Humeral Head Diameter-to-Glenoid Surface Area Ratio as a Morphometric Risk Factor for Posterior Labral Tears: A Retrospective Computed Tomography Analysis

TL;DR

This study found that a specific shoulder bone ratio is linked to posterior labral tears, suggesting it could help identify patients at risk for shoulder instability.

Contribution

The study introduces the HH/GA ratio as a potential morphometric risk factor specifically for posterior labral tears.

Findings

The HH/GA ratio was significantly higher in patients with posterior labral tears compared to controls.

The HH/GA ratio showed moderate predictive value for posterior tears with 84.2% sensitivity and 66.7% specificity.

Abstract

Objective: This study aimed to evaluate whether the humeral head diameter-to-glenoid surface area ratio (HH/GA ratio) is associated with the presence of labral tears and to determine whether this morphometric parameter differs between anteroinferior (Bankart), superior labrum from anterior to posterior (SLAP), and posterior tear subgroups.

Materials and methods: A retrospective analysis of 240 shoulder computed tomography (CT) scans (2014-2024) was performed. The study group included 120 patients with labral tears, classified into anterior (Bankart + SLAP; n = 88) and posterior (n = 32) subgroups. The control group consisted of 120 age- and sex-matched individuals without pathological findings. The HH/GA ratio (mm⁻¹ × 10³) was calculated by dividing humeral head diameter by glenoid surface area. All measurements were performed by two independent observers with excellent interobserver reliability (ICC = 0.91).

Results: The scaled HH/GA ratio (× 10³ mm⁻¹) was significantly higher in the labral tear group compared with controls (50.6 ± 3.3 vs. 48.6 ± 3.7; p < 0.001). Posterior tears demonstrated the highest ratios (52.8 ± 3.1; p < 0.001 vs. controls), whereas anterior tears did not significantly differ from controls (49.8 ± 3.0; p = 0.109). For predicting posterior labral tears, receiver operating characteristic (ROC) analysis showed an area under the curve (AUC) of 0.808, with an optimal cutoff of 49.8 × 10³ mm⁻¹ (corresponding to 0.0498 mm⁻¹), yielding 84.2% sensitivity and 66.7% specificity.

Conclusion: The HH/GA ratio is moderately but significantly associated with posterior labral tears and may reflect an underlying morphometric predisposition. While not diagnostic on its own, it may serve as an adjunctive quantitative parameter during the evaluation of patients at risk for posterior shoulder instability. Larger prospective studies are needed for external validation.

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