Extraskeltal Outgrowth of Solitary Synovial Osteochondroma of the Cervical Spine: A Case Report

We report a rare case of a solitary synovial osteochondroma (SSO) in the cervical canal. A 37-year-old man presented with neck pain and the forearm dysesthesia developed immediately after a trivial motor accident. Because of aggravation he visited our hospital though he was treated conservatively for 3 months. A computed tomography (CT) scan showed an oval shaped small mass with high density rim in the cervical canal at the level of the C6/7 facet joint. This mass compressing the dural sac was visualized with a high intensity signal in T2-weighted magnetic resonance imaging (MRI) and, interestingly, with high intensity in T1-weighted images. A surgical removal was carried out. Macroscopically, it consists of a solitary, firm, juxta-articular mass associated with synobia but lacking connection with the adjacent bone. Microscopically, it is similar to conventional osteochondromas. It differs from this entity by not arising from a bone surface and by a whole coverage of synobial tissue. The final diagnosis was a SSO. There have been anecdotal case reports of a SSO in various site including knee, fingers, buttocks, wrist, and so on. To the best of our knowledge, this is the first case report of SSO arising in the spinal canal.