Association between Temporomandibular Disorders with Head and Neck Posture: A Systematic Review

Keywords

Temporomandibular Disorders; Posture; Craniocervical Angle; Temporomandibular Joint; Systematic Review.

Introduction

The analysis of the postural control has been demonstrated to play a relevant role for the maximal mouth opening, pressure pain thresholds and musculoskeletal pain [1, 2]. Stabilometry and head and neck postures aredifferent methods for assessingpostural control. In fact, stabilometry is a valid tool in the postural approach of temporomandibular disorders (TMD) [3]. Nevertheless, an unclear association between temporomandibular disorders (TMD) and head and cervical posturehas been reported due to the poor methodological quality of the studies assessed [4].

TMD are a heterogeneous group of conditions affecting the temporomandibular joints (TMJ), the jaw muscles and/or the related structures [5]. TMD is a significant public health problem affecting the 5-12% of the entire population, being the second most common musculoskeletal condition after chronic low back pain resulting in pain and disability with a high economic impact ($4 billion in USA) [6]. Patients are clinically characterized by muscular or joint orofacial pain, limited range of mandibular movement, headache, ear pain, chewing difficulties or pain, and clicking [7].

An important stepto diagnose properly a TMD is to stablish clear, reliable, and valid criteria. The Diagnostic Criteria for TMD (DC/ TMD) and the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) have been the most widely employed diagnostic protocolduring the clinical practice and showed a sensitivity ≥ 0.86, specificity ≥ 0.98, an acceptable inter-examiner reliability (kappa ≥ 0.85) and is appropriate for use in both clinical and research settings [8].

To the best of our knowledge, the last systematic review investigating the association between TMD and head posture was conducted in 2013 by Rocha et al., [9], reporting an insufficient number of articles with acceptable methodological quality. Therefore, the current systematic review updates the information about the association between TMD and head posture.

Methods

This systematic review adheres to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement [10]. The international OPS Registry registration link is http:// doi.org/10.17605/OSF.IO/WZE5A.

Data Sources

Electronic literature searches were conducted on MEDLINE, PubMed, SCOPUS and Web of Science databases between January 2010 and December 2019. Bibliographical search strategies were conducted with the assistance of an experienced health science librarian and following the guidelines described by Greenhalgh [11]. Search strategies were based on a combination of Meshterms/key words following the PICO(Population, Intervention, Comparison, Outcome) question:

Population: Adults (older than 18 years old) withTMD
Intervention: Use of DC/TMD or RDC/TMD criteria for TMD diagnosis.
Comparator: Healthy population.
Outcomes: The quantification ofhead posture.

An example of the search strategy (PubMed database)was as follows:

Filters: [Title/Abstract]

#1 Temporomandibular Joint Disorders[Mesh]
#2Temporomandibular disorders
#3Temporomandibular dysfunction
#4#1 OR #2 OR #3
#5Posture[Mesh]
#6 Postural balance
#7 Postural control
#8 Head posture
#9 Neck posture
#10 Craniocervical angle
#11 #5 OR #6 OR #7 OR #8 OR #9 OR #10

Study Eligibility Criteria

Studies were eligible for inclusion if they evaluate the head and neck postural controlin adults with TMDand were published in the English language. Animal studies, cadaveric studies, published proceedings, and abstracts and articles including patients under orthodontic treatment were excluded.

Study Appraisal and Synthesis Methods

The Mendeley Desktop v.1.19.4 for Mac OS (Glyph & Cog, LLC 2008)program was used to insert the search hits from the databases. First, the duplicates were removed. Second, title/abstracts of the articles were screened for potential eligibility by two authors.

Third, the fulltext was analyzed to identify potentially eligible studies. Reviewers were required to achieve a consensus. In case of discrepancy between both reviewers, a third reviewer participated in the process to reach the consensus for including or not including the study.

A standardized data extraction form containing questions on sample population, methodology, results, and outcomes was used, according to the STARLITE guideline [12]. We specifically assessed the methodology used to evaluate the postural control and the reliability and validity of the method used.

The methodological quality of the included studies was assessed based on a previous checklist proposed by Olivo et al., [4]. This methodological scale for observational studies assessing the correlation between temporomandibular disorders with craniocervical angleconsists of 8 items focusing on the assessor blinding, the sample size, the use of standardized criteria for TMD diagnosis, the report of at least the 80% of participants, enough procedures and assessment information, clear data analysis statement, and statements about the validity and reproducibility of the measuring instrument or procedure. Higher score represents higher quality of the study.

Results

Study Selection

The electronic searches identified 475 potential studies for review. After removing duplicates, 342 studies remained. Two hundred and thirty-five (n=235) studies were excluded based on examination of their titles or abstracts, leaving 107 articles for full-text analysis. Ninety-eight articles were excluded because they did not use DC/TMD or RDC/TMD criteria for TMD diagnosisor they did not assess head nor neck posture. A total of nine studies were included in the systematic review [13-21]. Six studies assessed the head and neck posture by using a radiographic analysis [13, 16- 18, 20, 21] and four studies by using a photogrammetric analysis [14, 15, 18, 19]. In addition, one study included a baropodometry asessesment [14] (Figure 1).

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Methodological Quality

The methodological quality scores ranged from 4 to 7 (mean: 5.3, SD: 1.0) out of a maximum of 8 points (Table 1). The most consistent flaws were sample size (just 3 studies stated a representative sample estimation), absence of information about the validity or reliability of the procedures selected for the assessment (just 3 studies include validity information and 5 include reliability information) and no blinding of the assessor (5 studies blinded the assessor. Methodological quality of studies which usedradiographic analysis (mean±SD: 5.16±0.75) was slightly inferior to photogrammetric analysis (mean±SD: 5.25±1.50).

