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Year : 2020  |  Volume : 5  |  Issue : 1  |  Page : 26-32

The influence of forward head posture on cervical proprioception in dentists

Department of Medical Rehabilitation, College of Applied Medical Sciences, King Khalid University, Abha, Saudi Arabia

Date of Web Publication13-Aug-2020

Correspondence Address:
PhD, PT Ravi Shankar Reddy
Assistant Professor Department of Medical Rehabilitation, College of Applied Medical Sciences, King Khalid University Abha
Saudi Arabia
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1658-743X.291956

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Objective: The study aims to determine the influence of FHP on cervical proprioception in dentists. Method: In the study, 84 dentists were divided into two groups based on their craniovertebral (CV) angle: the FHP group (44 subjects with mean age 34.95 ± 6.68 years and CV angle 49° or less) and a healthy group (40 subjects with mean age 29.80 ± 6.46 years, CV angle ≥ 49°). CV angle: an angle formed between a line extending from 7th cervical vertebrae (C7) to the tragus of the ear and a horizontal line passing through C7. The cervical Joint Position Error (JPE) testing is performed as an estimate of cervical proprioception in sagittal (flexion, extension) and transverse plane (rotation to the left and the right). Three trials of JPE’s were tested in each direction, and the mean of these errors is used for analysis. Results: There were significant differences between the FHP and healthy subjects in the cervical JPEs (p<0.001) in all four directions. There was a weak to moderate negative correlation between the CV angle and the JPEs tested. Conclusion: The dentists with FHP demonstrated reduced cervical proprioception. Changes in the length-tension relationship in cervical musculature due to FHP may affect cervical position sense. Also, cervical proprioception may become worse as the degree of FHP increases.

Keywords: Forward head posture; Joint position sense; Dentists; Craniovertebral angle; Cervical proprioception.

How to cite this article:
Reddy RS. The influence of forward head posture on cervical proprioception in dentists. King Khalid Univ J Health Scii 2020;5:26-32

How to cite this URL:
Reddy RS. The influence of forward head posture on cervical proprioception in dentists. King Khalid Univ J Health Scii [serial online] 2020 [cited 2021 Jan 18];5:26-32. Available from: https://www.kkujhs.org/text.asp?2020/5/1/26/291956

  Introduction Top

For many years, the physical requirements of different types of work activities have influenced the health and wellbeing of people. Musculoskeletal disorders (MSDs) are common physical impairments with considerable financial penalties caused by workers’ claims for reimbursement and medical expenditures.[1] Dental health workers have a higher incidence of work-related MSDs[2] in comparison to other healthcare professionals. The onset of musculoskeletal (MS) pain occurs relatively early in the dental profession. Nearly 70% of dental students report musculoskeletal pains in different areas of the body towards the end of their dental training.[3] 74.3% is the reported prevalence of neck pain in dentists.[4] Dental work can lead to a wide range of musculoskeletal hazards. These are due to the nature of the high-precision work they need to maintain for a long time, exerting static loads onto the shoulder and cervical regions.[5]

One of the common postural deviations in dentists is Forward Head Posture (FHP)[6] and is described as “head positioned anterior to a vertical line passing through the centre of gravity, the line of vision will extend downward if the normal angle at which the head and neck connection are maintained. To correct these for visual needs, there is posterior cranial rotation resulting in tilting of the head backward, along with flexion of the neck over the thoracic spine and posterior migration of mandible”.[7] Higher levels of disability are associated with severe FHP.[8] Neck pain symptoms result from prolonged static maintenance of posture and muscle overload. Many studies have stated that FHP is correlated with temporomandibular disorders, headache, abnormal scapular movement, and myofascial pain syndrome.[9],[10]

Cervical proprioception has a significant influence on postural control, gait control, and body balance.[11] The cervical muscles are rich in muscle spindles and contribute to the enhanced sensorimotor function. They play an essential role in maintaining head and neck control during static and dynamic activities.[12]

In FHP, in addition to altered length, the capacity to generate tension in muscles is also decreased.[13] Cervical muscles possess mechanoreceptors in abundance, and the cervical region plays a crucial role in the afferent transmission of information.[14] Multifactor problems in this region may result in decreased joint position sense.[14] Any damage to muscles, joints, and connective tissues may alter proprioceptive and postural sense.[15] Conversely, a faulty posture may also bring about changes in functional anatomical structures, causing symptoms such as pain and altered proprioception.[15] Studies indicate that structural changes to the cervical spine as forward head posture may maintain symptoms for more extended periods or help to reoccur the symptoms in patients with neck pain, which needs to be tested.[16],[17] Assessing and managing these deficits in FHP or neck pain subjects may be an essential factor in rehabilitation. To date, different authors investigated the relationship between FHP and pain.[18],[19] However, assessments concerning whether FHP can affect cervical joint position sense - and if so to what extent - are few.[20],[21] Therefore, the purpose of the current study was to assess the effect of FHP on cervical joint position sense in dental subjects compared to healthy subjects without FHP and to see if there is any relationship between severity of FHP and cervical Joint Position Error (JPE).

