Three-dimensional assessment of accuracy for open reduction and internal fixation of the subcondylar fracture and its implications on the TMJ function.

This study used three-dimensional cone beam computed tomography (CBCT) to assist the accuracy of open reduction and internal fixation (ORIF) for the unilateral subcondylar fracture and the long-term temporomandibular joint (TMJ) function impairment. Bilateral TMJs were analyzed postoperatively on CBCT images, involving the following three-dimensional (3D) parameters: condylar position and inclination; circumferential joint space, ramus, and mandible length; and the volumetric joint space. The inclusion criteria for adult patients included having a displaced fracture >5°, a shortening in ramus length >2 mm, and mouth opening limitation. The non-fracture side was used as the comparison group. The Helkimo index was employed for the clinical assessment of the outcomes, while the paired student t-test and Pearson coefficient test were used to compare both sides. The study included 60 joints in 30 consecutive patients. The condylar inclination to the horizontal plane on the fracture and non-fracture sides was 9.29 ± 3.9°, 12.46 ± 4.2°, (p < 0.001) and was positively related to the subjective (Helkimo Hi) and objective (Helkimo Di) clinical outcomes. In contrast, the condylar position to the midsagittal plane in the fracture and non-fracture sides was 51.95 ± 3.5 mm, 50.17 ± 3.6 mm (P = 0.038), and was positively related to the objective outcomes. Additionally, the objective outcome was negatively related to the change of the posterior joint space. CONCLUSION: The three-dimensional assessments seem to demonstrate that the ORIF is an accurate approach for obtaining a three-dimensional reduction to the displaced subcondylar fracture.