Chiropractic Journal of Australia 2018 (Jun); 46 (2): 162–171 ~ FULL TEXT
Christian Fludder, B.Chiro.Sc, M.Chiro, DACCP, Braden G. Keil, B.App.Sc. (Chiropractic), M.C.Sc. (Paediatrics), FICC, FACCP
Chiropractic Children’s Healthcare,
9 Lower Plenty Road,
Rosanna, VIC, 3084
Introduction: Instrument-assisted delivery occurs regularly in Australia. This study aims to determine if there is a higher prevalence of restricted cervical spine range of motion (ROM) in infants born via instrumental delivery or Caesarean section compared to vaginal delivery without instrument assistance.
Methods: Data was collated from all 176 infants under 112 days of age in a paediatric chiropractic clinic. Details regarding method of delivery and instrumental assistance were obtained. Passive ROM assessment was recorded as either “Full” or “Reduced”.
Results: Reduced cervical spine ROM was apparent in 76.1% of infants born vaginally without intervention (n=88), 75.0% with forceps assistance (n=16), 88.9% with vacuum-assistance (n=18), 100% born with vacuum and forceps (n=3), and 82.3% born via Caesarean section (n=51).
Conclusion: Vacuum-assisted delivery and Caesarean section delivery were associated with a higher prevalence of reduced cervical spine ROM when compared to vaginal delivery without assistance. Further research in prospective studies is recommended.
From the Full-Text Article:
The use of instrument to aid in delivery, in the form of forceps or vacuum-assistance,
is a frequent occurrence, with instrument assistance occurring in up to 19% of births
in Australia. [1, 2] The morbidities associated with instrumental delivery are well
documented , but there is little data available detailing instrumental delivery and its
impact on cervical spine range of motion in infants.
There is evidence in adults that suggests in altering normal cervical spine motion,
there is an associated increased risk of alterations in autonomic function [4–6],
increased nociception , and cortical dysafferentation , but this information is
lacking for the infant population. However, afferent systems and cortical perceptions
of pain are well developed by 30 weeks’ gestation [9, 10], as are the autonomic
nervous system and Vagal tone.  Cortical effects of altered cervical spine motion
in infants has yet to be researched.
Normal values of range of motion in infants aged 2–10 months have been
documented, with a mean rotation of 110°, and 75° of lateral flexion.  Ohman and
Beckung stated that it is “rare for healthy infants to have an imbalance between left
and right.”.  Restrictions in range of motion are typically attributed to changes in
muscular tone. [13, 14] Two processes leading to increased muscle tone have been
described; trauma directly to the soft tissue of the neck creates hypertonicity of
muscles involved , and/or reflex activation of cervical musculature occurs
secondary to increased nociception from local articulation.  Recent research has
indicated that there is a threefold increased risk of birth trauma with forceps-assisted
delivery and a fourfold with vacuum-assisted delivery.  Furthermore, the process
of birthing places high amounts of force through the cervical spine, with up to 120N
of compressive force reported for vaginal delivery  and over 200N for assisted
delivery. [17, 18] This raises the hypothesis of whether the increased forces involved
with assisted delivery increases the prevalence of reduced cervical range of motion.
This study aims to determine if there is a higher prevalence of restricted cervical
spine range of motion as determined by 4 chiropractors with post-registration training
in chiropractic paediatrics in infants born via instrument-assisted delivery (vacuum,
forceps or vacuum and forceps) or caesarean section, compared to no instrument
assistance vaginal delivery.
Data were collected from 176 consecutive infants with complete birth details,
complete examination findings including birth weight, no previous chiropractic
treatment, and 112 days of age or younger that presented to a children’s only
chiropractic clinic between 1st January, 2010 to 31st December, 2010.
Passive range of motion assessment of the cervical spine was performed with the
parent/caregiver present while the infant was held supported in an upright position
on the parent/caregiver’s leg to remove external conditions that may limit movement.
Rotation was performed by bilaterally rotating the infant’s chin toward each shoulder
around the transverse plane. Lateral flexion brought the infant’s ear to the ipsilateral
shoulder in the coronal plane. Flexion was assessed by bringing the infant’s head
into 30° rotation before flexing the head toward the chest along the sagittal plane.
This was done to align the occipitoatlantal articulation to the sagittal plane. In
concurrence with methods of range of motion assessment in previous studies, range
of motion was decided to be “full” for rotation if the chin was above the acromion, for
lateral flexion if the ear touched the shoulder, for flexion if the chin touched the
anterior chest, and for extension if the occiput touched upper thoracic region. [13, 14]
These methods of motion assessment have been found to have substantial and
excellent level of intra- and inter-examiner reliability respectively for rotation and
moderate for lateral flexion.  If an infant was unable to perform this motion, the
finding was listed as “reduced”. Findings from 4 chiropractors with post registration
chiropractic paediatric training were collated (Table 1).
