International Journal of Oral & Maxillofacial Surgery
Volume 35, Issue 4 , Pages 312-317, April 2006

Dysgnathia, orthognathic surgery and spinal posture

  • K. Sinko

      Affiliations

    • University Hospital of Cranio-Maxillofacial and Oral Surgery, Medical University, Vienna, Austria
    • Corresponding Author InformationAddress: Klaus Sinko, University Hospital of Cranio-Maxillofacial and Oral Surgery, Medical University, Waehringer Guertel 18-20, A-1090 Vienna, Austria. Tel: +43 1 40400 4259; Fax: +43 1 40400 4253.
    • ,
  • J.-G. Grohs

      Affiliations

    • University Hospital of Orthopaedics, Medical University, Vienna, Austria
    • ,
  • G. Millesi-Schobel

      Affiliations

    • University Hospital of Cranio-Maxillofacial and Oral Surgery, Medical University, Vienna, Austria
    • ,
  • F. Watzinger

      Affiliations

    • University Hospital of Cranio-Maxillofacial and Oral Surgery, Medical University, Vienna, Austria
    • ,
  • D. Turhani

      Affiliations

    • University Hospital of Cranio-Maxillofacial and Oral Surgery, Medical University, Vienna, Austria
    • ,
  • G. Undt

      Affiliations

    • University Hospital of Cranio-Maxillofacial and Oral Surgery, Medical University, Vienna, Austria
    • ,
  • A. Baumann

      Affiliations

    • University Hospital of Cranio-Maxillofacial and Oral Surgery, Medical University, Vienna, Austria

Accepted 15 September 2005.

Article Outline

Abstract 

The aim of this study was to evaluate the spine by video rasterstereography before and after orthognathic surgery. Twenty-nine patients (17 patients with a skeletal class III, 7 patients with a skeletal class II, and 5 patients with mandibular asymmetry) were evaluated preoperatively and 1 year postoperatively. Video rasterstereography is a method of back surface measurement and shape analysis using the moire topography. Orthognathic surgery in cases of class III and asymmetry did not lead to significant changes in body posture. In class II patients it led to some changes in body posture, but without orthopaedic consequences. It is concluded that orthognathic surgery causes minimal or no change in body posture.

Key words: orthognathic surgery, video rasterstereography, spinal posture

 

In the 1990s, a possible association between occlusal and postural disturbances was widely propagated by the mass media. As a result, an increasing number of patients confronted medical practitioners with the issue. An association between dental occlusion and the vertebral column or body posture has been discussed in the published literature for a long time20. In 1933 D’Alise4 stated that orthopaedics of the trunk and extremities and orthodontics are indivisible parts of general orthopaedics. Some authors found strong evidence for an association between malocclusion and posture, especially with regard to the head and neck9, 10. In 1955 Duyzings7 observed an alteration in the position of the hyoid and an alteration of cervical lordosis in class II patients. As the cervical spine is a part of the vertebral column, he presumed that this influenced the body posture as well. Wachsmann26 stated that muscular weakness, which he considered to be related to a weakness of the mesoderm, might be a reason for breathing through the mouth, prognathism and a flabby body posture. Müller-Wachendorf16 also stated that malocclusion and postural disorders are manifestations of weak connective tissue.

Rickets19 and Vig et al.25 found that head posture is influenced by respiratory function. Some authors considered it possible, but not certain, that malocclusion and postural disorders are interrelated11. In a review published in 1999 Michelotti et al.13 found some evidence for a correlation between occlusion and posture, but it appears to be limited to the cranio-cervical portion of the vertebral column and tends to disappear when descending in the cranio-caudal direction. They concluded that it is not advisable to treat postural imbalance by means of occlusal therapy or vice versa, especially if the therapeutic modalities are irreversible. In 1996 Ferrario et al.8 stated that modifications in body posture secondary to stomatognathic alterations were mainly observed in patients, and diverse findings were obtained in healthy young adults5.

Following the introduction of orthognathic surgery as a routine procedure, very few studies have focused on the effect of these surgical procedures on posture1, 2, 17, 27. The method used in all of these previous studies was cephalometric analysis; thus, only the upper cervical spine was assessed. To the authors’ knowledge no one has yet tried to determine whether orthognathic surgery affects the entire vertebral column and body posture. This prospective study was designed to identify differences, if any, between class II and class III patients in respect to the vertebral column and body posture. In addition, the effect, if any, of orthognathic surgery on the curvature of the vertebral column and body posture was evaluated.

