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.

A Coupled Computational Framework for Bone Fracture Healing and Long-term Remodelling: Investigating the Role of Internal Fixation on Bone Fractures

In this study, a coupled computational modelling framework for bone fracture repair is presented that enables predictions of both healing and remodelling phases of the fracture region and is used to investigate the role of an internal fixation plate on the long-term healing performance of a fracture tibia under a range of different conditions. It was found that introduction of a titanium plate allowed the tibia to undergo successful healing at higher loading conditions and fracture gaps, compared to the non-plated versions. While these plated cases showed faster rates of repair in the healing phase, their performance was substantially different once they entered the remodelling phase, with substan-tial regions of stress shielding predicted. This framework is one of the few im-plementations of both fracture healing and remodelling phases of bone repair and includes several innovative approaches to smoothing, time-averaging and time incrementation in its implementation, thereby avoiding any unwanted abrupt changes between tissue phenotypes. This provides a better representa-tion of tissue development in the fracture site when compared to fracture healing models alone and provides a suitable platform to investigate the long-term performance of orthopaedic fixation devices. This would enable the more effective design of permanent fixation devices and optimisation of the spatial and temporal performance of bioabsorbable implants

Case series study: the diagnosis and treatment of fifty tumors and pseudotumors at the proximal femur

Introduction: Tumor and pseudotumor (TP) at the proximal femur (PF) can seriously affect mortality, extremity function, and body integrity. However, reports often focused on a specific tumor, not regional lesions. This study focuses on clinical findings, imaging, micro-pathology, and the treatment of all TP at the site. Methods: The study involved all patients who had a confirmed tumor or pseudotumor diagnosis at the PF. The clinical findings, X-ray, and biopsy were recorded and analyzed. Treatment was optional depending on the patient's situation and available condition of the hospital. The functional outcome, bone healing were defined at the last examination or two years of follow-up. Results: Fifty patients were involved in the study. Twenty-four patients had apparent tumors. TP at the PF, neck-trochanter, trochanters, and neck were 21 (42%), 16 (32%), 9 (18%), and 4 (8%) cases, respectively. There were 29 (58%) pathologic fractures. Biopsy was made for all patients. Twenty-three cases (46%) were malignant, and 8 (16%) cases were giant cell tumors. Thirtythree patients suffered from an operation. Ennerking's functional score was excellent, good, fair, and poor in 24 (48%), 5 (10%), 1 (2%), and 20 (40%) patients, respectively. For the last outcomes of 33 operated patients, 17 healed, three unchanged, one worse, and two dead. Conclusions: For the PF TP, the rate of malignant and pathological fracture was high. The giant cell tumor was not rare. The resection of the TP combined with grafts using ordinary fixation devices was satisfactory.

Crystallization and degradation behaviour of multiblock copolyester blends in Langmuir monolayers

Supporting the wound healing of soft tissues requires fixation devices becoming more elastic while degrading. To address this unmet need, we designed a blend of degradable multiblock copolymers, which is cross-linked by PLA stereocomplexation combining two soft segments differing substantially in their hydrolytic degradation rate. The degradation path and concomitant structural changes are predicted by Langmuir monolayer technique. The fast hydrolysis of one soft segment leads to a decrease of the total polymer mass at constant physical cross-linking density. The corresponding increase of the average spacing between the network nodes suggests the targeted increase of the blend’s flexibility. Graphic abstract

A filled chocolates technique to seal negative-pressure wound therapy around external fixation devices: a randomized controlled trial

Background In complex injuries, external fixation device represents a challenge to maintain negative-pressure wound therapy (NPWT). In this trial, we compared a combination of bone wax and colostomy paste versus bone wax alone to seal NPWT around external fixation devices. Methods Debridement surgeries of limbs with open fracture and large soft tissue defect need NPWT to be applied around the external fixation devices were randomized into two groups. The seal between external fixation devices and the drape was established using either bone wax first and then reinforced with colostomy paste or bone wax alone. The primary outcome was seal failure within 3 days of debridement. Secondary outcomes included the number of seal failure per debridement surgery and the time spent in repairing the seal within 3 days. Results A total of 56 debridement surgeries were enrolled: 28 to the bone wax/colostomy paste group versus 28 to the bone wax control group. One patient in the control group died 1 day after the first debridement surgery. One patient in the bone wax/colostomy paste group was transferred to other hospitals within 3 days. The final analysis included 27 debridement surgeries in the bone wax/colostomy paste group and 27 debridement surgeries in the control group. The rate of seal failure (defined by loss of negative pressure at anytime within 3 days) was 81.5% (22/27) in the control group versus 11.1% (3/27) in the bone wax/colostomy paste group (p < 0.001; χ2 test). The bone wax/colostomy paste group also had significantly lower number of seal failures per debridement (median of 0 vs. 2; p = 0.004), and shorter time spent in repairing the seal (median of 0 vs. 18 min; p < 0.001). Conclusions Using bone wax followed by colostomy paste to seal NPWT around external fixation devices reduces seal failure.

