European Journal of Physical and Rehabilitation Medicine · load-bearing of the cervical spine. ......

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EDIZIONI MINERVA MEDICA

Women with late whiplash syndrome have greatly reduced

load-bearing of the cervical spine. In vivo biomechanical,

cross-sectional, lateral radiographic study.

Eythor KRISTJANSSON, Magnus Kjartan GISLASON

European Journal of Physical and Rehabilitation Medicine 2017 Jul 17DOI: 10.23736/S1973-9087.17.04605-6

Article type: Original Article

2017 EDIZIONI MINERVA MEDICA

Article first published online: July 17, 2017

Manuscript accepted: July 14, 2017

Manuscript revised: June 15, 2017

Manuscript received: December 11, 2016

http://www.minervamedica.it/en/how-to-order-journals.phpmailto:[email protected]:[email protected]:[email protected]

1

Women with late whiplash syndrome have greatly reduced load-

bearing of the cervical spine. In vivo biomechanical, cross-sectional,

lateral radiographic study A short title: The cervical column is greatly weakened in late whiplash

Eythor Kristjansson,1 Magnus K. Gislason2

1 Faculty of Medicine, The University of Iceland, Reykjavik, Iceland

2 School of Science and Engineering, Reykjavik, Iceland

*Corresponding author: Eythor Kristjansson, Faculty of Medicine,

The University of Iceland, Reykjavik, Iceland.

E-mail: [email protected]

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ABSTRACT BACKGROUND: No study has been conducted to ascertain whether the load-bearing

capacity of the cervical spine is reduced in vivo in late whiplash syndrome (LWS).

AIM: To compare the segmental cervical angular values across C0C6, between two

conditions: without versus with external axial load upon the head in three groups of women.

DESIGN: A single-blind, age-Body Mass Index (BMI) matched, radiographic, cross-sectional

study.

SETTING: Radiographic Department at a University Hospital.

POPULATION: One hundred eighty-two women, aged between 1850 years were enrolled.

METHODS: Participants were divided into 3 groups: a group with LWS (N=62) and two

control groups: a chronic insidious neck pain (IONP) group (N=60) and an asymptomatic

group (N=60). Prior to and on the same day as the radiographic examination took place, BMI

in kg/m2 was recorded and all participants answered the Neck Disability Index (NDI). The

two symptomatic groups answered also three other pain and disability questionnaires.

RESULTS: Analysis of variance (mixed-model ANOVA) for repeated measures was used for

comparison. Significant differences between groups, and the two conditions tested

was revealed, but only within the asymptomatic and the IONP groups (p

3

The mobile cervical spine is primarily responsible for the location of the head over the body,

maintaining a horizontal gaze for maximal utilization of the vital organs in the head which

connect us to our environment.1 The center of gravity (COG) of the head is located at the

posterior inferior sella turcica approximately 1cm superior and anterior to the external

auditory meatus.2,3 This location is anterior to the instantaneous axis of rotations (IARs) of

the cervical vertebra which requires contractions of the posterior neck muscles to maintain

upright head posture with the eyes level with the earth-horizontal.4

The load on the cervical spine is primarily compressive, with the shear component at

approximately 10% of compression.5 The cervical spine can withstand substantial

compressive axial loads in vivo, which are approximately thrice the weight of the head

because of muscle co-activation forces functioning to balance the head in the neutral, relaxed

posture.6 The skull is approximately 7.55% of the total body mass, which means that if a

person weighs 95.3 kg, the skull weighs around 7.2 kg.3

Compressive load increases further during flexion and extension, contact sports, and other

activities of daily living, and is estimated to range from 120N to 1200N in activities involving

minimal and maximal exertions, respectively.5-7 In normal individuals, the cervical spine

sustains these loads without damage or instability. However, ex vivo experiments show that

the osseoligametous cervical spine buckles in the frontal plane under a small vertical load of

10N.8 Using a 10-muscle, 3-joint model of the head and neck, Winters & Peles found that the

head and neck were inherently unstable, especially around the neighborhood of an upright

posture and suggested that maintenance of head stability requires considerable co-contraction

of antagonists,9 which supports the aforementioned statement of Patwardhan et al.6

