Strength analyses of screws for femoral neck fractures

This article represents a multidisciplinary approach to biomechanics (engineering + medicine) in the field of "collum femoris" fractures. One possible treatment method for femoral neck fractures, especially for young people, is the application of cancellous (i.e. lag or femoral) screws (with full or cannulated cross-section) made of Ti6Al4V or stainless steel. This paper therefore aims to offer our own numerical model of cancellous screws together with an assessment of them. The new, simple numerical model presented here is derived together with inputs and boundary conditions and is characterized by rapid solution. The model is based on the theory of beams on an elastic foundation and on 2nd order theory (set of three differential 4th order equations, combination of pressure and bending stress-deformation states). It presents the process for calculating displacements, slopes, bending moments, stresses etc. Two examples (i.e. combinations of cancellous screws with full or cannulated cross-section made of stainless steel or Ti6Al4V material) are presented and evaluated (i.e. their displacement, slopes, bending moments, normal forces, shearing forces and stresses). Future developments and other applications are also proposed and mentioned.Web of Science38583481

Analysis of locking self-taping bone screws for angularly stable plates

Paper focuses on biomechanics, specifically on locking cortical bone screws in angularly stable plates used for the treatment of bone fractures in the medical fields of traumatology and orthopaedics. During extraction of titanium-alloy implants, problems are encountered in an effort to loosen some locking bone screws from the locking holes of an angularly stable plate and the subsequent stripping of the internal hexagon of the screw head. The self-locking of the screw-plate threaded joint was verified by calculation and the effect of the angle of the thread on the head of the locking cortical bone screw on self-locking was evaluated. The magnitude of the torque, causing the stripping of the internal hexagon (the Inbus type head) of a locking cortical bone screw with a shank diameter of 3.5 mm from Ti6Al4 V titanium alloy to ISO 5832-3, was determined experimentally. Also, it was experimentally found that the rotation of the screwdriver end with a hexagonal tip inside the locking cortical bone screw head during stripping of the internal hexagon causes strain of the screw head perimeter and thereby an increase of thread friction. The effect of tightening torque on the possibility of loosening of the locking cortical bone screw from the locking hole of an angularly stable plate was assessed experimentally. From the evaluation of five alternative shapes of locking cortical bone screw heads in terms of the acting stress and generated strains, it follows that the best screw is the screw with the Torx type head, which demonstrates the lowest values of reduced stress and equivalent plastic strain. Based on experiments and simulations the authors recommend that all global producers of locking cortical bone screws for locking holes of angularly stable plates use the Torx type heads, and not heads of the Inbus type or the Square, PH, PZ types.Web of Science37462561

Informování o konstrukci externího fixátoru pro léčení zlomenin pánve a acetabula

Main point in this contribution is the design of external fixators applied in traumatology and orthopaedics. These fixators can be used in the treatment of open and unstable (i.e. complicated) fractures of pelvis and its acetabulum. Numerical modelling (i.e. Finite Element Method), together with CAD modelling, experiments, material engineering, and nanotechnology are presented as a support for developing of a new design of external fixators.Hlavním bodem článku je návrh externích fixátorů aplikovaných v traumatologii a ortopedii. Tyto fixátory mohou být používány pro léčení otevřených a nestabilních (komplikovaných) zlomenin pánve a acetabula. Obory numerické modelování (Metoda konečných prvků), společně s modelováním v CAD, experimenty, materiálové inženýrství a nanotechnologie vytváří v dnešní době podporu pro vývoj nových směrů v konstrukci externích fixátorů

Stochastic strength analysis of compression headless screw

This article deals with strength and stiffness analysis of headless screw. This issue was solved in cooperation with engineering industry and doctors. The problem was solved using a stochastic approach, which utilizes the field of random events (simulations), which are applied for determination of input values. The prototype of headless (Herbert) screw Ti4.0/1.4x30/75 was used for solving this problem. Mathematical equations for analytical calculation of the maximal equivalent stress in screw were established. This issue is statically indeterminate problem in compressive and tensile stresses and needs one more equation (i.e. the condition of deformation), which describes relationship between extension of screw and contraction of bone. Resulting values are not defined for one specific model, but the simulation is taking into account a large amount of random samples (specifically 5x10(6) random simulations), which are distributed by bounded histograms. Furthermore, the probabilistic functions of simulated screw were determined. Due to stochastic strength analysis of headless screw, it meets reliability conditions for practical application in osteosynthetic treatment, see [Frydrysek 2016]Web of Science20203840383

Pasivní motodlaha v traumatologii a ortopedii

This article deals with analysis of the knee continuous passive motion (CPM) splint used for rehabilitation of patients after surgeries and injuries. CPM splints are used for speeding up the treatment and restoration of the joint mobility and to stop complications caused by immobilization. The goal is to solve kinematic, dynamic, deformation and stress parameters of “Artromot K1 Comfort” CPM splint.Tento článek se zabývá analýzou pasivní kolenní motodlahy sloužící k rehabilitaci pacientů po operacích a úrazech. Pasivní motodlahy se používají pro urychlení léčby, obnovu pohyblivosti kloubů a zamezení komplikacím způsobených imobilizací. Cílem je řešení kinematických, dynamických, deformačních a pevnostních parametrů pro motodlahu “Artromot K1 Comfort”

