Ultrasonographic and MRI Explorations of Infraspinatus Muscle in Postero-superior Rotator Cuff Tear

The rotator cuff of the shoulder consists of 4 tendinomuscular units including the infraspinatus. This complex system fulfils a double role: stabilization/coaptation (raising the arm) and arm mobility (especially external rotation). Rupture of rotator cuff tendons is frequent (> 80% among chronic shoulder pain). They go with a decrease in muscle volume (amyotrophy) and irreversible fat infiltration. The treatment is medical and then surgical (if necessary). The degrees of atrophy and muscle infiltration (especially infraspinatus) are the criteria of choice for surgery. Actually, they are assessed in MRI according to the classification of Fuchs; it is operator dependent, qualitative and poorly reproducible with a strong inter-observer variability. Our team highlighted (2016) the possibility of using texture analysis software to objectively measure the proportion of fatty tissue on MRI sections of the cuff rotator muscles. This work also showed the possibility of using mode B ultrasound for morphological imaging and shear wave elastography to estimate the elasticity of the infraspinatus. The project aims to evaluate the contribution of texture analysis on MRI sections, and the technical feasibility, reproducibility, and clinical relevance of quantitative ultrasound and elastography to characterize the composition and volume of infraspinatus muscle in postero-superior rotator cuff tears. The perspectives are to optimize the imaging to allow a quantitative, objective and reproducible analysis of the muscle tissue and its characteristics.