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Mechanical Analysis of the Influence of Fabrication Tolerances on Contact Conditions between the Acetabular Cup and the Femoral Head in Total Hip Replacement
Koukal, Milan ; Horyl, Petr (referee) ; Repko, Martin (referee) ; Janíček, Přemysl (referee) ; Florian, Zdeněk (advisor)
In endoprosthesis surgery there are typically a high percentage of implant defects, these can lead to failure of the whole prosthesis. One type of total hip replacement function loss is acetabular cup loosening from the pelvic bone. This disertation examines manufacture perturbations as one of the possible reasons for this kind of failure. Both dimension and geometry manufacturing perturbations of ceramic head and polyethylen cup were analyzed. We find that perturbations in the variables analysed here affect considered values of contact pressure and frictional moment. Furthermore, contact pressure and frictional moment are quantities affecting replacement success and durability. From obtained results it can be recommended to fit head and cup with a clearance of between 0 mm and 0.05 mm. It can not be recommend using interference type of fit because of strong deterioration of the contact conditions. Roundness perturbation of ceramic head should not exceed 0.025 mm.
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Polymethylmethacrylate augmented direct anterior screw fixation in type II odontoid fractures in low bone density C2 vertebrae - a biomechanical cadaveric study
Řehoušek, Petr ; Skála-Rosenbaum, Jiří (advisor) ; Klézl, Zdeněk (referee) ; Repko, Martin (referee)
Odontoid peg fractures are the most common injuries of the cervical spine in the elderly. Anterior screw stabilisation in type II odontoid peg fractures improves survival and function in these patients but may be complicated by failure of fixation. The purpose of our study was to determine whether cement augmentation of a standard anterior screw provides biomechanically superior fixation of type II odontoid fractures in comparison to a non-cemented standard screw. In the second part of the study the aim was focused the role of bone cement amount and its quality to the stiffness of odontoid and vertebrae body junction. Twenty human cadaveric C2 vertebrae from elderly donors (mean age 83 years) were obtained. Anderson and D'Alonzo type II odontoid fracture was created by transverse osteotomy and fluoroscopy guided anterior screw fixation was performed. The specimens were divided into two matched groups. The cemented group (n=10) had radiopaque high viscosity polymethylmethacrylate cement injected via Jamshidi needle into the base of the odontoid peg. The other group was not augmented. A V-shaped punch was used for loading the odontoid in an antero-posterior direction until failure. The failure state was defined as screw cut-out or 5% force decrease. Mean failure load and bending stiffness were...
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Monitoring of the development of the anatomical conditions in modern treatment of congenital foot deformities
Pellar, David ; Karpaš, Karel (advisor) ; Repko, Martin (referee) ; Trč, Tomáš (referee)
MONITORING OF THE DEVELOPMENT OF THE ANATOMICAL CONDITIONS IN MODERN TREATMENT OF CONGENITAL FOOT DEFORMITIES SUMMARY This dissertation discusses the questions related to the solution of residual defects after treatment of congenital clubfoot, mainly residual metatarsus adductus. The records of our patiens were divided into parts, namely historical and comparitive. In the historical part patients operated by basal osteotomy of I. - V. metatarsal (Berman - Gartland) and patients operated by transfer of anterior tibialis tendon were evaluated. The comparitive group comprised of patients operated by a double tarsal wedge osteotomy or a combination of medial cuneiform osteotomy along with basal osteotomy of II. - V. metatarsal. From 1996 - 2013, we operated a total of 58 children (39 boys, 19 girls) with residual deformity of the forefoot. A total of 66 feet were operated upon. The mean age at the time of surgery was 6.4 years (interval 3 - 20 years). In children older than 3 years with a flexible residual varus, transfer of tibialis anterior tendon to the outer aspect of foot was carried out. A total of 18 feet were operated upon by this technique. No postoperative complications were recorded. In two patients, for persistent postoperative residual deformity, basal osteotomy of I. - V. metatarsal (Berman -...
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Bone carriers with mesenchymal stem cells
Kučera, Tomáš ; Urban, Karel (advisor) ; Repko, Martin (referee) ; Gallo, Jiří (referee)
BONE CARRIERS WITH MESENCHYMAL STEM CELLS SUMMARY Thesis deals with certain issues relating to bone regeneration. It is divided into experimental and clinical part. In the experimental part is determined number, viability and proliferative ability of mesenchymal stem cells obtained from the bone marrow of proximal femur of 24 female patients with hip osteoarthritis, who had already undergone a total hip arthroplasty implantation. At the same time is ascertained the incidence of osteopenia / osteoporosis in coincidence with hip osteoarthritis and their influence on the properties of mesenchymal stem cells. The final outcome is a significant prevalence of low bone density and its coincidence with hip osteoarthritis, and moreover when identical viability of mesenchymal stem cells, in bones with lower density, there is smaller number and reduced proliferative capacity of such cells. In the second phase was monitored activity of mesenchymal stem cells in selected carriers. These cells were found either in the aspirate of complete bone marrow or in monocyte concentrate. From the carriers we tested cancellous bone allograft, demineralized bone matrix, porous β-tricalcium phosphate, molded hydroxyapatite and calcium sulfate. We evaluated the formation of collagen fibers and the mineralized extracellular matrix. We...
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Mechanical Analysis of the Influence of Fabrication Tolerances on Contact Conditions between the Acetabular Cup and the Femoral Head in Total Hip Replacement
Koukal, Milan ; Horyl, Petr (referee) ; Repko, Martin (referee) ; Janíček, Přemysl (referee) ; Florian, Zdeněk (advisor)
In endoprosthesis surgery there are typically a high percentage of implant defects, these can lead to failure of the whole prosthesis. One type of total hip replacement function loss is acetabular cup loosening from the pelvic bone. This disertation examines manufacture perturbations as one of the possible reasons for this kind of failure. Both dimension and geometry manufacturing perturbations of ceramic head and polyethylen cup were analyzed. We find that perturbations in the variables analysed here affect considered values of contact pressure and frictional moment. Furthermore, contact pressure and frictional moment are quantities affecting replacement success and durability. From obtained results it can be recommended to fit head and cup with a clearance of between 0 mm and 0.05 mm. It can not be recommend using interference type of fit because of strong deterioration of the contact conditions. Roundness perturbation of ceramic head should not exceed 0.025 mm.
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