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Fixation of distal fibular fractures: A biomechanical study of plate fixation techniques

Marvan J., Horak Z., Vilimek M., Horny L., Kachlik D., Baca W.

Acta of Bioengineering and Biomechanics

2017

Vol. 19, no. 1

33--39

Ankle fractures are complex injuries with variable prognoses that depend upon many factors. The aim of the treatment is to restore the ankle joint biomechanical stability with maximum range of motion. Most ankle fractures are fibular fractures, which have a typical oblique fracture line in the distal fibula located in the area of the tibiofibular syndesmosis. The aim of this study was to simulate numerically several fixation techniques of the distal fibular fractures, evaluate their stability, determine their impact on surrounding tissue load, and correlate the results to clinical treatment experience. The following three models of fibular fracture fixation were used: (a) plate fixation with three screws attached above/below and lag screws, (b) plate fixation with two screws attached above/below and lag screws, and (c) three lag screws only. All three fracture fixation models were analyzed according to their use in both healthy physiological bone and osteoporotic bone tissue. Based on the results of Finite Element Analysis for these simulations, we found that the most appropriate fixation method for Weber-B1 fibular fractures was an unlocked plate fixation using six screws and lag screws, both in patients with physiological and osteoporotic bone tissue. Conversely, the least appropriate fixation method was an unlocked plate fixation with four screws and lag screws. Although this fixation method reduces the stress on patients during surgery, it greatly increased loading on the bone and, thus, the risk of fixation failure. The final fixation model with three lag screws only was found to be appropriate only for very limited indications.

Force ratio in masticatory muscles after total replacement of the temporomandibular joint

Vilimek M., Horak Z., Baca W.

Acta of Bioengineering and Biomechanics

2016

Vol. 18, no. 3

131--136

The temporomandibular (TM) joint is one of the most active joints in the human body, and any defect in this joint has a significant impact on the quality of life. The objective of this study was to analyze changes in the force ratio after TM joint replacement on contralateral TM joint loading. Implantation of an artificial TM joint often requires removal of 3 of the 4 masticatory muscles (activators). In order to perform true loading of the TM joint, loading during mastication was investigated. Input kinematic variables and mastication force were experimentally examined. The inverse dynamics approach and static optimization technique were used for solution of the redundant mechanism. Muscle forces, and reactions in the TM joint were calculated. We modified the model for several different tasks. The m. temporalis and m. masseter were removed individually and together and the forces of mastication on the TM joint were calculated for each variation. To evaluate the results, a parametric numerical FE analysis was created to compare the magnitude of the TM joint loading during the bite process for four different muscle resections. The results show an influence relative to the extent of muscle resection on contralateral TM joint loading in a total TM joint replacement. The biggest increase in the loading magnitude on the contralateral TM joint is most evident after m. masseter and m. temporalis resection. The results from all simulations support our hypothesis that the greater the extent of muscle resection the greater the magnitude of contralateral TM joint overloading.