Pseudodefect of the Capitulum

The capitulum narrows distally, where there is a change in contour at the junction of the capitulum anteriorly with the lateral epicondyle posteriorly. This change in contour at the posterolateral margin can look like an osteochondral defect and is referred to as the "pseudodefect of the capitulum"

Coronal images through the posterior capitulum and sagittal images through the lateral epicondyle can demonstrate this apparent defect.

Real osteochondral defects can be differentiated from this pseudodefect by the presence of flattening and deformity of the anterior surface of the capitulum, which is normally smooth. In addition, acute osteochondral defects are usually accompanied by bone marrow signal abnormalities.

References

Hughes T, Chung CB. Chapter 12. In Chung CB and Steinbach LS. MRI of the Upper Extremity: Shoulder, Elbow, Wrist, and Hand. Lippincott Williams & Wilkins. 2010. pp 462.