Extra-Articular Tenosynovial Chondromatosis of the Finger: A Case Series Study of Three Cases, One Including Excessive Osseous Invasion

BACKGROUND Synovial chondromatosis is characterized by cartilaginous metaplasia in synovial tissues. Extra-articular tenosynovial chondromatosis is considered to be an anatomical counterpart of articular synovial chondromatosis. Extra-articular tenosynovial chondromatosis occurs preferentially in the hand, although its frequency is low. RESULTS We report three cases of extra-articular tenosynovial chondromatosis. A 65-year-old female presented with a history of symptoms over 40 years related to the dorsum of her index finger (Case 1), A 46-year-old female presented with a 6-month history of symptoms at the volar surface of her middle finger (Case 2), and a 66-year-old male presented with a 3-month history of symptoms in a dorsal ring finger. Case 2 had evidence of ossification, which could be classified as osteochondromatosis. Interestingly, the index finger lesions (Case 1) were accompanied by excessive bone involvement. The signal intensity of T2-weighted magnetic resonance imaging varies from low to high, possibly reflecting histological variations, such as ossification and fatty tissue changes. All lesions were resected without complications. CONCLUSION Variations in anatomical sites suggest that overuse or mechanical overloading was not causative. Extensive involvement of the nearby tendon and joint capsule, as well as the bone, would require attention during the resection. Preoperative analysis of images is important, not only for the diagnosis, but also to assess the extent of the lesion, particularly given the complex anatomy of the finger.