OBJECTIVES: To evaluate the safety and efficacy of a novel bone cement-injectable cannulated pedicle screw augmented with polymethylmethacrylate in osteoporotic spinal surgery. METHODS: This study included 128 patients with osteoporosis (BMD T-score −3.2±1.9; range, −5.4 to -2.5) who underwent spinal decompression and instrumentation with a polymethylmethacrylate-augmented bone cement-injectable cannulated pedicle screw. Postoperative Visual Analogue Scale scores and the Oswestry Disability Index were compared with preoperative values. Postoperative plain radiographs and computed tomography (CT) scans were performed immediately after surgery; at 1, 3, 6, and 12 months; and annually thereafter. RESULTS: The mean follow-up time was 42.4±13.4 months (range, 23 to 71 months). A total of 418 polymethylmethacrylate-augmented bone cement-injectable cannulated pedicle screws were used. Cement extravasations were detected in 27 bone cement-injectable cannulated pedicle screws (6.46%), mainly in cases of vertebral fracture, without any clinical sequela. The postoperative low back and lower limb Visual Analogue Scale scores were significantly reduced compared with the preoperative scores (<0.01), and similar results were noted for the Oswestry Disability Index score (p<0.01). No significant screw migration was noted at the final follow-up relative to immediately after surgery (p<0.01). All cases achieved successful bone fusion, and no case required revision. No infection or blood clots occurred after surgery. CONCLUSIONS: The polymethylmethacrylate-augmented bone cement-injectable cannulated pedicle screw is safe and effective for use in osteoporotic patients who require spinal instrumentation.

RESUMEN Las fuerzas de adhesión entre asfalto y diferentes minerales fueron obtenidas empleando el microscopio de fuerza atómica (AFM). El AFM permite el estudio de la interacción entre dos moléculas en la misma superficie o en interfaces y su comportamiento. En esta investigación, varias muestras de asfalto con diferentes propiedades fueron puestas en contacto con puntas modificadas para el AFM. Estas puntas fueron fabricadas con minerales comúnmente encontrados en los agregados empleados en mezclas asfálticas, como son en dióxido de silicio (SiO2) y el carbonato de calcio (CaCO3). El trabajo de adhesión fue obtenido empleando curvas de fuerza - distancia para cada sistema asfalto-mineral. La medición directa de las fuerzas desarrolladas entre asfalto y agregado en la interface empleando técnicas nanoscopicas proveen un mejor entendimiento del sistema y sus características. Esto, sin duda alguna contribuirá en la selección de combinaciones asfalto - agregado empleadas en mezclas asfálticas que desarrollen enlaces más fuertes, produciendo sistemas más resistentes a las diferentes fallas relacionadas al fenómeno de adhesión que pueden generarse en pavimentos asfálticos.

ABSTRACT The adhesion forces between bitumen and minerals were measured, using Atomic Force Microscopy (AFM). The AFM enables the study of the interactions between two molecules in a same surface or at interfaces and their behavior. In this case, bitumen samples with different properties were placed in contact with AFM modified tips. The tips were fabricated with minerals found in aggregates used in asphalt mixtures, like silicon dioxide (SiO2) and calcium carbonate (CaCO3). The work of adhesion was obtained measuring adhesion forces for each bitumen-mineral pair. The direct measurement of forces between asphalt and aggregates at interface level through nanoscopic techniques provides a better insight of the system and its characteristics. This will help to improve the selection of bitumen-aggregate combinations used in asphalt mixtures, obtaining systems with higher bond strength, therefore more resistant to failures.

RESUMO As forças de adesão entre o asfalto e diversos minerais foram obtidas através microscópio de força atômica (AFM) O AFM possibilita o estudo entre duas moléculas na mesma superfície ou em interfaces e seu comportamento. Várias amostras de asfalto com diversas propriedades foram colocadas em contato com pontas modificadas para o AFM, nesta pesquisa. Essas pontas foram fabricadas com minerais geralmente encontrados nas adições empregadas em misturas asfálticas, tais como dióxido de silício (SiO2) e o carbonato de cálcio (CaCO3). O trabalho de adesão obteve-se empregando curvas de força (distância para cada sistema asfalto-mineral). A medição das forças desenvolvidas entre asfalto e adição na interface utilizando técnicas nanoscópicas dão uma melhor compreensão do sistema e suas características. Isso, sem dúvida nenhuma, irá contribuir na seleção de combinações asfalto - adições utilizadas em misturas asfálticas que desenvolvam ligações mais fortes, produzindo sistemas mais resistentes às diversas falhas relacionadas com o fenômeno de atrito que podem ser geradas em pavimentos asfálticos.

Two series of polyols were obtained from castor oil modified by transesterification with various amounts of pentaerythritol and glycerol. The resultant polyol properties were characterized as a function of the hydroxyl functionality. Polyurethane elastomers (PU) were synthesized from the two series of polyols obtained. The crosslink density of those polyurethanes was determined by swelling tests data adjusted to the Flory-Rehner's equation and according to the elasticity theory. The variation of the crosslink density of polyurethanes was studied by following the hydroxyl value of the modified polyol utilized in the synthesis and based on the average structure of each polyurethane repeating unit, as determined by the method of matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy (MALDI TOF MS). The results show that the PU obtained through castor oil modified with pentaerythritol had a higher crosslink density than PU obtained from unmodified castor oil and from PU prepared by transesterification reaction of castor oil with glycerol. PU based on polyols with the higher hydroxyl functionality presented the higher crosslink density.

Se obtuvo una gama de polioles a partir del aceite de ricino modificado por transesterificación con pentaeritriol y glicerina. Los productos resultantes fueron caracterizados físico-químicamente. Se sintetizaron elastómeros de poliuretano a partir de los polioles derivados del aceite de ricino modificado. La densidad de entrecruzamiento se determinó por ensayos de hinchamiento a partir de la ecuación de Flory-Rehner apoyada en la espectroscopia MALDI TOF MS para determinar la estructura química de la unidad repetitiva promedio del poliuretano. Se estudió la variación de la densidad de entrecruzamiento de los poliuretanos con base en el índice de hidroxilo del poliol utilizado en la síntesis. Los resultados muestran que los PU obtenidos a través de la modificación del aceite con pentaeritriol tienen una mayor densidad de entrecruzamiento que los PU obtenidos a partir del aceite original y de los polioles derivados de la reacción de transesterificación del aceite con glicerina, debido a que estos polioles poseen una mayor funcionalidad hidroxílica.

Castor oil was reacted by transesterification with various percentages in mass of pentaerythritol to obtain different esters of pentaerythritol. Alternatively, glycerol was also used instead of pentaerythritol for the same reaction in order to establish comparative reference products. The products of the reactions were characterized by matrix-assisted laser desorption/ionization time-of-flight mass spectroscopy in order to detect and quantify (in terms of the molecular mass and structural information) the components of the products obtained. Analysis for hydroxyl value, acid value, viscosity and specific gravity were used to complete the characterization of the polyols obtained and also of the original castor oil. The polymer characterization was accomplished by tensile stress-strain tests, Shore A hardness, thermogravimetric analysis and chemical resistance to solvents.