The Perthes lesion is a variation of the Bankart lesion, where the scapula periosteum is lifted and stripped medially with the detached anterior labrum. The labrum may appear to be in a normal position at surgery, but is still unstable. It can be seen on MR or CT Arthrogram.
Perthes lesion on MR Arthrogram:
Ref: Perthes G. Ueber operationen bei habitueller schulterluxation. Dtsch Z Chir 1906;85: 199 -227