Estudio biomecánico de la tibia en el recambio de una artroplastia de rodilla / Biomechanical study of the tibia in knee replacement revision

No hay consenso en el tratamiento de elección de los recambios protésicos de rodilla con defectos óseos severos. Las opciones son variadas, cada una con sus ventajas e inconvenientes. Los trabajos clínicos publicados tienen sus limitaciones en cuanto al número de pacientes y el poco seguimiento clínico. Se presenta un trabajo biomecánico con elementos finitos comparativo de 5 diseños de implantes tibiales: vástago recto, con offset con/sin suplemento y vainas con/sin vástago, para poder analizar el comportamiento tanto del hueso tibial como del material a lo largo del tiempo. Dentro de las limitaciones que presenta un modelo matemático hemos podido ver que los implantes con vástago recto producen el mayor valor de reabsorción ósea alrededor del vástago, mientras que la menor reabsorción ósea tiene lugar en el hueso de la diáfisis proximal. Las vainas metafisarias tibiales sin vástago producen una menor reabsorción ósea que el resto en el canal medular (AU)

The best management of severe bone defects following total knee replacement is still controversial. Metal augments, tantalum cones and porous tibial sleeves could help the surgeon to manage any type of bone loss, providing a stable and durable knee joint reconstruction. Five different types of prostheses have been analysed: one prosthesis with straight stem; two prostheses with offset stem, with and without supplement, and two prostheses with sleeves, with and without stem. The purpose of this study is to report a finite element study of revision knee tibial implants. The main objective was to analyse the tibial bone density changes and Von Misses tension changes following different tibial implant designs. In all cases, the bone density decreases in the proximal epiphysis and medullary channels, with a bone density increase also being predicted in the diaphysis and at the bone around the stems tips. The highest value of Von Misses stress has been obtained for the straight tibial stem, and the lowest for the stemless metaphyseal sleeves prosthesis (AU)

Effect of intermittent administration of hPTH(1-34) on cortical bone geometry in rats treated with high-dose glucocorticoids.

High-dose glucocorticoids reduce cortical bone gain in rats. The aim of the present study was to examine the effect of the intermittent administration of human parathyroid hormone (1-34) (hPTH[1-34]) on cortical bone in rats treated with high-dose prednisolone (PSL). Twenty-five female Sprague-Dawley rats (6 weeks old) were randomized into the following three groups: a vehicle administration (control) group, a PSL (10 mg/kg s.c., 5 times a week) administration group, and a PSL + hPTH(1-34) (30 µg/kg s.c., 3 times a week) administration group. After 8 weeks of treatment, the bone mineral density (BMD) of the femoral diaphysis was determined using peripheral quantitative computed tomography, and a static bone histomorphometric analysis was performed on the tibial diaphysis. PSL administration induced a decrease in the BMD of the femoral diaphysis, compared with the control group, as well as decreases in the total tissue area, cortical area, percent cortical area, and periosteal perimeter and increases in the marrow area, percent marrow area, and endocortical perimeter of the tibial diaphysis, compared with the control group. The intermittent administration of hPTH(1-34) to PSL-treated rats attenuated PSL-related changes in the BMD of the femoral diaphysis and the percent cortical area, marrow area, percent marrow area, and endocortical perimeter of the tibial diaphysis. The findings of the present study suggest that the intermittent administration of hPTH(1-34) improves cortical BMD, acts on the endocortical bone surface, and improves cortical bone geometry, in rats treated with highdose PSL.

Local insulin therapy affects fracture healing in a rat model.

A significant number of lower extremity fractures result in mal-union necessitating effective treatments to restore ambulation. Prior research in diabetic animal fracture models demonstrated improved healing following local insulin application to the fracture site and indicated that local insulin therapy can aid bone regeneration, at least within an insulin-dependent diabetic animal model. This study tested whether local insulin therapy could accelerate femur fracture repair in normal, non-diabetic rats. High (20 units) and low (10 units) doses of insulin were delivered in a calcium sulfate carrier which provided sustained release of the exogenous insulin for 7 days after fracture. Histomorphometry, radiographic scoring, and torsional mechanical testing were used to measure fracture healing. The fracture calluses from rats treated with high-dose insulin had significantly more cartilage than untreated rats after 7 and 14 days of healing. After 4 weeks of healing, femurs from rats treated with low-dose insulin had significantly higher radiographic scores and mechanical strength (p < 0.05), compared to the no treatment control groups. The results of this study suggest that locally delivered insulin is a potential therapeutic agent for treating bone fractures. Further studies are necessary, such as large animal proof of concepts, prior to the clinical use of insulin for bone fracture treatment.

