Biomechanical Performance Analysis of the Monolateral External Fixation Devices with Steel and Composite Material Frames under the Impact of Axial Load

This paper describes comparative analysis of the biomechanical performances conducted on the external fixation devices whose frames are made out of two different material (stainless steel and composite material). Biomechanical properties were determined with experimental and FEM (finite element method) models which are used to study the movement of the fracture crack, establish stiffness of the design solutions and monitor generated stresses on the zones of interest. Geometric modeling of two fixation devices configurations B50 and C50 is used as a basis for structural analysis under the impact of axial load. Structural analysis results are confirmed with an experimental setup. Analyzed deflection values in the load and fracture zones are used to define the exact values of the stiffness for the construction design and fracture, respectively. The carbon frame device configuration has 28% lower construction stiffness than the one with the steel frame (for B50 configuration), i.e., 9% (for C50 configuration). In addition, fracture stiffness values for the composite frame application are approximately 23% lower (B50 configuration), i.e., 13% lower (C50 configuration), compared to steel frame. The carbon frame device has about 33% lower stresses at the critical zones compared to the steel frame at the control zone MM+ and, similarly, 35% lower stresses at the control zone MM-. With an exhausting analysis of the biomechanical properties of the fixation devices, it can be concluded that steel frame fixation device is superior, meaning it has better biomechanical characteristics compared to carbon frame fixation device, regarding obtained data for stresses and stiffnesses of the frame construction and fracture. Considering stresses at the critical zones of the fixation device construction, the carbon frame device has better biomechanical performances compared to steel frame devices.

Bioprinting of biomimetic self-organised cartilage with a supporting joint fixation device

Despite sustained efforts, engineering truly biomimetic articular cartilage (AC) via traditional top-down approaches remains challenging. Emerging biofabrication strategies, from 3D bioprinting to scaffold-free approaches that leverage principles of cellular self-organisation, are generating significant interest in the field of cartilage tissue engineering as a means of developing biomimetic tissue analogues in vitro. Although such strategies have advanced the quality of engineered cartilage, recapitulation of many key structural features of native AC, in particular a collagen network mimicking the tissue’s ‘Benninghoff arcade’, remains elusive. Additionally, a complete solution to fixating engineered cartilages in situ within damaged synovial joints has yet to be identified. This study sought to address both of these key challenges by engineering biomimetic AC within a device designed to anchor the tissue within a synovial joint defect. We first designed and fabricated a fixation device capable of anchoring engineered cartilage into the subchondral bone. Next, we developed a strategy for inkjet printing porcine mesenchymal stem/stromal cells (MSCs) into this supporting fixation device, which was also designed to provide instructive cues to direct the self-organisation of MSC condensations towards a stratified engineered AC. We found that a higher starting cell-density supported the development of a more zonally defined collagen network within the engineered tissue. Dynamic culture was implemented to further enhance the quality of this engineered tissue, resulting in an approximate 3 fold increase in glycosaminoglycan and collagen accumulation. Ultimately this strategy supported the development of AC that exhibited near-native levels of glycosaminoglycan accumulation (>5% WW), as well as a biomimetic collagen network organisation with a perpendicular to a parallel fibre arrangement (relative to the tissue surface) from the deep to superficial zones via arcading fibres within the middle zone of the engineered tissue. Collectively, this work demonstrates the successful convergence of novel biofabrication methods, bioprinting strategies and culture regimes to engineer a hybrid implant suited to resurfacing AC defects.

Development of Knowledge-Based Engineering System for Structural Size Optimization of External Fixation Device

The development process of the knowledge-based engineering (KBE) system for the structural size optimization of external fixation device is presented in this paper. The system is based on algorithms for generative modeling, finite element model (FEM) analysis, and size optimization. All these algorithms are integrated into the CAD/CAM/CAE system CATIA. The initial CAD/FEM model of external fixation device is verified using experimental verification on the real design. Experimental testing is done for axial pressure. Axial stress and displacements are measured using tensometric analysis equipment. The proximal bone segment displacements were monitored by a displacement transducer, while the loading was controlled by a force transducer. Iterative hybrid optimization algorithm is developed by integration of global algorithm, based on the simulated annealing (SA) method and a local algorithm based on the conjugate gradient (CG) method. The cost function of size optimization is the minimization of the design volume. Constrains are given in a form of clinical interfragmentary displacement constrains, at the point of fracture and maximum allowed stresses for the material of the external fixation device. Optimization variables are chosen as design parameters of the external fixation device. The optimized model of external fixation device has smaller mass, better stress distribution, and smaller interfragmentary displacement, in correlation with the initial model.

Modern approaches to the methods and treatment strategy in fractures of the ankle joint with tibiofibular syndesmosis rupture (literature review)

A review of the literature has shown that the problem of treatment for fractures of the ankle joint with rupture of the tibiofibular syndesmosis is still far from being solved, as evidenced by the frequency of unsatisfactory results during surgeries — 4.8–36.8 %. In the future, the issue and the need to develop a dynamic fixation device, which is able to duplicate the function lost due to damage to the tibiofibular syndesmosis, remain relevant.

Adjustable, Skin-Stretching External Fixation Device and Negative Pressure Wound Therapy Application for Infected Full-Thickness Skin Defects: A Case Series Study

Introduction. Skin defects—especially infected, massive full-thickness defects—can be challenging to manage. Traditionally, defects are repaired using free flaps or musculocutaneous flaps. Many side effects and complications are associated with flaps, however, such as infection, pain, donor site pain, and poor cosmesis. Objective. This case series evaluates the use of an adjustable, skin-stretching external fixation device and negative pressure wound therapy (NPWT) to repair soft tissue defects. Materials and Methods. In this retrospective series, 7 patients with skin defects were treated with an adjustable, skin-stretching external fixation device and NPWT between January 2014 and December 2017. All patients were followed until complete healing was achieved. Each patient’s age, sex, defect size, mechanism of injury, healing time, results, and complications were recorded. Results. The average patient age was 37.43 years ± 10.47 SD (range, 26–55 years). The average skin defect area was 14.5 cm2 ± 5.26 * 23.25 ± 9.01 cm2 (range, 7–15 cm2 * 10–30 cm2), and average healing time was 3.29 months ± 1.60 (range, 1–6 months). All defects healed, and 2 patients developed ulcers. Conclusions. This series showed the adjustable, skin-stretching external fixation device and NPWT to be a simple, safe, and effective means of managing skin defects, with minimal complications.