  Methods Top

This study was conducted between December 2017 to September 2018 (10 months) in the Department of Physical Therapy, xxx University, xxx country. Advertisement in the form of word of mouth was given in the dental schools and clinics for voluntary participation in this study. Eighty-four subjects were recruited and divided into two groups based on their craniovertebral (CV) angles. With the CV angle less than 49°: FHP group (n=44) and the angle more than 49°: control group (n=40)[22]. The subjects were excluded if they had fractures, neck pain or upper quarter pain or any musculoskeletal abnormalities. All the subjects read the patient information sheet and signed an informed consent form. The XXXX University ethics committee (REC # 2016-08-03) approved the study.

Measurement of FHP

We adopted the FHP measuring technique from Raine et al. (1997) [23]. To begin, the subjects stood comfortably with their hands hanging at their sides, and their left side facing a digital camera (12 megapixels). The base of the camera was aligned with the subjects’ shoulder height. The tragus of the ear and C7 spinous process were marked with one cm diameter fluorescent adhesive skin markers [Figure 1].
Figure 1: Measurement of Cranio-vertebral angle.

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The CV angle (i.e., the sagittal-C7-tragus angle) is measured on a digital photo, i.e., the angle (in degrees) between a horizontal line crossing the C7 and a line connecting the tragus to C7. The estimated CV angle of a healthy adult without postural deviations is from 49° to 59° (10 degrees range. Therefore, subjects with CV angles less than 49° are included as FHP in this study.

The test procedure for measuring cervical joint position sense

All the subjects were familiarized with the tests before the actual testing. The testing took place in a quiet environment. The guidelines of examination cervical JPE were adopted from Alahmari et al. study.[24] To measure JPE, the subjects sat in the chair with feet flat on the ground with back erect and head straight. The examiner blindfolded the subject with the travel mask and stabilized the shoulders to the chair with a webbing strap to prevent trick movements. The examiner then kept the Cervical Range of Motion (CROM) device on the top of the subject head and stabilized with the Velcro strap. The magnetic yoke of the CROM device was placed squarely on the subject neck, and then the examiner calibrated the CROM device to a neutral position [Figure 2].
Figure 2: Measurement procedure of cervical joint position sense

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The examiner guided the subjects head to the target position, maintained for three seconds to memorize the position and then brought the head back to the neutral position. The subjects then to reposition their head actively to the target position, and reposition accuracy or errors were recorded in degrees. The target position selected was 50 % subject’s available ROM in each movement direction previously measured. The JPE was measured in flexion, extension, rotation right and left. Three trials of reposition errors were measured in each movement direction, and the average three trails were used for analysis. The single investigator performed all the JPE tests, and the order of testing in each movement directions was randomized using the chit method.

Statistical analysis

SPSS software version helped the researchers compute the statistical data. The statistical significance value was set at less than or equal to 0.05, with a 95% confidence interval considered significant. JPE errors were absolute errors, and the mean of three trials in each direction was used for analysis. The study data variables followed normal distribution when checked by the Shapiro–Wilk test. Independent sample t-tests helped to identify any differences in JPE between subjects with and without FHP. The correlation between FHP and cervical JPE was assessed using the Pearson correlation coefficient (r). We interpret the correlation coefficient of 0.7 to 1 as strong, 0.40 to 0.60 as moderate, and 0.1 to 0.30 as weak.[25]

  Results Top

Eighty-four subjects (44 FHP and 40 healthy) aged between 20 to 50 years old participated in the study. Demographic characteristics for the study population are summarized in [Table 1].
Table 1: Demographic characteristics of study subjects

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There are no differences in age, height, weight, and BMI between groups. The mean absolute JPE in healthy subjects ranged from 2.37 (rotation right) to 4.50 degrees (extension), and FHP subjects ranged from 6.31 (rotation right) to 8.18 degrees (extension) [Table 2].
Table 2: Independent t-test statistics to compare cervical JPE’s between healthy and FHP subjects

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FHP group showed a significant difference (p ≤ 0.001) in cervical JPE measurements in all directions tested compared to healthy subjects [Table 2].

Pearson correlation coefficients showed negative correlations between FHP values and cervical JPEs [Figure 3] and [Table 3].
Figure 3: Relationship between FHP and A) JPE in flexion, B) JPE in extension, C) JPE in rotation left D) JPE in rotation right

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Table 3: Coefficient of correlation between FHP and cervical JPE’s.

