MRI Soft Tissue Interpretation

This is a chronic full-thickness supraspinatus tear with significant retraction. I would assess: (1) Tear size - measure AP dimension (small less than 1cm, medium 1-3cm, large 3-5cm, massive greater than 5cm). (2) Retraction - retraction to glenoid level is significant (approximately 3cm), affects repair tension. (3) Fatty infiltration - the high T1 signal in supraspinatus fossa indicates fatty replacement, I would grade using Goutallier (0-4). If Goutallier 3-4, repair outcomes are poor. (4) Tangent sign - supraspinatus below the line connecting scapular spine indicates atrophy. (5) Other rotator cuff tendons. Poor prognostic factors: Large tear, significant retraction, Goutallier 3-4 fatty infiltration, positive tangent sign.

The differential includes intramuscular lipoma versus well-differentiated liposarcoma. Concerning features present: (1) Size greater than 10cm - very large for benign lipoma. (2) Thick septae greater than 2mm - benign lipomas have thin septae less than 2mm. (3) Deep/intramuscular location. The mass following fat signal on all sequences is reassuring but doesn't exclude well-differentiated liposarcoma (also called atypical lipomatous tumour). I would recommend referral to a tumour centre for biopsy/excision. Even if histology shows lipomatous tumour, complete excision is warranted given concerning imaging features.

Diffuse muscle oedema (high T2/STIR with normal T1) in the calf has several differentials: (1) Denervation oedema - if following sciatic/tibial nerve distribution, consider nerve pathology (acute denervation shows oedema, chronic shows fatty replacement). (2) Inflammatory myopathy - would expect symmetric involvement, check CK and consider polymyositis/dermatomyositis. (3) Exercise-induced - recent intense exercise can cause diffuse muscle oedema. (4) Infection (pyomyositis) - usually more focal, look for abscess, systemic symptoms. (5) Early compartment syndrome - clinical correlation essential. Given the history of running, I would consider either exercise-induced changes or early exertional compartment syndrome. If symptoms persist post-exercise, compartment pressure measurement may be indicated.