Cervical spine stability has been described by dividing the bone anatomy of the cervical spine

into 3 primary columns (1 anterior and 2 posterior), which was first proposed by Louis10 and

validated by Pal and Sherk.11 The anterior column consists of the vertebral bodies and discs,

while the 2 posterior columns consist of the articulating facet joints.10,11 In the cervical spine,

the weight of the head is born through the condyles to the lateral masses of C1 and then to the

C1C2 joint. This load is then divided via the C2 articular pillars to the anterior column,

which includes the C2C3 disc, and the posterior column, which includes the C23 facets.11

The load distribution of the cervical spine is primarily in the posterior columns, with 36% in

the anterior column and 64% in the 2 posterior columns.11 This is in contrast to the lumbar

spine, in which the anterior loads (67%82%) have been reported as higher than the posterior

loads (18%33%).12



4

Cervical lordosis is considered to decrease the internal compressive load and is essential for

normal physiological flexion-extension as well as appropriate spinal coupling

movements.5,13,14 As examples: a straight lower cervical spine causes the articular facets to

become more vertical, obstructing rotation in the transverse plane as does increased lordosis

in the upper cervical spine.15,16 Normal range of motion is therefore confounded by altered

cervical sagittal alignments, which clinicians should be aware of when considering high

thrust-short amplitude techniques (cervical manipulation).

In the sagittal plane, when an external compressive load is applied along a vertical path,

which center lays just anterior to the origin of COG of the head it, it will create an increased

anterior moment of the head and the cervical spine (Figure 1.). Therefore, the expected natural

response would be increased lordosis of the whole cervical spine.

Insert Figure 1. A vertical line from the center of weight upon the head is anterior to the center

of gravity of the head, creating greater anterior moment, which the neck extensor muscles

must counteract.

The following hypothesis was tested: women with LWS will exhibit lesser changes in

segmental angular values between the two conditions tested (without and with axial load) due

to increased neck muscle stiffness to stabilize/protect the injured cervical spine. The

association between the test results and the self-reported pain and disability on the Neck

Disability Index (NDI) 17 and Borg-CR 10 Exertion Scale18, was also ascertained.

Materials and methods

Design

A single-blind, age-BMI matched, cross-sectional study was conducted to evaluate

differences in cervical spine segmental angular values in the sagittal plane, without versus

with external load upon the head, measured on standardized lateral radiographs.

Setting

Radiographic Department at the National University Hospital in Reykjavik, Iceland. The

recruitment period was from AprilJuly 2016. The National Bioethics Committee in

Reykjavik, Iceland, approved the study protocol and the written consent form, which all



5

participants read and signed before the study took place. Approval was also obtained from the

Icelandic Radiation Protection Institute. (Approval number VSN-14-108).

Participants

Altogether, 182 women participated, aged 1850 years for all groups who met the inclusion

criteria. Altogether 214 potential participants were contacted but 32 were not eligible. This

age range was used so that altered upper neck posture associated with different age groups19

and pronounced spondylosis with increasing age 20,21 were not confounding factors. Only

women were recruited because vertebral geometry and neck strength is different in height-

matched men and women.22 The two patients groups were recruited through specialists in

manual therapy in Reykjavik, Iceland, and the asymptomatic group was recruited from

University Hospital staff, students and relatives of the therapists. All subjects were screened

by telephone interview for inclusion. The asymptomatic control group (N=60) consisted of

women with a score < 4 on the NDI (on a scale 0100).17 The chronic insidious neck pain

(IONP) group (N=60) consisted of women with chronic recurrent neck pain of at least 1-year

duration who had not been exposed to accident(s) of any kind. The women in both

symptomatic groups had to have minimal pain 3 on the visual analogue scale (VAS)23 and

an NDI score 8. The women in the LWS could have been involved in more than 1 motor

vehicle collision (MVC) from 19982015. Chronic complaints are defined as being of 6-

month duration by the Task Force on Taxonomy of the International Association for the Study

of Pain (IASP), revised edition.24 Exclusion criteria for all groups were systemic diseases or

prior psychiatric diagnoses of any kind as well as pregnancy. Psychiatric diagnoses were

double checked by contacting the womens general practitioners (GPs) and in the written

consent form, it was specifically outlined that this was a radiographic study with a radiant

exposure (albeit low). When the women were not sure if they were pregnant, they were asked

to contact their GPs.

