In vitro assessment of Function Graded (FG) artificial Hip joint stem in terms of bone/cement stresses: 3D Finite Element (FE) study

Abstract Background Stress shielding in the cemented hip prosthesis occurs due to the mismatching in the mechanical properties of metallic stem and bone. This mismatching in properties is considered as one of the main reasons for implant loosening. Therefore, a new stem material in orthopedic surgery is still required. In the present study, 3D finite element modeling is used for evaluating the artificial hip joint stem that is made of Function Graded (FG) material in terms of joint stress distributions and stem length. Method 3D finite element models of different stems made of two types of FG materials and traditional stems made of Cobalt Chromium alloy (CoCrMo) and Titanium alloy (Ti) were developed using the ANSYS Code. The effects on the total artificial hip joint stresses (Shear stress and Von Mises stresses at bone cement, Von Mises stresses at bone and stem) due to using the proposed FG materials stems were investigated. The effects on the total artificial hip joint system stresses due to using different stem lengths were investigated. Results Using FG stem (with low stiffness at stem distal end and high stiffness at its proximal end) resulted in a significant reduction in shear stress at the bone cement/stem interface. Also, the Von Mises stresses at the bone cement and stem decrease significantly when using FG material instead of CoCrMo and Ti alloy. The stresses’ distribution along the bone cement length when using FG material was found to be more uniform along the whole bone cement compared with other stem materials. These more uniform stresses will help in the reduction of the artificial hip joint loosening rate and improve its short and long term performance. Conclusion FE results showed that using FG stem increases the resultant stresses at the femur bone (reduces stress shielding) compared to metallic stem. The results showed that the stem length has significant effects on the resultant shear and Von Mises stresses at bone, stem and bone cement for all types of stem materials.</p

Articular cartilage changes associated with bony contusions in anterior cruciate ligament injury

AbstractObjectivesThe goal of the present study was to determine whether a correlation exists between bone contusions sustained with anterior cruciate ligament injury and the articular cartilage changes observed during reconstructive surgery.MethodsAcross-sectional study was conducted over 5years for consecutive knees undergoing ACL reconstruction. Clinical data, MRI evaluation, and Arthroscopic findings were reported. Analysis of the data was achieved by using the Fisher’s exact test.ResultsThirty six patients with 37 knees were included. Their mean age was 23.9years. There were 19 males and 17 females. The mean time from injury to MRI was 3months. The mean time from injury to surgery was 9.86months. Bone contusions were seen in 30% of medial femoral condyles and medial tibial plateaus.A strong correlation was observed between presence of bone contusions and articular surface damage on the medial femoral condyle (p=0.026) and the medial tibial plateau (p=0.011). There were no correlation between bone contusions and articular surface damage on the lateral femoral condyle (p=1.0) and the lateral tibial plateau (p=0.69).ConclusionAlthough lateral compartment bone contusions are more commonly seen following injury, we have not found this to be associated with the status of the overlying cartilage.Degenerative changes in the ACL-deficient knee are multifactorial, but medial compartment bone contusion may be an important contributor that warrants further investigation

Fabrication of highly porous biodegradable biomimetic nanocomposite as advanced bone tissue scaffold

Development of bioinspired or biomimetic materials is currently a challenge in the field of tissue regeneration. In-situ 3D biomimetic microporous nanocomposite scaffold has been developed using a simple lyophilization post hydrothermal reaction for bone healing applications. The fabricated 3D porous scaffold possesses advantages of good bonelike apatite particles distribution, thermal properties and high porous interconnected network structure. High dispersion bonelike apatite nanoparticles (NPs) rapidly nucleated and deposited from surrounding biological minerals within chitosan (CTS) matrices using hydrothermal technique. After that, freeze-drying method was applied on the composite solution to form the desired porous 3D architecture. Interestingly, the porosity and pore size of composite scaffold were not significantly affected by the particles size and particles content within the CTS matrix. Our results demonstrated that the compression modulus of porous composite scaffold is twice higher than that of plain CTS scaffold, indicating a maximization of the chemical interaction between polymer matrix and apatite NPs. Cytocompatibility test for MC3T3-E1 pre-osteoblasts cell line using MTT-indirect assay test showed that the fabricated 3D microporous nanocomposite scaffold possesses higher cell proliferation and growth than that of pure CTS scaffold. Collectively, our results suggest that the newly developed highly porous apatite/CTS nanocomposite scaffold as an alternative of hydroxyapatite/CTS scaffold may serve as an excellent porous 3D platform for bone tissue regeneration

