Fracture Fixation Technique and Chewing Side Impact Jaw Mechanics in Mandible Fracture Repair

Abstract

Lower jaw (mandible) fractures significantly impact patient health and well-being due to pain and difficulty eating, but the best technique for repairing the most common subtype-angle fractures-and rehabilitating mastication is unknown. Our study is the first to use realistic in silico simulation of chewing to quantify the effects of Champy and biplanar techniques of angle fracture fixation. We show that more rigid, biplanar fixation results in lower strain magnitudes in the miniplates, the bone around the screws, and in the fracture zone, and that the mandibular strain regime approximates the unfractured condition. Importantly, the strain regime in the fracture zone is affected by chewing laterality, suggesting that both fixation type and the patient's post-fixation masticatory pattern-ipsi- or contralateral to the fracture- impact the bone healing environment. Our study calls for further investigation of the impact of fixation technique on chewing behavior. Research that combines in vivo and in silico approaches can link jaw mechanics to bone healing and yield more definitive recommendations for fixation, hardware, and postoperative rehabilitation to improve outcomes. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Keywords: FINITE ELEMENT ANALYSIS; IMPLANTS; MANDIBLE; MASTICATION; MAXILLOFACIAL SURGERY; RHESUS MONKEY; TRAUMA.

Fig. 1

Terminology. (A) Single‐plate (Champy) fixation. (B) Biplanar fixation. The angle of the mandible (in purple) is at the junction between the ramus (in red) and corpus (in green).The symphysis is indicated by the dotted line and bordered on either side by the parasymphysis (in yellow). Labial (close to lip), lingual (close to tongue), and buccal (close to cheek) surfaces are indicated in black.

Fig. 2

Flow chart of finite element analysis (FEA). (A) Patient‐specific computed tomography scans were processed to (B) create 3D models of the healthy controls and (C) the angle fracture fixation treatments. (D) All models were assigned the same tissue material properties and boundary conditions to simulate post‐canine chewing and (E) solved using Abaqus static implicit solvers.

Fig. 3

Moments (N‐m) acting about coronal sections through the mandible models during simulation of ipsilateral and contralateral chewing. Gray shading indicates fracture location.

Fig. 4

(A) Maximum (ε₁‐positive values indicative of tension) and minimum (ε₃‐negative values indicative of compression) principal strain in the bone implant interface and fracture zone of the angle fracture fixation treatments (Champy, biplanar) and in the healthy control during ipsi‐ and contralateral chews. Scale bar indicates strain magnitudes in microstrain. Warm colors = larger positive strain magnitudes. Cold colors = larger negative strain magnitudes. Green = low strain magnitudes. (B) Differences in maximum (ε₁) and minimum (ε₃) principal strain magnitudes between healthy control and fracture models repaired with Champy or biplanar technique during chews ipsilateral or contralateral to fracture. Plates and screws are not included in comparisons. Scale bar indicates difference in microstrain between fixed and healthy models. White = no difference in strain magnitudes. Warm colors = larger strains in fixed than control model. Cold colors = lower strains in fixed than control model. [Correction added on 16 December 2021, after first online publication: figure 4 has been replaced].

Fig. 5

Percentage change in interfragmentary distance (IFD) between nodes across the fracture plane during chewing ipsi‐ and contralateral to the fracture in macaques. Warm and cold colors show areas with high and low IFD.

Fig. 6

Differences in maximum (ε₁) and minimum (ε₃) principal strain magnitudes between healthy control and fracture models repaired with Champy or biplanar technique during chews ipsilateral or contralateral to the fracture. Plates and screws not included in these comparisons. Scale bar indicates difference in microstrain between healthy control and fracture models. White = no difference in strain magnitudes. Warm colors = larger strains in fixed than control. Cold colors = Lower strains in fixed than control.