Introduction
This study aimed to assess the static posture in patients with Angle Class II and III malocclusions in the first 2 months after orthognathic surgery.
Methods
This was a longitudinal observational study. Eligible participants were adult patients who had an indication of orthognathic surgery (bilateral sagittal split osteotomy of the maxilla and/or mandible, can be associated or not with genioplasty). Thirty-five patients were evaluated from the orthognathic surgery group (OSG) and control group (CG). Measurements in OSG were performed at 3 time points: preoperative orthognathic surgery (P0), first postoperative month (P1), and second postoperative month (P2). Static posture was evaluated using the PostureScreen Mobile (PostureCo Inc, Trinity, Fla) application in 4 views.
Results
Patients with Angle Class II malocclusion in the OSG evidenced a tendency to a left hip translation at P1 with a significant difference at P2 in the anterior view ( P = 0.052). In the right lateral view, patients with Angle Class II malocclusion in the OSG at P1 presented an accentuated anterior shoulder translation when compared with CG ( P <0.001). At P1, patients with Angle Class II malocclusion in the OSG showed a significant anterior knee translation compared with the CG and OSG at P0 and P2 ( P <0.001 for all). Patients in the OSG with Angle Class III malocclusion presented an average posterior head translation in the right lateral view at P1 when compared with those in the CG and OSG at P0, who presented an anterior translation ( P = 0.0008).
Conclusions
These findings suggest a realignment of static posture in the first 2 months after orthognathic surgery.
Highlights
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We evaluated static posture in patients for 2 months after orthognathic surgery.
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Class II malocclusion showed anterior shoulder translation at the first postoperative month.
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Patients with Class III malocclusion showed anterior head tilt in the preoperative period.
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Patients with Class III malocclusion showed posterior head tilt in the first postoperative month.
The stomatognathic system is a complex anatomic system composed of masticatory muscles, bone structures, teeth, and soft tissue. The static and dynamic structures fulfill the functions of chewing, breathing, swallowing, and speech. Modification to any part of the system leads to operational disarray, compromising its correct functioning. Structural and skeletal changes are associated with malocclusions; they occur in patients with Angle Class III malocclusion. ,
Patients with Class II malocclusion tend to have an anterior head position, whereas those with Angle Class III malocclusion have a propensity for a posterior head position. Similarly, mandibular prognathism reduction surgery in patients with Angle Class III malocclusion can also cause head posture alterations, including cervical flexion.
Orthognathic surgery aims to correct maxillofacial disproportions through the relocation of maxillofacial structures, providing a balance of the face structure, and improving the malocclusion, and facial esthetics. ,
Bone structure adjustments in orthognathic surgery promote soft tissue arrangement changes; however, it depends on several anatomic factors, such as teeth, bones, and tissue proximity. Consequently, the other body segment structures linked to the facial structures also change to balance the new anatomic variations. These alterations may involve modifications in the hyoid bone position, pharyngeal airway, and head posture (including cervical flexion) in patients who have undergone surgery to reduce mandibular prognathism. ,
Postural assessment is a tool to detect how the modifications of occlusal structures affect the global body posture, or conversely, a tool to detect whether any body postural variations owing to orthopedic procedures may interfere with the stomatognathic system. These postural transitions are related but not limited to postural stabilization, chronic neck pain, increased risk of temporomandibular disorder, and migraine.
The craniomandibular pattern may be related to the postural arrangement of the lower thoracic and lumbar vertebrae as well as the pelvis ; moreover, alterations in the head posture (which may occur in patients with Angle Class II and III malocclusions at 2.5 months after orthognathic surgery) may improve the postural stabilization and the body sway with eyes open and closed. To the best of our knowledge, only 1 study analyzed the influence of orthognathic surgery on body posture, and it was performed only on patients with Angle Class III malocclusion at 4 months postoperatively.
Changes in the standard occlusal mechanism also vary the force distribution during the occlusion. These force transitions directly involve masticatory muscles, which indirectly influence adjacent muscles because of activation of long muscle chains; thus, bone exchanges and multiple muscular involvements collaborate in the alteration of the global corporal posture. , ,
The mandibular advance after orthognathic surgery may promote stretching of suprahyoid and infrahyoid muscles, giving a constant opposite force to the mandible advancement. , The hyoid bone fixed in these muscles is pulled forward; notwithstanding, this bone tends to return to its original position several months postoperatively. In patients with Angle Class II malocclusion, skeletal relapse is observed 3 months after orthognathic surgery and is noted from the sixth month in postoperative setback patients with Angle Class III malocclusion. The decreased head posture and relaxation of suprahyoid musculature may correlate with the resolution of myofascial pain.