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Materials and methods 

Twenty-nine patients (11 men and 18 women) with a mean age of 24.5 years (range, 17–41 years) were examined by means of video rasterstereography (Jenoptic™, Software Deltamed™ version 2.11)6 2–4 weeks before orthognathic surgery and 1 year postoperatively. Seventeen patients had a skeletal class III, 7 patients had a skeletal class II, and 5 patients had mandibular asymmetry (Table 1). The surgical procedures performed are listed in Table 2.

Table 1. Male-to-female ratios of dysgnathia and control groups
Class IIClass IIIMandibular asymmetryControl
Men19112
Women6840

Total717512
Table 2. Orthognathic surgical procedures used for different types of dysgnathia
Class IIClass IIIMandibular asymmetryTotal
Le-Fort I1102
BSSO4127
Bimax215320

BSSO: Bilateral sagittal split osteotomy; Bimax: bimaxillary osteotomy.

All patients received orthodontic therapy with fixed appliances before and after the surgical procedure. As the aim was to evaluate the effects of orthognathic surgery on posture only, the first examination was performed immediately before surgery, when preoperative orthodontic alignment had been completed and the patients had been provided with passive wires (0.017″×0.025″ red-heated stainless steel wire in a 0.018″ bracket system). The second examination was performed 12 months after the surgical procedure. The fixed orthodontic appliance had been removed by this time in all patients. It was presumed that, if posture was altered by surgery, a new equilibrium would have been achieved after 12 months.

The first stage of the examination was clinical evaluation by an orthopaedist. After that, the patients were asked to walk to a marked point and stand barefoot in a self-chosen comfortable stance, corresponding to a ‘natural head and body posture’, looking straight ahead at a wall with both arms hanging freely adjacent to the trunk. The illumination was dimmed to twilight. Eighty-four horizontal lines (about 1 line/cm) were projected on to the naked dorsum by means of a slide (Fig. 1). The lines produced a unique pattern of light and heavy lines. The curved surface of the dorsum caused distortion of the lines. It has been shown that postural sway during the first 20s of quiet stance is subject to great variation and random characteristics. These transient changes in first- and second-order moments usually disappear during this time3. After a wait of 20s, therefore, a high-resolution video camera recorded the line pattern produced by the patient's back. A rasterstereograph was produced within seconds with the help of a video frame grabber and a microprocessor (Fig. 2); 25,000 primary data points were achieved in a patient of medium stature. A sophisticated surface shape analysis was produced by the computer (see Fig. 3, Fig. 4). The following measurements were recorded: the apex and angle of thoracic kyphosis measured between the 7th cervical vertebral body, better known as the vertebra prominens (VP), and the 12th thoracic vertebral body (T12); the apex and angle of lumbar lordosis between T12 and the midpoint (DM) between the right (DR) and left (DL) dimples of the posterior superior iliac spine; and the point of inflexion between kyphosis and lordosis (ITL). Vertical deviation of the spine was measured between the VP and the DM between the DR and DL of the posterior superior iliac spine. The tilt of the iliac crest was measured between the DL and DR of the posterior superior iliac spine.

The preoperative values for the different malocclusion groups were compared with a group of 12 ‘healthy’ male baseball players. A clinical orthodontic examination was performed to ensure that all individuals in this group had ‘normal’ occlusion without skeletal dysgnathia. The mean age of the control group was 16.4 years. In a second evaluation the effect of orthognathic surgery on the different malocclusion groups was assessed. The recording of data was not repeated because, in the recording of biological parameters, variations within the group of subjects under investigation are usually much larger than the method error of the parameter27.

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Statistical analysis 

All data are mean values. Preoperative differences between groups were evaluated with the Student's t-test for unpaired data. Changes within groups, resulting from surgery, were evaluated with the Student's t-test for paired data.

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Results 

Prior to treatment, the apex of thoracic kyphosis was more cranial in class III patients than in class II patients and healthy controls. The angle of lumbar lordosis was more pronounced in class III patients compared to healthy controls. The apex of lumbar lordosis was more caudal in class II than in healthy controls; the difference was equivalent to the height of one vertebral body. Before therapy the tilt of the iliac crest in class II and III patients differed minimally but significantly from that of healthy controls.

