Poster 108: The Deep Region of the Supraspinatus Is Architecturally Distinct

Objectives: The supraspinatus (SSP) tendon is the most frequently involved in rotator cuff tears, a common orthopedic condition. Previous anatomical studies have described distinct anterior and posterior regions of SSP muscle. purpose this study to determine if deep region muscle has significantly different architectural properties from other regions. This could implications on mechanical functional nature Methods: Architecture measurements were collected 25 cadaver SSPs (Figure 1). There 13 without tear, 3 with partial 9 full tears. dimension humeral head (APHH), musculotendinous junction length (MTJL), mass recorded. demarcated as deep, [superficial] anterior, posterior. Raw normalized fiber length, pennation angle, sarcomere number analyzed for each region. Measurements compared using repeated measures ANOVAs. intact first, then sub-analysis was performed based presence tear. Results: In tears 2), showed lower mean angle 3.3±1.0° than (11.0±3.9°, p<0.0001), which had higher (7.6±2.6°, p=0.0005). Normalized lengths 21.1% (p=0.0052) 34.5% (p<0.0001) shorter respectively. Deep sarcomeres measured 3.4±0.2 µm 3.1±0.2 (posterior, p=0.0012) 3.2±0.2 (anterior, p=0.0390). Sarcomere also decreased by 21.2% (p=0.0056) 34.2% regions, After including (n=3) (n=9) all architecture remained versus or Finally, help visualize SSP, diffusion tensor imaging tractography healthy volunteer’s MRI 3) depict tissue microstructure orientation/length. Conclusions: angles, lengths, fewer but longer sarcomeres. These structural differences suggest functionally unique ‘submuscle’ within supraspinatus.