Changes in load distribution after unilateral condylar fracture: A finite element model study

Area of Science:

• Biomechanics
• Orthodontics
• Oral and Maxillofacial Surgery

Background:

• Unilateral condyle fractures of the temporomandibular joint (TMJ) lead to dental malocclusion, including premature contact and contralateral open bite.
• The lateral pterygoid muscle's pull on the fractured condyle causes inward displacement, ramus shortening, and angulation, disrupting TMJ biomechanics.

Purpose of the Study:

• To quantify the changes in load distribution within the temporomandibular joint (TMJ) following unilateral condyle fracture.
• To test the hypothesis that fractured-side TMJ load decreases and non-fractured-side TMJ load increases post-fracture.

Main Methods:

• A finite element model (FEM) was employed to simulate TMJ loading conditions.
• Simulations incorporated varying degrees of ramus shortening (2-16 mm) and condyle angulation (6.25°-50°).

Main Results:

• Load on the non-fractured TMJ side increased only during maximal mouth opening (MMO).
• Load on the fractured TMJ side decreased at both MMO and closed mouth positions.
• A consistent decline in fractured condyle load was observed across all simulated parameters.
• A critical threshold around 6 mm shortening and 18.75° angulation revealed a secondary medial load point on the fractured condyle.

Conclusions:

• Restoring TMJ balance becomes challenging after fractures exceeding 6 mm shortening and 18.75° angulation.
• These findings highlight the complex biomechanical consequences of condylar fractures and their impact on TMJ load distribution.