Controlled surface nanotopography and oxygen plasma treatment of PEEK to improve cellular response

Poly(aryl-ether-ether-ketone) (PEEK) is a semi crystalline polymer which exhibits properties that make it an attractive choice for use as an implant material. It displays natural radiolucency, and MRI compatibility, as well as good chemical and sterilization resistance, both of which make it of particular interest in orthopaedic implants. However, PEEK has demonstrated poor cellular adhesion both in vitro and in vivo. This is problematic as implant surfaces that do not develop a layer of adhesive cells are at risk of undergoing fibrous encapsulation, which in turn leads to lack of a strong interface between the implant device and the patient tissue, which can in turn lead to failure of the implant and revision surgery . As incorporating nanotopography into a polymer surface has been demonstrated to be able to direct the differentiation behaviour of stem cells, a possible solution to PEEKs underlying issues with poor cellular response would be to incorporate specific nanoscale topography into the material surface through injection moulding, and then analysing if this is a viable method for addressing PEEKs issues with cellular response. In addition to nanoscale topography, the experimental PEEK surfaces were treated with oxygen plasma to address the underlying cytophobicity of the material. As this type of treatment has been documented to be capable of etching the PEEK surface, experiments were carried out to quantify the effect of this treatment, both on the ability of cells to adhere to the PEEK surface, as well as the effect it has upon the nanotopography present at the PEEK surface. The results demonstrated that there were a range of plasma treatments which would significantly improve the ability of cells to adhere to the PEEK surface without causing unacceptable damage to the nanotopography. Three different types of cells with osteogenic capacity were tested with the PEEK surfaces to gauge the ability of the topography to alter their behaviour: SAOS-2, osteoprogenitors and 271+ MSCs. Due to PEEKs material properties (it is non transparent, exhibits birefringence and is strongly autofluorescent) a number of histological techniques were used to investigate a number of different stages that take place in osteogenesis. The different cell types did display slightly different responses to the topographies. The SAOS-2 cells cultured on surfaces that had been plasma treated for 2 minutes at 200W had statistically significantly higher levels of von Kossa staining on the NSQ surface compared to the planar surface, and the same experiment employing alizarin red staining, showed a statistically significantly lower level of staining on the SQ surface compared to the planar surface. Using primary osteoprogenitor cells designed to look into if whether or not the presence of nanotopography effected the osteogenic response of these cells, we saw a lack of statistically significant difference produced by the surfaces investigated. By utilising HRP based immunostaining, we were able to investigate, in a quantitative fashion, the production of the two osteogenic markers osteopontin and osteocalcin by cells. When stained for osteocalcin, the SQ nanotopography had total percentage of the surface with stained material, average area and average perimeter all statistically significantly lower than the planar surface. For the cells that were stained for osteopontin, the SQ nanotopgraphy had a total percentage of the surface with stained material, average area and average perimeter all highly statistically significantly lower than those of the planar surface. Additionally, for this marker the NSQ nanotopography had average areas and average perimeters that were highly significantly higher than those of the planar surface. There were no significant differences for any of the values investigated for the 271+ MSC’s When plasma treatment was varied, the SAOS-2 cells demonstrated an overall trend i.e. increasing the energy of plasma treatment in turn leads to an increase in the overall percentage of staining. A similar experiment employing stem cells isolated from human bone marrow instead of SAOS-2 cells showed that for polycarbonate surfaces , used as a control, mineralization is statistically significantly higher on the NSQ nanopattern compared to the planar surface, whereas on the PEEK surfaces we observe the opposite trend i.e. the NSQ nanotopography having a statistically significantly lower amount of mineralization compared to the planar surface at the 200W 2min and 30W 1min plasma treatments. The standout trend from the PEEK results in this experiment was that the statistically significant differences on the PEEK substrates were clustered around the lower energy plasma treatments, which could suggest that the plasma treatment disrupted a function of the nanotopograhy which is why, as the energy increases, there are less statistically significant differences between the NSQ nanotopography and the Planar surface This thesis documents the response of a number of different types of cells to specific nanoscale topographies incorporated into the PEEK surface which had been treated with oxygen plasma. It outlines the development of a number of histological methods which measure different aspects of osteogenesis, and were selected to both work with PEEK, and produce quantitative results through the use of Cell Profiler. The methods that have been employed in this body of work would be of interest to other researchers working with this material, as well as those working with similarly autofluorescent materials.

Primary Joint Arthroplasty Surgery: Is the Risk of Major Bleeding Higher in Elderly Patients? A Retrospective Cohort Study

Increased risk of bleeding after major orthopedic surgery (MOS) has been widely documented in general population. However, this complication has not been studied in elderly patients. The purpose of this study is to determine whether the risk of major bleeding after MOS is higher in elderly patients, compared with those operated at a younger age. Methods: This retrospective cohort study included total hip and total knee arthroplasty patients operated during 5 consecutive years. The main outcome was the occurrence of major bleeding. Patients with other causes of bleeding were excluded. Relative risks (RRs) and confidence intervals (CIs) were calculated, anda multivariate analysis was performed. Results: A total of 1048 patients were included, 56% of patients were hip arthroplasties. At the time of surgery, 553 (53%) patients were older than 70 years. Patients aged >70 years showed an increased risk of major bleeding (RR: 2.42 [95% CI: 1.54-3.81]). For hip arthroplasty, the RR of bleeding was 2.61 (95%CI: 1.50-4.53) and 2.25 (95% CI: 1.03-4.94) for knee arthroplasty. After multivariate analysis, age was found to be independently associated with higher risk of major bleeding. Conclusion: According to European Medicines Agency criteria, patients aged 70 years are at a higher risk of major bleeding after MOS, result of a higher frequency of blood transfusions in this group of patients. Standardized protocols for blood transfusion in these patients are still required.

