Pathology and clinical outcomes after arthroscopic stabilization in shoulders with traumatic anterior instability older than 40 years: Comparison between shoulders with the first dislocation before or after 40 years (241)

OBJECTIVES: Traumatic anterior shoulder instability is common in young population but sometimes seen in middle-aged and elderly patients. The higher incidence of rotator cuff tears has been reported in middle-aged and elderly patients with anterior shoulder instability than young population. We, however, had an impression through clinical experiences that the pathology, including the incidence of rotator cuff tears, might be different by age at the first dislocation. There have been few articles that reported the pathology of shoulders with anterior shoulder instability in older population. The purpose of this study was to investigate pathology and clinical outcomes in patients who underwent arthroscopic stabilization at 40 years or older and to compare them between shoulders with the first dislocation before or after 40 years. METHODS: The inclusion criteria of this study were as follows: 1) shoulders that underwent arthroscopic stabilization between October 2005 and September 2017, 2) traumatic anterior shoulder instability, and 3) 40 year old or older. The exclusion criterion was < 2-year follow-up. Glenoid morphology was evaluated with preoperative 3-dimensional computed tomography, and the size of glenoid bone defect was measured. Intraoperative findings, including rotator cuff tear, Bankart lesion, and humeral avulsion of the glenohumeral ligament (HAGL) lesion, and surgical procedures were investigated with surgical records. Range of motion was assessed preoperatively and at the final follow-up. Postoperative re-dislocation was also investigated. The subjects were divided into two groups according to the age at the first dislocation: Group 1, < 40 years; Group 2, 40 years or older. The findings and outcomes were compared between the two groups. The unpaired t-test was used to compare continuous data between the groups, and the paired t-test was used for pre- and postoperative comparison of continuous data. The chi-square test was used for categorical variables. The level of significance was set at p < 0.05. RESULTS: Between October 2005 and September 2017, 198 shoulders (198 patients) underwent arthroscopic shoulder stabilization for traumatic anterior shoulder instability at 40 years or older. Fifty-six shoulders were excluded due to < 2-year follow-up, and 142 shoulders (142 patients) were included in this study. They consisted of 69 males and 73 females with a mean age of 51 (range, 40-78) years. The mean follow-up was 4 (range, 2-12) years. Group 1 included 105 shoulders (52 males and 53 females] with a mean age of 48 (range, 40-77) years. Group 2 included 37 shoulders (17 male and 20 females) with a mean age of 59 (range, 40-78) years. Group 1 had a longer time from the first dislocation to surgery (P<.001) and larger number of dislocation (P<.001) than Group 2 (Table 1). Bony Bankart lesion was more frequently seen in Group 2 than Group 1 (P=.02), and bone defect was greater in Group 1 than Group 2 (P=.02). The incidence of Bankart lesion or HAGL lesion was not significantly different between the groups. There were 2 full-thickness (1 small and 1 medium) and 16 joint-side partial-thickness rotator cuff tears in Group 1, while 16 full-thickness (4 small, 4 medium, 5 large, and 3 massive) and 8 joint-side partial-thickness tears were found in Group 2. The difference in the incidence of rotator cuff tears was significant between the groups (P<.001). Arthroscopic Bankart repair (ABR) with or without augmentation was performed in 103 shoulders (98 %) in Group 1 and in 35 shoulders (95%) in Group 2 (Table 2). There were 2 isolated HAGL repairs (2 %) in Group 1 and 2 isolated rotator cuff repairs (6 %) in Group 2. Two shoulders (6%) in Group 2 experienced re-dislocation. Forward flexion showed significant improvement from 159 (range, 100-180) to 170 (range, 140-180) degrees in Group 1 and from 148 (range, 40-180) to 163 (range, 70-180) degrees in Group 2 (P<.001 for each). Postoperative forward flexion showed no significant difference between the groups. External rotation showed no postoperative changes in both groups, while Group 1 had significantly better pre- and postoperative external rotation than Group 2. CONCLUSIONS: This study demonstrated that the incidence of rotator cuff tears was much higher in shoulders with the first dislocation after 40 years compared to shoulders with the first dislocation before 40 years. Shoulders with the first dislocation before 40 years had larger glenoid bone loss, while 51% of shoulders with the first dislocation after 40 years retained bony fragments. The longer time from the initial injury to surgery might be associated with the larger glenoid bone loss and absorption of bone fragments. Both groups showed satisfactory outcomes with the low rate of complications.