A formula for instability-related bone loss: estimating glenoid width and redefining bare spot

Abstract

Purpose: The aim of the study reveals a new intuitive method for preoperatively assessing defect ratio in glenoid deficiency based on the native glenoid width and the bare spot.

Methods: A linear relationship, i.e. the rh formula, between the native glenoid width (2r) and height (h) was revealed by a cadaver cohort (n = 204). To validate the reliability of the rh formula, 280 3D-CT images of intact glenoids were recruited. To evaluate the accuracy of rh formula in estimating glenoid defect, the 65 anterior-inferior defect models were artificially established based on the 3D-CT images of intact glenoids. Moreover, a clinically common anterior-posterior (AP) method was compared with the rh formula, to verify the technical superiority of rh formula.

Results: The regression analysis indicated a linear relationship between the width and height of intact glenoid: 2r = 0.768 × h - 1.222 mm (R² = 0.820, p < 0.001). An excellent reliability was found between the formula prediction and model width (ICC = 0.911, p = 0.266). An excellent agreement was found between the predicted values and model parameters (glenoid width, ICC_rh = 0.967, p_rh = 0.778; defect ratio, p_rh = 0.572, ICC_rh = 0.997). And, it is of higher accuracy compared to the AP method (glenoid width, ICC_AP = 0.933, p_AP = 0.001; defect ratio, ICC_AP = 0.911, p_AP = 0.033).

Conclusion: Applying the cadaver-based formula on 3D-CT scans accurately predicts native glenoid width and redefines bare spot for preoperatively determining glenoid bone loss.

Keywords: 3D-CT; Anterior glenohumeral instability; Bare spot; Best-fit circle; Cadaver-based formula; Glenoid bone loss.