INTRODUCTION

The orthodontic literature contains indications that there are correlations between orthodontic and orthopedic findings,1–8 and this literature was summarized by Korbmacher et al4 in a systematic review. In a sequence of studies, the relationship between the posture of the head and cervical inclination was evaluated by a cephalometric assessment of lateral cephalographs.19–11 Moreover, some studies describe the relationship of the length of the lower jaw and cervical lordosis. Here, Festa et al1 were able to determine a statistically significant correlation between distal jaw position, sagittal mandibular length, and increased cervical lordosis. Also, D'Attilio et al5 found a statistically significant correlation with mandibular position and length, overjet, and the mandibular plane angle to the cervical curvature.

Michelotti et al8 stated that although the relationships between the upper cervical spine and mandibular position are described in the literature, this could not be proven for further caudally located spine sections. In contrast to this, some studies deny the existence of correlations between specific orthopedic findings and certain sagittal jaw positions.1213

In view of the diagnostic methods used, lateral cephalographs obtained for the purpose of a diagnosis in orthodontics offer a valid means of analyzing parameters such as the sagittal and the vertical jaw position. However, in the orthopedic examination carried out within the framework of the presented studies, objective examination procedures were only rarely used.4 Often, forms of bad posture are diagnosed by means of a simple subjective clinical orthopedic examination.3467

Yet, apart from the radiographic diagnosis with a specific diagnostic and therapeutic aim, an objective examination of the spine is also possible by means of noninvasive procedures such as rasterstereography, which are highly accurate and can be used in studies without exposing patients to X-rays.14–18

The aim of this study is to determine correlations between the parameters of body posture in the sagittal profile and sagittal jaw position by obtaining objective and valid three-dimensional measurements of the dorsal profile using rasterstereography.

MATERIALS AND METHODS

Fifty-three healthy adults (32 females, 21 males; average age 24.6 years, SD 9.0 years) with skeletal Class II or III malformations who came to our center to consult regarding a combined orthodontic-orthognathic surgery treatment were examined. No comparison group with neutral occlusion (Class I) was established because there was no justification for the exposure of these persons to lateral cephalographs. None of the examined persons revealed anamnestically determined motor or neurological findings, medicinal diseases, or already existing orthopedic illnesses. All patients were informed of the procedures involved in a clinical examination and they gave written consent to the study procedure. The procedures were carried out according to the criteria of the local Ethics Commission and the Helsinki Declaration.

Cephalometric Analysis

For each of the examined patients, a standardized lateral radiograph (24 × 30-cm film, Planex Regular, Kodak, Germany) was made (Focus—Film distance 3.2 m; enlargement factor 1%; exposure: 15–25 mAs, 72–81 kV). The cephalographs were digitized at 300 dpi (scanner: Power Look III, Umax Systems, Willich, Germany). A cephalometric evaluation (Figure 1) was done using six angular skeletal parameters19 (Table 1) and orthodontic analyzing software (Onyx Ceph Version 2.7.8, Image Instruments, Chemnitz, Germany).

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Table 1. 

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The sagittal position of the maxilla and the mandible (maxilla position and facial depth), as well as the parameters for the analysis of the vertical craniofacial morphology (inner gonial angle, facial axis, mandibular plane angle, and lower facial height), were considered relevant for this study. The patients' names were blinded to maintain anonymity in the evaluation.

The methodological error within the cephalometric analysis was determined by having the six measurement values analyzed on randomly chosen cephalographs after a 2-week interval by the same examiner. The error was determined by means of the Dahlberg Formula20 (mean error ratio SE2 = d²/2n, where d = difference between the measurements at two different times; n = number of measurements).