Prior to the radiographic examination, Body Mass Index (BMI) in kg/m2 was recorded, all

participants answered the NDI17 and the two symptomatic groups also answered the VAS,23

the Tampa Scale of Kinesiophobia (TAMPA)25 and the Leeds Assessment of Neuropathic

Symptoms and Signs (LANSS)26 on the same day as the radiographic examination took place.

All participants answered the Borg-CR 1018 immediately after the radiographic examination

with the external load. A follow-up telephone interview was performed to reveal pain

intensityduration of the symptomatic women after carrying the external load. All

questionnaires had been used before in Icelandic language, translated into Icelandic and back



6

to English. All questionnaires were answered on paper. Two independent physical therapy

students on their last year of education, filled in the answers in Excel documents, which was

then double checked by the authors, as no missing data was found by the students. That was

confirmed by the authors.

Radiographic Examination

Radiographic Fluoroscopy (RF modality), (Prestige II, X-ray room with remote control table,

(General Electrics, Milwaukee VI, 2000) was used. All radiographs were taken in lateral

position in standardized standing position with fluoroscopic control for alignment. The left

side was closer to the film and the film-tube distance was 1.5m. The central beam was

centered at the C4 vertebral body. Two radiologists conducted the measurements within 1

month after the radiographic examination for each subject. The same research assistant putted

the custommade weight helmet on all participants. The radiographers and the research

assistant were blind to the participants group allocation. The examination procedure was as

follows: The participant gave her research number to the radiographers who explained the

examination procedure for the participants. Two radiographic examinations were performed.

The former was without weight and the latter with weight. The participant was instructed to

find her natural head posture looking straight ahead. The feet were the same distance apart

with a 12cm wide box between the feet and a tape marked the front line for the feet. The

participant rested the hands on a horizontal bar with circa 70 of flexion in the elbows, and

was instructed to relax the shoulder girdle muscles. In the second examination; the research

assistant placed the weight, 1.890 kg (4.16 lbs.) on the top of the head. The weight was

moveable in the sagittal plane and was secured fast when the center of the weight upon the

head was in a vertical line just anterior to the tragus of the right ear, which corresponded to 2

cm anterior to the external auditory canal. The center of weight upon the head corresponded

to the posterior part of sella turcica, at approximately 1cm in front of the COG of the head,

which is well in front of IARs of the cervical spine,2 (Figure 1.). Both radiographs were taken

in this position (Figure 2.).

Insert Figure 2. Experimental set-up.

A stop clock was used and the participant had to carry the weight for 5 minutes, but at least

for 90 seconds to pass the second examination. The participants were in the same footsteps

during the 5minute period but were allowed to walk on the place by alternately bending and

straighten the hips and knees without lifting the heels from the ground. When 20 seconds



7

were left, the participant was instructed to find her natural head posture looking straight ahead

and the radiographers prepared and finished the second examination.

Measurement Techniques

All radiographs were paired for each individual and marked without load and with load

and stored in DICOM format in the central imaging database in the picture archiving and

communication system (PACS) (Agfa; Impax, Version 6.5.3.1005) at the National University

Hospital in Reykjavik, Iceland. The radiographs were imported in DICOM format into

Matlab, as the measurements of the radiographs were made outside the University Hospital by

a radiologist with 34 years of experience. To evaluate inter-and intra-tester errors in the

measurements, 60 radiographs were randomly selected and measured twice on different

occasions by another radiologist with 28 years of experience. According to Rankin and

Stokes, at least 50 subjects are needed in reliability studies.27 Both radiologists were blind to

the womens group allocation.

Figure 3A and Figure 3B show the fiducials and lines used to form the measured angles for

the upper versus lower cervical spine, respectively. A negative value indicated lordosis, and a

positive value indicated kyphosis.

