Assessing Glenoid Defects in Anterior Shoulder Instability: Comparison of a Simple Linear Formula Method With Traditional Methods Using 3-Dimensional Computed Tomography

Anterior glenoid bone defects significantly influence surgical outcomes in shoulder instability cases. Various measurement methods based on 3-dimensional computed tomography (3D-CT) have been developed. Recently, the simple linear formula method, which establishes a correlation between glenoid height and width, has emerged as a promising technique. This study aimed to assess the differences in glenoid morphology between patients with anterior shoulder instability and healthy controls within a specific East Asian population (Han Chinese). The objectives included establishing linear formulas specific to both groups and comparing the efficacy of the simple linear formula method with traditional methods for measuring glenoid defects using 3D-CT. Cohort study (diagnosis); Level of evidence, 3. 3D-CT images of both the affected and unaffected shoulders of patients with anterior shoulder instability, as well as one shoulder of healthy controls, were analyzed. Glenoid height and width were measured, and linear formulas were established for this specific Han Chinese population. P values were determined using linear regression analysis to assess the statistical significance of the relationship between glenoid height (H) and width (W). A P value <.05 indicated a statistically significant relationship. R2 values were calculated to determine the strength of the relationship, with higher values (closer to 1) indicating a stronger correlation. The glenoid defect ratio was calculated using the simple linear formula method and compared with traditional methods: the Griffith, linear-based best-fit circle, and area-based best-fit circle methods. Interrater agreement was assessed using intraclass correlation coefficients (ICCs). There were 206 patients in the patient group and 206 participants in the healthy control group. In the patient group, the mean glenoid height and width of the unaffected shoulders were 35.21 ± 3.39 and 24.26 ± 2.74 mm, respectively (formula: W = 0.75H - 2.12; R2 = 0.86; P < .001). In the male patient subgroup, they were 37.57 ± 1.35 and 26.23 ± 0.91 mm, respectively (formula: W = 0.47H + 8.60; R2 = 0.79; P < .001). In the female patient subgroup, they were 31.63 ± 2.21 and 21.26 ± 1.65 mm, respectively (formula: W = 0.52H + 4.78; R2 = 0.74; P < .001). In the healthy control group, the mean glenoid height and width were 33.48 ± 3.32 and 24.18 ± 3.02 mm, respectively (formula: W = 0.86H - 4.58; R2 = 0.89; P < .001). In the male healthy control subgroup, they were 36.43 ± 1.35 and 26.89 ± 1.17 mm, respectively (formula: W = 0.67H + 2.63; R2 = 0.58; P < .001). In the female healthy control subgroup, they were 30.54 ± 1.70 and 21.47 ± 1.49 mm, respectively (formula: W = 0.61H + 2.90; R2 = 0.69; P < .001). The actual glenoid defect in the entire patient cohort averaged 12.3% ± 5.9%. The simple linear formula method demonstrated an ICC of 0.82, with a glenoid defect ratio averaging 15.7% ± 6.9%. The Griffith method had an ICC of 0.85, yielding a glenoid defect ratio of 16.5% ± 5.8%. The linear-based and area-based best-fit circle methods had ICCs of 0.73 and 0.77, respectively, with glenoid defect ratios of 16.9% ± 6.0% and 13.1% ± 6.2%, respectively. Glenoid morphology in patients with anterior shoulder instability, particularly among male patients, was characterized by elongation and narrowing compared with healthy participants. The simple linear formula method demonstrated excellent reliability and accuracy, comparable with traditional methods, offering an efficient approach to measuring glenoid defects. Further validation across diverse populations is warranted.