Changes in deep neck muscle length from the neutral to forward head posture. A cadaveric study using Thiel cadavers.

Guohao Lin,Tracey Wilkinson,Weijie Wang

doi:10.1002/ca.23834

Abstract

Forward head posture (FHP) is one of the most common postural deviations. Deep neck muscle imbalance of individuals with FHP is of primary concern in clinical rehabilitation. However, there is scarce quantitative research on changes in deep neck muscle length with the head moving forward. This study aimed to investigate changes in deep neck muscle length with different severity levels of FHP. Six Thiel‐embalmed cadavers (four males and two females) were dissected, and 16 deep neck muscles in each cadaver were modeled by a MicroScribe 3D Digitizer in the neutral head posture, slight FHP, and severe FHP. The craniovertebral angle was used to evaluate the degrees of FHP. Quantitative length change of the deep neck muscles was analyzed using Rhinoceros 3D. In slight FHP significant changes in length occurred in four muscles: two shortened (upper semispinalis capitis, rectus capitis posterior minor) and two lengthened (longus capitis, splenius cervicis). In severe FHP all occipital extensors were significantly shortened (10.6 ± 6.4%), except for obliquus capitis superior, and all cervical extensors were significantly lengthened (4.8 ± 3.4%), while longus capitis (occipital flexor) and the superior oblique part of the longus colli (cervical flexor) were lengthened by 8.8 ± 3.8% and 4.2 ± 3.1%, respectively. No significant length change was observed for the axial rotator. This study presents an alternate anatomical insight into the clinical rehabilitation of FHP. Six muscles appear to be important in restoring optimal head posture, with improvements in FHP being related to interventions associated with the occipital and cervical extensors.

Highlights

Modern lifestyles and work requirements mean that many people spend long periods of time looking at screens on electronic devices, often resulting in awkward postures (Toh et al, 2017; Yadegaripour et al, 2021)
The present study investigated changes in deep neck muscle length between the neutral head posture, defined as a craniovertebral angle (CVA) of 55, and two severity levels of Forward head posture (FHP), defined by CVA 45 and 35, using Thiel cadavers
The observations showed that some muscles were subject to significant length changes when placed in the two simulated FHPs, with consistent patterns of change with increasing FHP severity

Summary

| INTRODUCTION

Modern lifestyles and work requirements mean that many people spend long periods of time looking at screens on electronic devices, often resulting in awkward postures (Toh et al, 2017; Yadegaripour et al, 2021). According to recent reviews on FHP, this postural deviation is associated with neck pain, vestibular deficits, decreased proprioception, abnormal muscle activity, and altered breathing patterns (Mahmoud et al, 2019; Migliarese & White, 2019; Szczygiel et al, 2020). Rehabilitation of the deep neck muscles has been observed to improve stability of head and neck posture, manifested as increased ability to maintain an upright position of the cervical spine (Blomgren et al, 2018; Falla et al, 2007). Most of the literature provides qualitative descriptions, with only a single study (Khayatzadeh et al, 2017) reporting quantitative data on neck muscle length changes using a computer-generated model based on fresh-frozen cadaveric spines. The present study investigated the length changes in deep neck muscles from the neutral posture to different FHP severity levels using Thiel cadavers, with the aim of identifying the changing lengths in deep neck muscles and the muscles most affected by FHP

| MATERIALS AND METHODS

| RESULTS

| DISCUSSION

Findings

| Limitations