Factores que influyen sobre los resultados de los ensayos de ultra-microindentación ósea. Un estudio experimental en ratas / Factors that influence the results of bone ultra-microindentation tests. An experimental study in rats

OBJETIVO: Las propiedades de los materiales que constituyen el tejido óseo son determinantes en su resistencia mecánica pero los factores que influyen sobre ella son parcialmente desconocidos en la actualidad. MATERIAL Y MÉTODOS: En esta investigación medimos la dureza ósea mediante ensayos de ultra-microindentación con punta tipo Berkovich y una carga de 150 mN en fémures de ratas Sprague-Dawley sometidas a una fractura transversal o a una osteotomía de sustracción, y comparamos los resultados en diferentes localizaciones óseas y grupos experimentales. El estudio comprende los siguientes cuatro grupos experimentales, cada uno de ellos constituido por cuatro ratas: a) fractura diafisiana estándar; b) fractura más osteotomía de 2 mm; c) osteotomía tratada con hormona paratiroidea humana, PTH (1-84); d) osteotomía tratada con ranelato de estroncio. RESULTADOS: Encontramos que la dureza del material era consistentemente mayor en el hueso cortical que en el hueso trabecular. También fue consistentemente más alto en las epífisis femorales superiores que en las epífisis inferiores (diferencia de 1,2 desviaciones estándar). La cirugía redujo la dureza en el fémur operado (diferencia de 0,3 desviaciones estándar, p = 5,5 x 10-2). El tratamiento con PTH indujo un aumento leve pero consistente de la dureza en todos los sitios (p = 1,8 × 10-5) mientras que el efecto del ranelato de estroncio fue inconsistente. CONCLUSIONES: Estos datos muestran que la microdureza tisular está influida por una variedad de factores, incluyendo la anatomía, el tipo de tejido óseo, la lesión esquelética y la terapia farmacológica. Por lo tanto, los estudios futuros sobre la calidad del tejido deberían diseñarse cuidadosamente teniendo en cuenta estos factores

OBJETIVE: The properties of the materials that constitute the bone tissue are decisive in its mechanical strength but the factors that influence it are partially unknown at present. Material and method: In this paper, we gauge bone hardness by means of ultra-microindentation tests with a Berkovich tip and a 150 mN load in femurs of Sprague-Dawley rats subjected to a transverse fracture or a subtraction osteotomy. The results are compared in different bone locations and experimental groups. The study includes the following four experimental groups, each consisting of four rats: a) standard diaphyseal fracture; b) fracture plus osteotomy of 2 mm; c) osteotomy treated with human parathyroid hormone, PTH (1-84); d) osteotomy treated with strontium ranelate. RESULTS: We found the hardness of the material was consistently greater in cortical bone than in trabecular bone. It was also consistently higher in the upper femoral epiphyses than in the lower epiphyses (difference of 1.2 standard deviations). The surgery reduced hardness in the operated femur (difference of 0.3 standard deviations, p = 5.5 x 10-2). PTH treatment induced a slight but consistent increase in hardness at all sites (p = 1.8 x 10-5) while the effect of strontium ranelate was inconsistent. CONCLUSIONS: These data show that tissue micro-hardness is influenced by a variety of factors, including anatomy, type of bone tissue, skeletal injury and drug therapy. Therefore, future studies on tissue quality should be carefully designed with these factors in mind

Comparative study of the effect of PTH (1-84) and strontium ranelate in an experimental model of atrophic nonunion.

