Bone marrow edema in the acromioclavicular joint after arthroscopic rotator cuff repair.

BACKGROUND: Bone marrow edema (BME) in the acromioclavicular joint (ACj) may occur after arthroscopic rotator cuff repair (ARCR), resulting in persistent postoperative ACj pain. We investigated the incidence and clinical characteristics of BME in ACj after ARCR.

METHODS: Patients exhibiting ACj-related symptoms prior to ARCR surgery, no BME in the ACj on MRI, and an ability to undergo 2-year postoperative physical and MRI examinations of the ACj were included. Patients who underwent distal clavicle resection or osteophyte resection below the ACj and those unable to achieve primary repair of the rotator cuff were excluded. MRI evaluation was performed preoperatively and at 3, 6, 12, and 24 months postoperatively. Patients who showed BME in ACj on fat-suppressed T2 MRI at 24 months postoperatively were classified into the BME + group, and those with no BME were classified into the BME- group. Patient background, operation time, Japanese Orthopedic Association (JOA) score, re-tear rate, ACj tenderness, and cross-body adduction test were compared between groups. In addition, we examined the time of occurrence of BME.

RESULTS: A total of 345 ARCRs were performed during the study period. After the exclusion of 114 shoulders, the remaining 231 shoulders were included in this study. There were 208 cases in the BME- group and 23 cases in the BME + group. The incidence of BME was 9.96 %. Although the JOA scores of both groups showed a significant improvement postoperatively compared to preoperatively, there was no significant difference between the two groups. In terms of re-tear, there was 1 case in the BME + group and 7 in the BME- group. Positive ACj tenderness and cross-body adduction test were significantly higher in the BME + group (P < 0.001). BME occurred in 6 cases at 3 months, 9 cases at 6 months, and 8 cases at 1 year postoperatively. None of the patients developed BME at more than 1 year postoperatively. BME was observed on MRI in all cases at 2 years postoperatively.

CONCLUSIONS: The rate of occurrence of BME in the ACj after ARCR was 9.96 %. Patients with BME were significantly more likely to have ACj tenderness and positive cross-body adduction test. BME in the ACj often occurs within 6 months to 1 year after ARCR of small-to-medium rotator cuff tears, suggesting a relationship with postoperative functional improvement of the shoulder joint. The ACj should be considered as a potential site of persistent pain after ARCR for small-to-medium rotator cuff tears.