3. Discussion and Conclusions
Morphological changes in the upper respiratory tract and pharynx occur due to morphological changes and position movements of the mandible due to correction surgery, and changes in respiratory physiology are observed [9]. Therefore, in Europe and the United States, one of the treatment methods for OSA is corrective surgery such as simultaneous upper and lower jawbone movement and genioglossus/anterior traction of the tongue muscle group, and its usefulness has also been reported [10]; however, it is not yet common in Japan. In our literature search, we found that LF+HS and MDO and GP were performed on patients with mandibular condyle who had resorption changes in the mandibular condyle, as in the present case, and had OSA. Consequently, mandibular and malocclusion failures occur. In addition, there are no reports on improvements in OSA.
Regarding the selection of technique: Regarding the maxillary procedure, LF has a limited amount of upward movement of the maxilla, but when HS is used in combination with LF, it is possible to move the maxillary bone fragment significantly upward. As it has been reported that LF+HS is indicated for cases with an upward movement of ≥4 mm [11], in the present case, the maxillary alveolar bone fragment was used for maxillary molars measuring 5 mm and anterior teeth measuring 7 mm. The mandibular movement was secured by raising it counterclockwise.
Regarding the mandibular procedure, PCR is one of the complications after anterior mandibular movement by SSRO, and its incidence has been reported to be from 4.5% to 21% [12, 13]. In contrast, compared with SSRO, MDO can avoid the generation of tension and overloading of mandibular condyle due to the rapid extension of soft tissue caused by surgical procedures and blood flow to the mandibular condyle due to minimal periosteal detachment. Several reports [5, 14] indicate that it is more suitable than SSRO as a treatment method considering PCR because it can maintain the blood flow. In particular, Strijen et al. mentioned that the one-time anterior movement of the mandible by SSRO causes heavy burden on the mandibular condyle, and as a result of slow anterior extension of the mandible by MDO in 40 patients with PCR, we have reported the usefulness of MDO for these patients, describing that PCR was not observed in 39 of those patients (97.5%)[15]. Therefore, in the present case, in which an absorption image was observed in the mandibular condyle before surgery, MDO was selected to prevent the enhancement of PCR.
PCR: The distance from the mandibular condyle to the mandibular notch was measured using 3D-CT images obtained preoperatively March 7, 2013) and 1 year and 3 months after LF+HS and MDO (August 14, 2014). Comparing the distances, the right side decreased by 0.4 mm from 12.5 to 12.1 mm, and the left side decreased by 1.6 mm from 8.3 to 6.7 mm. In other words, the right side was almost the same as before the operation, but the left side demonstrated mild bone resorption.
Sato et al. stated that follow-up is important for at least 2 years, as bone changes in PCR can last for more than 1 year after surgery [16]. We also planned a long-term follow-up, and because of the difficulty to assess PCR from the cephalometric profile image alone, we planned to follow up with CT images, especially 3D-CD images, in addition to the cephalometric profile image. However, although the cephalometric profile image could be tracked until Nov 17, 2015 (LF+HS, 2 years and 6 months after MDO) just before the patient moved to a distant place, CT imaging was obtained at good timing. However, we were reluctant to complete the examination without realizing it.
Relapse: Regarding relapse, McCarthy et al. reported a rate of 22% and Miyamoto et al. reported a rate of 30%–40% relapse [6,7]. To evaluate the relapse in the present case, we modified the method described by Miyamoto et al. to measure the distance between the left and right Condylion-B points in the cephalometric side view image [7]. As a result, when the time points immediately after LF+HS and MDO surgery and 2 years and 6 months after surgery were compared, 25.6% relapse was observed on the right side and 33.0% relapse was observed on the left side, but we considered that the upper and lower jaws were stable because occlusal tightness was obtained by the postoperative orthodontic treatment.
The anterior–posterior diameter of the pharynx: Comparing the posterior part of the soft palate before surgery with that 7 months after LF+HS and MDO (Dec 9, 2013), (1) PPS decreased from 35.1 to 34.8 mm (−0.3 mm), and (2) SPPS decreased from 17.7 to 19.3 mm. It increased by +1.6 mm, and (3) MPS increased from 4.6 to 10 mm (+5.4 mm).