Insert Figure 3A. For the upper cervical spine, the angle a (C0C1) was formed by a line

connecting the most caudal point on the occipital bone posteriorly, aligning with the posterior

surface of the spinal canal at the C1 level, and the deepest point in the groove formed by the

occipital condyle and the occipital bone anteriorly versus the line tangential to the inferior

aspect of the atlas; angle b (C1C2) by the lines tangential to the inferior aspects of the atlas

and axis, respectively.

Insert Figure 3B. Radiographic measurements for the lower cervical spine. The Harrison

posterior tangent method was used which involves drawing lines parallel to the posterior

surfaces of all cervical vertebral bodies from C2 to C7 and then summing the segmental

angles for an overall cervical curvature angle.28

Measurements of the Rotation of the Vertebrae using Matlab

A custum build program was written in Matlab which allowed the user to identify two points

defining a straight line on multiple locations in the cervical spine. This was implemented by



8

creating an interactive tool, where the X-ray image was read in as an image, thus allowing the

radiologists to click on the screen where the corresponding lines should be drawn. The image

size of each scan was 1920x1080 pixels and with each click from the user, the pair of pixles

coordinates representing each line were contverted into unit vectors in two dimensional space.

The angle, , between each the lines r1 and r2, was calculated using the formula

The program allowed the user to zoom into each region of interest for each line created,

therefore allowing the radiologists to locate anatomical landmarks with sufficient accuracy on

a 2 mega pixel screen, which size wae 21.5. The lines were created separetely for the upper

versus the lower cervical spine, respectively. For the Harrison posterior tangent method28 the

program deleted all previous lines on the screen to ensure that none of the prior lines would

block anatomical landmarks. The radiologists carried out the routine both for the subjects with

and without external load. All angular values were written as a text files which were read into

another post processing routine summarizing and analyzing all corresponding angles for all

of the participants. All the images with the lines superimposed onto the xray image were

saved, separetely for the upper and the lower cervical spine, with and without the load,

respectively. This was done to allow verification of the accuracy of the location of each

drawn line.

Statistical analyses

A pilot study was conducted with different weights upon the head on asymptomatic and

symptomatic women. The responses varied considerably between groups and it was therefore

unknown how many participants would be required to test the hypothesis as no comparative

studies have been conducted to reveal changes in cervical segmental values of the cervical

spine without versus with anterior axial load upon the head between different patients

groups. It was estimated that at least 60 women would be required in each of the 3 groups

tested.

The mean absolute difference of raters measurements was used to calculate the reliability

between radiologists and within the second radiologist.29 The intraclass correlation

coefficients (ICCs) using an absolute agreement definition, the 2-way random effects model,

single measures ICC and standard error of measurement (SEM) as well as systematic error



9

between/within raters (SER) (ICC 2,1)30 was used for assessing interrater and intrarater

reliability.

To test the hypothesis across all segments (C0C6), analysis of variance (mixed-model

ANOVA) for repeated measures (SAS Statistical Software 9.4) was used for comparison

between the 2 independent variables, conditions, and groups, using segments, NDI and Borg-

CR 10 as covariates. Angular values and subjects were the random effects. Also included are

the 2way group-condition, condition-angle, and group-angle interaction. Number, subjects,

means, and SDs were used for description of data. Tukey-Kramer adjustments were used for

post hoc analysis. The significant level was set at p < 0.05 for all tests.

Results There was no missing data in this study. The inter-and intra-radiologists reliability is shown

in Table I. The changes in segmental angular values (across all segments) within the two

conditions tested and between the 3 participating groups are shown in Figure 4.

Insert Figure 4. Angular rotation in the sagittal plane in upright standing position measured in

degrees (mean, standard error), without and with axial load upon the head. Significant

differences were revealed within the asymptomatic and the IONP groups but not within the

LWS group. Abbreviations: IONP=insidious onset neck pain; LWS= late whiplash syndrome

The statistical analysis revealed significant differences between groups, and the two

conditions tested (F2,178 =21.78, p< 0.0001). The Tukey-Kramer post-hoc test revealed

significant differences within the asymptomatic and the IONP groups (p

10

score for neuropathic pain).26 Increase in pain duration and pain intensity in the days after

carrying the external load is shown in Table III. The comorbid disorders in the two

symptomatic groups with odds ratio and 95% (CI) and p-values are shown in Table IV. The

most important descriptive variables for the LWS group are shown in Table V.

