Kinematic analysis of the lower cervical spine in the protracted and retracted neck flexion positions

Abstract

[Purpose] The aim of this study was to analyze lower cervical spine kinematics in protracted and retracted neck flexion positions in healthy people. [Subjects and Methods] The craniovertebral angle (CVA) and intervertebral body angles of the lower cervical spine of 10 healthy individuals were analyzed using fluoroscopy in a neutral sitting with the head in the neutral (N), protracted (Pro), and retracted (Ret) positions and with the neck in full flexion with the head in the neutral (N-fx), protracted (Pro-fx), and retracted (Ret-fx) positions. [Results] There were significant differences in the CVA and intervertebral body angle at the C3–4 level, and the Ret position showed the highest values followed by the N and Pro positions. Regarding the intervertebral body angle at the C4–5 level, the Pro position showed a higher value than the N and Ret positions. At the C6–7 level, the Pro position showed the lowest value compared with the N and Ret positions. In the CVA, the Ret-fx position showed a higher value than the N-fx and Ret-fx positions. [Conclusion] The results suggest that in the neutral sitting position, protraction is an ineffective posture due to overstress of the C6–7 segment, which is placed in a hyperflexed position at this level. Instead, retraction is the recommend posture for the patient with C6–7 degeneration, which makes for a more flexed position in the upper cervical spine and a less flexed position in the lower cervical spine.

Impact of Cervical Spine Rehabilitation on Temporomandibular Joint Functioning in Patients with Idiopathic Neck Pain

“…The distance between the jugular notch of the sternum and mental protuberance of the lower jaw was measured in centimetres twice, both times while seated, with habitual and neutral head posture (the subject was asked by the researcher to assume a position with the head within body axis avoiding protracted head position) [28]. Head posture was also evaluated visually-qualitatively differentiating between correct and forward head posture [29][30][31][32]. Measurements of the forward head position performed by the same physical therapist were highly reliable (ICC = 0:93).…”

A Two Joint Neck Model to Identify Malposition of the Head Relative to the Thorax

“…The cervical spine has the largest mobility of all sectors of the human spine. Since the head moves with six degrees of freedom relative to the thorax, the cervical spine has six degrees of freedom [ 17 , 37 , 46 ]. The range of motion differs between directions.…”

“…Cervical range of motion (ROM) has been found reduced when performed out of a FHP [ 15 ] and altered for coupled movements [ 16 ]. Park et al found reduced upper cervical (UCS) flexion ROM due to sustained computer work [ 17 ] and Ernst et al demonstrated strong associations between reduced UCS flexion and headache [ 18 ]. Protraction and retraction are regarded as combined and opposite movements of the upper cervical (UCS = occiput to cervical vertebra 3), and the lower cervical-spine (LCS = cervical vertebrae 3–7) [ 19 ].…”

“…However, other approaches to measure FHP already exist. Instead of measuring the displacement of the head [ 27 , 28 ], the craniovertebral angle (CVA) method is widely used to assess FHP [ 17 , 29 , 30 , 31 ]. Pürkhauer et al used the Kinect ® face tracking algorithm to measure FHP [ 32 ].…”

Concurrent validity and reliability of a mobile tracking technology to measure angular and linear movements of the neck

“…The prototype 56 system was shown to be valid, although the reliability of the repositioning and upper cervical 57 flexion tests needs to be reconsidered. The anatomical and physiological characteristics of the cervical spine allow humans to rotate 65 and translate their head relative to the thorax in all directions (six degrees of freedom) 66 (Ordway et al, 1997;Park, 2015;Seo et al, 2013). Impairment of the neck is related to the 67 cervical range of motion (Ernst et al, 2015;Hall et al, 2010).…”