Different therapeutic resources promote fast rehabilitation by reducing edema and pain such as manual therapies, transcutaneous electrical stimulation, and photobiomodulation.
Early postural evaluation in patients undergoing orthognathic surgery is necessary to enable a fast rehabilitation, aiming to improve the mandibular function and masticatory muscle activity and to reduce the incidence of myofascial pain, postural imbalances, and skeletal relapse. Early rehabilitation can restore mandibular function and masticatory muscle activity after orthognathic surgery, and different upper cervical spine positions influence the masticatory muscle activity. Therefore, this study aimed to assess the static posture in patients with Angle Class II and III malocclusions in the first 2 months after orthognathic surgery.
Material and methods
This study has a longitudinal observational design. Inclusion criteria were as follows: patients with Angle Class II or III malocclusions, aged between 18 and 60 years, of both sexes, with an indication of orthognathic surgery (bilateral sagittal split osteotomy of the maxilla and/or mandible, may be associated or not with mentoplasty). We excluded patients with previous dentofacial surgery, previous facial neurologic disorders, and patients with associated dysfunctions or diseases that could interfere in the proposed analyses. For the CG, patients with Angle Class I malocclusion and subjects without malocclusion were eligible; there was no diagnosis of Angle Class II and III malocclusions in this group.
The sample size was calculated on the basis of Souza et al, considering the outcome of horizontal alignment of the head. The calculation was run with a power of 80% and α ≤ 5% using the Statemate 2 software (version 2.0; Graphpad Software, San Diego, Calif).
Two types of patients were included: patients with eligible criteria and who had an indication of orthognathic surgery, and patients without malocclusion and consequently were not eligible for orthognathic surgery. Thus, they were divided into 2 groups: (1) orthognathic surgery group (OSG) and (2) control group (CG). Controls were matched by age, sex, and body mass index (BMI).
Patients were enrolled and followed at the Department of Maxillofacial Surgery and Traumatology Bucco-Facial and Periodontics, Ribeirão Preto Dental School, University of São Paulo. The OSG was examined at 3-time points: the preoperative period (P0), the first postoperative month (P1), and the second postoperative month (P2). The CG was evaluated once.
This study was approved by the local Human Research Ethics Committee (approval no. 8775/2017), after the ethical standards of the Helsinki Declaration of the World Medical Association. The participants were informed about the study purposes, and all signed an informed consent form.
Static posture assessment was performed by PostureScreen Mobile (PostureCo Inc, Trinity, Fla) installed in a smartphone with an iOS system (Apple Inc, Cupertino, Calif), which had reliability and validation by some studies. Boland et al found a high and substantial interrater agreement (ranging from 0.60 to 0.81) during the evaluation for certain variables. Intrarater agreement was also high and valuable for specific variables. Szucs et al showed that the intraclass correlation for intrarater reliability was higher than 0.75, with good and excellent reliability for most variables. The reliability of interrater agreement was good to excellent for all translations. , The smartphone was positioned precisely 3 m from the patient at a height of 1.30 m to standardize the image. The height and weight of each subject were entered into PostureScreen Mobile. Briefly, the patient, minimally dressed, was positioned comfortably standing upright on a kraft paper base with weight evenly distributed. Anterior, posterior, right-side, and left-side view images were captured through the mobile application ( Fig 1 ). After framing and before capturing the picture, the mobile application displays an image establishing the appropriate positioning employing x- and y-axes, which, when found, the application emits a light warning. The image was captured cropped to the patient’s height and with a linear marker applied to the upper end of the head and the other below the feet, followed by instructions for indicating the anatomic interest points in the image, highlighted with spherical markers of 15 mm. The points were as follows:
- 1.
Anterior view. Twelve anatomic points were evaluated: pupils, right (1) and left (2); (3) the midpoint between the nose and upper lip; upper acromioclavicular joint, right (4) and left (5); sternal notch (6); lateral rib level T8, right (7) and left (8); anterior superior iliac spine, right (9) and left (10); and center of the talus, right (11) and left (12).
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Lateral view. Five anatomic points were evaluated: external auditory meatus (1); the center of the shoulder joint at cervicothoracic junction level (2); greater trochanter (3); the center of the tibiofemoral joint (4); and center of the lateral malleolus (5).
