34 cm 3 at 1 year postoperatively, and 1.86 ± 0.35 cm 3 at final follow-up. In cases with bone union, the coracoid bone graft volume increased significantly over time ( p < 0.001). The mean time to bone union was 3.6 months. The coracoid bone graft volume was significantly increased at 1 year and final follow-up postoperatively compared with Time 0 ( p < 0.001). Furthermore, significant increases in graft volume were observed from 6 months to 1 year and from 1 year to final follow-up ( p < 0.05). In shoulders with recurrent instability treated with the Bristow procedure, the volume of the coracoid bone graft continued to increase even after bone union had been achieved. Significant increases were observed from 6 months to 1 year and from 1 year to the final follow-up. These findings suggest that further bony support may be achieved over time after bone union. Clinical trial number: not applicable.