Several animations are displayed in Appendix I, each showing the changes of the cervical

spine lordosis without load versus with load for a typical woman in the asymptomatic group,

the IONP group, and within four subgroups of the LWS group, respectively. The rigid neck

strategy observed in the LWS group when loaded was an unexpected finding, most often

accompanied by horizontal translation of the head and the cervical spine as a whole, with

slight or no changes in segmental angular values, which was not a common feature in the two

control groups. When this rigid horizontal translational strategy was detected, radiographs

of the whole spine were taken of 6 women with LWS. No compensations for the horizontal

headneck translation was observed in the thoracic, lumbar, or hip joints.

Discussion

Key Findings

The results of this study strongly indicate that the cervical spine in most women with LWS

functions such as a rigid cylinder when external load is applied upon the head instead of

creating normal cervical lordosis as in the 2 control groups. This means that the load-bearing

capacity of the cervical spine is more greatly reduced in women with LWS than previously

anticipated (Figure 4.).

The results of the inter-and intra-radiologist reliability indicate that the measurements are

highly reliable (Table I). When the curvature approaches a completely straight alignment,

measurement values will approach zero and the difference between and within raters will

inevitable become larger due to small value. This explains the significant differences in Table

I.

Women with LWS were in significantly more pain and disabled and tolerated the external

load on the head significantly less at the moment of the examination according to Borg-Scale

(Table I). The women with LWS were also more affected in the days after the radiographic

examination (Table III). Table IV shows that women with LWS had significantly more

comorbid disorders and complained significantly more about feeling the head is too heavy.

Thirty-seven women with LWS (68.5%) rated themselves to be worse compared to when the



11

insurance claim was closed (Table V). This means that the subjective stability point of

symptoms commonly used by the insurance companies to close a claim has not been

reached. Characterization of most people with common whiplash is a few early symptoms and

many late symptoms, which emphasizes tailored early management.

Findings in Relation to other Studies

Only one radiographic experimental study has been conducted before where weight was put

on the head and the sagittal alignment of the cervical spine observed on lateral radiographs.31

This was done on 100 asymptomatic medical students in Sweden in 1942. The results

demonstrated an increased lordosis in the upper cervical spine and decreased lordosis in the

lower cervical spine in all participating subjects when load was applied to the region. The

subjects had to bear 12 kilos on their head in one part of the study and 18 kilos (12 kilos for

women) in their arms on either side in another part of the study. Prior research ascertained

that the ratio of lower/upper cervical spine lordosis was lowest in women in the LWS

compared to an IONP group and an asymptomatic control group without external load, i.e.

reduced cervical lordosis in the lower cervical spine and increased lordosis in the upper

cervical spine.32

Several studies have been conducted in Africa on people carrying heavy weights on their

head. These studies conclude that the axial strain of load carrying on the head exacerbates

degenerative change in the cervical spine which, becomes straight or kyphotic in the lower

cervical spine. 3335 It can be reasoned that these greater load conditions in all the above-

mentioned studies increased the activity in the torque-producing superficial neck muscles and

that the deep pre-and paravertebral neck muscles could not maintain the normal alignment of

cervical lordosis under such high load conditions.

This in accordance with the findings of the women with LWS in this study, where a rigid neck

muscle strategy was revealed, obstructing segmental cervical movements, when extra load

was applied to the top of the head, in most women in the LWS. This may reflect long-term

consequences of short-term benefits.36 The rigid neck muscle strategy may be protective in

nature in the shortterm to decrease the mechanical load on injured lower and/or upper

cervical spine structures. The weight-bearing zygapophysial joints have been found to be the

single most common source of neck pain in WAD.37 In the long term, overactive superficial

neck muscles together with delayed activity and/or atrophy with fatty infiltrations in the deep

local cervical muscles have been manifested as the most prominent physical features in LWS.

