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

Purpose: 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 and 2022 using screw fixation who have completed postoperative clinical follow-up for a minimum of 2 years and have an available postoperative computed tomography (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 the predicted glenoid width based on height using the following equation: Width = 2.53 + 0.71 ∗ Height, and the difference between the 2 variables was calculated. Data analysis used a paired t test, Pearson correlation, and receiver operating characteristic curve at a .05 significance level.

Results: In 109 patients included in this study, the mean ± SD age at surgery was 28.2 ± 9.6 years, mean ± SD body mass index was 26.1 ± 5.0, and mean ± SD CT follow-up was 1.0 ± 1.1 years, including 73 primary surgeries (67%), 81 men (74%), and 52 right-sided operative shoulders (48%). In all 109 patients, the predicted glenoid width (28.5 ± 2.5 mm) was significantly smaller than the measured glenoid width (30.7 ± 4.2 mm) (P < .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 became more similar as time passed postoperatively). A cutoff time of 6.9 months was identified for graft remodeling (area under the curve, 0.759; P < .001). In patients with ≥6.9 months between surgery and postoperative CT (n = 65), there was no difference between predicted and measured postoperative glenoid width (28.6 ± 2.6 mm, 29.4 ± 3.7 mm, respectively; P = .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 ± 2.3 mm, 32.7 ± 3.9 mm, respectively; P < .001).

Conclusions: 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 the size of bone blocks used in AAGR with DTA in the future to optimize surgical outcomes.