Optimal design of the titanium plate based on flexible multibody dynamic analysis of mandibular musculoskeletal system: a proof-of-concept study

Rigid internal fixation has become a widely-used treatment method for mandibular fractures, and the utilization of titanium plates can maintain the stability of the mandibular bone while minimally affecting soft tissues. However, until now, it has been impossible to design patient-specific titanium plate implants based on postoperative functions of mandibular movement. This paper proposes a simulation framework to optimize the mechanical design of titanium plate fixation based on flexible multibody modeling and biomechanical experiments. A flexible multibody dynamic model of the mandibular musculoskeletal system, driven by mandibular kinematic data and surface electromyography of masticatory muscles, was established for patients with mandibular fractures. Muscle forces of the healthy subject, obtained through forward–inverse coupling simulations, were then utilized in the fracture model as force inputs. A fracture line was defined in the mandibular bone according to the standard osteotomy line, ignoring contact characteristics at the fracture interface, and the dynamic response of the titanium plate with complex geometry was described based on the modal neutral file. A geometrically accurate beam (GEBF) description was further developed to optimize the geometric parameters of the titanium plates. The simulation results indicated that the titanium plate could effectively mitigate the bone fragment displacement due to fracture magnitude from 1.32 mm to 0.24 mm during the jaw opening–closing movement. The proposed dynamic modeling method provides a quantitative analysis platform for surgical planning and implant design, offering a digital design scheme based on patient-specific mandibular movement functions.