Biocompatibility properties of polyamide 6/PCL blends composite textile scaffold using EA.hy926 human endothelial cells

Enhancing the cytocompatibility profiles, including cell attachment, growth and viability, of designed synthetic scaffolds, has a pivotal role in tissue engineering applications. Polymer blending is one of the most effective methods for providing new desirable biomaterials for tissue scaffolds. This article reports a novel polyamide 6/poly(ϵ-caprolactone) (PA6/PCL) blends solution which was fabricated to create composite fibrous tissue scaffolds by varying the concentration ratios of PA6 and PCL. Highly porous blends of fibrous scaffold were fabricated and their suitability as cell-support for EA.hy926 human endothelial cells was studied. Our results demonstrated that the unique nanoscale morphological properties and tune porosity of the blends scaffold were controlled. We found that these properties are mainly dependent on the PA6/PCL blending viscosity value, and the viscosity of the blending solution has an intense effect on the properties of the blends scaffold. The influence of the scaffolds extraction fluids and the scaffold direct contact of both the metabolic viability and the DNA integrity of EA.hy926 endothelial cells, as well as the cell/scaffold interaction analysis by scanning electron microscope, after different co-culturing intervals, demonstrated that PA6/PCL blend scaffolds showed different behaviors. Blend scaffolds of PA6/PCL of 90:10 ratio proved to be excellent endothelial cell carriers, which provided a good cell morphology, DNA integrity and viability, induced DNA synthesis/replication, and enhanced cell proliferation, attachment, and invasion. These results indicate that blends of PA6/PCL composite fibers are a promising 3D substitute for the next generation of synthetic tissue scaffolds that could soon find clinical applications

Thromboprophylaxis and mortality among patients who developed venous thromboembolism in seven major hospitals in Saudi Arabia

Introduction: Venous thromboembolism (VTE) during hospitalization is a serious and potentially fatal condition. Despite its effectiveness, evidence-based thromboprophylaxis is still underutilized in many countries including Saudi Arabia. Objective of the Study: Our objectives were to determine how often hospital-acquired VTE patients received appropriate thromboprophylaxis, VTE-associated mortality, and the percentage of patients given anticoagulant therapy and adherence to it after discharged. Methods: This study was conducted in seven major hospitals in Saudi Arabia. From July 1, 2009, till June 30, 2010, all recorded deep vein thrombosis (DVT) and pulmonary embolism (PE) cases were noted. Only patients with confirmed VTE diagnosis were included in the analysis. Results: A total of 1241 confirmed VTE cases occurred during the 12-month period. Most (58.3%) of them were DVT only, 21.7% were PE, and 20% were both DVT and PE. 21.4% and 78.6% of confirmed VTE occurred in surgical and medical patients, respectively. Only 40.9% of VTE cases received appropriate prophylaxis (63.2% for surgical patients and 34.8% for medical patients; P 0.05). Appropriate thromboprophylaxis was associated with 4.11% absolute risk reduction in mortality (95% confidence interval: 0.24%–7.97%). Most (89.4%) of the survived patients received anticoagulation therapy at discharge and 71.7% of them were adherent to it on follow-up. Conclusion: Thromboprophylaxis was underutilized in major Saudi hospitals denoting a gap between guideline and practice. This gap was more marked in medical than surgical patients. Hospital-acquired VTE was associated with significant mortality. Efforts to improve thromboprophylaxis utilization are warranted

Rapid fabrication of highly porous and biocompatible composite textile tubular scaffold for vascular tissue engineering

Three dimensional (3D) constructs for vascular tissue engineering applications require scaffolds with highly porous architectures, high biocompatibility and mechanical stability. In this paper, composite fibrous tubular scaffolds composed of different ratios of poly(epsilon-caprolactone) (PCL) and polyamide-6 (PA-6) were simultaneously deposited layer by layer by employing the air jet spinning (AJS) textile technique. Specifically, we report on the optimal parameters for the fabrication of composite porous scaffolds that allow for precise control over the general scaffold architecture, as well as the physical and mechanical properties of the scaffolds. In vitro cell culture study was performed to investigate the influence of polymer composition and scaffold architecture on the adhesion of EA.hy926 human endothelial cells onto the fabricated scaffolds. The cell culture results indicated that a composite scaffold with low PA-6 fibrous content is the most promising substrate for EA.hy926 adhesion and proliferation. Based on the present findings, these highly porous composite tubular constructs support endothelial cell migration and cellular infiltration, and hence represent promising nano-fibrous scaffolds for vascular tissue engineering