Gait analysis of patients undergoing knee endoprosthesis: functional differences between tibia and femur resections.

With the improvement in survival of patients undergoing knee reconstructive surgeries, the functional parameter became widely studied heading optimize and minimize motor sequelae. In patients undergoing knee endoprosthesis, proximal tibial or distal femoral resections affect the functioning of the knee extensor mechanism, with possible repercussions on gait. Seventeen patients were selected, divided into two groups, undergoing distal femoral or proximal tibial resection, and gait analysis examination was performed. Changes in gait velocity, cadence, step length, and alterations in the support and balance phase were observed. No major statistically significant differences were found in the kinetic and kinematic parameters between the operated groups. The study corroborates that although tibial resections have a higher theoretical risk of compromising the extensor mechanism, such data were not observed in the analyzed sample.

Fabrication and characterization of a bioactive polymethylmethacrylate-based porous cement loaded with strontium/calcium apatite nanoparticles.

Polymethylmethacrylate (PMMA)-based cements are used for bone reparation due to their biocompatibility, suitable mechanical properties, and mouldability. However, these materials suffer from high exothermic polymerization and poor bioactivity, which can cause the formation of fibrous tissue around the implant and aseptic loosening. Herein, we tackled these problems by adding Sr2+ -substituted hydroxyapatite nanoparticles (NPs) and a porogenic compound to the formulations, thus creating a microenvironment suitable for the proliferation of osteoblasts. The NPs resembled the structure of the bone's apatite and enabled the controlled release of Sr2+ . Trends in the X-ray patterns and infrared spectra confirmed that Sr2+ replaced Ca2+ in the whole composition range of the NPs. The inclusion of an effervescent additive reduced the polymerization temperature and lead to the formation of highly porous cement exhibiting mechanical properties comparable to the trabecular bone. The formation of an opened and interconnected matrix allowed osteoblasts to penetrate the cement structure. Most importantly, the gas formation confined the NPs at the surface of the pores, guaranteeing the controlled delivery of Sr2+ within a concentration sufficient to maintain osteoblast viability. Additionally, the cement was able to form apatite when immersed into simulated body fluids, further increasing its bioactivity. Therefore, we offer a formulation of PMMA cement with improved in vitro performance supported by enhanced bioactivity, increased osteoblast viability and deposition of mineralized matrix assigned to the loading with Sr2+ -substituted hydroxyapatite NPs and the creation of an interconnected porous structure. Altogether, our results hold promise for enhanced bone reparation guided by PMMA cements.

Estabilidade mecânica da fixaçäo tipo tirante de tensäo no fêmur proximal / Mechanical stability of tension band fixation in proximal femur

Foram realizados ensaios mecânicos de flexäo-compressäo e de torçäo para estudar a resistência de osteotomias intertrocantéricas com diferentes inclinaçöes do plano de secçäo, fixadas segundo o princípio da banda de tensäo. Fêmures de caes foram submetidos a osteotomias intertrocantéricas varizantes de 30 graus Celsius, de maneira que o plano de secçäo fosse transversal em um grupo e oblíquo em outro. Todas elas foram fixadas pela técnica de Pauwels, aprimorada por Weber, que consiste na transfixaçäo da osteotomia com dois fios de Kirschner e cerclagem em "oito" na facelateral do osso, tipo banda de tensäo. Foram confeccionados gráficos com momento flexor versus deformaçäo de cada ensaio e, destes, obtidos os seguintes parâmetros: inclinaçäo da curva na fase de deformaçäo elástica, momento no limite da proporcionalidade da curva e momento máximo suportado pela síntese. A osteotomia oblíqua proporcionou maior estabilidade da fixaçäo quando submetida aos esforços de flexäo-compressäo e, principalmente, aos esforços de torçäo. Concluiu-se que a inclinaçäo do plano de secçäo da osteotomia aumentou significativamente a estabilidade da fixaçäo, sendo este aspecto mais evidente nos ensaios de torçäo.