Effect of Epimedium pubescen flavonoid on bone mineral density and biomechanical properties of femoral distal end and femoral diaphysis of passively smoking male rats.

BACKGROUND: Based on a rat model of human relatively high exposure to cigarette smoke, this study aimed to estimate whether Epimedium pubescen flavonoid (EPF) may prevent a smoke-induced decrease in bone mineral density (BMD) and weakening of the biomechanical properties of bone. METHODS: Fifty male Wistar rats were randomized into five groups: controls, passively smoking groups and passively smoking rats administered EPF at three dosage levels (75, 150 or 300 mg/kg/day) in drinking water for 4 months. A rat model of passive cigarette smoking was prepared by breeding male rats in a cigarette-smoking box for 4 months. Bone metabolic makers, BMD and biomechanical properties of the femoral distal end and femoral diaphysis were examined. RESULTS: Exposure to cigarette smoke decreased the BMD, affected bone turnover (inhibited bone formation and stimulated its resorption) and weakened the biomechanical properties of the femur at its distal end and diaphysis. EPF supplementation during cigarette smoke exposure prevented the decrease in BMD, accelerated bone turnover and weakened the biomechanical properties of bone. CONCLUSION: Our data suggest that EPF supplementation can prevent the adverse effects of smoke exposure on BMD and biomechanical properties by inhibiting bone turnover and preventing bone resorption, and in this way it can decrease the risk of bone fractures.

Mechanical assessment of effects of grape seed proanthocyanidins extract on tibial bone diaphysis in rats.

We studied the effects of grape seed proanthocyanidins extract (GSPE) given as a ratio of 3 mg in 100 g in a standard diet, on the tibial bone diaphysis in low-calcium fed rats. Measurements of bone density, mineral content, geometry, and bone strength using peripheral quantitative computed tomography (pQCT). Further, the whole tibia bones were tested for mechanical resistance using a material-testing machine, and mineral elements were also determined. Forty male Wistar rats, 5 weeks old, were divided into control (Co), low-calcium diet (LC), low-calcium diet . standard diet (LCS), and low-calcium diet . standard diet with supplementary GSPE (LCSG) groups. We found no significant differences in body weight among the 4 groups, whereas all of the bone parameters in LC were significantly lower than those in Co (p<0.01, except in periosteal perimeter (Peri) p<0.05). The cortical bone mineral content (CtBMC), cortical bone density (CtvBMD) and Peri in LCSG were significantly higher than those in LCS (p<0.01; p<0.01; p<0.05, respectively). All bone parameters in LCSG were significantly higher than those in LC (p<0.01, except in Peri, and stress strain index to reference axis x (xSSI) p<0.05)). In addition, Ca, P, and Zn contents in LCSG were significantly higher than those in LCS (p<0.01; p<0.01; p<0.05, respectively). Our results suggest that GSPE included in a diet mixture with calcium has a beneficial effect on bone formation and bone strength for the treatment of bone debility caused by a low level of calcium.

Dynamic bone remodeling in later Pleistocene fossil hominids.

Histomorphometric analysis of femoral and tibial diaphyseal fragments from seven Late Archaic and three Early Modern humans are compared with those of the Pecos, a pre-Columbian Native American population. The ten samples, from Broken Hill (EM-793), Shanidar 2, 3, 4, 5, and 6, Tabun 1, and Skhul 3, 6, and 7, provide age-at death results consistent with earlier estimates for most individuals. The Pleistocene groups exhibit less bone turnover and smaller osteons than Recent populations. Resorption and formation were both coupled and balanced in these Pleistocene populations, but the overall vigor of individual cells from both the osteoclast and osteoblast cell lines was less than in Recent populations. Thus the greater bone mass in Later Pleistocene members of the genus Homo is not the result of higher levels of bone turnover, at least among adults.