38,39



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Clinical Significance

Many symptoms in the late whiplash syndrome remain obscure. The unrelenting neck muscle

stiffness in chronic cases generates multiply joint reaction forces through the cervical spine,

especially on the intervertebral disc in straight or kyphotic sagittal cervical alignments. 40 Ex

vivo experiment has verified that axial distraction reduces intradiscal pressure, 41 which may

parallel the clinical observation that many patients with LWS feel temporarily relief when

slight manual traction is applied to the cervical spine in its axial direction. Patwardhan et al. 6

have shown ex vivo that the load-carrying capacity of the ligamentous cervical spine sharply

increased under a compressive follower load in contrast to compressive vertical loads (Figure

5), which emphasizes the importance of training the deep pre- and paravertebral cervical

muscles in patients with LWS to maintain physiological lordosis.38

Insert Figure 5. Depiction of compressive vertical load path (A) And compressive follower

load path (B). A compressive vertical load induces bending moments (due to the moment arm

illustrated by an arrow labeled MA) and causes large angular changes at small load levels.

Under the compressive follower load path, the resultant internal load on the spine remains

tangential to the spinal curve, passing through the instantaneous center of rotation of each

segment. This minimizes bending moments and shear, and allows the cervical spine to support

the large compressive loads seen in vivo. From Patwardhan et al. (2000) (6). With kind

permission from Wolters Kluwer Health.

In terms of clinical practice, this means that a lordotic alignment of the cervical spine is a

desirable clinical outcome,42 as unphysilogic alignment of the cervical spine results in an

increase in cantilever loads,6 which subsequently induces an increase in muscular energy

expenditure43 and flexural stresses on the vertebrae with formation of osteophytes (Wolffs

Law),40 which are signs of dramatic decreases in load-bearing capacity of the cervical spine.6

Translating this evidence into clinical practice means that if the skull weighs 4,5 kg (10

pounds), then for every inch the skull displaces forward, there is a tenfold increase in the

effort needed from the posterior neck muscles to support the weight of the head, which

induces great compressive forces on the inert structures of the cervical spine.44 This is the

case during daily work, for example, at a computer and to-day the terms text-neck or tech-

neck are used to reflect increased load on the neck by sustained forward-bended head-neck

posture. These increased compressive loads inserted from the patients muscles may be one of



13

the most important clinical significant effects on late neck-related symptoms after a whiplash

trauma.

Insert Figure 6. Some common physical features in women with LWS.

Notwithstanding the above-mentioned biomechanical results, it is clear that the women in the

LWS are more affected by kinesiophobia and pain after innocuous stimuli or central

sensitization (Table II). Research has shown that addition of posttraumatic stress and sensory

hypersensitivity more accurately estimates disability and pain than fear avoidance measures

alone early after whiplash injury.45 It has been shown in LWS that central sensitization was

not maintained by a nociceptive input from the painful body areas because local anesthesia

did not affect the pain thresholds. 46 However, nociceptive stimulation associated with the

injury may produce excitation of the central nervous system, which in turn is responsible for

reduced pain thresholds in uninjured tissues. 46 Central sensitization may not require an

ongoing nociceptive input, but an initial peripheral event is required to induce central

sensitization.46 Once established, central sensitization may therefore be independent of the

peripheral input.46 The psychological distress found in women with LWS in this study (Table

II and Table IV) is similar to the profile of patients with chronic pain resulting from other

musculoskeletal injuries46. If psychological factors were the primary determinant of altered

pain perception, it would affect all the pain thresholds and not spare heat pain.46 Central

sensitization and psychological factors, which were only detected in part of the women with

LWS, are not responsible for the biomechanical results in this biomechanical study, rather

these factors are contributing to maintaining the pain and disability in the LWS.

Limitations

The whole spine was not imaged. The entire spine functions as 1 global unit whose individual

regions can have a significant effect on each other.47 This study is not representative for all

women in the chronic state, as the women in this study were recruited by sample of

convenience from specialists in manual therapy, who often get the worst cases. The reliability

and validity of the questionnaires used have not yet been ascertained in Icelandic language.