Analysis of the lower jaw exoskeleton in finite element programs

A special place in the methods of surgical treatment of bone fractures is occupied by transosseous osteosynthesis using external fixation devices of various designs.Objective: to analyze the lower jaw exoskeleton in finite element programs.Materials and research methods. During the research, 36 human lower jaws were involved from the museum of the Department of Oper-ative Surgery and Topographic Anatomy of the Volgograd State Medical University. They were scanned in 3D. All obtained images were loaded into a virtual scene reconstruction program. Fractures of the lower jaws in the corner area were modeled, an apparatus for external fixation of the lower jaw exoskeleton was installed, and the chewing load on the lower jaw was simulated. The place of application of the force was an area on a small fragment of a repositioned 3D model of the mandibular bone corresponding to the place of attachment of the masseter muscle. The evaluation of virtual studies was carried out according to the results of the stress-strain states of the bones and apparatus, the schedule of displacements of objects and the results of the analysis of the safety factor.Research results and discussion. In the course of evaluating the virtual placement of the mini-fixator wires of the apparatus for external fixation of the lower jaw exoskeleton, it was revealed that the main load is applied to the mini-fixator wires on a large fragment and the bone in the area of the wires. For the possibility of precise positioning of the osteofixers of the external fixation device, a device for the safe installation of the spokes of the lower jaw exoskeleton was also developed.Conclusion. Thus, on the basis of computer mathematical analysis, it can be argued that the developed design of the apparatus for external fixation of the lower jaw exoskeleton works under conditions of the maxillofacial region, performs reposition and fixation of bone fragments of the lower jaw under conditions of chewing functioning of the restored fracture of the lower jaw.

Development of a device for safe spatial orientation of the spokes of an extra-focal osteosynthesis apparatus

A special place in the methods of surgical treatment of bone fractures is occupied by transosseous osteosynthesis using external fixation devices.The aim of the study is to develop a device for the safe spatial orientation of the wires of the extrafocal osteosynthesis apparatus.Materials and methods. To develop a device for the spatial orientation of the external fixation spokes, a 3D model was designed with further reproduction on a 3D printer. The development of the device was carried out by placing the wires of the external fixation apparatus on 36 bones of the human lower jaw, on which a fracture in the angle was simulated.Results and discussion. The device for the spatial orientation of the spokes of the external fixation device for the lower jaw exoselet is partially reproduced using a 3D printer, which allows individualizing the device parts at the stages of preparation for surgery.Conclusions. Effect: control of the depth of immersion of osteofixers over the entire thickness of the bone and simplification of the choice of the optimal angle of mutual spatial orientation during their introduction and the greatest stable fixation of the fragments of the lower jaw during closed extrafocal osteosynthesis.

FEATURES OF MECHANICAL TESTS OF OSTEOSYNTHESIS SYSTEMS

Various methods of measuring the characteristics of stiffness and strength of systems "bone with a fracture - a means of fixation" are considered. Methods for measuring deformations of osteosynthesis systems are systematized, which take into account the nature of the action of external loads and allow to compare different systems of osteosynthesis. The rational arrangement of drugs at tests taking into account features of a structure of bones and the real loadings arising at functioning of musculoskeletal system is recommended. It is proposed to use the stiffness characteristics of the systems "bone - means of fixation" under the action of axial compression, transverse bending and torsion, including in cyclic modes; considered systems of osteosynthesis with the most common methods of fixing fractures to select the optimal in terms of quality methods of fixing fragments in fractures. It is established that the stability indicators of osteosynthesis systems, measured in the process of cyclic tests, are more sensitive to the type of fixing means and can be used to rank these systems according to the degree of mechanical reliability. The results of research obtained using these methods are implemented in surgical practice in the selection of optimal designs of fixation devices and the rational location of fixing elements.