External Fixator Combined With Limited Internal Fixation For The Treatment Of Calcaneal Fracture In Finite Element Analysis

Purpose Calcaneal fractures are the most common tarsal bone fractures.The surgical methods have been Orthopedic research highlights, and there arestill controversial. In order to reduce fractures and soft tissue complicationsafter surgery, minimally invasive technique provides a new idea. In recentyears, we use minimally invasive technique that external fixator combinedwith limited internal fixation treats calcaneal fractures, and the surgicalclinical efficacy is well, with fewer complications. This study aimed toestablish postoperative finite element model of calcaneal fracture treated byexternal fixator combined with limited internal fixation, and then the finiteelement analysis was done through biomechanics of simulation. We hope thisstudy can provide theoretical basis for treatment of clinical calcanealfractures.MethodThe coordinate date of healthy men’s foot and ankle was obtained by CT. Thefinite element model of normal foot and ankle was established and verified byMimics, Patran, Solidworks, Abaqus finite element software.1. The finite element model of external fixation, external fixator combinedwith limited internal fixation for the treatment of SandⅡercsalcaneal fracture were established by Mimics, Patran, Solidworks finite elementsoftware. Using Abuqus software simulating of lower limbnon-weight-bearing status, calcaneal tendon is subjected to the maximumtensile stress. The displacement condition between fracture fragments wasanalyzed, and the same as stress distribution of foot and ankle bones,external fixator and limited internal fixation.Results1. The established finite element model of normal foot and ankle contains atotal of101625nodes,451374tetrahedron units,42link units. Theverification model contains a total of55909nodes,295453tetrahedronunits,31link units.2. The established finite element model of external fixator for the treatmentof SanderⅡscalcaneal fracture contains a total of134422nodes,706720tetrahedron units,42link units. The relative displacement between fractureblocks to the medial, back, above the ankle is0.02722mm,0.09511mmand0.1398mm respectively. The maximum relative displacement betweenthe fracture fragments is0.1753mm, which is less than separation ordisplacement of the fracture line1mm of the surgical indications ofintra-articular calcaneal fractures. The maximum stress value of externalfixator is37.06MPa, which is less than the yield strength of externalfixation of225MPa. The maximum stress distribution of foot and anklefocused on calcaneocuboid joint, and the stress value is32.94MPa. 3. The established finite element model of external fixator for the treatmentof SanderⅡscalcaneal fracture contains a total of163617nodes,765848tetrahedron units,42link units. The relative displacement between fractureblocks to the medial, back, above the ankle is0.1983mm,0.07049mm and0.1094mm respectively. The maximum relative displacement between thefracture fragments is0.1363mm, which is less than separation ordisplacement of the fracture line1mm of the surgical indications ofintra-articular calcaneal fractues. The maximum stress value of externalfixator and screw is30.88MPa and21.16MPa respectively, which are lessthan the yield strength of external fixation of225MPa. The maximumstress distribution of foot and ankle focused on calcaneocuboid joint, andthe stress value is27.45MPa.Conclusion1. The finite element model of external fixator combined with limitedinternal fixation for the treatment of Sanders Ⅱcalcaneal fracture is2. effective and reliable, which looks realistic with the experimentalrequirements, and the date and images can be reused.3. External fixator combined with limited internal fixation for thetreatment of SandersⅡcalcaneal fracture can provide sufficient stability.Foot and ankle bone stress distribution is relatively reasonable. There isstress concentration in external fixator and internal limited fixationscrews, but still within the ideal range.