PURPOSE: The X index is a measure of the antero-inferior glenoid @entity604 on unilateral 2D CT-scans in the preoperative analysis of chronic anterior shoulder instability. Recurrence rate was shown to be higher after stabilization surgery if X index is superior or equal to 0.4. The objective of this study was to assess the intra- and inter-observer reliability of the X index. METHODS: Sixty @entity1 with an X index >= 0.4 were included retrospectively. The X index was measured twice by two independent evaluators, 15 days apart. The measurement was performed on a unilateral 2D CT-scan by dividing the length of the antero-inferior @entity154 over the maximal antero-posterior diameter of the glenoid. Reliability of X index was assessed with intra-class correlation coefficient (ICC,   ). Two points were added to the ISIS calculation if its glenoid criterion was "zero" and we compared this modified score to the original one. RESULTS: The intra-observer reliability of the X index measurement was "excellent" (   = 0.95    0.01, p < 0.0001) while the inter-observer reliability was "good" (   = 0.59    0.08, p < 0.0001). In @entity1 with a glenoid @entity604 visualized by the X index, 48.3 % had a negative @entity3808 glenoid line sign. This proportion significantly decreased with the augmentation of the X index, p = 0.02. The average original ISIS score was 3.4    1.9 and became 4.3    1.7 (p < 0.00001) when the X index was incorporated. CONCLUSIONS: The X index is a reliable and simple unilateral 2D CT-scan measurement. AP shoulder radiographs significantly underestimated @entity75 .

The intra- and inter-observer reliability of the CT-scan based X index to quantify glenoid XXXX in chronic anterior shoulder instability and its impact on decision making.

@entity1 :: ('9606', 'Species') :: ['patients'] @entity154 :: ('MESH:D000013', 'Disease') :: ['glenoid defect'] @entity75 :: ('MESH:D001927', 'Disease') :: ['glenoid bony lesions'] @entity604 :: ('MESH:D016301', 'Disease') :: ['bone loss'] @entity3808 :: ('MESH:C538213', 'Disease') :: ['sclerotic']
@entity604 :: (MESH:D016301,Disease) :: ['bone loss']