After treatment the apex of thoracic kyphosis in the group with mandibular asymmetry had moved cranially by about half the height of one vertebral body. In class II patients, the apex of lumbar lordosis had moved caudally to an insignificant extent, and the tilt of the iliac crest was altered after therapy. Class III patients revealed no significant changes after therapy. For details, see Table 3.

Table 3. Pre- and postoperative spinal posture data for different types of dysgnathia measured by video rasterstereography
Vert. dev. VP–DM (mm)SDPelv. dev. DL–DR (°)SDt-testApex of kyphosis (mm)SDCorr. to V.b.h.t-testITL (mm)SDCorr. to V.b.h.Apex of lordosis (mm)SDCorr. to V.b.h.t-testAngle of kyphosis VP–T12 (°)SDt-testAngle of lordosis T12–DM (°)SDt-test
PRE-OP
Healthy controls−0.6211.231.132.00ns−149.8028.40T7ns−265.5346.09T11/12−343.8838.91L2ns43.319.73ns27.457.50ns
Class III−0.837.69−1.423.420.0257−151.1129.53T7ns−275.2649.74T11/12−382.9839.31L30.010447.019.57ns33.0212.39ns
Class II−4.287.281.274.260.0273−129.4420.42T6/7ns−246.8341.97T11−365.7726.21L2/3ns43.9512.91ns36.248.680.0191
Mandibular asymmetry0.307.750.503.51ns−140.3228.65T7ns−264.5821.62T11/12−361.8627.97L2/3ns52.848.770.066140.5810.370.0071

POST-OP
Class III−2.527.320.602.970.0005−150.9329.60T7/8ns−284.5138.22T 12−393.5038.22L3/40.060547.599.78ns34.4110.92ns
Class II−3.336.29−1.234.42ns−109.1523.43T5/6ns−248.9516.45T 11−356.7823.41L2/3ns47.258.65ns44.188.88ns
Mandibular asymmetry−2.247.512.664.03ns−132.0024.50T6/70.0374−258.6816.08T11/12−360.1029.51L2/3ns54.169.17ns42.287.45ns

Vert. dev.: vertical deviation; VP: vertebra prominens; DM: midpoint between the right (DR) and the left dimple (DL) of the posterior superior iliac spine; Pelv. dev.: pelvic deviation (deflection of the connection line of DR–DL to the true horizontal line); Corr. to V.b.h.: corresponding to vertebral body height; ITL: point of inflexion between kyphosis and lordosis; T1–12: thoracic vertebral body 1–12; L1–5: lumbar vertebral body 1–5; ns: not significant.

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Discussion 

This investigation was based on the premise that if occlusion and posture are inter-dependent, the greatest difference would be seen between extreme class II and extreme class III occlusions. Patients were examined before and after orthognathic surgery. If the surgical procedure alters body posture, it was presumed that a new equilibrium would be achieved after 12 months.

All patients for the study were recruited from those being treated for dysgnathia at the oral and maxillofacial surgery clinic. No patient had general orthopaedic problems or chronic back pain requiring orthopaedic therapy. This is not surprising because, in general, orthopaedic problems such as chronic back pain are known to commence after the age of 30; the mean age of our patients was 24 years.

There appears to be a major difference between patients undergoing primary orthognathic surgery and orthopaedic patients with idiopathic scoliosis or spondylolisthesis. While orthodontic problems have been very commonly observed in general orthopaedic patients10, 15, 18, no or very slight orthopaedic differences were found between class I, class II and class III angle relationships or crossbites. Hirschfelder & Hirschfelder11 found no significant differences between the different angle classes with regard to pelvic tilt. Sterzig et al.24 observed no typical head posture for the different angle classes. These two groups conducted their examinations in children and adolescents: the former in those less than 18 and the latter in those less than 13 years of age. One reason for their results may have been that, in general orthopaedic disease, habitual scoliosis and a flabby body posture develop due to general weakness of the connective tissue, which also leads to malocclusions16. Class III and severe class II may be influenced by genetic factors, with no accompanying disorder of the vertebral column.

