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. 2022 May 28;6(5):763-768.
doi: 10.1016/j.jseint.2022.05.001. eCollection 2022 Sep.

A ratio estimating glenoid bone loss

Evan S Lederman  1 , Anup A Shah  2
Affiliations

A ratio estimating glenoid bone loss

Evan S Lederman et al. JSES Int. .

Abstract

Background: Estimating glenoid bone loss when assessing the unstable shoulder can be challenging. The aim of this article was to describe a simple derived ratio to estimate glenoid bone loss.

Methods: When the glenoid is damaged and bone is damaged because of instability, the anterior aspect of the glenoid loses its normal curvature and becomes flattened. In geometry, this represents a chord. There are 3 assumptions for the calculations: (1) the lower glenoid is a circle; (2) there is a relationship between the glenoid height and the diameter of the glenoid circle; and (3) the length of the measured bone loss of the glenoid is a chord. Two measurements are required: glenoid height and length of the glenoid defect. The calculations involved in the ratio are reviewed.

Results: If the ratio of the length of the bone defect to the glenoid height is 0.5 (otherwise, 50% of the height), the estimated bone loss is 12%.

Conclusion: Glenoid bone loss can be estimated by measuring the length of the glenoid and the length of the defect.

Keywords: Bone loss; Glenoid; Instability; Ratio; Shoulder surgery; Surgical technique.

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Figures

Figure 1
Figure 1
Glenoid with lower glenoid as a circle. Two measurements are the glenoid length and the length of the bone defect. Relationship between glenoid length and maximal diameter is 0.65. Radius of the lower glenoid circle is 0.325 of glenoid length.
Figure 2
Figure 2
The triangle has the 3 sides known. Sides a and b are the radius of the circle, and side c is the chord. The central angle (C) is calculated with the sin rule. Calculate the area of the segment. The ratio of area of the segment/area of the circle = % bone loss.
Figure 3
Figure 3
The ratio of anterior glenoid bone loss to glenoid height vs. the percent of glenoid bone loss.
Figure 4
Figure 4
Glenoid bone loss calculation.
See this image and copyright information in PMC

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