In the posterior part of the tongue, (4) IPS increased from 7.4 to 11.2 mm (+3.8 mm), and (5) EPS increased from 6.7 to 10.3 mm (+3.6 mm). It is considered that this finding is because the tongue tuft became larger due to the anterior extension of the mandible by MDO, and the anterior–posterior diameter of the pharynx behind the tongue increased due to the anterior extension of the tongue.
Regarding the position of the hyoid bone: Comparing preoperative values and those measured 7 months after LF+HS and MDO (Nov 6, 2013), it was observed that (6) S-H decreased from 106.4 to 104.4 mm (−2.0 mm), and (7) C3-H decreased from 42.7 to 48.2. It increased to mm (+5.5 mm), and the hyoid bone moved upward and anteriorly. It is speculated that this is because the hyoid muscles and geniohyoid muscles attached to the hyoid bone and geniohyoid spines were pulled upward and anteriorly by the MDO, and the hyoid bones to which these muscles were attached moved upward and anteriorly. Moreover, the AHI measured 5 months after LF+HS and MDO (Oct 10, 2013) decreased from 22.5 to 9.8/h, and the ESS score decreased from 14 to 2 points, which we felt were during the daytime. The drowsiness almost disappeared.
Comparing the values measured immediately before GP (Nov 6, 2013) and after GP (Dec 13, 2013), it was observed that (4) IPS behind the tongue increased from 11.2 to 11.8 mm (+0.6 mm), and (5) EPS increased from 10.3 to 8.6. It decreased to (−1.7 mm). In other words, no significant change was observed in the anterior–posterior diameter of the pharynx behind the tongue depending on the GP. However, the AHI before and after GP decreased from 9.8 to 7.8/h, and daytime sleepiness disappeared completely. Tonogi et al. reported that when the pharynx was observed using an endoscope after SSRO, the pharynx expanded not only in the anterior–posterior diameter but also in the left–right diameter [17]. In the present case, MDO was performed instead of SSRO, but as reported by Tonogi et al., the changes in the size of pharynx after MDO are not limited to the anterior–posterior diameter of the cephalometric profile image but will be affected by result of endoscopy and CT in the future. It was suggested that the change in diameter should be measured and examined.
Comparing the values ​​of (6) S-H and (7) C3-H, which indicate the position of the hyoid bone, immediately before GP (Nov 6, 2013) and 1 week after GP (Dec 13, 2013), (6) S-H was 104.4 mm. It increased from 107.8 mm (+3.4 mm), and (7) C3-H decreased from 48.2 to 46.5 mm (−1.7 mm). Since GP pulls the genioglossus muscle and geniohyoid muscle attached to the genioglossus anteriorly, it is considered that the hyoid bone moves upward and anteriorly after GP. However, as indicated by Shimamine et al., MDO performed before GP caused the infrahyoid muscles that had once stretched to contract again as the anterior movement of the mandible caused the tongue to expand forward[8]. Therefore, (5) EPS decreased, and it was considered that the force to move the hyoid bone downward was exerted.
The increase in pharyngeal anterior–posterior diameter before surgery, after LF+HS and MDO and after GP, was the largest in (1) PPS (+6.1 mm). This result and AHI, which was 22.5/h at the first visit, decreased significantly to 7.8/h after all surgeries (LF+HS and MDO and GP), and daytime sleepiness disappeared completely as a clinical symptom. Therefore, it was speculated that the site of obstruction in the present case was the posterior part of the soft palate, especially (1) PPS. Isono reported that among the 124 patients with OSA who underwent general anesthesia hypopharyngeal endoscopy, 111 patients whose obstruction pressure was above the atmosphere were examined, and the obstruction site was found to be the soft palate. The number of patients was 54% [18].
After LF+HS and MDO surgery, drowsiness did not appear during the daytime, and fortunately, in the present case, the corrective surgery was able to improve both small mandibular disease and OSA. However, the criteria for adaptation and the prediction of improvement in symptoms associated with jawbone movement are not yet sufficient. Especially, Takehiro et al. report that it is necessary to consider the balance between the amount of change in soft tissues and the size of bone around the soft tissue for the mechanism of OSA onset [19]; also, it is necessary to consider that not only changes in bone movement but also neural regulatory mechanisms by orthognatic surgery are involved. Moreover, it is necessary to evaluate the size of soft tissues such as the tongue and soft palate and analyze the functional changes, and we believe that elucidation of these aspects will be the future task.