| According to existing studies, there is considered to be a correlation between craniofacial morphology and natural head posture(NHP). For example, an over growth of mandibular usually appear with tilted NHP and a wider upper airway. On the other hand,NHP is evidence supported in its value on predicting the maxillofacial growing pattern:Subject tend to develop a retrognathic mandible with an extended NHP, while those has crouched one tend to develop a prognathic mandible.In order to further study the possible correlation among NHP, craniofacial morphology and upper airway after the subject went through orthognathic surgery. We designed this present study. This is a hospital based retrospective study on effects of jaw surgery on NHP, craniofacial morphology and upper airway. The eligible cases are selected from the patients undergone orthognathic surgeries in The Craniofacial Center of University of Illinois, Chicago. All the subject’s pre-op(T1), 6-12 weeks post-op(T2), and 1-2years(T3)CBCT data was scanned when the subject was manipulated to NHP. We evaluate the quality of the data and do the 3D morphological analysis in third party software. There is single observer to measure the data twice after the first time observation. The study was part of the approved IRB protocol pass the evaluation of Institutional Review Board of University of Illinois, Chicago.(No. #2015-1075.) The study was composed of seven parts as follows.Part 1. The effect of Le Fort I advancement on NHP.Aim: Testing the null hypothesis that NHP were not changing after Le Fort I.Subjects and methods: Subjects were those who did Le Fort I single piece advancement, Le Fort I segmentation advancement. The workflow was collecting the CBCT data at T1/T2/T3, importing the data to software Invivo Dental 5.2(Anatomage Inc.,San Jose, CA) and 3D analysis. Pre-op and post-op craniofacial morphology and NHP were measured using 14 related parameters as follow : NSPNS(maxillary position in angle), PNS-S_FH, PNS-S_CP(maxillary position in distance), NSC2(NHP in angle),NSL, L-S_CP, L-S_FH, CIP-S_CP and CSP-S_CP(NHP in distance). a repeated-measure ANOVA was designed to compare the T2T1, T3T1 changes in all the parameters to their pre-operative counterparts and the variance within the interaction of the group and the time factors, and the correlation between craniofacial morphology and NHP was analyzed using a Spearman correlation test.Results: 17 subjects were eligible and included. 14 cases were single piece, 3 cases were segmented maxillary advancement. Compared to the T1 values, NSPNS 、NSC2-NSPNS、GPF R-L、L-CIP、PNS-CSP had significant difference in the time factor,no parameters had significant difference in group or interaction. GPF R-L and L-CIP had significant correlation.Conclusion: Le Fort I has a relation in the time factor, with the morphology parameter GPF R-L and L-CIP had significant correlation.Part 2.The effect of Le Fort I advancement on upper airway.Aim: Testing the hypothesis that upper airway were not changing after Le Fort ISubjects and methods: Subjects who did Le Fort I single piece advancement, Le FortI segmentation advancement. Collecting the CBCT data at T1/T2/T3, importing the data to software Mimics and 3D analysis. Pre-op and post-op Volume, Length, CSAmin were measured and the CSAavg, Uniformity and Resistance is calculated. Then a repeated-measure ANOVA was designed to compare the T2, T3 change in all the parameters to their T1 counterpart, and the correlation between parameters from the part 1and CSAavg and CSAmin was analyzed using a Spearman correlation test.Results: 17 subjects were collected. 14 cases were single piece, 3 cases were segmented maxillary advancement. Compared to the T1 values, No overall increase of the upper airway was statically significant. Changes of CSAmin is positively associated with changes of cranio-cervical angle(NSC2), NSC2-NSL(p﹤0.05). Both in short-term and long term.Conclusion: Despite the negative over all change of upper airway, the minimal CSA is positively associate with cranio-cervical angle.Part 3. The effect of BSSO advancement on NHP.Aim : Testing the null hypothesis that NHP has no association with BSSO advancement.Subjects and methods: Subjects who underwent single jaw mandibular(possible with genioplasty) or double jaw advancement were recruited and classified as 1)group 1, the BSSO group, 2) group 2, double jaw advancement with genioplasty group and 3)group 3,double jaw advancement group. T1/T2/T3 CBCT data were imported into the Invivo Dental 5.2(Anatomage Inc., San Jose, CA) and the 3D analysis was done under its3 DAnalysis module. T1/T2/T3 and NHP were measured with parameters as follows :NSPNS(maxillary position in angle), PNS-S_FH, PNS-S_CP(maxillary position in distance), NSC2(NHP in angle), NSL, L-S_CP, L-S_FH, CIP-S_CP and CSP-S_CP(NHP in distance). A repeated-measure ANOVA was designed to to compare the change in all the parameters, and the correlation among parameters were analyzed using Spearman correlation test.Results: 25 subjects were collected. 