Challenges and Features Facing Contemporary Orthognathic Surgery

Background and Objectives: Obstructive sleep apnea is an extremely diffuse pathology that, if left untreated, can lead to very serious cardiovascular consequences. The primary goal of treatment is to maintain airflow in the upper airway tract, which can be obtained thanks to orthognathic surgery such as maxillo-mandibular advancement (MMA). This procedure increases the volume of the posterior airway space (PAS)—a parameter considered fundamental in OSA physiology. However, the correlation between the degree of advancement, the volume increase, and the clinical improvement in OSA is not yet clear, even in patients who undergo virtual surgical planning. Aiming to test the correlation of these parameters and the role of PAS volume changes, we present our pre- and post-operative volumetric analysis of the PAS using cone beam computed tomography (CBCT) following CAD/CAM-assisted maxillomandibular advancement. Materials and Methods: We collected information from patients who underwent MMA for moderate or severe OSA, planned virtually with custom-made devices, between 2020 and 2022 at the Maxillofacial Surgery and Odontostomatology Unit of the Policlinico Hospital in Milan. The degree of mandibular advancement (pogonion antero-posterior advancement) was noted. All patients underwent pre- and post-operative CBCT and pre- and post-operative polysomnography to measure the Apnea–Hypopnea Index (AHI) parameters. Both exams were performed within six months before and after surgery. The surgeries were planned virtually along with the production of custom-made devices (cutting guides and mandibular osteosynthesis plates). Volumetric analysis of the PAS was performed pre- and post-CBCT images using medical segmentation software (Mimics, Materialise, Mimcs 26.0). Results: Ten patients (nine men and one woman) with a mean age of 51 years were included in this study. The mean pogonion advancement was 14.5 mm, ranging from 13.8 to 15.6. The mean pre-surgical AHI was 52.31 events/h, while the mean post-surgical AHI was 5.94 events/h (SD 5.34). The improvement in AHI was statistically significant (Wilcoxon matched-pairs signed-rank test, p value 0.004). The mean pre-surgical PAS volume was 8933 mm³, while the mean post-surgical volume was 10,609 mm³. In 8 out of 10 patients, the volume increased, with a mean increase of 2640 mm³ (max. 5183, min. 951), corresponding to a percentage increase variation ranging from 78% to 6%. In two patients, the volume decreased by 1591 (−16%) and 2767 mm³ (−31%), respectively. The difference between pre- and post-operative results was not statistically significant (paired t-test, p value 0.033). Conclusions: The results obtained confirm the efficacy of virtually planned MMA performed with custom-made devices in OSA therapy. However, they also show that PAS volume should not be used as a comprehensive parameter for OSA treatment evaluation because it does not always have a positive correlation with advancement and AHI. Full article

Background and Objectives: Orthognathic surgery is used to restore a correct anatomical and functional relationship between the jaws, with postoperative nasal septal deviation (NSD) being a common complication of Le Fort I osteotomy (LF-IO). The aim of this study was to evaluate the occurrence of NSD after LF-IO and to identify possible risk factors. Materials and Methods: Pre- and postoperative cone beam computed tomography (CBCT) scans from 2018 to 2023 of 102 patients after LF-IO were analyzed. After categorizing the preoperative NSDs according to the Mladina classification, the next step was to measure the angle of deviation and classify the severity grades. Pre- and postoperative NSDs were compared using a paired Wilcoxon signed-rank test and postoperative changes in NSD were correlated with surgery-relevant characteristics by calculating Spearman’s correlation coefficients. Results: Postoperatively, an increase in NSD was observed in 62 cases and 35 patients showed a decrease. In both cases with an increase and a decrease in NSD, the preoperatively measured deviations showed a highly significant difference compared to postoperative NSDs (both p < 0.001). Age correlated significantly with increases in deviation (r = 0.28, p = 0.014, CI: −1.0–−0.068) and anterior maxillary displacement showed a significant correlation with a decrease in NSD (r = 0.296, p = 0.042, CI: 0.006–1.0). Gender, cranial and caudal movements of the maxilla had no influence on the results of the NSDs. Conclusions: LF-IO has an influence on NSD and can both intensify and attenuate it. In addition, the risk of an increase in nasal deviation after this surgical procedure rises with the patient’s age and decreases with anterior displacement of the maxilla. Full article

Background and Objectives: Spring-assisted surgery is a popular option for the treatment of non-syndromic craniosynostosis. The main drawback of this procedure is the need for a second surgery for spring removal, which could be avoided if a distractor material could be metabolised over time. Iron–Manganese alloys (FeMn) have a good trade-off between degradation rate and strength; however, their biocompatibility is still debated. Materials and Methods: In this study, the neuro-compatibility of Fe-20Mn (wt.%) was assessed using standard assays. PC-12 cells were exposed to Fe-20Mn (wt.%) and stainless steel via indirect contact. To examine the cytotoxicity, a Cell Tox Green assay was carried out after 1, 2, and 3 days of incubation. Following differentiation, a neurite morphological examination after 1 and 7 days of incubation time was carried out. The degradation response in modified Hank’s solution at 1, 3, and 7 days was investigated, too. Results: The cytotoxicity assay showed a higher toxicity of Fe-20Mn than stainless steel at earlier time points; however, at the latest time point, no differences were found. Neurite morphology was similar for cells exposed to Fe-20Mn and stainless steel. Conclusions: In conclusion, the Fe-20Mn alloy shows promising neuro-compatibility. Future studies will focus on in vivo studies to confirm the cellular response to Fe-20Mn. Full article