Allograft Resorption Following Arthroscopic Anatomic Glenoid Reconstruction is part of Remodeling to Restore the Native Glenoid Size and Shape 6.9 Months Postoperatively.

Purpose: The purpose of this study was to determine if the distal tibia allograft (DTA) remodels after Arthroscopic Anatomic Glenoid Reconstruction(AAGR) to restore the native glenoid size and shape postoperatively.

Methods: This is a retrospective study on patients who underwent AAGR with DTA between 2013-2022 using screw fixation-who have completed postoperative clinical follow-up for a minimum of two years and have available postoperative CT scan. Glenoid width(anterior-posterior) and height(superior-inferior) were measured using Horos and Meshmixer on an en face view. The measured glenoid width was compared to predicted glenoid width based on height using equation Width_(mm)=2.53_mm+0.71*Height_(mm), and the difference between the two variables was calculated. Data analysis used paired t-test, Pearson correlation, and ROC curve, at 0.05 significance level.

Results: In 109 patients included in this study, the mean age at surgery was 28.2 years(± 9.6), mean BMI 26.1 kg/m²(±5.0), mean CT follow-up 1.0 years(±1.1 years), 73 primary surgery(67%), 81 male(74%), and 52 right-sided operative shoulder(48%). In all 109 patients, the predicted glenoid width(28.5±2.5mm) was significantly smaller than the measured glenoid width(30.7±4.2mm)(p<0.001). A significant negative correlation was found between CT follow-up time and the difference between measured and predicted glenoid width (i.e., measured and predicted glenoid width become more similar as time passes postoperatively). A cut-off time of 6.9 months was identified for graft remodelling(AUC=0.759,p<0.001). In patients with>6.9 months between surgery and postoperative CT(N=65), there is no difference between predicted and measured postoperative glenoid width(28.6±2.6mm,29.4±3.7mm,respectively,p=0.099). In patients with<6.9 months between surgery and postoperative CT(N=44), the predicted glenoid width was significantly smaller than the measured glenoid width(28.4±2.3mm,32.7±3.9mm,respectively,p<0.001).

Conclusion: Predicted and measured postoperative glenoid width did not differ significantly in patients who had undergone AAGR with at least 6.9 months between surgery and postoperative CT. These findings support the hypothesis that the allograft remodels following AAGR with DTA to restore the native glenoid size and architecture.

Clinical relevance: These findings will help direct size of bone blocks used in AAGR with DTA in the future to optimize surgical outcomes.