Kinematics of Mandible After Alloplastic Total TMJ Replacement
Kinematics of mandible after alloplastic total TMJ replacement
Myeong Gyun KIM1*, James Q. Swift2, Dong Sung KIM1, Jae-Young KIM1, Hyung-Gon KIM1, Jong- Ki HUH1
1Department of Oral and Maxillofacial Surgery, Gangnam Severance Hospital, College of Dentistry, Yonsei University, SOUTH KOREA
2Department of Oral and Maxillofacial Surgery, School of Dentistry, University of Minnesota, USA
Alloplastic temporomandibular joint (TMJ) replacement surgery is performed in case of ankylosis, condylar resorption, benign or malignant tumor, congenital deformity, severe arthritis and failed TMJ arthroplasty. Although the procedure is regarded reliable and efficient treatment, the patients are obligated to have limitation of mandibular movement due to attachment loss of surrounding muscles. Especially translational movement is difficult because limited protrusive movements occur as lateral pterygoid muscle function is absent or decreased. We can expect some translational movement when unilateral total TMJ replacement (UniTJR) was performed as normal attachment of lateral pterygoid muscle exist on contralateral side. It becomes more difficult to expect translation in bilateral total TMJ replacement (BiTJR) due to total loss of lateral pterygoid muscle attachment. Studies comparing the patients who underwent unilateral and bilateral total TMJ replacement surgery are not sufficient. Thus, we investigated and analyzed the characteristics of these patients including comparisons of pre- and post-operative amounts of mouth opening.
Patients and methods: Forty-four patients were included in this study among 81 who underwent total joint replacement (TJR) from 1999 to 2013. We investigated operation site, pre-operative diagnosis, and history of previous joint surgery. The amounts of maximum inter-incisal opening (MIO) at pre- and post-operative 1 month, 3 months, 6 months, and 12 months were also recorded. The patients were divided into two groups according to their operation site as follows: UniTJR group and BiTJR group. The patients were subdivided according to increase or decrease of MIO in both groups. Descriptive analysis, paired t-test, repeated ANOVA were used to assess results.
Results: Twenty-two patients were classified in both groups, respectively. MIO was increased with statistically significant in both groups (p<0.05). However, there was no difference between two groups; 33.30±7.18 BiTJR group and 37.43±5.99 UniTJR group. The maximum increase of MIO was occurred between post-operative 1 month and 3 months with statistically significant (p<0.001). In BiTJR group, 15 patients showed less than 30mm of pre-operative MIO. Among them, 8 patients (53.3%) showed improvement of MIO more than 10mm. Among 7 patients whose MIO was larger than 30mm before surgery, 4 patients showed decrease of MIO more than 5mm. In UniTJR group, all the patients whose pre-operative MIO was less than 30mm showed more than 10mm of MIO improvement. On the contrary, the amounts of MIO increase were not significant for the patients whose original MIO was more than 30mm. There were 12 patients who were diagnosed as fibrous ankylosis. Maximum MIO increase was 24mm in both groups. Maximum MIOs were 43mm in BiTJR and 41mm in UniTJR at post-operative 12months, respectively.
Conclusion: Even though MIO after TJR is not significant different between Unilateral and bilateral TJR, UniTJR group shows bigger MIO than BiTJR group. We cannot achieve normal range of mouth opening as expected despite of active mouth opening exercise. Thus we need more trials to improve mouth opening for the patients who underwent total TMJ replacement.
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