TEMPOROMANDIBULAR JOINT INTERPOSAL MATERIAL STUDY TEMPOJIMS PHASE 1 – IMAGING OUTCOMES Ângelo DF (1,6), Monje F (2), González R (2), Mónico L (3), Sanz D (3), Neto L (4), Sousa R (4), Caldeira R (4), Morouço P (5), Alves N (5), Salvado F (1) Faculty of Medicine, Lisbon, Portugal; (2) Infanta Cristina Hospital, Faculty of Medicina, University of Extremadura, Badajoz, Spain; (3) Coimbra University, Coimbra Portugal; (4) Radiology Department of Santa Maria Hospital, Lisbon, Portugal; (5) Instituto Politécnico de Leiria, Centre for Rapid and Sustainable Product Development (CDRSP), Leiria, Portugal Introduction The domain of temporomandibular joint (TMJ) bioengineering is growing fast and the potential of a TMJ interposal disc is immense. Rigorous preclinical trials are needed to progress in translational medicine in TMJ domain. Before use valuable efforts and funds in TMJ bioengineering is important to understand basic concepts related to temporomandibular surgical interventions effects. Despite the large number of discectomy procedures performed annually, we are not aware of any high-quality randomized, blinded, controlled trial that have investigated in human or animal the imaging implication of bilateral discectomy and bilateral discopexy using a sham surgery control group. Material and Methods Temporomandibular Joint Interposal Material Study (TEMPOJIMS) is an exploratory randomized preclinical trial divided in 2 phases in 18 animals. This poster is aimed to understand the imaging effects of TMJ bilateral discectomy versus TMJ bilateral discopexy versus sham surgery control group. Six months after surgery the animals were euthanatized and the TMJ blocks were scanned by Computerized Tomography (CT). Imaging evaluation was performed using the specific criteria and score for radiologic assessment. This assessment was performed and classified independent by 3 experienced radiologists who were blinded to the intervention. A B Figure 1. A- Preoperative CT. B – Final CT of the TMJ block 6 months after surgery. Results For global appreciation differences were very high (η2p corresponding to 90.8%, statistical power > .999). There was statistical differences for all outcomes, excluding calcification (M =0 and SD =0). Considering each outcome, differences were higher for shape, followed by condyle sclerosis, temporal sclerosis, condyle marrow, temporal erosion, condyle erosion, and, at last, temporal marrow. Excluding the difference between discopexy and sham surgery for temporal erosion (Cohen’s d = 0.59), all the other differences were classified as a large effect size, according to Cohen (Cohen’s d > 0.80). The larger differences were between discectomy and sham surgery (R2 corresponding to 92.9% of degeneration in global appreciation), mainly due to shape (R2 = 96.0%), condyle marrow (R2 = 83.4%), and condyle sclerosis (R2 = 80.1%). Condyle erosion and temporal marrow were the least affected, although with an effect size of R2 of 50.3% and 50.8%, respectively; temporal sclerosis and temporal erosion showed effect sizes of R2 of 71.1% and 62.3%, respectively. Discopexy also differed from sham surgery (R2 corresponding to 80.3% of deterioration in global appreciation), although with lower effect sizes in comparison to the differences between discectomy and sham surgery, and only for shape (R2 = 80.3%), condyle sclerosis (R2 = 76.6%), and condyle marrow (R2 = 56.7%). Figure 2. A- Sham surgey . B – Discopexy group. C- Discectomy group. Conclusions Bilateral discectomy have severe influence in CT images with major degenerative changes. However, bone ankylosis was not found in this study, probably due to the ruminant profile of this animal model. Bilateral discopexy was not innocuous and was associated with minor/moderate changes. The CT imaging still a good predictor of bone changes regarding TMJ. 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