Data extraction

Table 2 summarizes the 9 studies investigating the association between head and neck posture with TMD. The number of studies assessing head and neck posture were balanced in the instrument selection: photogrammetry (n=4) and radiography (n=6). Further, onestudy investigated the balance [13]. The nine studies involved a total sample of 490 subjects (100 men and 390 women), where 230 were patients with TMD (22 had TMD and migraine). In addition to the radiographic studies which assessed the craniocervical angle [13, 16-21], three studies assessed the distance between C0-C1 [13, 17, 21]; one the C1-C2 [17] distance;three assessed thehyoid bone position [13, 17, 19]; one study assessed the craniocervical mobility index, forward head posture angle and cervical lordosis angle [20]; and one study assessed specifically the high cervical angle, the low cervical angle, and the anterior translation angle [21].

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All the studies which used photogrammetry assessed only the craniocervical angle [14, 15, 18, 19], but one which also assessed the lumbar lordosis difference between patients with TMD and healthy controls [15].

In general, results were consistent among studies assessing craniocervical angle. Patients with TMD showed alterations in craniocervical angle in most of the studies, but no differences between TMD and healthy controls were found in any study nor association between head and neck posture nor hyoid bone position with TMD [13, 16-21]. However, a greater cranio-cervical distance in patients with TMD [14], lumbar lordosis differences between migraine and healthy controls (but no differences in migraine patients with or without TMD) [15], disc displacement differences between TMD and healthy subjects [17], and an increased ANB angle in TMD patients compared with controls [19].

Discussion

The main finding of this systematic review was that most studies reported that TMD is not associated with craniocervical angle, C0-C1 distance, C1-C2 distance norhyoid bone position.The studies included in this review did not considered important features regarding the sample size estimation to be considered as representative nor the validity and reliability of the measurement procedures. Therefore, future studies should consider reporting validity and reliability estimates of the procedures and including larger sample sizes for improving the methodological quality of the studies.

To the best of our knowledge, the last systematic review assessing the association between TMD and head and neck posture was conducted in 2006 [4]. Based on recent and available literature to date, we found 9 studies assessing the association between TMD and head and neck posture [13, 21] compared to the only 2 studies in the previous systematic review [4].

Up to the date, the association between TMD (either muscular or intra-articular etiology) with head and neck posture was unclear due to the lack of studies without methodological defects (e.g., TMD diagnosis, sample size, and assessment procedures). Although some methodological defects were found, the studies included in this systematic review fixed several methodological defects reported in the previous systematic review conducted by Olivo et al., [4] including consistent TMD diagnosis (DC/TMD or RDC/TMD criteria).

The studies included in this systematic review assessed the head and neck posture by radiographic analysis and/or photogrammetry. Gadotti et al., [22] conducted one study for assessing the reliability of both methods to assess the craniocervical posture. Results showed a good to excellent intra- and inter-rater reliability estimates on both methods for measuring angles to quantify the craniocervical posture, but visual assessment showed poor agreement between raters.Although not all the studies included in this systematic review reported the validity/reliability of the procedures, all used at least one of these methods for the head and neck posture assessment and avoided the visual assessment.

Most of the studies included in this systematic review are consistent with the lack of association between craniocervical angle and TMD. Barbosa et al. [13] reported that 47.5% of subjects with TMD presented this alteration, but no differences with healthy subjects were found; Ferreira et al. [15] reported that the craniocervical angle was not different in migraine patients with and without TMD; de Farias Neto et al. [16] assessed independently the higher and lower cervical angle finding no differences between TMD and healthy populations; and Saddu et al. [18], Weber et al. [20] and Rakesh et al. [21] neither found relationship between head posture and TMD. However, when combined a reduction of this angle with an increase of the ANB angle [19] or assessing the anterior translation distance of the head [14, 16, 21], differences were found between TMD and healthy subjects.

Also, the included studies were consistent with the association between TMD and the hyoid bone position [13, 17, 19]. Although Barbosa et al. [13] reported a 62% of altered hyoid bone position, no differences were found compared with healthy subjects. Similar results were found in the studies conducted by Matheus et al. [17] and Giacomo et al. [19].

Just one study assessed disc displacement differences between patients with TMD and healthy subjects[17], ANB angle[19] and cervical lordosis [20]. Therefore, even if differences were found between patients with TMD and healthy people, more studies are necessary to conclude if these features are clearly associated or not with TMD.

Finally, there are some limitations of the current systematic review. First, we have only included articles written in the English language, so we may have missed some relevant studies published in other languages. Furthermore, we did not include those studies which were unpublished. Secondly, although we used a comprehensive tool for the assessment of the methodological quality ofreliability and validity studies, this tool was not validated for assessing observational studies including patients with TMD. Therefore, some relevant findings for head and neck posture in patients with TMD could have been missed, although this is unlikely. Lastly, due to the variability of the statistical estimates, populations and procedures, a meta-analysis could not be conducted.

Conclusion

We found in this systematic review that altered craniocervical angle, hyoid position, C0-C1 distance and C1-C2 distance could be found both in healthy and TMD populations. More high-quality with a proper TMD diagnostic criteria, sample size and valid and reliable assessment procedures are needed to confirm these findings and controversial features associated with TMD including differences in disc displacement, ANB angle and cervical lordosis.

Highlights

- Craniocervical angle, hyoid bone position and C0-C1-C2 distances are not associated with TMD
- Most of the included studies presented methodological quality defects including sample size and validity/reliability information of the assessment procedures
- There is not enough evidence to confirm the association between TMD with disc displacement, ANB angle nor cervical lordosis.

Clinical Significance

Altered clinical findings in craniocervical angle, hyoid position or distance between cervical segments should not be considered to make irreversible treatment decisions since the current evidence found that these features are not associated with TMD.