Sample size calculation prior to the study could not be performed because it took too long to

test different weights born upon the head and the variable responses obtained with different

weights between groups. No cause effect relationship can be established. This cross-

sectional study is a snap-shot in time, as the radiographic test results and the pain and



14

disability measures of the women in the 2 symptomatic groups were obtained at the same

time. A longitudinal study is required which includes both the biomechanical and pain

processing mechanisms as well as diverse psychological factors to ascertain the causeeffect

relationship.

Future Directions

To understand the peculiar biological consequences of soft tissue injuries to the cervical

spine, clear questions such as: "why is the cervical spine not able to tolerate the normal loads

of activities of daily living?" must be asked. It is important in current psychosocial research

trend that the biomechanical behavior of the cervical spine is not underrepresented, as

whiplash-type distortion injuries are biomechanical events with diverse biomechanical

consequences.48 For example, evidence from a few recent studies suggests correlations

between radiographic parameters in the cervical spine and health-related quality of life

(HRQL).49 It seems that women with LWS in this study were using the ankle strategy to

maintain postural balance when the weight was born upon the head, which requires a force

plate to measure alternation in the center of pressure from their feet.

One clinical option to produce normal lordosis might be to put a weight upon the head in front

of the COG. For visualization of how normal lordosis can be created by anterior load on the

head, see animation 7 in Appendix 1. A prerequisite for this treatment option, which merits

clinical investigations, is that the cervical spine is not a rigid cylinder due to unrelenting

hyperactivity in the torque-producing superficial neck muscles.

Conclusion

The study implies that the load-bearing capacity of the cervical spine is greatly reduced in

vivo in most women with LWS. The rigid horizontal translation strategy of the head and the

cervical spine as a whole implies that the cervical spine predominately functions such as a

rigid cylinder when loaded in the LWS. This merit further investigation. This is the case

despite numerous research, which emphazises the muscular imbalance between the the deep

and superficial neck muscles, has been published. There is therefore ugent need to better

translate research findings into everyday practice by easy-to-use technology (tools) to address

the loss of load-bearing capacity of the cervical spine in symptomatic people after a whiplash



15

injury. The altered pain processing mechanisms and diverse psychological factors contribute

to maintain the pain and disability in many women in the LWS.

Acknowledgements

The authors would like to thank all participants in this study, manual therapists, and staff

involved at any stage of the study. Special thanks to Professor Thorarinn Sveinsson at the

Department of Physical Therapy at the University of Iceland, for critical suggestions during

the statistical analyses.

Financial disclosure: No funds were received for this study.



16

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HRQOL improvement in adult thoracolumbar deformity patients at 2-year follow-up. J

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Figure captions

Figure 1. A vertical line from the center of weight upon the head is anterior to the center of

gravity of the head, creating greater anterior moment, which the neck extensor muscles must

counteract.

Figure 2. Experimental set-up.

Figure 3A. For the upper cervical spine, the angle a (C0C1) was formed by a line connecting

the most caudal point on the occipital bone posteriorly, aligning with the posterior surface of

the spinal canal at the C1 level, and the deepest point in the groove formed by the occipital

condyle and the occipital bone anteriorly versus the line tangential to the inferior aspect of the

atlas; angle b (C1C2) by the lines tangential to the inferior aspects of the atlas and axis,

respectively.

Figure 3B. Radiographic measurements for the lower cervical spine. The Harrison posterior

tangent method was used which involves drawing lines parallel to the posterior surfaces of all

cervical vertebral bodies from C2 to C7 and then summing the segmental angles for an overall

cervical curvature angle.28

Figure 4. Angular rotation in the sagittal plane in upright standing position measured in

degrees (mean, standard error), without and with axial load upon the head. Significant

differences were revealed within the asymptomatic and the IONP groups but not within the

LWS group. Abbreviations: IONP=insidious onset neck pain; LWS= late whiplash syndrome

Figure 5. Depiction of compressive vertical load path (A) And compressive follower load path

(B). A compressive vertical load induces bending moments (due to the moment arm

illustrated by an arrow labeled MA) and causes large angular changes at small load levels.

Under the compressive follower load path, the resultant internal load on the spine remains

tangential to the spinal curve, passing through the instantaneous center of rotation of each



22

segment. This minimizes bending moments and shear, and allows the cervical spine to support

the large compressive loads seen in vivo. From Patwardhan et al. (2000)6. With kind

permission from Wolters Kluwer Health.