Details regarding age at consultation, birth type (listed as vaginal (V), or Caesarean
section (CS)), and birthing assistance data regarding forceps or vacuum extraction
were recorded. Those born vaginally were categorised based on intervention, listed
as nil intervention, forceps, vacuum, and both vacuum and forceps.
Statistical analysis was performed using JASP statistical analysis software.
Contingency tables were created where infants with cervical spine ROM restriction
were compared to those with normal ROM against infants born without instrumental
assistance to those born via forceps, vacuum, or forceps and vacuum to generate a
χ2 value. Further analysis was performed to determine the impact of weight and
gender. Weights were normally distributed and separated into 6 groups. Differences
with values of p≤0.05 were considered significant, and all results were expressed
with a 95% Confidence Interval.
In 125 cases of vaginal and 51 cases of caesarean section data, there were 98
cases with reduced cervical spine range of motion from vaginal delivery (78.4%) and
42 from caesarean section (82.3%). 67 cases born vaginally without intervention
presented with reduced cervical spine range of motion (76.1%), 12 from forceps
delivery (75.0%), 16 from vacuum-assistance (88.9%), and 3 from Vacuum with
Chi-squared analysis of infants with or without reduced cervical ROM showed a not
statistically significant difference between infants born vaginally compared to
Caesarean section (χ2 = 0.348, df = 1, p = 0.55). There was a not statistically significant
difference between nil intervention and forceps, vacuum, or forceps and vacuum
assistance regarding cervical ROM (χ2 = 1.957, df = 3, p = 0.581).
On range of motion analysis, 140 infants were observed to have restrictions in their
range of motion (Table 2). Lateral flexion was most frequently reduced, with all
infants with restrictions being limited in this motion (Table 3).
There was a modest increase in prevalence of reduced cervical ROM as weight
increased, with this peaking in the 3.64–3.98kg cohort (Table 4).
When assessing based on gender, there are strong similarities across all cohorts
except that of those born via Caesarean section (Table 5). Chi-squared analysis of
this was not statistically significant (χ2 = 1.323, df = 1, p = 0.25).
The main result from this study demonstrated that in infants born with vacuum, and
vacuum with forceps, we observe a higher prevalence of reduced cervical range of
motion compared to infants born without assistance, forceps-assisted delivery or via
Caesarean section. However, while we can observe a higher prevalence, we must
note that statistical significance was not reached. This is likely due to the low
numbers involved in each cohort and the already high prevalence of infants with
reduced cervical spine ROM in infants born without intervention.
The use of instrument-assisted deliveries has steadily increased over time, with
2015 data indicating 19% of vaginal deliveries requiring instrument assistance ,
compared to 12.4% in 2011.  A recent study by Ashton–Miller et al examined the
forces placed on foetal head during labour, with the authors estimating the forces
applied to range from 15N (corresponding to a mass equivalent of 1.6 kilograms) at
rest to 120N (12.2 kilograms mass equivalence) of compressive force during
volitional contraction.  Additional studies have demonstrated up to 132N (13.5
kilograms mass equivalence) of tractional force with vacuum-assisted delivery ,
and 196N (20 kilograms mass equivalence) of tractional force with forceps
intervention.  A recent study by Pettersson et al provided more information on
forces involved with vacuum extraction, demonstrating significantly higher forces
involved than previously reported.  Repeated attempts, posterior position or midcavity extractions showed much higher force involved – up to 452N, or the mass equivalence of 46 kilograms, with “33.5% of the vacuum extractions study employed a maximum traction force exceeding the suggested safe maximum force level of 216
This is concerning as the risk for injury increases above 225N of tractional force, with
above 290N seen as “excessively traumatic”.  The increased prevalence of
cervical spine decreased range of motion after vacuum use found in this study is
likely due to the increased tractional force associated with vacuum use. The
structure of the infant cervical spine is different to that of an adult, with a more
horizontal facet joint angle suggesting stronger biomechanical resistance to
compressive rather tractional forces.  These findings suggest an underappreciation of the forces being employed with vacuum delivery, and are certainly consistent with the higher prevalence of reduced cervical spine range of motion in
the cohorts involving vacuum assistance. The relationship between vacuum forces
and degree of cervical spine range of motion restriction needs further research.
