A new significance of an old structure: Aponeurotic expansion of supraspinatus tendon and its relationships with biceps brachii long head and rotator cuff tendons

Purpose: To investigate the relationship between aponeurotic expansion of supraspinatus tendon and disorders of biceps brachii long head (LHB), supraspinatus and subscapularis tendons. Methods: Images of 3.0 T shoulder magnetic resonance images (MRI) of a total of 154 patients and 157 shoulders (3 cases with bilateral imaging) between the ages of 18-45 were retrospectively evaluated for the presence of aponeumtic expansion. When identified it was further categorized according to its thickness. Tendinopathy and tears of LHB, supraspinatus and subscapularis tendons and LHB subluxations were evaluated individually. Statistical analyses were performed using Chi-square, Fisher's exact, Mann-Whitney U and Kruskall-Wallis tests. Odds ratio and multiple logistic regression analyses were performed when applicable. p < 0.05 was considered as statistically significant. Results: A total of 82 male and 72 female cases with a mean age of 34 (+/- 8.2) were included. Aponeurotic expansion could be identified in 31 cases (19.8 %). MRI findings for LHB disorders in this group was significantly higher (p = 0.01). The adjusted odds ratio of having LHB tendinopathy in the presence of aponeurotic expansion was 3.25 (% 95 CI:1.29-8.19). No significant correlation was found between presence of aponeurotic expansion and subscapularis or supraspinatus tendon disorders (p = 0.66 and p = 0.792 respectively). Age was a significant variable for disorders of all three tendons (p < 0.001). Conclusion: On 3.0 T MRI, findings of LHB tendon disorders were significantly more common in cases with aponeumtic expansion of supraspinatus tendon. This anatomical variation may have an unrecognized clinical significance.