Figure 6. Some common physical features of women in late whiplash

TABLE captions

TABLE I. Inter and intra-rater reliability.

TABLE II. Comparison of Age, Body Mass Index and Questionnaires.

TABLE III. Increase in symptoms after carrying the external load on the head.

TABLE IV. Comorbid Disorders.

TABLE V. LWS* Group Descriptive Variables.



Table I. Reliability Inter-rater (R2a vs R1)

Systematic error

Segments ICC (2,1) SEM SER Diff (2a - 1) p-value C0-C1 0.78 0.62 0,08 -0.19 0,08 C1-C2 0.93 0,35 0,00 -0.15 0,61 C2-C3 0,88 0.45 0,00 -0.04 0,72 C3-C4 0,90 0.23 0,26 -0.39

Table II. Comparison of Age, Body Mass Index and Questionnaires

LWS* N=62

IONP N = 60

Asymptomatic N =60

Mean age in years (SD) 39.13 (8.64) 38.45 (8.76) 35.93 (9.75)

Mean Body Mass Index (kg/m2)(SD) 25.0 (4.8) 25.9 (3.8) 24.3 (5.2)

Mean VAS 0 -10 (SD) 6.71 (1.38) 5.13 (1.61) N/A

Medication use in number of patients and percentage 34 (55) 6 (10) N/A

Mean Borg-CR 10 Exertion Scale 0-10 (SD) 5.06 (2.23) 2.63 (1.48) 1.46 (1.34)

Mean Neck Disability Index 0-100 (SD) 40.82 (15.38) 21.8 (11.33) 1.07 (1.62)

Mean Leeds Assessment of Neuriopathic Symptoms and Signs 0-24 (SD)

12.66 (6.27) 8.65 (5.61) N/A

Mean Tampa Scale for Kinesiophobia (TAMPA) 17-68 (SD) 33.88 (8.18) 28.1 (8.18) N/A

* LWS (Late Whiplash Syndrome)

IONP (Insidious Onset Neck Pain)

No significant differences by One-Way Anova and Independent tTest

Significant differences by One-Way Anova and/or Independent tTest



Table III. Increase in symptoms after carrying the external load on the head

WAD IONP

No symptoms 7 24

*Mild symptoms (same day) 11 19

Moderate symptoms (1-3 days) 25 13

Severe symptoms (3 -14 days) 19 4

Total 62 60 *

Table IV. Comorbid Disorders

LWS N =62 IONP=60 OR (95% CI) p

General symptoms Yes/No Yes/No Headache 49/13 39/21 2,0 (0,9 to 4.5) 0.08

Pain and stiffness in the neck 52/10 50/10 1.0 (0.4 to 2.7) 0.93

Pain and stiffness in the shoulder girdle 54/8 39/21 3.6 (1.5 to 9.1) 0.01*

Pain and stiffness berween the shoulder plates 54/8 34/26 5.2 (2.1 to 12.7)

Table V. LWS* Group Descriptive Variables

Number of collisions (%)

One collision 36 (58%) /36

Two collisions 17 (27,4%) /34

Three collisions 4 (6,5%) /12

Four collisions 4 (6,5%) /16

Five collisions 1 (1,6%) /5

Total 62 (100%); Total 103

Type of collision Number (%)

Rear-end 56 (54,4%)

Front 16 (15,5%)

Side 15 (14,6%)

Combined 13 (12,6%)

Roll-over 3 (2,9%)

Total 103 (100%)

Dominate side of symptoms Number (%)

Right 27 (43,5%)

Left 18 (29%)

Bilateral 9 (14,5%)

Changing sides 8 (13%)

Total 62 (100%)

Claim closed Number (%)

Yes 54 (87,1%)

No 5 (8,1%)

NA 3 (4,8%)

Total 62 (100%)

After the claim was closed Number (%)

Worse 37 (68,5%)

Same 12 (22,2%)

Better 5 (9,3%)

NA 8

Total 62 (100%)

*LWS = Late whiplash syndrome




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