Natural head posture changes after maxillomandibular procedures – A prospective study

Thenmozhi Thirumavalavan; T Selvakumar; M Shanmuga Sundaram; T Guru Prasad; V B Krishna Kumar Raja

doi:10.4103/srmjrds.srmjrds_25_19

ORIGINAL ARTICLE

Year : 2019 | Volume : 10 | Issue : 3 | Page : 145-148

Natural head posture changes after maxillomandibular procedures – A prospective study

Thenmozhi Thirumavalavan, T Selvakumar, M Shanmuga Sundaram, T Guru Prasad, V B Krishna Kumar Raja
Department of Oral and Maxillofacial Surgery, SRM Dental College, Chennai, Tamil Nadu, India

Date of Submission	15-Mar-2019
Date of Acceptance	03-Sep-2019
Date of Web Publication	15-Oct-2019

Correspondence Address:
Dr. Thenmozhi Thirumavalavan
Department of Oral and Maxillofacial Surgery, SRM Dental College, Ramapuram Campus, Chennai - 600 089, Tamil Nadu
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/srmjrds.srmjrds_25_19

Abstract

Purpose of the Study: The aim of this study is to evaluate the natural head posture changes in the individuals after orthognathic surgery assessed using cone-beam computed tomography (CBCT) scan. Materials and Methods: The study was conducted in the age group above 18 years who underwent mandibular advancement for the correction of the skeletal deformity. The difference was evaluated in cases with the help of CBCT scan which was taken preoperatively and 3 months postoperatively. The inclusion criteria were patients undergoing mandibular advancement with or without maxillary procedures. The CBCT scan was taken in a natural head position with lips in a relaxed position and without any other tongue movements like swallowing. The exclusion criteria include patients with pharyngeal pathology, syndromic conditions, and history of orthognathic surgery. The head posture was determined by measuring the craniocervical angle (CCA) before and after surgery to evaluate the changes. The study was divided among bilateral sagittal split osteotomy (BSSO) advancement cases and maxillomandibular procedures. The statistical analysis was done using a paired t-test. Results: The head posture changes present in mandibular advancement cases show a decrease in the angulation of CCA in both types. The P value of head posture in BSSO advancement cases was 0.25, and for maxillomandibular cases, it was 0.007. Conclusion: The study was concluded by showing a decrease in the angulation of the CCA after orthognathic surgery. This shows improvement in the facial profile and structural positions.

Keywords: Craniocervical angle, natural head posture, orthognathic surgery

How to cite this article:
Thirumavalavan T, Selvakumar T, Sundaram M S, Prasad T G, Raja V B. Natural head posture changes after maxillomandibular procedures – A prospective study. SRM J Res Dent Sci 2019;10:145-8

How to cite this URL:
Thirumavalavan T, Selvakumar T, Sundaram M S, Prasad T G, Raja V B. Natural head posture changes after maxillomandibular procedures – A prospective study. SRM J Res Dent Sci [serial online] 2019 [cited 2023 Mar 31];10:145-8. Available from: https://www.srmjrds.in/text.asp?2019/10/3/145/269210

Introduction

Orthognathic surgery is one of the most promising surgical procedures which help in obtaining the normal esthetic, functional skeletal, and dental position. The individuals with dentofacial deformity show various issues including postural disturbances of the head, decreased airway patency, and malocclusion.^[1] The proper case history and clinical evaluation should be done before surgical planning by the patient to the natural head position (NHP). Evaluation of the patient's head posture can be done in a NHP by various methods. The study focuses on changes on natural head posture after orthognathic surgery which helps in eradication of forwarding head posture in individuals.

Materials and Methods

The study was conducted in SRM Dental College, Ramapuram, Chennai, from the year 2016 to 2019. Fourteen patients were included in this study. These patients are evaluated by taking cone-beam computed tomography (CBCT) scan preoperatively (T1) and 3 months postoperatively (T2). The scan should be taken in a NHP in the standing position. The sagittal section was selected for measuring the craniocervical angle (CCA). The section should show the first and second cervical vertebrae along with sella and nasion point.

Inclusion criteria

Age group above 18 years
Patients included in this study were undergoing

Bilateral sagittal split osteotomy (BSSO) advancement
Maxillary advancement with BSSO advancement
Maxillary impaction with BSSO advancement.

Exclusion criteria

Patients who have already undergone orthognathic surgery
Pathological conditions of the jaws
Cervical spine problems and syndromic conditions.

The head posture was measured by marking the CCA. The first plane was from sella (S) to nasion (N), and the second plane was from the posterosuperior point on the odontoid process to the posteroinferior point on the body of the second cervical vertebrae [Figure 1]. The angle formed by these two planes makes the CCA. The angle was measured separately for BSSO advancement cases and maxillomandibular procedures. The study was statistically analyzed using a paired t-test for BSSO advancement and maxillomandibular procedures (IRB approval number: SRMDC/IRB/2016/MDS/No. 408).{Figure 1}

Statistical analysis

An independent t-test was used to determine the differences between the T1 and T2 measurements in each group. Statistical significance was determined at the 95% level of confidence. The study was statistically analyzed using the paired t-test for both BSSO advancement and maxillomandibular advancement, and their significance level was determined.

Results

The head posture was assessed by determining the CCA. The patients underwent both with BSSO advancement, and maxillomandibular procedures were assessed. The graphical representation of both cases is shown in [Figure 2] and [Figure 3].

