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

Philipp M Schmid,Bettina Sommer,Markus J Ernst,Christoph M Bauer,Martin Weisenhorn,Lars Lünenburger

doi:10.3390/s21093297

Abstract

Neck pain is a frequent health complaint. Prolonged protracted malpositions of the head are associated with neck pain and headaches and could be prevented using biofeedback systems. A practical biofeedback system to detect malpositions should be realized with a simple measurement setup. To achieve this, a simple biomechanical model representing head orientation and translation relative to the thorax is introduced. To identify the parameters of this model, anthropometric data were acquired from eight healthy volunteers. In this work we determine (i) the accuracy of the proposed model when the neck length is known, (ii) the dependency of the neck length on the body height, and (iii) the impact of a wrong neck length on the models accuracy. The resulting model is able to describe the motion of the head with a maximum uncertainty of 5 mm only. To achieve this high accuracy the effective neck length must be known a priory. If however, this parameter is assumed to be a linear function of the palpable neck length, the measurement error increases. Still, the resulting accuracy can be sufficient to identify and monitor a protracted malposition of the head relative to the thorax.

Highlights

IntroductionA forward head posture” (FHP) has frequently been reported for multiple activities and postures, such as driving, computer work, or reading [4]
The error in the predicted position of J2 was directly linked to the error of the predicted forehead position via the vector v2h, which is a constant when expressed in the h-frame
The aim of this work was (i) to introduce a simple neck model that describes the relative motion of the head to the thorax and (ii) to measure relative protraction by means of this model and 3D-orientation measurements of the neck and thorax

Summary

Introduction

A FHP has frequently been reported for multiple activities and postures, such as driving, computer work, or reading [4]. It has strongly been associated with headaches such as migraines, tension-type, and cervicogenic headache [5,6], neck pain, and even shoulder problems [7,8,9,10]. 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]. Different initial positions will lead to different axial rotation values and these axial rotation values differ between younger and older, female and male persons [24]

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Methods

Conclusion