Impact on hip fracture mortality after the establishment of an orthogeriatric care program in a colombian hospital

El objetivo del estudio es evaluar la mortalidad a un año en pacientes con fractura de cadera, mayores de 65 años tratados en un programa establecido de orto-geriatría. 298 se trataron de acuerdo al protocolo de orto-geriatría, se calculo la mortalidad a un año, se establecieron los predictores de mortalidad orto-geriátrico. La sobrevida anual se incremento de 80% a 89% (p = .039) durante los cuatro años de seguimiento del programa y disminuyo el riesgo de mortalidad anual postoperatorio (Hazard Ratio = 0.54, p = .049). La enfermedad cardiaca y la edad maor a 85 años fueron predictores positivos para mortalidad.

Luxación esternoclavicular posterior

Paciente masculino de 24 años, ingresa a urgencias por trauma contundente en clavícula derecha durante accidente de tránsito. Presenta dolor en articulación esternoclavicular que se exacerba con la movilización del hombro y disfagia. Al examen físico, leve depresión del extremo medial de la clavícula y limitación de los arcos de movimiento del hombro. Las imágenes confirmaron el diagnostico de LEC posterior. El paciente fue llevado a cirugía para reducción y cerclaje, sin complicaciones.

Factores asociados a transfusión sanguínea en el manejo quirúrgico del canal lumbar estrecho en la Fundación Santa Fe de Bogotá 2003 - 2013

Introduccion: El canal lumbar estrecho es un motivo de consulta frecuente en el servicio de columna de la Fundación Santa Fe de Bogotá. Derivado del tratamiento quirurgico se pueden generar múltiples complicaciones, entre las que se encuentra la transfusión sanguínea. Objetivo: Identificar los factores sociodemográficos, antecedentes personales y factores quirúrgicos asociados a transfusión sanguínea en cirugía canal lumbar estrecho en la Fundación Santa Fe de Bogotá 2003- 2013. Materiales y métodos: Se aplicó en diseño de estudio observacional analítico transversal. Se incluyeron 367 pacientes sometidos a cirugía de canal lumbar estrecho a quienes se les analizaron variables de antecedentes personales, características sociodemograficas y factores quirúrgicos. Resultados: La mediana de la edad fue de 57 años y la mayoría de pacientes fueron mujeres (55,6%). La mediana del Índice de Masa Corporal (IMC) fue de 24,9 clasificado como normal. Entre los antecedentes patológicos, la hipertensión arterial fue el más común (37,3%). La mayoría de pacientes (59,1%) presentaron clasificación ASA de II. El tipo de cirugía más prevalente fue el de descompresión (55,6%). En el 79,8% de los pacientes se intervinieron 2 niveles. Se realizó transfusión de glóbulos rojos en 26 pacientes correspondiente a 7,1% del total. En la mayoría de procedimientos quirúrgicos (42,5%) el sangrado fue clasificado como moderado (50-500 ml). En el modelo explicativo transfusión sanguínea en cirugía de canal lumbar estrecho se incluyen: antecedente de cardiopatía (OR 4,68, P 0,034, IC 1,12 – 19,44), Sangrado intraoperatorio >500ml (OR 6,74, p 0,001, 2,09 – 21,74) y >2 niveles intervenidos (OR 3,97, p 0,023, IC 1,20 – 13,09). Conclusión: Como factores asociados a la transfusión sanguínea en el manejo quirúrgico del canal lumbar estrecho a partir de la experiencia de 10 años en la Fundación Santa Fe de Bogotá se encontraron: enfermedad cardiaca, sangrado intraoperatorio mayor de 500ml y más de dos niveles intervenidos.

Evaluación de costo efectividad de la profilaxis versus tratamiento a demanda en pacientes con Hemofilia A moderada y severa para prevenir sangrado articular de una aseguradora en Colombia

Introducción: En Colombia existe un protocolo de manejo para pacientes con hemofilia A severa sin inhibidores que recomienda el manejo de profilaxis primaria y secundaria con FVIII. Objetivos: Estimar la relación incremental de costo-efectividad (RICE) de la profilaxis con Factor VIII vs tratamiento a demanda para prevenir sangrados articulares en pacientes con hemofilia A moderada y severa de una aseguradora en Colombia. Materiales y Métodos: Se adaptó un modelo de Markov desde la perspectiva del tercer pagador. Las probabilidades de transición se ajustaron mediante un modelo de regresión logística multinomial explicadas por la edad y el peso. Las tasas de eventos son anuales. Las efectividades se extrajeron de la cohorte de la aseguradora y de la literatura. Los costos incluyeron el FVIII, medicamentos, hospitalización, procedimientos quirúrgicos, apoyo diagnóstico y consultas médicas. La tasa de descuento fue del 3%. Resultados: En pacientes con hemofilia A moderada y severa la profilaxis con FVIII evitará en promedio 7 sangrados articulares, el RICE para el sangrado articular es de $303.457. Conclusiones: La profilaxis con Factor VIII es una estrategia costo-efectiva en el manejo de pacientes con hemofilia A moderada y severa para la aseguradora, disminuyendo el número de sangrados articulares al año.