Rasterstereography

Rasterstereography1517 (Formetric 2, Diers, Schlangenbad, Germany) is based on photogrammetric methods and reveals a three-dimensional image of the back shape profile (Figure 2a). For this, a light raster emitted by a projection unit is projected on the dorsal surface of a patient standing in a defined manner toward the device. The light raster then determines data about the surface profile via a video-optic unit from another direction.21 The measuring speed with 0.04 seconds can be considered quick with the whole dorsal surface being recorded at the same time. Rasterstereography excels by its high precision (methodic error < 0.1 mm) and allows for a radiation-free representation of the profile.

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The reproducibility of an individual raster-stereographic picture is indicated for angular measures as 2.8°.21 By means of the connected software, the anatomic structures (vertebra prominens “VP” and spinae iliacae “SI”; acc. Figure 3b) are anatomically recognized, providing the basis for a reconstruction of the sagittal profile of the back surface.22 Figure 2b shows a typical three-dimensional profile and Figure 2c the automatically produced output protocol in the sagittal direction.

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By means of mathematical algorithms, a two-dimensional median sagittal dorsal profile is generated. Stagnara23 and Stagnara et al24 describe the sagittal distance between the lowest point of the cervical spine lordosis and the lumbar lordosis toward the vertical as the “Fleche Cervicale” and “Fleche Lombaire,” respectively (Figure 3a). As another parameter, the trunk inclination in comparison with the vertical of the upright standing patients was determined. This is defined as the angle between the line connecting the vertebral point (VP) and the calculated middle of the right and left spinae iliacae (SI) in relation to the vertical (Figure 3b).

RESULTS

The methodic error when evaluating angular measurements on the lateral cephalographs was below 0.5°. This value was applied with reference to Trpkova et al.25

Within the framework of the cephalometric evaluation of the lateral cephalographs, the following values could be determined:

• for the facial axis (I) a mean value of 88.6° (SD 6.0°; minimum 71.9°, maximum 101.0°);

• for the mandibular plane angle (II) 26.6° (SD 7.8°; minimum 10.6°, maximum 46.7°);

• for the inner gonial angle (III) 147.1° (SD 7.7°; minimum 124.5°, maximum 164.0°);

• for the angular lower facial height (IV) 46.9° (SD 6.9°; minimum 34.0°, maximum 65.1°);

• for the face depth (V) 88.2° (SD 7.0°; minimum 75.0°, maximum 102.3°);

• for the maxilla position (VI) 61.4° (SD 5.0°; minimum 52.8°, maximum 75.0°).

The evaluation of the raster-stereographic pictures revealed:

• for the Fleche Cervicale a mean value of 39.4 mm (SD 14.2 mm; minimum 11.0 mm, maximum 67.6);

• for the Fleche Lombaire 39.3 mm (SD 13.1 mm; minimum 12.7 mm, maximum 72.7 mm);

• for the trunk inclination 1.7° (SD 2.4°; minimum −3°, maximum 6.1°).

The results of the correlation calculation are shown in Table 2. Statistically significant correlations (P < .05) were found between the facial axis and the Fleche Cervicale, the mandibular plane angle and the Fleche Cervicale, and the facial depth and the Fleche Cervicale. To determine the direction and the strength of the dependency the following values were determined.

Table 2. 

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For the relationship of the parameter Fleche Cervicale:

• in respect of the facial axis R² = 0.074;

• in respect of the mandibular plane angle R² = 0.127;

• in respect of the facial depth R² = 0.075.

For the trunk inclination and the Fleche Lombaire:

• no statistically significant correlations to the cephalometric values were determined.

DISCUSSION

In the literature, objective examination methods for a valid study of the correlation between body posture and jaw position are postulated to verify the body posture and the jaw position which should make it possible to obtain valid results.48 This study is based on exact cephalometric measuring values for which a low methodological error could be proven. Thus, the precondition of objectifying the results has been fulfilled. An examination of the skeletal posture using objective methods could also have been carried out by radiographs of the thorax.26 Considering the radiation exposure of the patient, however, this approach would be not justified for a clinical study.