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  Discussion Top

The present study aimed to see the effect of FHP on cervical joint position sense in dentists. It confirmed that FHP subjects have significantly larger absolute cervical JPE’s compared to those without FHP. These differences were observed in all the cervical directions (flexion, extension, rotation left, and right) tested. FHP subjects established a moderate to weak negative relationship with JPE, stating that an increase in the degree of FHP (decrease in CV angle) would increase the magnitude of JPE (decrease in cervical position sense). This study results showed that dentists with FHP had impaired cervical position sense.

Dentists suffer more frequently from work-related MSDs.[26] One of the most common MSDs is FHP, which is considered by upper cervical extension and lower cervical flexion[27]. FHP maintained for a prolonged period places increases stress on contractile and non-contractile structures and thereby a predisposition to neck pain.[8] Watson et al. state that the insidious, painless nature of repetitive microtrauma, like the continued flexed posture of head and neck, alters the length-tension relationship of cervical muscles and thereby increase in flexion moment of the head.[28] This may result in FHP subjects using different motor synergy strategies when they are trying to relocate to the target head position, resulting in higher absolute JPE compared to healthy subjects. Another possible reason could be due to a change in muscle spindle afferent signaling pattern due to FHP. Previous studies demonstrated impaired muscle spindle afferent signaling affecting proprioception due to fatigue, disease, or aging.[29],[30] Further, FHP predisposes to neck and shoulder pain,[31] and these pains can cause a reduction of cervical joint position and poor postural balance.[32],[33]

Lee et al. study found significant differences in the absolute error value of the joint position sense (cervical flexion, extension, and rotation) between the FHP and control groups, which is in accordance with this study results, and he stated FHP is associated with reduced proprioception [20]. Although, Sajjadi et al. found no significant difference in repositioning errors between FHP and control group in absolute and constant errors (p > 0.05) but found significantly different in variable errors (p<0.05).[34] These differences could be due to methodological considerations adopted between these studies. Sajjadi et al. used laser pointers, whereas the current study used a CROM device to assess the cervical JPE, the subjects in the Sajjadi et al (2014). study assessed neutral head positioning tests and the present study assessed target head positioning tests.

The mean JPE in FHP subjects in this study was more considerable in extension (8.16 degrees), followed by JPE in flexion (7.18 ± 2.10 degrees), rotation left (6.93 ± 1.80 degrees) and rotation right (6.31 ± 2.05 degrees). Lee et al. study in FHP subjects have shown larger JPE in rotation right (7.08 ± 2.27 degrees) followed by flexion (6.23 ± 1.91 degrees), extension (6.23 ± 2.20 degrees) and rotation left (5.60 ± 2.03 degrees) [20]. Overall mean JPEs in this study are more significant compared to the Lee et al. study. This may be because of the difference in the age of FHP subjects who participated in this study (34.95 ± 6.68 years) compared to the Lee et al. study (22.2 ± 1.9 years). Age can influence cervical position sense. As age increases, cervical position sense decreases (JPE increases).[35] Another possible reason is that FHP subjects who are dentists adopt a more-static neck posture compared to other occupations and thereby greater magnitude in JPE.

This study results established that subjects with FHP demonstrate significant impairment in cervical proprioception. Therefore, rehabilitation programs should aim to assess and restore proprioception in dentists with FHP and neck pain. Conservative rehabilitation protocols have been formulated and designed to help dentists with postural neck pain. However, the effect of proprioceptive training programs in cervical subjects is less understood and less reported. Jull et al. (2007) examined the effect of proprioception training in patients with chronic neck pain and measured their results using JPE. They compared conventional proprioceptive training with cranio-cervical flexion exercises. Jull et al. reported a significant decrease in JPE, as well as in perceived neck pain and perceived disability in both groups.[36] Due to the scarcity of research in this area, further investigations are needed to determine the effectiveness of neck position sense in the prevention and treatment of FHP and neck pain. Proprioceptive training is an invaluable component of rehabilitation in the recovery process of major joints, including the shoulder, knee, hip, and ankle,[37] which could potentially be incorporated into cervical joint rehabilitation pending further examination.

Limitations of the study

The single investigator grouped the subjects based on FHP and measured the proprioceptive outcome measures, so the investigator was not blinded. In this study, we did not consider years spent by subjects in dental practice, duration of time in a day spent in a dental clinic, and previous history of neck pain. A future study may take such factors taken into consideration to understand better the effect of FHP on cervical position sense in dentists.

  Conclusion Top

FHP is associated with an increase in cervical proprioceptive impairment. Rehabilitation of dentists with FHP should consider proprioceptive evaluation and treatment. Furthermore, the present study also found a weak to moderate negative correlation between FHP and position sense.

Conflict of Interest: None

  References Top

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  [Figure 1], [Figure 2], [Figure 3]

  [Table 1], [Table 2], [Table 3]


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