8 were BSSO advancement, 5 were double jaw advancement with genioplasty, and 12 were double jaw advancement. The difference ofthe craniofacial morphology measurements are affected by BSSO advancement during time, including NSPNS, NSL, L-S_CP, while L-S_CP is significant different interactively among surgery groups and times. Meanwhile, the difference of parameters indicating relationship of NHP and craniofacial morphology are affected by BSSO advancement during times, including L-CIP, PNS-CSP. NSC2 is positively associated with NSL in T1,T2, and T3.Conclusion: BSSO advancement changes the craniofacial morphology and the patient’s NHP.Part 4. The effect of BSSO advancement on upper airway.Aim: Testing the null hypothesis that upper airway were not changing after BSSO advancement.Subjects and method: Subjects who underwent single jaw mandibular(possible with genioplasty) or double jaw advancement were recruited and classified as the BSSO group,the double jaw advancement with genioplasty group and the double jaw advancement group. Collecting the CBCT data at T1/T2/T3, importing the data to software Mimics and3 D analysis. T1/T2/T3 Volume, Length, CSAmin were measured and the CSAavg,Uniformity and Resistance is calculated. Then a repeated-measure ANOVA was designed to to compare the T2 T3 change in all the parameters to their T1 counterpart, and the association between parameters from the part 1 and CSAavg and CSAmin was analyzed using Spearman correlation test.Results: Compared to T1, NSPNS、NSC2-NSPNS had significance with CSAavg in the time factor. The association of PNS-CSP and CSAavg had significant correlation.Conclusion: BSSO advancement has a cause-effect relation on CSAavg.Part 5. The effect of BSSO setback on NHP.Aim:Testing the null hypothesis that NHP were not changing after a BSSO setback.Subjects and methods: Subjects who underwent single jaw mandibular(possible with genioplasty) or double jaw surgery with BSSO setback were recruited and classified as the BSSO group, the double jaw surgery with BSSO setback and genioplasty group and the double jaw group. T1/T2/T3 CBCT data were imported into the Invivo Dental 5.2(Anatomage Inc., San Jose, CA) and the 3D analysis was done under its 3DAnalysis module. T1/T2/T3 and NHP were measured with parameters as follows : NSPNS(maxillary position in angle), PNS-S_FH, PNS-S_CP(maxillary position in distance),NSC2(NHP in angle), NSL, L-S_CP, L-S_FH, CIP-S_CP and CSP-S_CP(NHP in distance). A repeated-measure ANOVA was designed to compare the change in all the measurements, and the association among measurements was analyzed using a Spearman correlation test.Results: 27 subjects were collected. 7 were BSSO setback, 7 were double jaw surgery with BSSO setback and genioplasty and 13 were the double jaw surgery with BSSO setback. Compared to T1, Long-term changes of NSL is positively associated with changes of cranio-cervical angle(NSC2). Meanwhile, changes of PNS-S_CP has a positive effect on changes of CSP-S_CP.Conclusion: NHP is correlated increasing the cranio-cervical inclination following a mandibular setback.Part 6 The effect of BSSO setback on upper airway.Aim: Testing the null hypothesis that upper airway were not changing after BSSO setback.Subjects and method: Subjects who underwent single jaw mandibular(possible with genioplasty) or double jaw surgery with BSSO setback were recruited and classified as the BSSO group, the double jaw surgery with BSSO setback and genioplasty group and the double jaw surgery with BSSO setback group. Collecting the CBCT data at T1/T2/T3,importing the data to software Mimics and 3D analysis. Pre-op and post-op Volume,Length, CSAmin were measured and the CSAavg, Uniformity and Resistance is calculated.Then a repeated-measure ANOVA was designed to compare the T2 T3 changes in all the parameters to their T1 counterpart and analyze the association between parameters from the part 1 and CSAavg and CSAmin was analyzed using a Spearman correlation test.Results: Compared to T1, CSAavg is related to NSC2 and NSC2-NSL, both in short-term and long term.Conclusion: BSSO setback changes the craniofacial morphology, following acorrespondence changes of natural head posture, therefore to some extent can be a compensation of upper airway reduction.Part 7: A systematic comparison of craniofacial morphology, NHP and upper airway in patients undergoing single jaw or double jaw surgeryAim: This part is to compare the craniofacial morphology, NHP and upper airway in patients undergoing single jaw or double jaw surgerySubjects and method: Cases in the part 1, 3 and 5 were included, including 17 single jaw Le Fort I, 8 single jaw BSSO advancement, 7 single jaw BSSO setback, 17 double jaw advancement and 20 Le Fort I + BSSO setback. Parameters and their changes of single jaw or double jaw surgery were analyzed with ANOVA compare the difference in phases T1/T2/T3/ respectively. The upper airway morphological change in single jaw was compared to that in the double jaw techinique using ANOVA.Results: From the long term respect, the double jaw setback group tend to has wider craniocervical angle, the cervical vertebrae tend to move backward, compared to other single jaw or double jaw group. no significant difference was seen in the upper airway parameters; at T1/T2/T3, the advancement still had significantly smaller NSL and longer L-S_CPConclusion: With the reconstruction of a relatively normal craniofacial mophology, the procedure of mandibular advancement/setback changes the craniofacial morphology,following a correspondence changes of natural head posture, therefore to some extent can be a compensation of upper airway reduction. |
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