Therefore, a procedure was chosen for the sagittal analysis of body posture (trunk inclination, Fleche Cervical, and Lombaire) that represents a video-optic method to measure the dorsal surface without using ionizing radiation2127 and excels with very high accuracy. On a clinical level this was confirmed by Drerup et al16 on scoliosis patients and in comparison with customary cephalographs of the thorax, by Hackenberg et al.1418

The great dispersion of the cephalometric measuring values obtained from the lateral cephalographs results from the specific range of patients. These were referrals for the implementation of combined orthodontic surgery treatments, which are only indicated in the case of distinct forms of dysgnathia. Thus, only patients with Angle Class II and III were examined as well as vertical forms of malocclusions. No reference was made to the dental parameters because, due to the natural compensation of the malocclusion, they do not say anything about the degree of the skeletal dysplasia. Because there was no justification for the preparation of lateral radiographs, no patient group with neutral sagittal or vertical skull relation was established.

Analyzing the correlation between Fleche Lombaire and the vertical jaw relation, a significant value could be determined for the facial axis. By evaluating the respective range diagram, the direction of the dependency was determined. Patients with horizontal craniofacial morphology (facial axis >90°) displayed a greater distance between the lowest point of the spine lordosis and the vertical plumb line than those with vertical craniofacial morphology. The sagittal mandibular position (facial depth) revealed a statistically significant correlation to the Fleche Cervicale. In the case of patients with a mesial mandibular position, higher values were measured than in the case of those with a distal position. The position of the mandibular plane in respect of the Frankfort horizontal is characterized by the angle of the mandibular plane, which is correlated to the Fleche Cervical in the case of the examined patient group. Probands with a skeletal “vertical” mandibular type revealed less distance between the vertical and the lowest point of the spinal lordosis.

Because the documented correlations measured for the upper spine area (Fleche Cervicale) and the sagittal and the vertical mandibular position are based on angular parameters relating not to the upper jaw but to the lower jaw, it can be concluded that the lower jaw is more closely related to the musculoskeletal anatomy of the cervical spine. In the literature, this is explained by the tight spatial and neuronal (sensory and motor) entwinement of these structures.46710

In accordance with studies describing the inclination of the upper spine sections toward the craniofacial morphology,9–122829 we were able to determine a correlation of these areas. Moreover, the method we used enabled us to assess not only the cervical spine by means of the video-stereography but also the structures below this area (thoracic and lumbar spine sections). In this study, no correlations between the Fleche Lombaire and the trunk inclination could be found in the case of patients with different sagittal or vertical craniofacial morphology.

These results conform to the statements made by Michelotti et al,8 who reported the correlations between jaw position and body posture for the upper spine sections but not for lower spine sections. The noninvasive examination method of the body posture reveals possibilities for the analysis of the prospective development between the jaw position and body posture in the case of children and youths. Studies of these groups should also include the possible influence of orthodontic therapy.

It would be interesting to know how much modification of the sagittal or vertical relationship of the craniofacial morphology by means of an operative mandibular transposition combined with orthodontics and with the subsequent modification of the balance in the musculoskeletal area would also automatically influence the sagittal spine static. Further clinical studies could examine the possible influence of jaw-shifting surgery on the spine position to provide prognostic indications for the interaction of the dentition and the spine in the case of patients before orthognathic surgery.

CONCLUSIONS

• In the case of patients with skeletal malformations of Angle Class II and III as well with a high degree of vertical craniofacial morphology, this study provides evidence for a relationship between the jaw position and the body posture in the upper part of the spine and excludes any connection for the lower part of the spine—at least within the framework of this study.

• Further examinations are necessary to analyze the prospective development of the mandibular position and the body posture in the case of children and youths. Here the possible influence of an orthodontic therapy on the body posture also should be considered.

• As a clinical consequence of our own results, an extension of the multidisciplinary concept in the sense of a noninvasive orthopedic examination could be considered for patients undergoing a combined orthodontic-surgery therapy.