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E1136. Novel Lesions: A Case of Friendly Fire?
Authors
  1. Ramon Saucedo; Houston Methodist Hospital
  2. Aydin Soheili; Houston Methodist Hospital
  3. Michael Trakhtenbroit; Houston Methodist Hospital
  4. Devon Divito; Houston Methodist Hospital
  5. Rupert Stanborough; Mayo Jacksonville
  6. John Labis; Houston Methodist Hospital
  7. Stephen Herrmann; Houston Methodist Hospital
Background
Rotator cuff tears are common and typically located at the distal tendon insertion, most frequently the supraspinatus tendon. Less common are myotendinous junction injuries with rapid progression to muscular atrophy. Orthopedic literature described a novel lesion, isolated tear/rupture of the Infraspinatus myotendinous junction, which can be arthroscopically occult with intact distal tendon fibers. Multiple risk factors have been discussed such as inadvertent steroid injection administered into the infraspinatus myotendinous junction. Rat studies demonstrated steroid injection causing cuff collagen structural degradation/fragmentation with worsening upon repetitive injection. Subacromial/posterior glenohumeral injections are common and typically performed in clinics without imaging guidance. The path of these injections approximates the infraspinatus myotendon putting it at risk for injection. Cadaveric studies have demonstrated inaccuracy with accidental rotator cuff injections and may explain the uncommon isolated myotendinous junction injury with intact distal tendon. Due to the rapid progression to muscular atrophy and poor clinical outcomes it is important for radiologists to convey this atypical injury to orthopedic surgeons and improve understanding of atypical mechanism of injury.

Educational Goals / Teaching Points
Novel lesions have been described in orthopedic literature as isolated delaminating tears of the infraspinatus tendons with intact tendon root insertion. There has been minimal radiological discussion of this unique tendon pathology. The intact tendon can be arthroscopically occult with imaging important in making referring orthopedics aware of occult arthroscopic lesion. Orthopedic literature has evaluated potential risk for this unique injury with steroid injections reported as possible risk factor. We review multiple cases of Novel lesions from both our institutions to educate attending and resident radiologists about these uncommon presentations. Additionally, each case will have clinical history including history of prior steroid injection

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Multiplanar Shoulder MRI demonstrating isolated delaminating infraspinatus myotendinous junction tears with intact distal tendon. Evaluation of inaccurate subacromial and posterior glenohumeral injections from prior studies as well as tendon degeneration from steroid injection.

Conclusion
We identified 5 cases of isolated infraspinatus myotendinous junction delaminating tears with intact distal tendon insertions. These unique patterns of injuries can be arthroscopically occult and it is important for radiologists to be aware of these uncommon injuries. A majority of these tears had a prior history of steroid injection which has been reported as a risk factor. Additionally, non-image guided steroid injections have been shown to be inaccurate from both the subacromial/posterior glenohumeral approaches. Inaccuracy of non-image guided injections may explain this unique pattern of myotendinous delaminating injury with intact tendon insertion. Further evaluation of this association is needed to establish this relationship.