UNLABELLED: This study aimed to set up an experimental model of long bone atrophic nonunion and to explore the potential role of PTH-1-84 (PTH 1-84) and strontium ranelate (SrR). A model of atrophic nonunion was created in Sprague-Dawley rats at the femoral midshaft level. The animals were randomised into four groups. Group A1: control rodents, fracture without bone gap; Group A2: rodents with subtraction osteotomy (non-union model control) treated with saline; Group B: rodents with subtraction osteotomy treated with human-PTH (PTH 1-84); and Group C: rodents with subtraction osteotomy treated with strontium ranelate (SrR). The groups were followed for 12 weeks. X-rays were be obtained at weeks 1, 6 and 12. After sacrificing the animals, we proceeded to the biomechanical study and four point bending tests to evaluate the resistance of the callus and histological study. In second phase, the expression of genes related to osteoblast function was analysed by reverse transcription-quantitative PCR in rats subjected to substraction osteotomy and treated for 2 weeks. The animals were randomised into three groups: Group A2: rodents treated with saline; Group B: rodents treated with PTH 1-84 and Group C: rodents treated with SrR. RESULTS: No significant histological differences were found between animals subjected to subtraction osteotomy and treated with either saline or PTH (p=0.628), but significant difference existed between animals receiving saline or SrR (p=0.005). There were no significant differences in X-ray score between the saline and PTH groups at either 6 or 12 weeks (p=0.33 and 0.36, respectively). On the other hand, better X-ray scores were found in the SrR group (p=0.047 and 0.006 in comparison with saline, at 6 and 12 weeks, respectively). In line with this, biomechanical tests revealed improved results in the SrR group. Gene expression analysis revealed a slightly decreased levels of DKK1, a Wnt pathway inhibitor, in rats treated with SrR. CONCLUSIONS: SrR increases has a beneficial effect in this atrophic non-union model in rats. This suggests that it might have a role may have important implications for the potential clinical role in the treatment of fracture nonunion.

Mortalidad al año en fracturas de cadera y demora quirúrgica / Relationship between one-year mortality in hip fractures and surgical delay

Objetivo: Analizar la relación entre el retraso en la cirugía de fractura de cadera por causas administrativo organizativas y el índice de mortalidad. Material y método: Estudio retrospectivo de 634 fracturas de cadera intervenidas durante 5 años que incluían a pacientes que retrasaron su cirugía por motivos administrativo organizativos y preparados para cirugía desde el momento de su ingreso. Se excluyó a pacientes con enfermedad previa o agudizada, a menores de 65 años, con fracturas patológicas, politraumatizados, con anticoagulación o con demencia. Se comparó la mortalidad de los pacientes intervenidos el día de su ingreso o al siguiente día con los pacientes intervenidos el segundo o el tercer día y con los pacientes intervenidos más tarde. Se efectuó un análisis univariado y multivariado para estudiar la relación del retraso quirúrgico con diversas variables. Resultados: El 18,6% de los pacientes incluidos falleció al año. La edad, el sexo masculino y el riesgo quirúrgico se asociaron a una mayor mortalidad. El tipo de fractura, la cirugía y la anestesia no influyeron en el pronóstico vital. Los pacientes intervenidos el día del ingreso o al día siguiente tuvieron menor mortalidad que los intervenidos más tarde, independientemente de la edad, el sexo o el riesgo quirúrgico. Conclusiones: El índice de mortalidad en pacientes autónomos, sin enfermedad aguda al ingreso e intervenidos por fractura de cadera durante el primer día desde su ingreso hospitalario o al siguiente es significativamente menor al de los pacientes intervenidos más tarde (AU)

Purpose: To analyze the relationship between surgical delay for hip fractures due to administrative-organizational reasons and the mortality index. Materials and methods: We present a retrospective study of 634 hip fractures operated over a 5-year period. These also included patients whose surgery was postponed for organizational-administrative reasons but who were ready for surgery from the moment they were admitted. We excluded from the study patients who had a prior or an acute condition, patients under 65, patients with pathological fractures, multiple-trauma patients, and patients with anti coagulation or dementia. A comparison was made between the mortality rate of patients operated the same or the following day they were admitted with those operated the second or third days and with those operated after that. Uni- and multivariate analyses were performed to analyze the relationship between surgical delay and several variables. Results About 18.6% of patients included in the study died at one year. Age, male gender and surgical risk were associated to higher mortality. The type of fracture, surgery or anesthesia did not influence final prognosis. Patients operated the same or the following day they were admitted had a lower mortality rate than those operated subsequently, regardless of age, gender or surgical risk. Conclusions: The mortality index in autonomous patients, who did not present with an acute condition on admission and who were operated for a hip fracture the same or the following day they were admitted is significantly lower than that for patients operated at a later date (AU)