PURPOSE: The X index is a measure of the antero-inferior glenoid bone loss 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 patients 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 glenoid defect over the maximal antero-posterior diameter of the glenoid. Reliability of X index was assessed with intra-class correlation coefficient (ICC, ρ). 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" (ρ = 0.95 ± 0.01, p < 0.0001) while the inter-observer reliability was "good" (ρ = 0.59 ± 0.08, p < 0.0001). In patients with a glenoid bone loss visualized by the X index, 48.3 % had a negative sclerotic 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 glenoid bony lesions.
PURPOSE: The X index is a measure of the antero-inferior glenoid bone loss 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 patients 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 glenoid defect over the maximal antero-posterior diameter of the glenoid. Reliability of X index was assessed with intra-class correlation coefficient (ICC, ρ). 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" (ρ = 0.95 ± 0.01, p < 0.0001) while the inter-observer reliability was "good" (ρ = 0.59 ± 0.08, p < 0.0001). In patients with a glenoid bone loss visualized by the X index, 48.3 % had a negative sclerotic 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 glenoid bony lesions.
Authors: Patrick E Greis; Matthew G Scuderi; Alexander Mohr; Kent N Bachus; Robert T Burks Journal: J Shoulder Elbow Surg Date: 2002 Sep-Oct Impact factor: 3.019
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