Surface pretreatments for medical application of adhesion

Medical implants and prostheses (artificial hips, tendono- and ligament plasties) usually are multi-component systems that may be machined from one of three material classes: metals, plastics and ceramics. Typically, the body-sided bonding element is bone. The purpose of this contribution is to describe developments carried out to optimize the techniques , connecting prosthesis to bone, to be joined by an adhesive bone cement at their interface. Although bonding of organic polymers to inorganic or organic surfaces and to bone has a long history, there remains a serious obstacle in realizing long-term high-bonding strengths in the in vivo body environment of ever present high humidity. Therefore, different pretreatments, individually adapted to the actual combination of materials, are needed to assure long term adhesive strength and stability against hydrolysis. This pretreatment for metal alloys may be silica layering; for PE-plastics, a specific plasma activation; and for bone, amphiphilic layering systems such that the hydrophilic properties of bone become better adapted to the hydrophobic properties of the bone cement. Amphiphilic layering systems are related to those developed in dentistry for dentine bonding. Specific pretreatment can significantly increase bond strengths, particularly after long term immersion in water under conditions similar to those in the human body. The bond strength between bone and plastic for example can be increased by a factor approaching 50 (pealing work increasing from 30 N/m to 1500 N/m). This review article summarizes the multi-disciplined subject of adhesion and adhesives, considering the technology involved in the formation and mechanical performance of adhesives joints inside the human body

Drug dosing during pregnancy—opportunities for physiologically based pharmacokinetic models

Drugs can have harmful effects on the embryo or the fetus at any point during pregnancy. Not all the damaging effects of intrauterine exposure to drugs are obvious at birth, some may only manifest later in life. Thus, drugs should be prescribed in pregnancy only if the expected benefit to the mother is thought to be greater than the risk to the fetus. Dosing of drugs during pregnancy is often empirically determined and based upon evidence from studies of non-pregnant subjects, which may lead to suboptimal dosing, particularly during the third trimester. This review collates examples of drugs with known recommendations for dose adjustment during pregnancy, in addition to providing an example of the potential use of PBPK models in dose adjustment recommendation during pregnancy within the context of drug-drug interactions. For many drugs, such as antidepressants and antiretroviral drugs, dose adjustment has been recommended based on pharmacokinetic studies demonstrating a reduction in drug concentrations. However, there is relatively limited (and sometimes inconsistent) information regarding the clinical impact of these pharmacokinetic changes during pregnancy and the effect of subsequent dose adjustments. Examples of using pregnancy PBPK models to predict feto-maternal drug exposures and their applications to facilitate and guide dose assessment throughout gestation are discussed

Evaluation of a minimally invasive procedure for sacroiliac joint fusion – an in vitro biomechanical analysis of initial and cycled properties

Derek P Lindsey,1 Luis Perez-Orribo,2 Nestor Rodriguez-Martinez,2 Phillip M Reyes,2 Anna Newcomb,2 Alexandria Cable,2 Grace Hickam,2 Scott A Yerby,1 Neil R Crawford21SI-BONE, Inc., San Jose, CA, USA; 2Spinal Biomechanics Research Laboratory, Barrow Neurological Institute, St Joseph's Hospital and Medical Center, Phoenix, AZ, USAIntroduction: Sacroiliac (SI) joint pain has become a recognized factor in low back pain. The purpose of this study was to investigate the effect of a minimally invasive surgical SI joint fusion procedure on the in vitro biomechanics of the SI joint before and after cyclic loading.Methods: Seven cadaveric specimens were tested under the following conditions: intact, posterior ligaments (PL) and pubic symphysis (PS) cut, treated (three implants placed), and after 5,000 cycles of flexion–extension. The range of motion (ROM) in flexion–extension, lateral bending, and axial rotation was determined with an applied 7.5 N • m moment using an optoelectronic system. Results for each ROM were compared using a repeated measures analysis of variance (ANOVA) with a Holm–Šidák post-hoc test.Results: Placement of three fusion devices decreased the flexion–extension ROM. Lateral bending and axial rotation were not significantly altered. All PL/PS cut and post-cyclic ROMs were larger than in the intact condition. The 5,000 cycles of flexion–extension did not lead to a significant increase in any ROMs.Discussion: In the current model, placement of three 7.0 mm iFuse Implants significantly decreased the flexion–extension ROM. Joint ROM was not increased by 5,000 flexion–extension cycles.Keywords: biomechanics, iliosacral, arthrodesis, cadave

Correlação entre o posicionamento dos parafusos pediculares no corpo vertebral e sua força de arrancamento Correlation between pedicular screws positioning on vertebral body and its pullout strength

O objetivo foi estudar as alterações da força de fixação dos parafusos pediculares nos corpos vertebrais ao variar a angulação durante o reposicionamento. Foram utilizados 8 suínos, totalizando 40 vértebras lombares. Dividimos em 4 grupos de estudo. No primeiro grupo os parafusos foram colocados a 0º (zero graus), no segundo introduzidos, retirados e recolocados na mesma posição (zero graus), no terceiro houve uma variação da angulação de 14º no reposicionamento e no quarto uma variação da angulação inicial de 28 graus. Todos os parafusos foram testados quanto à força de arrancamento. No resultado o grupo I apresentou uma média de arrancamento de 146,85N; o grupo II uma média de arrancamento de 77,34N. O grupo III 97,75N. O grupo IV teve uma média de 110,02N. Isso mostrou a necessidade de evitar o reposicionamento dos parafusos devido a perda de força de fixação no corpo vertebral. Quando reposicionados recolocá-los em angulações as mais diferentes possíveis da inicial, comprometendo assim, o mínimo possível a fixação.<br>The objective of this paper was to study pedicular screws fixation strength on vertebral bodies by varying its repositioning angle. For this Study, eight pigs were selected, making up a total of 40 lumbar vertebrae, which were divided into 4 study groups. In the first group, the screws were inserted at zero degree, and in the second group, they were inserted and reinserted at the same position, while in the third group, the screws were reinserted within a 14-degree range, and, in the fourth group, within a 28-degree range. All screws were tested for pullout strength. Group I presented a pullout average of 146.85N. Group II presented a pullout average of 77.34N. Group III had an average of 97.75N. Group IV had an average of 110.02. It was concluded that the procedure of replacing screws should be avoided. Should any repositioning is required, this should be performed by changing repositioning angles as much far from the first one as possible