Cintilografia óssea trifásica para guiar a retirada de implantes metálicos em fraturas: estudo preliminar / Three-phase bone scintigraphy as a guide to metallic implant removal

O objetivo deste estudo foi avaliar o papel da cintilografia óssea trifásica na indicação da retirada do material de síntese de pacientes com fratura diafisária do fêmur, submetidos à fixação com haste intramedular bloqueada (HIB) ou com placa em ponte (PP), já que, atualmente, a indicação da retirada é feita por critérios não totalmente confiáveis. Foram estudados 13 pacientes, seis com colocação de HIB e sete com PP. Todos os pacientes foram submetidos a cintilografia óssea trifásica com 740MBq de MDP-99mTc em uma câmara de cintilação computadorizada. Em quatro pacientes (dois com HIB e dois com PP) houve retirada do material de síntese, em média, 42,2 meses após a fratura. Os pacientes com HIB apresentaram alterações discretas na fase tardia da cintilografia óssea e formação discreta do calo ósseo, enquanto os com PP mostraram alterações cintilográficas moderadas e formação anormal do calo ósseo. As discretas alterações descritas na cintilografia óssea nos pacientes com HlB indicam que este tipo de fixação leva a menor exigência mecânica do calo ósseo com remodelação mais fisiológica, comprovada pelo estudo tomográfico em dois pacientes, mostrando sua anatomia semelhante à do fêmur contralateral. Isto não ocorreu nos pacientes com PP, talvez devido a uma maior movimentação dos fragmentos ósseos permitida por este material. Esta movimentação sugere que este tipo de fixação talvez não seja o mais fisiológico, não proporcionando à fratura condições adequadas para se consolidar.

Biomechanical and histological evaluation of hydrogel implants in articular cartilage

We evaluated the mechanical behavior of the repaired surfaces of defective articular cartilage in the intercondylar region of the rat femur after a hydrogel graft implant. The results were compared to those for the adjacent normal articular cartilage and for control surfaces where the defects remained empty. Hydrogel synthesized by blending poly(2-hydroxyethyl methacrylate) and poly(methyl methacrylate-co-acrylic acid) was implanted in male Wistar rats. The animals were divided into five groups with postoperative follow-up periods of 3, 5, 8, 12 and 16 weeks. Indentation tests were performed on the neoformed surfaces in the knee joint (with or without a hydrogel implant) and on adjacent articular cartilage in order to assess the mechanical properties of the newly formed surface. Kruskal-Wallis analysis indicated that the mechanical behavior of the neoformed surfaces was significantly different from that of normal cartilage. Histological analysis of the repaired defects showed that the hydrogel implant filled the defect with no signs of inflammation as it was well anchored to the surrounding tissues, resulting in a newly formed articular surface. In the case of empty control defects, osseous tissue grew inside the defects and fibrous tissue formed on the articular surface of the defects. The repaired surface of the hydrogel implant was more compliant than normal articular cartilage throughout the 16 weeks following the operation, whereas the fibrous tissue that formed postoperatively over the empty defect was stiffer than normal articular cartilage after 5 weeks. This stiffness started to decrease 16 weeks after the operation, probably due to tissue degeneration. Thus, from the biomechanical and histological point of view, the hydrogel implant improved the articular surface repair.

Inflammatory reaction of rat striated muscle to particles of carbon fiber reinforced carbon

1. Carbon fiber reinforced carbon (CFRC) was implanted in rats as particles measuring 30 microns or 11 microns, denoted as CFRC-A and CFRC-B, respectively. Titanium (Ti) and vitreous carbon (VC) were used as controls. Ti was used with the same particle size as CFRC (Ti-A or Ti-B). The VC particles measured 11 microns. All materials were separately sterilized on ethylene oxide before use. 2. One hundred and ten female Wistar rats, weighing 180 to 220 g, were divided into six groups of 4 to 5 animals each, according the time of the observation (1, 2, 4, 8, 16 and 52 weeks). 3. Under aseptic conditions, one 3-0 curette full of CFRC-A or CFRC-B was implanted into the right triceps surae muscle in each animal and the same quantity of Ti-A (paired with CFRC-A) or Ti-B or VC (paired with CFRC-B) was implanted into the left muscle. 4. Histological analysis did not show necrosis of muscular tissue nor exudative reaction during the acute phase. 5. During the chronic phase the particles induced a chronic inflammatory infiltration containing fibroblasts, macrophages and giant cells. VC and CFRC-B induced the lowest inflammatory infiltration and CFRC-A induced the highest one. 6. We suggest that the longer carbon fiber fragments contained in CFRC-A may be responsible for this more intensive reaction, which may restrict the medical use of the preparation