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Quantifying Glenoid Bone Loss: CT versus Arthroscopy

September 8, 2009
Written by: , Filed in: Musculoskeletal Radiology
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The objective of a recent study was to determine the presence and severity of glenoid bone loss in patients with prior shoulder dislocations. It has concluded that bone loss of the glenoid after shoulder dislocations may necessitate the need of augmentation surgery rather than capsulolabral repair alone.

Background
Glenoid bone loss is commonly seen after shoulder dislocation, especially recurrent dislocations. In severe cases, glenoid rim augmentation is necessary, rather than capsulolabral repair alone for joint stabilization. During arthroscopy, bone loss is assessed, measuring the distance from the glenoid bare spot to the anterior and posterior glenoid rims. CT assessment is based on comparison with the normal shoulder.

Participants
50 patients with unilateral shoulder dislocation underwent CT examination prior to arthroscopy. In this group, 74% of patients had recurrent prior shoulder dislocations, ranging from 2 to 50 dislocations. The mean time interval between CT and arthroscopy was 28.5 days (range, 9 to 73 days).

Methodology
Axial CT images were obtained and reconstructed in the oblique sagittal plane. The long axis of the glenoid was determined, and glenoid width was measured perpendicular to this axis in the mid-aspect of the glenoid. Bone loss was diagnosed if there was an anterior straight line to the glenoid and there was a reduced size compared with the normal side; both criteria needed to be present. The percentage of bone loss was calculated. Arthroscopic measurements were reported in 5% intervals.

MDCT and MR Update: Body and Musculoskeletal Imaging

University of California San Francisco, Department of Radiology and Biomedical Imaging
MDCT and MR Update: Body and Musculoskeletal Imaging program features helical multi-detector row CT (MDCT) and MRI as it applies to diseases in the chest, abdomen and pelvis, and musculoskeletal system. Newer and established cross-sectional methods are discussed. Click here to read more or order:

MDCT and MR Update: Body and Musculoskeletal Imaging


Results
41 of the 50 patients (82%) had bone loss at arthroscopy. Glenoid bone loss was diagnosed in 80% (40 patients) on CT, which had a sensitivity of 92.7%, a specificity of 77.8%, a positive predictive value of 95%, and a negative predictive value of 70%. There were 3 false-negative CTs, with arthroscopy showing 5%, 10%, and 10% bone loss in those cases. Two of the CTs were false positive.

The amount of bone loss on CT was determined to be 5.7% and 8.7%. No significant difference was found between mean glenoid bone loss seen on CT compared with arthroscopy. The degree of severity of the bone loss correlated very strongly with CT with respect to arthroscopy (correlation coefficient, 0.79; 95% CI, 0.659 to 0.877; P <0.0001). Reviewer’s Comments
Glenoid bone loss is common in patients with shoulder dislocations, especially if they are recurrent. CT has a high sensitivity and specificity of bone loss detection. CT does use radiation, and there is known side variability in glenoid size, although this has shown to be small. In addition, it results in additional time and cost. Arthroscopy, although used as the gold standard, is not ideal. Measurements may be inaccurate and can both under- and over-estimate bone loss.

Conclusions
CT has a high sensitivity and specificity for the detection of bone loss. There is good agreement between CT and arthroscopy.

Author: Cornelia Wenokor, MD

Reference:
Griffith JF, Yung PSH, et al. CT Compared With Arthroscopy in Quantifying Glenoid Bone Loss. AJR; 2007; 189 (December): 1490-1493

MDCT and MR Update: Body and Musculoskeletal Imaging

University of California San Francisco, Department of Radiology and Biomedical Imaging
MDCT and MR Update: Body and Musculoskeletal Imaging program features helical multi-detector row CT (MDCT) and MRI as it applies to diseases in the chest, abdomen and pelvis, and musculoskeletal system. Newer and established cross-sectional methods are discussed. Click here to read more or order:

MDCT and MR Update: Body and Musculoskeletal Imaging

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