RESUMO
Mandibular fractures are very common in maxillofacial trauma surgery. While previous studies have focused on possible risk factors related to post-operative complications, none have tried to identify pre-existing conditions that may increase the risk of mandibular fractures. We hypothesized, through clinical observation, that anatomical conditions involving poor dental contacts, such as malocclusions, may increase the risk of mandibular fractures. This work was subdivided into two parts. In the first part, Digital Imaging and Communications in Medicine (DICOM) data of four healthy patients characterized by different dentoskeletal occlusions (class I, class II, class III, and anterior open bite) have been used to develop four finite element models (FEMs) that accurately reproduce human bone structure. A vertical and lateral impact have been simulated at increasing speed on each model, analyzing the force distribution within the mandibular bone. Both vertical and lateral impact showed higher level of stress at the impact point and in the condylar area in models characterized by malocclusion. Specifically, the class III and the open bite models, at the same speed of impact, had higher values for a longer period, reaching critical stress levels that are correlated with mandibular fracture, while normal occlusion seems to be a protective condition. In the second part of this study, the engineering results were validated through the comparison with a sample of patients previously treated for mandibular fracture. Data from 223 mandibular fractures, due to low-energy injuries, were retrospectively collected to evaluate a possible correlation between pre-existing malocclusion and fracture patterns, considering grade of displacement, numbers of foci, and associated CFI score. Patients were classified, according to their occlusion, into Class I, Class II, Class III, and anterior open bite or poor occlusal contact (POC). Class I patients showed lower frequencies of fracture than class II, III, and open bite or POC patients. Class I was associated with displaced fractures in 16.1% of cases, class II in 47.1%, class III in 48.8% and open bite/POC in 65.2% of cases (p-value < 0.0001). In class I patients we observed a single non-displaced fracture in 51.6% of cases, compared to 12.9% of Class II, 19.5% of Class III and 22.7% of the open bite/POC group. Our analysis shows that class I appears to better dissipate forces applied on the mandible in low-energy injuries. A higher number of dental contacts showed a lower rate of multifocal and displaced fractures, mitigating the effect of direct forces onto the bone. The correlation between clinical data and virtual simulation on FEM models seems to point out that virtual simulation successfully predicts fracture patterns and risk of association with different type of occlusion. Better knowledge of biomechanics and force dissipation on the human body may lead to the development of more effective safety devices, and help select patients to plan medical, orthodontic/dental, and/or surgical intervention to prevent injuries.
RESUMO
OBJECTIVE: The objective of this study is to investigate whether age is a significant risk factor for spinal nerve injury following selective neck dissection (SND) in patients with head and neck cancer. METHODS: A retrospective cohort study was conducted on patients who had undergone SND for head and neck cancer at a tertiary hospital between 2020 and 2022. The primary outcome was the incidence of spinal nerve injury after SND. The secondary outcomes included the types and severity of spinal nerve injury and the impact of age on these outcomes. RESULTS: A total of 78 patients were included in the study and subdivided into two groups. Two shoulder-specific questionnaires (the Shoulder Pain and Disability Index (SPADI) and the Shoulder Disability Questionnaire (SDQ)) were administered to assess shoulder morbidity postoperatively. Twelve patients showed shoulder impairment following surgery. We divided the sample into two age-based groups; the older group showed a higher rate of SAN injury and the younger group showed a lower rate of improvement over time. CONCLUSION: This study suggests that age is a significant risk factor for spinal nerve injury following SND in patients with head and neck cancer. Older patients are more likely to experience spinal nerve injury after SND than younger patients. The findings of this study may help in the development of strategies to prevent spinal nerve injury in older patients undergoing SND for head and neck cancer.
