Results
Postoperative course: From the day after the operation, the length of the extenders was extended by 1 mm per day, and in consideration of relapse, a 7-mm extension was performed in 7 days to the incisal occlusion including the overcorrection (total, 10 mm), and the device was indwelled. Intermaxillary rubber traction was applied to the anterior teeth to prevent bite.
On Oct 10, 2013 (LF+HS, 5 months after MDO), the AHI decreased from 22.5 to 9.8/h, and the ESS score decreased from 14 to 2 points, and she said her drowsiness had disappeared (Table 1). Moreover, in the cephalometric analysis of the cephalometric profile image obtained on Nov 6, 2013 (LF+HS, 7 months after MDO), the SNB was increased from 69° to 73° (Table 1, Fig 3B, 4). The occlusal state was Angle I, the horizontal overlap was 1 mm, and the vertical overlap was 1 mm. The occlusal state was improved, and the facial angle increased from 68° to 72°. However, as the patient was still worried about the feeling of receding of the chin, we planned to move the chin forward and applied the callus extension device on Dec 6, 2013 (LF+HS, 7 months after MDO). GP was performed at the time of removal.
Intraoperative findings of GP: GP was started from 20 mm above the lower edge of the mandible in the midline of the mandible, passed through the anterior part of the mental foramen, and cut the bones toward the lower edges of the mandible on both sides to form small bone fragments. This small bone fragment was towed forward 13 mm and fixed with one Depuy Synthes Matrix LOCK Chin Plate. Biopex® (calcium phosphate bone paste; manufactured by Nipro) 3 cc was inserted into the bone gap created by the movement of the bone fragments. No bone fixation was performed after the removal of the callus extension device.
Postoperative course: On Sep 1, 2014 (9 months after GP), the AHI further decreased from 9.8 to 7.8/h. ESS score was not remeasured because improvement was already observed after LF+HS and MDO (Oct 10, 2013: 5 months after LF+HS and MDO). She stated that the drowsiness felt during the day had completely disappeared.
Postoperative orthodontic treatment resulted in closer occlusion and stable upper and lower jaws. Cephalometric analysis was performed on the cephalometric profile image taken on Nov 17, 2015 (1 year and 11 months after GP) and Dec 9, 2013 (7 months after LF+HS, MDO). The SNB decreased from 73° to 72°, and the facial angle increased from 72° to 76° (Figs 3C, 4, Table 1).
The patient reported that she was satisfied with her facial appearance and occlusion, and after the surgery, she did not experience drowsiness again during the day and her OSA improved.
As mentioned earlier, in this case, the anterior extension of the mandible was performed for small mandibular disease, and it was expected that the load on the mandibular condyle would cause PCR enhancement and relapse after surgery. We were planning to observe it closely for a long period of time. However, due to family reasons, the patient abruptly moved to a distant place 2 years and 6 months after the LF+HS and MDO surgery, and our department was closed.
The anterior–posterior diameter of the pharynx: According to the method described by Shimamine et al., the anterior–posterior pharyngeal diameter and the amount of movement of the hyoid bone were measured using the cephalometric profile images taken before surgery, after LF+HS and MDO and GP (Fig. 5, Table 1) [8].
1. June 14, 2013 (1 month after LF+HS and MDO): (1) PPS decreased from 35.1 to 32.6 mm (−2.5 mm), (2) SPPS increased from 17.7 to 18.0 mm (+ 0.3 mm), (3) MPS increased from 4.6 to 10.1 mm (+5.5mm), (4) IPS increased from 7.4 to 12.2 mm (+4.8mm), (5) EPS increased from 6.7 to 11.6 mm (+4.9 mm). These parameters were measured parallel to the virtual FH plane. (6) S-H decreased from 106.4 to 104.9 mm (−1.5 mm), and (7) C3-H decreased from 42.7 to 41.1 mm (−1.6 mm) (Table 1).