In the present study only a few measurements were found to differ significantly between the malocclusion groups. Variations within the different malocclusion groups were very large (see SD in Table 3). Some of these significant differences may have been due to the different sex ratios in the control group (all males) and the study group (two thirds female, Table 1). Significant differences between males and females were noted in the class III group. This may have been due to the different average body height of men and women; the height of the subjects was not measured. The number of patients was too small to allow gender-specific statements. Some of the differences recorded may have been due to the difference in mean age of the controls (16.4 years; growing age) and the study group (24.5 years; not of growing age). The significant differences were, in fact, not homogenous. Hence, it is not confirmed whether a typical form of vertebral column exists for the different malocclusions.

Despite the small number of patients, the present study revealed that factors other than occlusion play a more important role in head and body posture. There is strong evidence that breathing impediments, such as large tonsils or allergies, causing the individual to breathe through the mouth may alter head posture25. The exclusive presence of a skeletal class II is no guarantee for forehead posture. A skeletal class III patient with large tonsils or an allergy causing restricted nose breathing may have a more pronounced forehead posture than a class II patient with unimpeded nose breathing. In humans, head and body posture may be primarily related to resisting the force of gravity5, 23. Two mechanisms have been proposed for the control of head and body posture. Propriosensitive nerve inputs from muscles, tendons, joints and the balancing system of the inner ear serve as ‘crude’ positioning systems. Fine adjustment is effected by inputs from the visual righting system21. The patient's psychological state is also known to be a relevant factor11. Skeletal dysgnathia alone is not a major factor in the alteration of body posture. Milani et al.14 stated that ‘much of the ideas about occlusion are based more on belief than on evidence. It should not be thought that all occlusal disorders have repercussions on posture’.

The effects of orthognathic surgery on the cervical portion of the vertebral column have been studied by several authors. Achilleos et al.1 observed cervical hyperflexion after mandibular setback osteotomy and a more upright cervical spine after mandibular advancement2. Wenzel et al.27 explained the increase in cranio-cervical angulation after mandibular setback as being due to psycho-social factors which stimulate the patients to lift their head after surgery. Phillips et al.17 studied 201 patients who had undergone 5 different surgical procedures; the authors observed no significant short- or long-term changes in neck posture in any of the surgical groups. As cephalometric X-rays were used for evaluation in all of these studies, only the upper, or at best the entire, cervical spine was examined. This method only allows two-dimensional assessment of the cervical spine in the sagittal plane; lateral bending or rotation may escape detection. Video rasterstereography, as used in the present study, is a method of back surface measurement based on automatic back surface reconstruction and shape analysis, depending on the moire topography. It is a non-invasive and non-injurious way of evaluating body posture and allows the investigator to measure alterations in the curvature of the vertebral column without the use of X-rays12. Video rasterstereography compares well with plain films in terms of accuracy and is an adequate method for use in the clinical setting6.

The vertebral column was assessed in all three dimensions. The differences between the preoperative and postoperative examinations were minimal. No significant differences were found in class III patients. One limitation of video rasterstereography is that the vertebral column can only be examined from the vertebra prominens to the sacrum. It should be noted that the entire cervical spine has been extensively investigated by standard X-rays in previous studies.

The small number of patients may have been a limitation of the present study. Given the minimal differences between the malocclusion groups, the results are likely to have been similar for a larger sample. It was difficult to convince patients without pain of the necessity of two additional visits to evaluate their vertebral column. This was especially true for the second assessment after the completion of the whole treatment.

The accuracy of the recording of natural posture is a major issue. A large number of published studies have used the so-called mirror position; however, the position of the head and body determined by an external reference (mirror) may not be identical to the habitual position. In the mirror position the head is kept higher than in the self-balance position. The so-called orthoposition (self-balance position) was found to be reproducible in posture studies22 and was used in the present study as being more natural than the mirror position.

In summary, all measured values of the spine before and after orthognathic surgery were within the physiological range. No patient required any orthopaedic intervention before or after orthognathic surgery. Head and body posture seems to be primarily related to resisting gravity and not to malocclusion. In individual cases, when dysgnathia is associated with orthopaedic problems or cervical muscle dysfunction, additional orthopaedic treatment or physiotherapy might be beneficial.

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References 

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PII: S0901-5027(05)00320-6

doi:10.1016/j.ijom.2005.09.009

International Journal of Oral & Maxillofacial Surgery
Volume 35, Issue 4 , Pages 312-317, April 2006

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