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Posterior view. Sixteen anatomic points were evaluated: (1) vertebral prominence of C7/T1; acromioclavicular joint, right (2) and left (3); spinous processes of T4 (4), T8 (5), T12 (6) and L3 (7); posterior superior iliac spines, right (8) and left (9); ankles, right (11) and left (12); earlobes, right (13) and left (14), and lateral rib level of T8, right (15) and left (16).
All angles formed from these reference points were also calculated. In addition, the application also provided anteroposterior and total lateral translations using as references the angles and translations of the head, shoulders, knees, and pelvis ( Fig 1 ). The translation of the point is determined in relation to the next point below; for example, in the lateral view, the translation of the head is measured through the point of the ear compared with the point of the shoulder, and in the anterior view through the midpoint of the line of the eyes compared with the sternal manubrium. The angle of the point is determined in the anterior and posterior views, using the horizontal plane, and in the lateral view, using the vertical plane. The translation is the displaced distance, and the angle is the deviation angle of inclination.
To avoid external influences in the static posture, patients at the OSG were guided by the odontologist surgeon not to perform strenuous physical activity.
Statistical analysis
Data were summarized using tables, summary statistics (mean), confidence intervals, and P values. The preferred method of analysis for continuous variables was parametric. Parametric model assumptions were assessed using a normal plot. Variables were organized into 4 columns: CG, OSG P0, OSG P1, and OSG P2. Groups were compared using the analysis of variance test. Significance was set at α ≤ 5%, using a 2-tail comparison. All P values reported are rounded to 3 decimal places. The statistical analysis was performed using SPSS software (version 21.0; IBM Corp, Armonk, NY). The analyses were performed by subgroup (Angle Class II and III malocclusions).
Results
Thirty-five volunteers were included, distributed as follows: 19 patients in the OSG (mean age of 34.7 [7.43] years; mean BMI of 25.07 [2.86] kg/m 2 ), and 16 patients in the CG (mean age of 31.6 [9.08] years; mean BMI of 24.68 [3.79] kg/m 2 ). No significant differences were found between groups related to age and BMI. In the OSG, 13 patients were classified with Angle Class III malocclusion, and 6 were classified as Angle Class II malocclusion.
Regarding static posture analysis, the anterior view evidenced a difference in hip translation between patients with Angle Class II malocclusion at P1 and P2 ( P = 0.052). At the first postoperative month, the hip showed an average translation of 0.47 cm to the left. At the second postoperative month, the hip had an average translation of 0.73 cm to the right ( Table I ).
| Variables | CG | OSG P0 | OSG P1 | OSG P2 | P value |
|---|---|---|---|---|---|
| Head translation | 0.07 (−0.28 to 0.43) | −0.39 (−0.97 to 0.19) | −0.02 (−0.60 to 0.55) | 0.12 (−0.69 to 0.94) | 0.554 |
| Head angulation | 0.67 (−0.48 to 1.82) | −1.98 (−3.86 to −0.10) | −0.78 (−2.66 to 1.10) | 0.47 (−2.19 to 3.12) | 0.101 |
| Shoulder translation | −0.03 (−0.21 to 0.15) | 0.06 (−0.23 to 0.36) | −0.08 (−0.37 to 0.22) | 0.19 (−0.23 to 0.60) | 0.699 |
| Shoulder angulation | 0.03 (−0.83 to 0.88) | −0.43 (−1.83 to 0.96) | 0.55 (−0.84 to 1.94) | 0.2 (−1.77 to 2.17) | 0.782 |
| Rib translation | −0.11 (−0.39 to 0.18) | −0.11 (−0.57 to 0.36) | −0.04 (−0.50 to 0.43) | −0.7 (−1.36 to −0.05) | 0.355 |
| Hip translation | −0.25 (−0.55 to 0.06) | −0.21 (−0.70 to 0.29) | −0.47 (−0.96 to 0.03) | 0.73 (0.03 to 1.44) | 0.052 |
| Hip angulation | 0.36 (−0.61 to 1.33) | 0.57 (−1.02 to 2.15) | 0.48 (−1.10 to 2.07) | −1.53 (−3.78 to 0.71) | 0.411 |
| Total body translation | 1.76 (1.28 to 2.24) | 1.41 (0.63 to 2.19) | 1.5 (0.71 to 2.28) | 2.25 (1.14 to 3.35) | 0.585 |
The patients classified with Angle Class III malocclusion had a significant difference ( P = 0.015) related to head angulation when compared with CG and OSG P1 in the anterior view, in which the CG presented a mean angulation of 0.67° to the right, and the OSG P1 had a mean angulation of 2.81° to the left ( Table II ). In the same anterior view, an alteration in the hip translation was observed, with a change in the left translation in OSG P0 to the right translation in OSG P1 and P2.
