Int Orthop. 2012 May;36(5):1019-24. doi: 10.1007/s00264-012-1499-4. Epub 2012 Feb 8.


PURPOSE: The purpose of this study was to identify the relationship between an acromion index (AI) and the size of a rotator cuff tear. The hypothesis of our study was that an AI will be higher in patients with a full-thickness tear than in patients with a partial-thickness articular-side tear, and that it can be used as a predictor for the size of a rotator cuff tear.
METHODS: We included 284 patients who had been diagnosed with rotator cuff tears and had undergone arthroscopic rotator cuff repair at our institute. All patients were divided into five distinct groups (partial-thickness articular side tear, and four subgroups of full-thickness tears) depending on the size of the rotator cuff tear on arthroscopy. In each patient, an AI was measured on the pre-operative oblique coronal MR images and then analysed to determine the difference between groups.
RESULTS: There were statistically significant differences between the partial-thickness articular side rotator cuff tear and large-to-massive rotator cuff tear groups (p < 0.01), and the mean value of an AI was highest in the large-sized full-thickness tear group. The AI of the partial-thickness articular-side rotator cuff tear group was statistically different from the large-to-massive rotator cuff tear groups.
CONCLUSIONS: The AI can be a predictor which can differentiate a partial-thickness articular-side tear and a large-to-massive rotator cuff tear pre-operatively. However the AI could not provide useful guidance on predicting the differences in tear size in full-thickness tear patients. We suggest that a high AI can be one of the associated factors for progression to large-to-massive rotator cuff tears in a rotator cuff disease.