Complete 3D Kinematics Parameters of the Temporo-Mandibular Joints Using in Vivo Data Fusion

Objectives

The temporo-mandibular joint (TMJ) has implications in vital functions and its disorder prevalence is between 5% and 12%. The mandible motions rely on two joints where mandibular condyles are generally asymmetric and highly individual. They rotate during jaw opening and closing and translate vertically and anteroposteriorly. Quantitative motion analysis tools are of interest to better understand normal and abnormal TMJ behavior. Previous studies have reported the asymmetrical behavior of the mandible compared to the skull as well as the synchronism of rotation and translation during its motions. But none of them has developed an experimental protocol using in vivo motion data fused with a tridimensional (3D) model. Therefore, we aim to provide the detailed kinematic parameters of the mandible compared to the skull, of the 2 condyles compared to their sockets and the instantaneous helicoidal axis (IHA) calculation through a clearly described new technology: in vivo data motion fused with virtual palpation on 3D models. We also compare the accuracy and the consistency of our results with the existing literature.

Material and methods

Five healthy subjects fitted with a tailor-made dental and head clusters performed mouth opening/closing, diduction and chewing motions. 15 anatomical landmarks (ALs) were palpated on their skull and their mandible. The trajectory of the markers and ALs was recorded by opto-electronic cameras. 3D models created from magnetic resonance imaging (MRI) from the 5 subjects were processed through a segmentation procedure and imported into a musculo-skeletal data processing software. Virtual palpation was used to locate specific ALs and to build coordinate systems following the ISB recommendations. The ALs coordinates, the motion files and the morphological model were fused. Motion cycles were normalized from 1 to 100% of rotations and translations duration in coordinate systems, instantaneous helical axis (IHA) parameters were computed for the 3 motions.

Results

Median RMSE between manually and virtually palpated ALs was 8,0 mm.

During opening motion, rotation around the Z-axis (median 24,9°), translations along the X-axis and the Y-axis (median 9,7 mm and 6,3 mm respectively) were happening all at once. The IHA was obliquely orientated.

During diduction motion, rotations around the Y-axis and the X-axis (median 10,7° and 3.3° respectively), translation on the Z-axis is (median −9.4 mm) occurred simultaneously. The IHA orientation was oblique and changed accordingly to the diduction side.

During chewing motion, median rotation around the Z-axis was −2.2° and median translation on the Y-axis −1.0 mm. The IHA pathway high asymmetry coincided with typical movements of working and balancing condyles.

Conclusion

Complete 3D kinematics parameters of the TMJs, corresponding to the ISB recommendations, have been extracted with our methodology. Our values matched previous studies if available and the palpation RMSE was within the bounds of precedent experimental protocol. It is therefore efficient to study in vivo motion.

Motion data have been registered in an open access data repository, allowing other researchers to exploit them and develop their own TMJ model.