Authors’ Disclosure Statement: The authors report no actual or potential conflict of interest in relation to this article.
Dr. Frank is Assistant Professor, Department of Orthopaedic Surgery, University of Colorado School of Medicine, Aurora, Colorado. Mr. Golijanin is a Medical Student, Geisel School of Medicine, Dartmouth Medical School, Hanover, New Hampshire. Dr. Vopat is Assistant Professor, Department of Orthopaedic Surgery, University of Kansas, Kansas City, Kansas. Dr. Gross is a Resident, DGMD Medical, Omaha, Nebraska. Dr. Chauhan is a Resident, Ninewells Hospital, Dundee, United Kingdom. Dr. Romeo is Chief of Orthopaedics, Rothman Institute New York, New York. Dr. Provencher is an Orthopaedic Surgeon, The Steadman Clinic, Vail, Colorado.
Address correspondence to: Rachel M. Frank MD, Department of Orthopaedic Surgery, University of Colorado School of Medicine, Aurora, CO 80045 (email, Rachel.Frank@ucdenver.edu).
Am J Orthop. 2018;47(6). Copyright Frontline Medical Communications Inc. 2018. All rights reserved.
Rachel M. Frank, MD Petar Golijanin, BS Bryan G. Vopat, MD Daniel J. Gross, MD Vidhya Chauhan, BS Anthony A. Romeo, MD CAPT Matthew T. Provencher, MD, MC, USNR . Impact of Sagittal Rotation on Axial Glenoid Width Measurement in the Setting of Glenoid Bone Loss. Am J Orthop.
June 5, 2018
References
The current gold standard for GBL measurement is a perfect-fit circle performed on a 3-D CT scan.22 To that end, it would have been useful to measure the glenoids from this study on 3-D CT scans and compare the data with both UNCORR and CORR measurements. This would have provided a better understanding to what extent the CORR measurements on 2-D scans are relatable with the gold standard. As 3-D CT scans provide a better en face view of the glenoid, more accurate GBL measurements, and ease of 3-D manipulation, they have become more widely used across the country.29,30 Nevertheless, in situations where 3-D imaging is more challenging to obtain because of technology or cost limitations, having a strategy for ensuring proper orientation of 2-D scans would have a substantial impact on clinical decision-making. If such corrections are not made, the inaccuracy of current 2-D scanning protocols justifies the cost 3-D reconstruction protocols. The difference in GBL measurements are critical in cases of increasingly large degrees of GBL, as in these instances, the inferior glenoid becomes more of an inverted-pear shape as opposed to a perfect circle, and differences in CORR and UNCORR images are likely to be more profound.
LIMITATIONS
This study has limitations, such as the relatively small sample size and the selection bias by the reviewers with potential differences in interobserver reliability. Further, minor modifications during the reformatting process may be found with each attempt to manipulate the images and may result in minor, insignificant differences in AP width measurements. Performing 1 or more additional CT scans on the same cohort of patients would have been helpful; however, due to the increased risk of radiation exposure, this was not performed. Performing CT scans on cadaveric specimens with GBL and applying the study methodology would also have been helpful to provide independent verification of our clinical findings; however, specimens were not available for this study. Another limitation of this study is that we did not compare our findings with the findings of glenoid width, and bone loss, as determined using the circle method, which is commonly utilized when 3-D reconstructions are available. In this study, the purpose was to utilize only the 2-D reformatted images, with the assumption that 3-D reconstructions are not always available, and cannot always be measured. To minimize selection bias, the investigators measured the correction effects within groups of patients with similar degrees of GBL (10%-14.9%, 15%-19.9%, and >20%). In addition, not all the selected patients showed degenerative glenoid changes or irregular glenoid shape indicating previous bone augmentation.
CONCLUSIONS
UNCORR 2D CT scans inaccurately estimate glenoid width and the degree of anterior GBL. The clinical implications of these findings are profound and suggest corrected 2D CT scans or 3D reconstruction allow measurements to be taken in the axis of the glenoid to accurately define the anatomy and quantity of anterior GBL in patients with shoulder instability.