Pathological changes after the surgical creation of a vertical intracapsular condylar fracture.

The aim of this study was to create in a sheep model an intracapsular oblique vertical split fracture, and observe the histopathological changes in the temporomandibular joint (TMJ) condylar head. In 10 sheep, the right TMJ was operated through the preauricular region. The anterior and posterior attachments of the disc were cut; an oblique vertical osteotomy was made from the lateral pole of the condyle to the medial side of condylar neck. The condylar fragment was pushed anteriorly, inferiorly and medially together with the disc. The non-operated left TMJ served as control. Two sheep were killed at 1 week and four at both 4 and 12 weeks. Computed tomography scans were taken and histopathological changes of the joint observed. There was severe bone erosion and a new bony outgrowth on the lateral side of the condylar stump and temporal bone. The joint spaces were filled with fibrous tissue, cartilage tissue and bone in the 4 and 12 weeks operated groups. These results show that an oblique vertical intracapsular fracture through the lateral condylar pole, combined with an anteriorly and medially displaced condylar fragment and disc and damaged lateral capsule, are likely to result in the pathological changes of osteoarthritis, and the progressive development of ankylosis in a sheep TMJ.