Birthing injuries are defined as “structural or functional deteriorations to the
neonate’s body due to a traumatic event at birth”.  There are well recognised risk
factors associated with birth trauma including higher birth weight and instrumental
intervention. [22–24] There is a four times higher chance of birth injury associated
with forceps use and three times higher with vacuum extraction.  This is partially
consistent with our data, with vacuum-assisted deliveries having a higher prevalence
of reduced cervical spine range of motion than forceps-assisted or unassisted
Birth trauma has been reported to be of a higher incidence in vaginal delivery (30 per
1,000 live births) compared to caesarean section (10 per 1,000 live births) placing
vaginal delivery itself as a potential risk factor.  This was not consistent with our
data, suggesting four possibilities; firstly, the small size of our cohort has skewed the
representation of infants presenting with reduced cervical spine range of motion,
secondly, that cervical spinal range of motion assessment has been based on
previous data from motion assessments in infants with muscular torticollis as
reference; not normal, healthy neonates , thirdly, the lack of practitioner blinding
in assessment produced a biased result, or fourthly, data did not include or assess
cervical spine range of motion restriction. A review of 624 cases of infants with
infantile torticollis found nearly 50% (304) had a history of requiring forceps or
delivery by caesarean section, compared to 37.8% (236) normal vaginal, with over
70% of the cases involved demonstrating reduced cervical range of motion.  It is
likely that the increased prevalence of cervical spine range of motion restriction
associated with vaginal deliveries identified in this study is the result of a more
detailed assessment of cervical spine restriction.
Birthweight has been stated as a risk factor for birth trauma, with infant birthweight of
4,000g to 4,500g associated with a twofold increase in birth trauma.  In our data
we did observe a moderate increase in prevalence of reduced cervical spine ROM
as weight increased in Caesarean cases but not in vaginally delivered cases.
One question that arises from this research is that of the impact of reduced cervical
spine range of motion resulting from birth. In this study, 140 of the 176 cases
presented with restrictions in cervical spine range of motion (79.5%), with 31 of 37 of
infants being born with assistance having reduced cervical ROM (83.8%). One
concern with reduced range of motion is the development of positional preference. In
a 2006 study of 649 infants, Sergueef found a correlation between the development
of deformational plagiocephaly and assisted delivery , and in a 2016 study of 150
infants with deformational plagiocephaly, over 90% had restrictions in cervical spine
range of motion.  An additional concern is possible increased risk of
developmental delay. In infants with plagiocephaly, Hutchison et al observed a
higher prevalence of developmental delay based on results from the Ages and
Stages Questionnaire (ASQ) in infants with neck dysfunction (41%) than those
without (29%).  A 2017 systematic review of plagiocephaly and developmental
delay concluded a that there is a strong association. 
In the neonatal and infant ages, it is difficult to use specific outcome measures such
as pain or cognition tests due to immature cortical development. Evidence of
alteration to autonomic function may be used to determine neurological insult. 
Cervical spine involvement in altered autonomic function as reflected by
improvement in heart rate variability upon correction of cervical spine joint
dysfunction has been demonstrated. [4–6] Autonomic changes apparent with altered
cervical spine function or demonstrated after correction of cervical spine dysfunction
are likely to be a result of changes in Vagal nerve function. The Vagus nerve has a
key role in gastrointestinal function and consequently may present with signs such
as regurgitation or vomiting. This is explained by the role the Vagus nerve has in
tonal regulation of the lower oesophageal sphincter. 
This may then suggest that the presence of regurgitation, vomiting, reflux or “Silent
Reflux” is a reflection of altered autonomic function (Vagal nerve) secondary to
altered cervical spine function. This study observed a high prevalence of reduced
cervical spine range of motion in infants. It is likely that a significant number of these
cases may have Vagal nerve involvement. Further research is needed to compare
Vagal nerve function in infants with and without restrictions in cervical spine range of
motion as well as Vagal nerve function changes after correction of any restriction in
the cervical spine. Future research in this area is strongly recommended as current
medical management of these symptoms with proton-pump inhibitors has not been
found to be beneficial and may have significant negative outcomes. [31, 32]
There are several limitations with this retrospective analysis. There are small
numbers involved in each cohort, a lack of blinding of the practitioner upon
assessment, and a confounder based on neonates and infants with reduced cervical
spine range of motion being more likely to attend a chiropractic clinic for evaluation.
To address these limitations, future prospective studies with a larger cohort, with
neonates preferably being assessed by a blinded practitioner shortly after birth,
would reduce the impact of these confounders.
There is a high prevalence of reduced cervical spine range of motion with unassisted
vaginal birth, yet there is a higher prevalence involved with vacuum-assisted
delivery. However, there was a not statistically significant difference between those
born with assistance to those born without assistance or via Caesarean section.
Further prospective studies with larger cohorts is recommended.
Ethics Approval and Consent to Participate
This study, as defined by section 5.1.8 of the National Statement of Ethical Conduct
of Human Research (2007), carries only negligible risk and as such does not require
Ethics Approval. Furthermore, it done in accordance with the Declaration of Helsinki
The authors declare that they have no competing interests
This study received no external funding, with the project done at the authors’
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