Analysis of the Impact of Configuration of the Stabilisation System for Femoral Diaphyseal Fractures on the State of Stresses and Displacements.

INTRODUCTION: The treatment of femoral diaphyseal fractures by intramedullary nailing has become a common procedure in orthopaedic surgery. The purpose of this numerical simulation was to present how the changes in configuration of the stabilisation system can affect the stress and displacement state in the bone tissue and implanted device. MATERIAL AND METHODS: The numerical comparison of the stabilisation variants for the type 32-A2 femoral diaphyseal fracture (according to the AO classification) performed by using the Charfix2 (ChM®) anatomical nail locked in a number of chosen ways. The displacement and the stress distributions both in the bone and implant were obtained and analysed by computational simulation. RESULTS: In all models, there was the same characteristic distribution, which shows there were minimal rotational movements of the bone around the anatomical axis. In all cases, stress concentrations were generated in the nail material in the area of the fracture gap. CONCLUSIONS: The obtained results indicate that there is a visible advantage to one-plane distal stabilisation in the reduction of stresses regardless of the type of proximal stabilisation. The results of calculations indicate that the use of proximal stabilisation with a neck screw reduces the possibility of damage to the implant.

Numerical modeling of the traction process in the treatment for Pierre-Robin Sequence.

INTRODUCTION: The goal of this numerical study was to identify the results of modulated growth simulation of the mandibular bone during traction in Pierre-Robin Sequence (PRS) treatment. METHODS: Numerical simulation was conducted in the Ansys 16.2 environment. Two FEM (finite elements method) models of a newborn's mandible (a spatial and a flat model) were developed. The procedure simulated a 20-week traction period. The adopted growth measure was mandibular length increase, defined as the distance between the Co-Pog anatomic points used in cephalometric analysis. RESULTS: The simulation calculations conducted on the developed models showed that modulation had a significant influence on the pace of bone growth. In each of the analyzed cases, growth modulation resulted in an increase in pace. The largest value of increase was 6.91 mm. The modulated growth with the most beneficial load variant increased the basic value of the growth by as much as 24.6%, and growth with the least beneficial variant increased by 7.4%. CONCLUSIONS: Traction is a simple, minimally invasive and inexpensive procedure. The proposed algorithm may enable the development of a helpful forecasting tool, which could be of real use to doctors working on Pierre-Robin Sequence and other mandibular deformations in children.

Complication of a Femoral Fracture Treated by Intramedullary Nailing - Numerical Analysis of a Clinical Case.

The aim of this paper is to conduct a numerical analysis of a case of femoral fracture treated by intramedullary nailing and confirm the conditions which led to the formation of a pseudarthrosis at the fracture site. A low-energy femoral fracture was treated by placing a ChFN System intramedullary nail with a derotation pin. Using the finite element method, a bone-implant system was generated which made it possible to observe the displacement area and strains in the region of the fracture gap. The calculations were conducted for 3 variants of the model, using a titanium nail (10 mm and 12 mm) and a steel one (10 mm). Analysis of strain distribution indicated that the highest strain values occur in the fracture gap and that they are higher when a titanium alloy is used (0-17% vs 0-11%). Interfragmentary movements caused by an imposed load were also higher when a titanium alloy implant was used. Strain analysis showed that the percentage of elements in the gap area which are potentially able to grow bone tissue is higher when a steel implant is used. It is possible to indicate sites where unfavourable fracture gap healing will take place, which may lead to the development of a pseudarthrosis. The use of a steel implant increases the probability of obtaining stable bone union.