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Effect of elliptical deformation of the acetabulum on the stress distribution in the components of hip resurfacing surgery

Stempin R., Dragan S. Ł., Kulej M., Filipiak J., Dragan S.

Acta of Bioengineering and Biomechanics

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2017

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Vol. 19, no. 4

35--41

EN

Hip resurfacing surgery is a matter of controversy. Some authors present very good late results of 99% survival outcomes. However, national records of implants point to the series of complications connected with biomechanical flaws of the implant. These results implicate the experimental research on biomechanical properties of HRS. The aim of the research was to define the nature of cooperation between the components of hip resurfacing surgery (HRS) and the influence of the deformation of acetabulum, the size of the implant and the nature of the bone surface on the stress distribution in the acetabulum and the femoral component. The calculations were run with the use of the finite element method (FEM), using the ANSYS bundle for this purpose. Four decrete models of the studied system were made: a model with the elements of the system connected with glue, a perfect spherical model with cooperating surfaces, a model reflecting an elliptical deformation of the acetabulum, and a model with different sizes of the implant. The results indicate that the stress values obtained for models with the ideally spherical acetabulum cannot cause significant deformation of cooperating implants. In the case of loads of the elliptically deformed acetabulum significant point stress concentrations can be observed in the spots of joint. The size of the acetabular and femoral components of HRS has influence on the stress concentration on the internal surface of the acetabulum as well as in the bone tissue surrounding the madrel of the femoral component. Moreover, physical properties of the base surface surrounding the HRS components have influence on the size of stress in the acetabulum and the femoral component.

2

Kyphosis correction after vertebroplasty in osteoporotic vertebral compression fractures

Dragan Sz.F., Urbański W., Żywirski B., Krawczyk A., Kulej M., Dragan Sz.Ł.

Acta of Bioengineering and Biomechanics

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2012

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Vol. 14, no. 4

63-69

EN

Percutaneous vertebroplasty is a minimally invasive method of treating vertebral compression fractures aimed mainly at reduction of pain. It has been observed that fractured vertebral bodies filled in with cement might also influence the increase of their height and thus lead to reduction of post-traumatic spine kyphosis. The aim of the research was to assess the possibility of reducing the kyphotic deformation of operated spine through kyphosis measurement of vertebras adjacent to fracture. 24 patients underwent percutaneous vertebroplasty on account of compression fracture of 40 vertebral bodies in thoracic and lumbar regions. On digital x-ray spine images taken in patients before and after surgery the angle of kyphosis or lordosis of bodies above and below the fractured vertebra was measured with the use of the Cobb method. Vertebroplasty in the material examined caused reduction of kyphosis in 33 cases (80.48%) and correction by 5.78 degrees on average. No regularity was found either between the occurrence of correction (and its level) and operated spine region or between the possibility of kyphosis correction and time that passed between fracture and surgery.

3

Influence of cementless cup surface on stability and bone fixation 2 years after total hip arthroplasty

Urbański W., Krawczyk A., Dragan Sz.Ł., Kulej M., Dragan Sz.F.

Acta of Bioengineering and Biomechanics

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2012

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Vol. 14, no. 2

27-35

EN

Loss of fixation between bone and implant surface is one of the main treatment problems in total hip arthroplasty. It might lead to implant instability, bone loss and treatment failure resulting in revision surgery. Surface modification is a method for improving bone response to implant and increasing implant osseointegration. However, the currently applied modifications such as hydroxyapatite coatings do not meet expectation and do not provide good clinical result. The object of the study was to evaluate the influence of acetabular cup surface modification on fixation and bone remodelling in total hip arthroplasty. Clinical and radiological outcomes were evaluated in patients two years after cementless total hip replacement. Two groups were compared: patients with acetabular component with uncoated titanium surface and patients with hydroxyapatite-coated acetabular surface. Hips X-rays were analysed for early signs of losing stability of acetabular cups. Two years after surgery the analysis of X-rays did not reveal any statistical differences in stability, migration of acetabular components of endoprosthesis between both groups. No differences were also observed in bone remodelling around implants. Particularly high percentage of cups, i.e. 17.64%, were classified into the group with high risk of early implant loosening, i.e., the group with HA coatings. Hydroxyapatite coatings on titanium cementless acetabular cups implanted by press-fit technique have no influence on their stability, bone-implant fixation and the remodelling of bone surrounding an implant two years after surgery.

4

Influence of whiplash injury on cervical spine stability

Martynkiewicz J., Dragan Sz.F., Płocieniak K., Krawczyk A., Kulej M., Dragan Sz.Ł.

Acta of Bioengineering and Biomechanics

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2011

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Vol. 13, no. 4

59-63

EN

The aim of this study was to define the influence of whiplash injury on cervical spine stability. The study involved 72 patients who had suffered from sprain injury to cervical spine of 0(degree)-III(degree) according to QTF. To verify the results the authors examined the control group whose representatives have never suffered from any cervical spine injury and met all the exclusion criteria. Conventional plain radiographs in both groups showed three lateral views: maximum flexion, neutral (resting) position and maximum extension view. The results of image studies were subjected to roentgenometric analysis to find mechanical symptoms of instability according to radiological criteria: AADI, anterior translation and regional angulation. The authors demonstrated that there was no influence of whiplash injury on mechanical stability of cervical spine measured on radiograms in static-functional lateral views.

5

Evaluation of dynamic formation of cervical spine column based on functional radiological studies in patients after cervical spine injury

Martynkiewicz J., Dragan S. F., Płocieniak K., Krawczyk A., Kulej M., Dragan S. Ł.

Acta of Bioengineering and Biomechanics

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2011

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Vol. 13, no. 3

105-109

EN

The purpose of this study was to evaluate cervical spine function, based on our own functional method of roentgenometric analysis in patients who suffered from cervical spine sprain injury. Study involved 72 patients who suffered from cervical spine whiplash injury. Conventional plain radiographs in all patients included three lateral views: maximum flexion, neutral (resting) and maximum extension. All views allowed roentgenometric evaluation of ligament instability of the lower cervical spine C5–C7 according to the White and Panjabi criteria. Furthermore, based on literature analysis and their own clinical observations, the authors proposed new classification of dynamic formation of cervical spine column. The dynamic formation of cervical column is evaluated based on pathomechanical chain of being between normal and unstable. Authors’ own evaluation system in flexion views can be useful in diagnosis and treatment of this type of injury.

6

Improved solutions for vehicle routing and scheduling with fuzzy time windows and fuzzy goal

Kobylański P., Kulej M.

Badania Operacyjne i Decyzje

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2003

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nr 4

97-113

EN

In this paper, we consider a vehicle routing and scheduling problem with fuzzy time windows and a fuzzy goal. A two-stage method for obtaining the improved optimal solution to the problem under consideration is presented. This method uses the constraint programming as an effective tool for solving the problem.

PL

W artykule omówiono problem planowania I harmonogramowania tras dla samochodów w warunkach istnienia rozmytych okien czasowych klientów I rozmytego celu. Sformułowano model mieszany programowania całkowitoliczbowego bazującego na kryterium max-min i wykorzystujący zasadę uogólniania Zadeha. Rozwiązanie optymalne tego modelu, nazywane rozwiązaniem max-min optymalnym, ma tendencję obniżania stopni satysfakcji ograniczeń czasowych lub celu. W celu wyeliminowania tego mankamentu zastosowano koncepcję poprawionych rozwiązań optymalnych (Dubois i Fortemps, 1999). Zaproponowano dwuetapową metodę znajdowania takich rozwiązań, opartą na programowaniu z więzami jako efektywnym narzędziem do rozwiązywania rozpatrywanego problemu.