TECHNICAL NOTE In vivo measurement of the 3D kinematics of the temporomandibular joint using miniaturized electromagnetic trackers: technical report J.-P. Baeyens • H. Gilomen • B. Erdmann • R. Clijsen • J. Cabri • D. Vissers Received: 25 September 2012 / Accepted: 4 December 2012 Ó International Federation for Medical and Biological Engineering 2012 Abstract Objective: The aim of this study was to eval- uate the use of miniaturized electromagnetic trackers (1 9 0.5 9 0.5 cm) fixed on teeth of the maxilla and mandible to analyse in vivo the 3D kinematics of the temporomandibular joint (TMJ). A third sensor was fixed to the forehead, and a fourth sensor was used as a stylus pointer to detect several anatomical landmarks in order to embed a local frame on the cranium. Temporomandibular opening/closing, chewing, laterotrusion and protrusion were examined. Results: The prime objective within this study was to rigidly attach electromagnetic minisensors on teeth. The key for a successful affixation was the kevlar interface. The distances between the two mandibular affixed sensors and between the two maxillar affixed sen- sors were overall smaller than 0.033 cm for position and 0.2° for attitude throughout the temporomandibular motions. The relative motions between a forehead sensor and the maxilla affixed sensor are too big to suggest a forehead sensor as an alternative for a maxilla affixed sensor. Conclusion: The technique using miniaturized electromagnetic trackers furthers on the methods using electromagnetic trackers on external appliances. The method allows full range of motion of the TMJ and does not disturb normal TMJ function. Keywords Temporomandibular joint Á Kinematics Á Electromagnetic tracking 1 Introduction The temporomandibular joint (TMJ) consists of a concave articular surface (fossa) on the temporal bone, a convex articular surface (condylar head) on the mandible and a biconcave fibrocartilaginous articular disc and articular ligaments interfacing between the joint surfaces. The TMJ is one of the most complex joints in the human body and with mastication and speech one of the most used. The most common TMJ disorders have a mechanical origin, at least partially, leading to TMJ pain dysfunction syndromes, internal derangement or arthritis [1]. As such, there is a strong need for biomechanical insights into orthodontic interventions (surgery and dental orthotics design) or the effect of physio- or manual musculoskeletal therapeutic techniques on TMJ dysfunction [2]. Despite this urge, there is relative paucity of in vivo 3D arthrokinematics research on the TMJ. The reason for the scarcity of studies on TMJ 3D arthrokinematics is partially methodological. Different in vivo methods have been used to record 3D joint kine- matics of the TMJ: MRI reconstructions on incremental J.-P. Baeyens Á H. Gilomen Á R. Clijsen Á J. Cabri Á D. Vissers (&) University College Physiotherapy Thim Van Der Laan, Landquart, Switzerland e-mail: dirk.vissers@ua.ac.be J.-P. Baeyens Á R. Clijsen Department Human Biometry and Biomechanics, Vrije Universiteit Brussel, Brussels, Belgium J.-P. Baeyens Á D. Vissers Faculty Medicine and Health Sciences, University of Antwerp, Antwerp, Belgium B. Erdmann Á R. Clijsen Department Health Sciences, University of Applied Sciences and Arts of Southern Switzerland, Manno, Switzerland J. Cabri Department Physical Performance, The Norwegian School for Sport Sciences Oslo, Oslo, Norway 123 Med Biol Eng Comput DOI 10.1007/s11517-012-1015-4