Study of Heterotopic Ossification after Alloplastic Temporomandibular Joint Replacement

Background: Heterotopic ossification (HO) is one of the serious complications leading to the failure of alloplastic temporomandibular joint replacement (TJR). However, there was few research on its exact incidence and occurrence. Severe HO might result in pain and limited mouth opening after surgery. Therefore, it is necessary to clarify its clinical and imaging manifestations. The purpose of this study was to study the occurrence and classify HO after the alloplastic TJR. Method Patients who underwent standard TJR with fat graft and at least 1-year-follow-up were included. HO was classified into 4 types according to postoperative computed tomography (CT) scans. Type and occurrence in different TMJ disease were compared. Joint space was measured between HO and non-HO TJRs. Maximum mouth opening (MIO), pain, and quality of life (QoL) were recorded and their relevance with HO was analyzed statistically. Result 81cases with 101 joints were included in the study. The mean follow-up time was 22.9 months. 48 joints (47.5%) had varying degrees of HO. Among them, 27 (56.3%) were type I (bone islands); 16 (33.3%) were type II (bone spurs from the mandibular ramus); 3 (6.3%) were type III (bone spurs from the fossa); and 2 (4.2%) were type IV (bone spurs from both the mandibular ramus and fossa). Joint space in type IV HO was significantly smaller than the other 3 types (9.9 ± 1.1mm, p = 0.01). Pain scores in HO were significantly greater than non-HO patients before and after operations (p < 0.05). Conclusion HO after alloplastic TJR with fat graft was not severe except for type IV, which was easy to cause ankylosis. Preserving sufficient TJR space was important for ankylosis prevention.