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Παρασκευή 10 Νοεμβρίου 2017

Comparison of three-dimensional helical axes of the cervical spine between in vitro and in vivo testing

Publication date: Available online 23 October 2017
Source:The Spine Journal
Author(s): René Jonas, Robert Demmelmaier, Steffen P. Hacker, Hans-Joachim Wilke
Background ContextThe range of motion is a well-accepted parameter for the assessment and evaluation of cervical motion. However, more qualitative data of the kinematics of the cervical spine is needed for the development and success of cervical disc arthroplasty [1].PurposeThe aim of this study was to provide basic information about helical axes of human cervical spine under in vitro conditions. Furthermore it should clarify whether the three-dimensional helical axes of cervical motion gained from in vitro experiments are in agreement with those gained from in vivo experiments and therefore to prove its reliability.Study Design/SettingAn in vitro test with pure moments and mono-segmental specimens was designed in order to investigate and compare the helical axes of the cervical spine.MethodsSix human cadaveric specimens (3 male and 3 female) with an average age of 47.5 y (range: 34 – 58 y) were carefully selected. Each specimen was divided into three motion-segments: C2/3, C4/5 and C6/7. 3.5 full cycles of rotation about all axes: Flexion-Extension, Lateral Bending and Axial Rotation were performed by applying pure moments of 1.5 Nm without any preload. Following the in vitro tests the three-dimensional helical axes were calculated and projected into the x-ray images.ResultsRotation analysis of all three directions revealed similar results for all six specimens. All calculated helical axes were similar to the published in vivo data. Furthermore the instantaneous centers of rotation were in agreement with in-vivo data.ConclusionsThe data gained from this study verifies cervical kinematics during in vitro testing using pure moments. It can be assumed that other soft tissue such as muscles are not necessarily needed to simulate cervical kinematics in vitro.



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