Shoulder instability may have distinct, identifiable imaging features on CT, MRI
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Key takeaways:
- Shoulder instability has distinct imaging features, according to a presenter.
- MRI, MR arthrography and CT may be useful in identifying and evaluating instability conditions.
KOLOA, Hawaii — Characteristics of shoulder instability may be identified by distinct imaging features on MRI, MR arthrography and CT, according to a presenter here.
In her presentation at Orthopedics Today Hawaii, Pamela J. Lund, MD, national director of musculoskeletal imaging at SimonMed Imaging, said an integral key to accurately identifying shoulder instability is adherence to MRI anatomy and protocols.
“We like to do high-field imaging and dedicated shoulder coils,” Lund said. “We want to be in an externally rotated position, and we are going to do fat- and fluid-sensitive sequences in three planes. We do not just scan it as it lies. In our sagittal plane, we want to go parallel to the glenoid. And in the coronal plane, parallel to the supraspinatus tendon. It should take about 15 to 20 minutes. The tendons are going to be homogeneously low signal in the normal state.”
Lund utilizes MR arthrography, which she said is optimal in certain situations.
“I find it helpful in capsular injuries and throwers that have those shoulder girdle muscle injuries,” Lund said. “[For] recurrent instabilities with postoperative patients with re-injury and normal MRIs with recurrent instability, you might want to get the arthrogram.”
In addition, Lund said CT and MRI are both accurate for detecting and quantifying Hill-Sachs lesions and glenoid bone loss. However, she noted there are several pitfalls when working with Hill-Sachs deformities and glenoid bone loss.
“Remember, you cannot just measure the Hill-Sachs deformity and the glenoid,” Lund said. “You have to correct for the actual size of the rotator cuff attachment to the Hill-Sachs and the functional availability of the surface of the glenoid.”
She added, “Traumatic shoulder instability has distinct imaging features. MRI can determine the chronicity, severity and location of abnormalities, and the arthrogram may add accuracy for labral and capsular abnormalities. But be familiar with specific artifacts. Measurements are good on CT and MRI, and specific instability patterns can be seen in specialized athletes.”
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Lund PJ. Shoulder MRI interpretation: Traumatic and atraumatic instability. Presented at: Orthopedics Today Hawaii; Jan. 12-16, 2025; Koloa, Hawaii.
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