2. Nov 6, 2013 (7 months after LF+HS and MDO); (1) PPS increased from 32.6 to 34.8 mm (+2.2 mm), (2) SPPS increased from 18.0 to 19.3 mm (+1.3 mm), (3) MPS decreased from 10.1 to 10.0 mm (−0.1mm), (4) IPS decreased from 12.2 to 11.2 mm (−1.0mm), (5) EPS decreased from 11.6 to 10.3 mm (−1.3 mm), (6) S-H decreased from 104.9 to 104.4 mm (−0.5 mm), and (7) C3-H increased from 41.1 to 48.2 mm (+7.1 mm) (Table 1).
3. Dec 13, 2013 (LF+HS, 7 months after MDO, immediately after GP operation); (1) PPS increased from 34.8 to 35.9 mm (+1.1 mm), (2) SPPS increased from 19.3 to 19.7 mm (+0.4 mm), (3) MPS decreased from 10.0 to 6.6 mm (−3.4 mm), (4) IPS increased from 11.2 to 11.8 mm (+0.6 mm), (5) EPS decreased from 10.3 to 8.6 mm (−1.7 mm), (6) S-H increased from 104.4 to 107.8 mm (+3.4 mm), and (7) C3-H decreased from 48.2 to 46.5 mm (−1.7 mm) (Table 1).
4. Nov 17, 2015 (LF+HS, 2 years and 6 months after MDO, 1 year and 11 months after GP); (1) PPS increased from 35.9 to 41.2 mm (+5.3 mm), (2) SPPS increased from 20.1 to 19.7 mm (+0.4 mm), (3) MPS increased from 6.6 to 6.7 mm (+0.1 mm), (4) IPS decreased from 11.8 to 11.1 mm (−0.7 mm), (5) EPS decreased from 8.6 to 7.6 mm (−1.0 mm), (6) S-H decreased from 107.8 to 105.8 mm (−2.0 mm), and (7) C3-H decreased from 46.5 to 44.5 mm (−2.0 mm) (Table 1).
Comparison of preoperative values ​​with final follow-up values (Nov 17, 2015); (1) PPS (+6.1 mm), (2) SPPS (+2.4 mm), (3) MPS (+2.1 mm), (4) IPS (+3.7 mm), (5) EPS (+0.9 mm), (7) C3-H (+1.8 mm) increased, and (6) S-H decreased (−0.6 mm).
Regarding PCR: When the distance from the mandibular condyle to the mandibular notch was measured using 3D-CT images, it was 12.5 mm on the right side and 8.3 mm on the left side before the operation in March 7, 2013. However, in August 14, 2014 after the operation (LF+HS, 1 year and 3 months after MDO, 9 months after GP), it was 12.1 mm (−0.4 mm) on the right side and 6.7 mm (−1.6 mm) on the left side, compared with values measured preoperatively. The right mandibular condyle was similar, but the left side showed mild PCR progression (Figs 2C, D).
Regarding relapse: The amount of anterior extension of the mandible achieved by LF+HS and MDO was evaluated by measuring the distance between Condylion-B points on both sides using the cephalometric profile image obtained before and after the modification of reported by Miyamoto et al. The amount of relapse was then calculated (Fig. 5) [7]. The distance between Condylion-B points was 89.5 mm on the right side and 92.7 mm on the left side before surgery. Immediately after LF+HS and MDO (Jun 14, 2013), it was 101.3 mm on the right side and 101.8 mm on the left side. In other words, the extension amount was +11.8 mm on the right side and +9.1 mm on the left side. Seven months after LF+HS and MDO, the size was 98.7 mm on the right side and 99.6 mm on the left side immediately before GP surgery (Dec 13, 2013) and 98.6 mm on the right side and 98.9 mm on the left side immediately after GP. It was 98.2 mm on the right side and 98.8 mm on the left side 2 years and 6 months after LF+HS and MDO and 1 year and 11 months after GP (Nov 17, 2015).
A difference of +11.8 mm on the right side and +9.1 mm on the left side was observed between before surgery and immediately after LF+HS and MDO and 8.7 mm on the right side compared with values measured 2 years and 6 months after LF+HS and MDO surgery. The left side was 6.1 mm, the right side was 25.6% relapse, and the left side was 33.0% relapse (Table 1, Figs 1C, D).