Rotator Cuff Muscular Edema in Human: A Clinical and Radiological Analysis From the LaTour Group.

Background: Early formation of muscle edema after rotator cuff injury has previously been demonstrated in an animal model. Purpose: To describe the same phenomenon in humans through analysis of rotator cuff muscle edema on magnetic resonance imaging/arthrography (MRI/MRA). Study Design: Cross-sectional study; Level of evidence, 3. Methods: Demographic, clinical, and radiological characteristics of patients with both a history of trauma and clear muscle edema of the rotator cuff were analyzed. Two groups were established based on the degree of concomitant fatty infiltration: (1) an acute group with little to no fatty infiltration of the rotator cuff muscle, and (2) an acute-on-chronic group with significant presence of fatty infiltration. Results: Of the 71 shoulders, 45 (63.4%) were identified as acute lesions and 26 (36.6%) as acute-on-chronic lesions. Patients in the acute group were younger (60 ± 11 years [range, 38-83 years] vs 68 ± 11 years [range, 52-90 years]; Conclusion: Muscle edema of retraction helps to distinguish new traumatic rotator cuff injury from acute extensions of preexisting lesions via fatty infiltration and age at presentation. The difference in time between symptom onset and MRI/MRA is also a discriminating factor.