| Variables | CG | OSG P0 | OSG P1 | OSG P2 | P value |
|---|---|---|---|---|---|
| Head translation | 0.07 (−0.26 to 0.41) | −0.1 (−0.47 to 0.27) | −0.21 (−0.61 to 0.20) | −0.16 (−0.60 to 0.29) | 0.716 |
| Head angulation | 0.67 (−0.68 to 2.02) | −1.49 (−2.99 to 0.01) | −2.81 (−4.44 to −1.18) | −0.82 (−2.63 to 0.98) | 0.015 ∗ |
| Shoulder translation | −0.03 (−0.29 to 0.24) | −0.04 (−0.33 to 0.26) | 0 (−0.32 to 0.32) | 0.18 (−0.17 to 0.54) | 0.768 |
| Shoulder angulation | 0.03 (−0.77 to 0.82) | −0.46 (−1.34 to 0.42) | −0.04 (−0.99 to 0.92) | −0.29 (−1.34 to 0.77) | 0.843 |
| Rib translation | −0.11 (−0.43 to 0.21) | −0.04 (−0.39 to 0.32) | −0.01 (−0.40 to 0.37) | −0.5 (−0.93 to −0.07) | 0.304 |
| Hip translation | −0.25 (−0.68 to 0.18) | −0.36 (−0.83 to 0.12) | 0.07 (−0.45 to 0.59) | 0.65 (0.08 to 1.22) | 0.041 ∗ |
| Hip angulation | 0.36 (−0.58 to 1.31) | −0.73 (−1.78 to 0.32) | 0.15 (−0.98 to 1.29) | −0.86 (−2.11 to 0.40) | 0.277 |
| Total body translation | 1.76 (1.14 to 2.39) | 2.18 (1.49 to 2.88) | 1.64 (0.88 to 2.39) | 2.41 (1.58 to 3.25) | 0.436 |
In the right lateral view patients with Angle Class II malocclusion, there was a significant difference ( P = 0.0005) in shoulder translation when compared with CG and OSG P1. The CG showed an average shoulder translation of 0.99 cm, whereas the OSG P1 presented an average anterior translation of 8.21 cm. The OSG P1 also presented a significant anterior knee translation ( P <0.001) when compared with the CG and OSG P0 and OSG P2 ( Table III ).
| Variables | CG | OSG P0 | OSG P1 | OSG P2 | P value |
|---|---|---|---|---|---|
| Head translation | 1.8 (1.00 to 2.60) | 1.31 (0.002-2.62) | 1.05 (−0.26 to 2.36) | 1.62 (−0.23 to 3.47) | 0.759 |
| Head angulation | 9.01 (5.22 to 12.80) | 9.25 (3.05-15.44) | 8.21 (2.02-14.41) | 9.82 (1.06-18.58) | 0.990 |
| Shoulder translation | 0.99 (−0.83 to 2.80) | 0.68 (−2.29 to 3.65) | 8.21 (5.24-11.18) | −1.66 (−5.86 to 2.54) | <0.001 ∗ |
| Shoulder angulation | 0.47 (−0.93 to 1.86) | 0.87 (−1.40 to 3.14) | 0.98 (−1.29 to 3.26) | −0.29 (−3.50 to 2.92) | 0.909 |
| Hip translation | −0.24 (−1.26 to 0.79) | −0.68 (−2.35 to 1.00) | −0.15 (−1.82 to 1.53) | 0.87 (−1.49 to 3.24) | 0.749 |
| Hip angulation | 0.47 (−1.95 to 2.89) | −1.67 (−5.62 to 2.28) | −1.17 (−5.12 to 2.78) | 1.19 (−4.40 to 6.77) | 0.703 |
| Knee translation | 2.24 (1.40 to 3.08) | 1.82 (0.45 to 3.19) | 7.81 (6.44 to 9.18) | 1.31 (−0.63 to 3.24) | <0.001 ∗ |
| Knee angulation | 4.95 (3.69 to 6.20) | 5.86 (3.81 to 7.92) | 7.81 (5.76 to 9.87) | 3.69 (0.78 to 6.59) | 0.069 |
| Total body translation | 7.45 (5.70 to 9.19) | 4.96 (2.11 to 7.81) | 4.9 (2.05 to 7.75) | 6.54 (2.51 to 10.57) | 0.310 |
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