Figure 1: Head posture (N – Nasion, S – Sella, C2s, C2i- an imaginary line connecting posterosuperior and posteroinferior point in the second cervical vertebrae, CCA – Craniocervical angle)

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Figure 3: Comparison of preoperative and postoperative head posture in maxillomandibular surgeries

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Bilateral sagittal split osteotomy advancement cases

The mean preoperative value was 95.8° and postoperative value was 93.2° in BSSO advancement cases. Thus, a decrease in the angulation of head posture showing statistical analysis was P = 0.25, insignificant [Table 1]. The head position varies with BSSO advancement cases. The CCA reduced after BSSO advancement in this study but does not show a significant level of reduction in the angulation.

Table 1: Significance level of head posture in bilateral sagittal split osteotomy advancement cases

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Maxillomandibular procedures

The mean preoperative value of head posture was 96.3° and postoperative showing 91.1° in maxillomandibular procedures. The statistical analysis shows significant results which were about 0.00 [Table 2]. The CCA was decreased to a significant level when compared to the single jaw procedure. Hence, maxillomandibular surgeries show better results in changing the head posture postoperatively which was stable even after a long term of follow-up.

Table 2: Significance level of head posture in maxillomandibular surgeries

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Horizontal growth and vertical growth of the jaws are determined by head posture. Thus, increase in the CCA helps in improvement in the facial, dental, and skeletal profiles of the patient. Head posture improvement also shows a direct impact on the pharyngeal airway.

Discussion

The concept of NHP was first proposed by Downs, Bjerin, Moorrees, and Kean in 1950.^[2] This raises the question of what is the natural ahead position and how it can be achieved? NHP is a standardized and reproducible position, of the head in an upright posture, the eyes focused on a point in the distance at eye level, which implies that the visual axis is horizontal.^[3] Posture is defined as the positioning of all body segments at a given point.^[4] The natural head posture is the position of the patient in a dynamic state during walking and any other physical activities. These head posture can show variation in the different types of the skeletal pattern.^[5],[6] These variations can be assessed by measuring the CCA showing the relation of the cranial base with cervical vertebrae. These can be measured with the help of cephalometric analysis. The patients can have varying skeletal and dental relations. The changes in head posture can be due to various conditions such as skeletal discrepancies, cervical problems, neck injuries, syndromic conditions, and upper crossed syndrome.^[7],[8]

The patient who was evaluated for dentofacial deformity was positioned in the NHP. The NPH is one of the rationales to evaluate the face, jaws, teeth in physiological, and anatomical orientation.^[9],[10] The natural head posture is used to evaluate the quality of the soft tissues, the symmetry of the upper facial skeleton, the morphology of the unique esthetic units, the history of temporomandibular joint diseases, etc.^[11],[12] The orientation of the head posture was the simplest procedure by obtaining the photographs and lateral cephalometric radiographs in NHP by instructing the patients to sit upright and look straight ahead to a point at eye level on the wall in front of them. In our study, the head posture was measured with the help of CBCT scan.

The relationship of head posture with Class II malocclusion, which showed that upright posture of the head and greater extension of the spinal column were more evident in individuals with Class II malocclusion, was also documented by Arntsen and Sonnesen in their study.^[13] The mandible was rotated downward and backward in cases of Class II patients. The forward movement of the mandible along with natural head posture was noted which helps to compensate airway patency. In the current study, we did not distinguish between gender and age subgroups. Gresham and Smithells compared 61 children with a poor neck posture to a control group and showed that children with poor posture had longer faces and a significant increase in the prevalence of Angle's Class II malocclusion.^[14]

Bjork theorized that the relationship between the form of the cranial base and craniofacial morphology was often masked by the posture of the head on the cervical vertebra and concluded that the size and position of the mandible are strongly related to the head posture. Changes in head posture have been reported also after orthognathic mandibular surgery.^[15] Our study shows the relation of cervical vertebrae to cranial base resulting in a decrease in craniocervical angulation after mandibular advancement. The CCA was significantly decreased by 2.5° after mandibular advancement surgery.^[16] The craniocervical angulation was decreased by 2.6° 3 months after mandibular advancement surgery which correlates to our study.

Woodside and Linder-Aronson postulated that mouth breathers tip their heads backward in an attempt to increase their airway, while the creation of a normal airway by adenoidectomy results in a less extended posture of the head. Subjects with increased lower anterior face height and an increased inclination of the mandibular to the palatal and anterior cranial base planes have been found to have extended head posture and increased CCAs.^[17] No difference was found between the variability of the Frankfort horizontal plane and the sella–nasion line concerning the horizontal plane in the study postulated by Lundström and Lundström.^[18] Our study was correlated to the previous study where we have used the Frankfort horizontal plane (FHP) as a reference plane for assessment of the head posture.

Wenzel et al. proposed that a decrease in this angle would reflect the increased airway patency as a result of rapid maxillary expansion in their study.^[19] Patients with a CCA with FHP are more likely to be seen in severe and obese obstructive sleep apnea patients with certain morphological characteristics of the upper airway and related structures in the study described by Ozbek et al.^[20]

Conclusion

The individuals who underwent BSSO advancement and maxillomandibular procedures show variation in the natural head posture. When comparing to BSSO advancement to the maxillomandibular procedures, the second set of procedures shows a significant decrease in the CCA. The individuals show improvement in the facial profile and skeletal and dental relations. Head posture changes show an increase in pharyngeal airway patency with the hyoid bone and accompanying muscles after mandibular advancement. The natural head posture of growing individuals shows a direct impact on the development of malocclusion.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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