The main objective of this study was to evaluate the association between the acromial index (AI) and the incidence of recurrent tears of the rotator cuff (RC) in a cohort of patients with full thickness tears who underwent arthroscopic primary repair. A prognostic study of a prospective case series of 103 patients with full thickness RC tears was undertaken. The average age was 59.5 years (39-74) and follow-up was 30.81 months (12-72). True anterior-posterior X-rays were obtained during the pre-operative evaluation. Pre and post-operative magnetic resonance imaging (MRI) were recorded. Eighteen cases with recurrent tears (17.4%) were seen on post-operative MRI. The average AI for patients with recurrent tears was 0.711 ± 0.065 and for patients without recurrent tears 0.710 ± 0.064 (p < 0.05). A positive association between age and recurrent tears of the RC was noted (average ages: recurrent tears group 63 ± 5.9 years; group without recurrent tears 58.8 ± 7.5 years) (r = -0.216; p = 0.029). We did not find an association between size of the primary tear and recurrent tears (r = -0.075; p < 0.05) or between degrees of retraction of the primary and recurrent tears of the cuff (r = -0.073; p < 0.05). We observed that 38.9% of the recurrent tears cases presented with more than one tendon affected before the arthroscopy. At follow-up, none of these recurrent tears showed more than one tendon affected on MRI evaluation. In this study, we found that the AI radiological measurement is not a predictor for recurrent tears of the RC after primary arthroscopic repair.