Nonsurgically treated rotator cuff tears sometimes become irreparable in the lead up to surgical repair. The purposes of our study were to identify predictive factors in the progression of tear size, and determine the changes in tear location.

Eighty shoulders from 71 patients (mean age 69.4 years) diagnosed with rotator cuff tears by MRI were treated nonsurgically. MRI was repeated after more than 1 year of initial diagnosis. Tear size was measured from the edge of the tear to the lateral aspect of the greater tuberosity. Tears were classified into 5 groups based on tear size and 4 groups based on tear location. Changes in tear size and location were examined.

The mean follow-up period was 22.3 months. The average progression of tear size was 5 mm during follow-up, averaging 3 mm per year. Tears that were initially <1 or ≥4 cm were unlikely to progress in tear size. On the other hand, 1- to 2-cm tears on the initial MRI exhibited the greatest progression in tear size, followed by 2- to 3-cm tears. Furthermore, 62.5 % of localized tears in the posterior of the superior facet spread anteriorly, whereas 88.9 % of localized tears in the anterior of the superior facet did not change.

Medium-sized tears are at high risk of tear progression. In contrast, there is little risk of early development of irreparable damage in partial tear or small full-thickness tears. In addition, typical tears may start in the posterior of the superior facet, and subsequently spread anteriorly. Our present findings may serve as a useful reference in determining the treatment course for rotator cuff tears.

Level IV, Case Series, Prognosis Study.