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Effect of Sagittal Rotation on Axial Glenoid Width and Version: CT Scan Analysis in the setting of Anterior Bone Loss

      Introduction

      As standard 2-dimensional (2D) CT scans of the shoulder are often aligned to the body as opposed to the plane of the scapula/glenoid, the 3-dimensional (3D) anatomy of the glenoid may be distorted, and result in inaccurate measurements of glenoid width, version, and degree of GBL. The purpose of this study was to determine the effect of sagittal rotation on axial anterior-posterior (AP) glenoid width measurements in the setting of GBL.

      Methods

      A total of 44 CT scans from patients with a minimum of 10% anterior GBL were reformatted utilizing open-source DICOM software Osirix MD (version 2.5.1 65-bit) multi-planar reconstruction (MPR). Patients were grouped according to degree of anterior GBL: I) 10-14.9% (N=8), II) 15-19.9% (N=18), and III) >20% (N=18). The uncorrected (UCORR) and corrected (CORR) images were assessed in the axial plane at 5 standardized cuts and measured for AP glenoid width. When the measured AP width of the UCORR scan was less than that measured on the CORR scan, the AP width of the glenoid was considered underestimated, and the degree of GBL was considered overestimated.

      Results

      For Groups I and III, the UCORR scans underestimated the axial AP width in cuts 1 and 2, while in cuts 3-5, the axial AP width was overestimated. In Group II, the axial AP width was underestimated, while in cuts 2-5, the axial AP width was overestimated. Overall, AP glenoid width was consistently underestimated in Cut I, the most caudal cut, while AP glenoid width was consistently overestimated in cuts 3-5.

      Conclusion

      Uncorrected 2D CT scans inaccurately estimate glenoid width and the degree of anterior GBL and the findings of this study suggest a role for the utilization of corrected 3D reconstructions to allow more accurate measurements of the glenoid in order to accurately define the anatomy and quantity of GBL.