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This study was conducted as an in vivo experiment in adult miniature pigs with the aim to test two new biomaterials. An iatrogenic defect was made into the central femoral diaphysis in the experimental animals and subsequently fixated by bridging plate osteosynthesis. Into the defect we implanted a cancellous autograft (control group), a pasty injectable scaffold (EXP A), anda porous 3D cylinder (EXP B). Radiological examination was performed in all animals at 0, 10, 20, 30 weeks after surgical procedure and histological assessment was performed. In the newly formed bone the osteoblastic activity was monitored. In terms of radiology, the most effective method was observed in the control group (completely healed 100%) compared to experimental groups EXP A (70.0%) and EXP B (62.5%)., Tato studie byla provedena jako experiment in vivo na dospělých miniaturních prasatech s cílem otestovat dva nové biomateriály. U centrálních femorálních diafýz byl u experimentálních zvířat proveden iatrogenní defekt, který byl následně fixován přemostěním osteosyntézy dlahy. Do defektu jsme implantovali spongiózní autotransplantát (kontrolní skupina), injektabilní skafold (EXP A) a porézní 3D válec (EXP B). Radiologické vyšetření bylo provedeno u všech zvířat v 0, 10, 20, 30 týdnech po chirurgickém zákroku a bylo provedeno histologické hodnocení. V nově vytvořené kosti byla sledována osteoblastická aktivita. Pokud jde o radiologii, nejúčinnější metoda byla pozorována u kontrolní skupiny (zcela uzdravená 100%) ve srovnání s experimentálními skupinami EXP A (70,0%) a EXP B (62,5%).

The study deals with mechanical testing of newly developed material polyethylene terephtalate coated with polycaprolactone nanofibers in combination with biodagradable Hexalon ACL/PCL screws as a new possibility of intra-articular reinforcement of partially ruptured cranial cruciate ligament. Four groups of ex vivo models of pig stifle joints were prepared and tested: a model with intact CCL (group 1), a model with partial CCL rupture (group 2), a model with CCL rupture stabilized with 7 mm Mersilene strip (group 3), and a model with CCL rupture stabilized with 5 mm PET/PCL biomaterial strip (group 4). The models were loaded in the standing angle of 100deg and the maximum load (N) and the shift (mm) were monitored. The mean maximum peak power and the shift were 1266.0 +/- 146.9 N and 13.7 +/- 2.5 mm for group 1, and 1164.7 +/- 228.2 N and 1 6.8 +/- 3.3 mm for group 2, respectively. In all cases after reaching the maximum load, a tibial fracture occurred but never a CCL rupture. In groups 3 and 4, the initial fixation failure occurred in the mean values of 375.7 +/- 81.5 and 360.4 +/- 52.0 N, respectively, and with a bigger shift of 52.3 +/- 11.9 mm and 39.4 +/- 14.6 mm, respectively, compared to group 1. A critical point of failure was the anchoring in the bone. It can be concluded that the PET/PCL substitute in the ex vivo model has mechanically comparable properties with the clinically used Mersilene, and based on its proven ability to carry stem cells it could be appropriate for partially ruptured CCL protection., The study deals with mechanical testing of newly developed material polyethylene terephtalate coated with polycaprolactone nanofibers in combination with biodagradable Hexalon ACL/PCL screws as a new possibility of intra-articular reinforcement of partially ruptured cranial cruciate ligament. Four groups of ex vivo models of pig stifle joints were prepared and tested: a model with intact CCL (group 1), a model with partial CCL rupture (group 2), a model with CCL rupture stabilized with 7 mm Mersilene strip (group 3), and a model with CCL rupture stabilized with 5 mm PET/PCL biomaterial strip (group 4). The models were loaded in the standing angle of 100deg and the maximum load (N) and the shift (mm) were monitored. The mean maximum peak power and the shift were 1266.0 +/- 146.9 N and 13.7 +/- 2.5 mm for group 1, and 1164.7 +/- 228.2 N and 1 6.8 +/- 3.3 mm for group 2, respectively. In all cases after reaching the maximum load, a tibial fracture occurred but never a CCL rupture. In groups 3 and 4, the initial fixation failure occurred in the mean values of 375.7 +/- 81.5 and 360.4 +/- 52.0 N, respectively, and with a bigger shift of 52.3 +/- 11.9 mm and 39.4 +/- 14.6 mm, respectively, compared to group 1. A critical point of failure was the anchoring in the bone. It can be concluded that the PET/PCL substitute in the ex vivo model has mechanically comparable properties with the clinically used Mersilene, and based on its proven ability to carry stem cells it could be appropriate for partially ruptured CCL protection.

