In Silico Modeling of Safe Force Limits for Trismus Therapy Following Jaw Reconstruction

Area of Science:

• Biomechanical Engineering
• Oral and Maxillofacial Surgery
• Medical Device Design

Background:

• Trismus (restricted mouth opening) is a common complication after segmental mandibulectomy and autologous bone reconstruction.
• The biomechanical limits of reconstructed mandibles, especially without bone union, are not well understood.
• Current trismus therapy may pose risks due to unquantified loading parameters.

Purpose of the Study:

• To estimate patient-specific loading limits in compromised mandibular reconstructions using finite element analysis (FEA).
• To guide the safe application of forces during trismus therapy for patients with reconstructed mandibles.
• To inform the development of safer jaw-stretching devices like Restorabite.

Main Methods:

• FEA was employed to model stress distribution in reconstructed mandibles (bone, plate, screws) lacking bone union, based on patient imaging.
• Simulations evaluated various factors including friction coefficients, force application sites, and concentrated versus distributed loading.
• Patient-specific loading parameters were determined to identify safe limits for trismus therapy.

Main Results:

• Low friction coefficients between bone segments and the plate significantly increased stress on the reconstruction plate.
• Concentrated loading on the posterior segment of grafted bone resulted in the lowest stress levels.
• Distributed loading over a 4cm region on the anterior graft bone segments led to higher plate stress.

Conclusions:

• Tailored trismus therapy approaches are crucial to minimize osteolysis and plate failure in mandibular reconstruction.
• Concentrated loading on biomechanically favorable regions is safer than distributed loading, often associated with traditional jaw-stretching devices.
• These findings offer valuable insights for improving clinical practices and developing safer devices for trismus management.