Summary

Glenoid bone loss calculation presents variability depending on the measurement technique, with different consistencies and accuracies. The Barchilon method, based on area measurement, should be used in the surgical decision making process as it presented the best combined consistency and accuracy.

Abstract

Background

Preoperative quantification of bone loss has a significant impact on surgical decision making and patient outcomes. Various measurement techniques for calculating glenoid bone loss have been proposed in the literature. To date, no studies have directly compared measurement techniques in order to determine which techniques, if any, is the most reliable. The aim of this investigation was to identify the most consistent and accurate measurement technique(s) for measuring glenoid bone loss in anterior glenohumeral instability.

Methods

Six fresh-frozen human shoulders with 3 incremental bone defects were sequentially created resulting in a total of 18 glenoid bone defect samples. Two- and three-dimensional representative CT scan en face images were used for analysis. Six observers (three experienced and three with less experience) measured the bone defect of all the samples with HOROS imaging software using 5 commonly employed methods. The methods included 2 linear techniques (Shaha, Griffith), 2 surface techniques (Barchilon, PICO) and one statistical shape model formula (Giles). Intraclass correlation (ICC) using a consistency model was used to determine consistency between surgeons for each of the measurement methods. Paired t-tests were used to calculate the accuracy of each measurement technique relative to physical measurement.

Results

For more experienced observers, all methods indicated good consistency (ICC>0.75), except the Shaha method which indicated moderate consistency (0.65<ICC<0.75). Estimated consistency among the experienced observers was better for 2D than 3D images though the differences were not significant (intervals contained 0). For less experienced observers the Giles method in 2D had the highest estimated consistency (ICC: 0.88, 95%CI: 0.76, 0.95), though Giles, Barchilon, Griffith and PICO were not significantly different. Among less experienced observers the 2D images using Barchilon and Giles methods had significantly higher consistency than the 3D images. Regarding accuracy, most of the methods significantly overestimated the actual physical measurements by a small (mean within 5%) amount. The smallest bias was observed for the 2D Barchilon measurements and the largest differences were observed for Giles and Griffith methods for both observer types.

Conclusion

Glenoid bone loss calculation presents variability depending on the measurement technique, with different consistencies and accuracies. We recommend the use of the Barchilon method by surgeons who frequently measure glenoid bone loss because it presents the best combined consistency and accuracy. However, if glenoid bone loss is measured occasionally, the most consistent method is Giles method, although an adjustment for the overestimation bias may be required.