The study deals with the possibility of substituting time- and material-demanding mechanical testing of a bone defect fixation by mathematical modelling. Based on the mechanical model, a mathematical model of bone-implant construct stabilizing experimental segmental femoral bone defect (segmental ostectomy) in a miniature pig ex vivo model using 4.5 mm titanium LCP was created. It was subsequently computer-loaded by forces acting parallel to the long axis of the construct. By the effect of the acting forces the displacement vector sum of individual construct points occurred. The greatest displacement was noted in the end segments of the bone in close proximity to ostectomy and in the area of the empty central plate hole (without screw) at the level of the segmental bone defect. By studying the equivalent von Mises stress SIGMAeqv on LCP as part of the tested construct we found that the greatest changes of stress occur in the place of the empty central plate hole. The distribution of this strain was relatively symmetrical along both sides of the hole. The exceeding of the yield stress value and irreversible plastic deformations in this segment of LCP occurred at the acting of the force of 360 N. These findings are in line with the character of damage of the same construct loaded during its mechanic testing. We succeeded in creating a mathematical model of the bone-implant construct which may be further used for computer modelling of real loading of similar constructs chosen for fixation of bone defects in both experimental and clinical practice., Studie se zabývá možností náhrady časově i materiálově náročného mechanického testování implantátu fixujícího defekt kosti matematickým modelováním. Na základě mechanického modelu byl vytvořen matematický model segmentálního ostektomického defektu diafýzy femuru miniaturního prasete fixovaného přemosťující 4,5 mm LCP (konstrukce kost-implantát), který byl následně computerově zatížen silami působícími paralelně s dlouhou osou konstrukce. Účinkem působících sil došlo k vektorovému posunu jednotlivých bodů konstrukce. Největší posun byl zaznamenán v koncových úsecích kosti v těsné blízkosti ostektomie a v místě centrálního otvoru LCP nevyplněného šroubem přemosťujícího defekt. Studií průběhu ekvivalentního von Misesova napětí SIGMAeqv na LCP, jakožto součásti testované konstrukce, bylo zjištěno, že k největším změnám napětí dochází v místě centrálního otvoru LCP nevyplněného šroubem. Rozložení tohoto napětí bylo relativně souměrné po obou stranách otvoru. K překročení napětí na mezi kluzu a nevratným plastickým deformacím v tomto úseku LCP došlo při působení síly 360 N. Tato zjištění odpovídají charakteru poškození stejné konstrukce při zátěži během jejího mechanického testování. Podařilo se vytvořit funkční matematický model konstrukce kost-implantát, který bude možno dále využívat pro computerovou modelaci reálného zatížení podobných konstrukcí zvolených k fixaci kostních defektů v experimentu i v klinické praxi.

The study deals with the determination of mechanical properties, namely resistance to bending forces, of flexible buttress osteosynthesis using two different bone-implant constructs stabilizing experimental segmental femoral bone defects (segmental ostectomy) in a miniature pig ex vivo model using 4.5 mm titanium LCP and a 3 mm intramedullary pin ("plate and rod" construct) (PR-LCP), versus the 4.5 mm titanium LCP alone (A-LCP). The "plate and rod" fixation (PR-LCP) of the segmental femoral defect is significantly more resistant (p < 0.05) to bending forces (200 N, 300 N, and 500 N) than LCP alone (A-LCP). Stabilisation of experimental segmental lesions of the femoral diaphysis in miniature pigs by flexible bridging osteosynthesis 4.5 mm LCP in combination with the "plate and rod" construct appears to be a suitable fixation of non-reducible fractures where considerable strain of the implants by bending forces can be assumed. These findings will be used in upcoming in vivo experiments in the miniature pig to investigate bone defect healing after transplantation of mesenchymal stem cells in combination with biocompatible scaffolds., Studie se zabývá stanovením mechanických vlastností, zejména odolnost vůči ohybu, pružné opěrné osteosyntézy s použitím dvou různých kostních implantátů (4.5 mm titanium LCP a 3 mm drát, 4.5 mm titanium LCP bez drátu). Implantát stabilizuje porušenou stehenní kost.

