Summary

We propose a novel method estimates glenoid bone defects using the proportional relationship between glenoid width and height, and this approach, relying only on CT data from the affected shoulder, simplifies calculations and retains conventional accuracy, offering clinical benefits in evaluating defects and guiding surgery.

Abstract

Background

Surgical planning for anterior shoulder instability (ASI) requires accurate measurements of glenoid bone defects, but current methods are either challenging or too complex for practical use. This underscores the need for a simplified, yet precise, assessment technique for anterior glenoid bone defects.

Purpose

The aim is to introduce a new measurement technique that requires only the computed tomography (CT) scan of the affected shoulder joint and simultaneously simplifies the assessment of bone defects in the anterior glenoid.

Methods

CT scans of the glenoid from 285 healthy individuals and 43 patients with unilateral ASI were collected and reconstructed in three dimensions. Initially, we established the proportional relationship between the maximum height and width in the superior-inferior and anterior-posterior directions of the glenoid and the location of their intersection (point O) in healthy individuals. Subsequently, glenoid bone defects in ASI patients were measured using the contralateral comparison method, the best-fit circle method, the CT-specific formula method, and our novel proportional method. We analyzed the differences in defect ratios and sizes, as well as glenoid track calculations among the four methods.

Results

The Width-to-Height ratio of the glenoid was determined to be 0.69±0.04, allowing for the simplification of the calculation to Width=0.7Height for clinical convenience. The intersection point O was consistently located at the lower third of the glenoid height. There were no statistically significance noted in the measurements of bone defect size and bone defect ratio when comparing the novel proportional method, the contralateral comparison method, and the best-fit circle method; however, a significant increase was observed in the values obtained through the CT-specific formula method (defect size: F=19.20, p<0.0001; defect ratio: F=15.99, p<0.0001), as determined by Analysis of Variance (ANOVA).

Conclusion

We had developed a promising new method for estimating the width of bone defects using the aspect proportion of glenoid width to height. Our findings suggest that 70% of the glenoid height at the lower third of the glenoid accurately approximates its maximum width. Compared to the contralateral comparison and best-fit circle methods, our novel proportional approach necessitates only CT data from the affected shoulder and streamlines the calculation process while maintaining similar accuracy. Clinically, this new proportional method can facilitate the assessment of glenoid bone defects, aiding in the selection of appropriate surgical strategies. Further research is needed to support the clinical application of this method.