The effect of gap arthroplasty on temporomandibular joint ankylosis: an experimental study

The aim of this study was to demonstrate the functional and anatomical chan ges after gap arthroplasty release of unilateral temporomandibular joint (T MJ) ankylosis. Five adult sheep weighing an average of 57 kg were used. All right joints were operated. Ankylosis was induced in the right TMJ by arti cular damage, disk removal and placement of a bone graft plus immobilizatio n wire. At 3 months the gap arthroplasty were performed. All TMJs were exam ined functionally, radiologically, macroscopically and histologically, Func tionally, the range of jaw movements decreased following induction of ankyl osis (P <0.0001), increased immediately on release but was reduced again at 3 months after release (the vertical movement, no statistically significan t difference; the right movement, P <0.001, the left movement, P <0.0001). Histologically, all operated joints showed fibrous adhesions across the gap , and further, the articular surface was irregular with osteophytes and wit h bony islands in the gap. This appearance is more consistent with a fibrou s reankylosis than a functioning pseudo joint. This study shows that the ga p arthroplasty for TMJ ankylosis did not restore the TMJ functionally and h istologically to the preexisting state.