About the development of external fixators applied in emergency surgery

At first, the doctors mentioned their own medical experience with treatment of complex pelvic injury in patients with polytrauma and give reasons for necessity of early stabilization of pelvic fractures by means of external fixation, especially with continuous hemorrhage into lesser pelvis region and the retroperitoneum. Afterwards, they used damage control surgery methods including selective embolization. However, this article is focused also on the design of external fixators applied in traumatology and orthopaedics (i.e. skills of engineers). These fixators can be used in the treatment of open and unstable (i.e. complicated) fractures of pelvis and its acetabulum. Two versions (i.e. old and new) are compared. Numerical modelling (i.e. Finite Element Method), together with CAD modelling, experiments, material engineering, and nanotechnology are presented as a support for developing of a new design of external fixators.Nejprve, lékaři zmiňují své vlastní lékařské zkušenosti s léčbou komplexního poranění pánve u pacientů s polytraumaty a udávají důvody pro neodkladnou včasnou stabilizaci pánevních zlomenin pomocí zevních fixátorů, obzvláště u plynulého krvácení do nižších oblastí pánve a retroperitonea. Potom využívají metod “damage control surgery” včetně selektivní embolizace. Nicméně, tento článek je také zaměřen na design nových externích fixátorů aplikovaných v traumatologii a ortopedii (tj. zkušenosti inženýrů). Tyto fixátory mohou být využívány v léčbě otevřených a nestabilních (tj. komplikovaných) zlomenin pánve a acetabula. Dvě verze fixátorů (tj. stará a nová) jsou porovnány. Počítačové modelování (tj. metoda konečných prvků), společně CAD sw, experimenty, materiálovým inženýrstvím a nanotechnologií jsou prezentovány jako podpora vývoje nových konstrukcí zevních fixátorů

Extremity compartment syndrome: A review with a focus on non-invasive methods of diagnosis

The article deals with an overview of acute extremity compartment syndrome with a focus on the option of non-invasive detection of the syndrome. Acute extremity compartment syndrome (ECS) is an urgent complication that occurs most often in fractures or high-energy injuries. There is still no reliable method for detecting ECS. The only objective measurement method used in clinical practice is an invasive measurement of intramuscular pressure (IMP). The purpose of this paper is to summarize the current state of research into non-invasive measurement methods that could allow simple and reliable continuous monitoring of patients at risk of developing ECS. Clinical trials are currently underway to verify the suitability of the most studied method, near-infrared spectroscopy (NIRS), which is a method for measuring the local oxygenation of muscle compartments. Less explored methods include the use of ultrasound, ultrasound elastography, bioimpedance measurements, and quantitative tissue hardness measurements. Finding a suitable method for continuous non-invasive monitoring of the syndrome would greatly improve the quality of care for patients at risk. ECS must be diagnosed quickly and accurately to prevent irreversible tissue damage that can occur within hours of syndrome onset and may even warrant amputation if neglected.Web of Science10art. no. 80158

Immunohistochemical evaluation of tissues following bone implant extraction from upper and lower limb

Fractured bones can regenerate and restore their biological and mechanical properties to the state prior to the damage. In some cases, however, the treatment of fractures requires the use of supportive implants. For bone healing, three processes are essential: the inflammatory phase, the repair phase and the remodelling phase. A proper course of the first - inflammatory - stage is important to ensure a successful fracture healing process. In our study, we evaluated tissue samples immunohistochemically from the area surrounding the fractures of upper and lower limbs (bone tissue, soft tissue, and the implant-adhering tissue) for markers: CD11b, CD15, CD34, CD44, CD68, Cathepsin K, and TRAcP that are linked to the aforementioned phases. In soft tissue, higher expressions of CD68, CD34, CD15 and CD11b markers were observed than in other locations. TRAcP and Cathepsin K markers were more expressed in the bone tissue, while pigmentation, necrosis and calcification were more observed in the implant-adhering tissue. Since even the implant materials commonly perceived as inert elicit the observed inflammatory responses, new surface treatments and materials need to be developed

Endovascular repair of thoracic aorta injury: 17 years of single-center experience

Background: Traumatic thoracic aortic transection is one of the most severe complications of high-energy injuries, but pa-tients rarely receive treatment, and it is fatal in the vast majority of cases. Due to the complexity of surgical revision for transection, endovascular repair with stent graft implantation is the preferred approach. Material/Methods: We retrospectively analyzed the short-term and long-term treatment results for 31 patients (29 men, 2 wom-en) treated at the Interventional Radiology Department, University Hospital Ostrava, for the isthmus part of a descending thoracic aorta injury between 2004 and 2020. Results: The median patient age was 48 years (interquartile range [IQR]: 28-63 years). The most common causes of in-jury were traffic accidents and falls or jumps, with the trauma location at the Ishimaru zones 2 to 4 of the aor-tic isthmus. Aortic stent grafts were successfully implanted in all patients; 13% of patients had complications and 10% died due to the trauma severity. The median procedure duration was 30 min (IQR: 25-43 min) and the median hospital stay was 29 days (IQR: 28-63 days). Conclusions: Aortic stent graft implantation appears to be a safe and effective method for dealing with thoracic aorta inju-ry, with a low complication rate and high patient survival. The endovascular approach is the method of choice for treating this severe disease, and a multidisciplinary approach for emergency medical treatment with a com-prehensive trauma protocol is essential.Web of Science27art. no. e93447

Mechanics of screw joints solved as beams placed in a tangential elastic foundation

This article deals with a new original analytical solution of deformation, force and stress states in wood screw joints up to the limit values of pulling out/breaking the screw. The screws are under tension. The wood-to-screw interaction is effectively simplified by introducing several physical model variants using a tangential elastic non-linear foundation. The experimental verification of the proposed models using pull-out tests (i.e., pulling out screws from dry spruce wood in laboratory conditions) confirms the correctness of the proposed models of the elastic linear/non-linear foundation. The validity of the model is also analytically and experimentally verified in the biomechanical model of pulling out screws from the femur of a bovine/human cadaver, which confirms and expands the validity of newly designed screw joint models outside the timber structure area.Web of Science1112art. no. 561