At present, attention is focused on research into possibilities of healing large bone defects by the method of mini-invasive osteosynthesis, using implantation of biomaterials and mesenchymal stem cells (MSCs). This study evaluates the healing of segmental femoral defects in miniature pigs based on the radiological determination of the callus: cortex ratio at 16 weeks after ostectomy. The size of the formed callus was significantly larger (p < 0.05) in animals after transplantation of an autogenous cancellous bone graft (group A, callus : cortex ratio of 1.77 ± 0.33) compared to animals after transplantation of cylindrical scaffold from hydroxyapatite and 0.5% collagen (group S, callus : cortex ratio of 1.08 ± 0.13), or in animals after transplantation of this scaffold seeded with MSCs (group S + MSCs, callus: cortex ratio of 1.15 ± 0.18). No significant difference was found in the size of callus between animals of group S and animals of group S + MSCs. Unlike a scaffold in the shape of the original bone column, a freely placed autogenous cancellous bone graft may allow the newly formed tissue to spread more to the periphery of the ostectomy defect. Implanted cylindrical scaffolds (with and without MSCs) support callus formation directly in the center of original bone column in segmental femoral ostectomy, and can be successfully used in the treatment of large bone defects., V současné době se soustředí pozornost na hledání možností léčby rozsáhlých defektů kostí cestou miniinvazivní osteosyntézy, implantací biomateriálů a mezenchymových kmenových buněk. Tato studie hodnotí hojení segmentálních defektů femurů miniaturních prasat na základě rentgenologického stanovení poměru kalus:kortex za 16 týdnů po ostektomii. Velikost vzniklého svalku byla statisticky významně větší (p < 0,05) u zvířat po implantaci autogenního spongiózního štěpu (skupina A, poměr kalus:kortex 1,77 ± 0,33) ve srovnání se zvířaty po implantaci cylindrického skafoldu z hydroxyapatitu a 0,5% kolagenu (skupina S, poměr kalus:kortex 1,08 ± 0,13) a zvířaty ze skupiny S po transplantaci tohoto skafoldu osazeného MSCs (skupina S+MSCs, poměr kalus:kortex 1,15 ±0,18). Nebyl zaznamenán statisticky významný rozdíl ve velikosti svalku u zvířat ze skupin S a S + MSCs. Volně vložený autogenní spongiózní štěp může, na rozdíl od skafoldu ve tvaru původního sloupce kosti, umožňovat šíření novotvořené tkáně více k periferii ostektomického defektu. Implantované cylindrické skafoldy (s a bez MSCs) podporují tvorbu svalku přímo v místě původního sloupce kosti po segmentální ostektomii femuru, a mohou být úspěšně použity v léčbě rozsáhlých kostních defektů.

Synthesis and characterization of biodegradable hydrogels based on collagen modified by addition of synthetic biodegradable copolymer intended for preparation of porous scaffolds for mesenchymal stem cells used for possible implantation to animals with articular surface defects was investigated. The synthetic biodegradable tri-block copolymer used was the block copolymer of polyethylene glycol (PEG), polylactic acid (PLA), polyglycolic acid (PGA) (PEG-PLGA) endcapped with itaconic acid (ITA). The water-soluble carbodiimide and N-hydroxysuccimide system (EDC-NHS) was chosen as the cross-linking agent used to control the rate of hydrogel resorption. Dependence of the physical properties of the prepared hydrogels on the concentration of the EDC-NHS cross-linker, reaction time and concentration of PEG-PLGA-ITA copolymer was examined. Swelling behaviour, thermal stability, surface morphology and degradation rate were also characterized. Based on the obtained results, it can be concluded that increase in concentration of the cross-linking agent, as well as prolonged cross-linking time and increased amount of synthetic copolymer lead to enhanced thermal stability of the gels together with a reduced swelling ratio and degradation rate in saline. The resorption rate of these gels used in preparation of cartilage scaffolds can be controlled over a wide time interval by varying the collagen/(PEG-PLGA-ITA) blend composition or the conditions of the cross-linking reaction., Byla zkoumána příprava tkáňových substrátů na ázi kolagenu modifikovaného syntetickým PLA-PGA-PEG copolymerem a stabilita těchto substrátů v simulovaném tělním prostředí.