title: Relationship between kinematic center and TMJ anatomy and function.
abstract: The kinematic center (KC)-defined by coinciding jaw-opening/-closing and protrusion-retrusion trajectories-has been proposed in the literature as a reference point to represent TMJ movements. In this study, we tested whether the KC lies in a peculiar anatomical point and whether its trajectory reflects intra-articular distance. In 11 asymptomatic individuals (seven females, four males, aged 24-37 yrs), 4 openings/closings and 4 protrusions/retrusions were tracked with dynamic stereometry. In a 3D lattice (0.5 mm grid) constructed solidly around each condyle, the KC was the point with maximal cross-correlation between opening-closing and protrusion-retrusion paths. KC trajectories were more cranial on closing than on opening, consistent with intra-articular distances being smaller on closing than on opening. However, KCs were never located on condylar main axes (distance, 4.5 +/- 2.9 mm), nor did they coincide with points best approximating fossa shapes (distance, 12.5 +/- 6.4 mm). The kinematic center's anatomical and functional significance therefore appears to be questionable.
authors.affiliation: Center for Oral Medicine, Dental and Maxillo-Facial Surgery, University of Zürich, Plattenstrasse 11, CH-8032 Zürich, Switzerland. luigi@zui.uzh.ch
authors.forename: L M
authors.initials: LM
authors.lastname: Gallo
authors.forename: D B
authors.initials: DB
authors.lastname: Gössi
authors.forename: V
authors.initials: V
authors.lastname: Colombo
authors.forename: S
authors.initials: S
authors.lastname: Palla
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D016302:Centric Relation; D002508:Cephalometry; D003768:Dental Occlusion, Centric; D005260:Female; D006801:Humans; D007568:Jaw / Q000033:anatomy & histology / Q000502:physiology; D008279:Magnetic Resonance Imaging; D008297:Male; D008335:Mandibular Condyle / Q000033:anatomy & histology*; D009068:Movement / Q000502:physiology; D016059:Range of Motion, Articular / Q000502:physiology*; D012016:Reference Values; D013704:Temporomandibular Joint / Q000033:anatomy & histology* / Q000502:physiology