Soon Yong Kwon

Enhanced Cell Integration to Titanium Alloy by Surface Treatment with Microarc Oxidation: A Pilot Study

Microarc oxidation (MAO) is a surface treatment that provides nanoporous pits, and thick oxide layers, and incorporates calcium and phosphorus into the coating layer of titanium alloy. We presumed such modification on the surface of titanium alloy by MAO would improve the ability of cementless stems to osseointegrate. We therefore compared the in vitro ability of cells to adhere to MAOed titanium alloy to that of two different types of surface modifications: machined and grit-blasted. We performed energy-dispersive x-ray spectroscopy and scanned electron microscopy investigations to assess the structure and morphology of the surfaces. Biologic and morphologic responses to osteoblast cell lines (SaOS-2) were then examined by measuring cell proliferation, cell differentiation (alkaline phosphatase activity), and αvβ3 integrin. The cell proliferation rate, alkaline phosphatase activity, and cell adhesion in the MAO group increased in comparison to those in the machined and grit-blasted groups. The osteoblast cell lines of the MAO group were also homogeneously spread on the surface, strongly adhered, and well differentiated when compared to the other groups. This method could be a reasonable option for treating the surfaces of titanium alloy for better osseointegration.

The Biocompatibility of Silk Scaffold for Tissue Engineered Ligaments

The aim of this study was to estimate the mechanical properties and evaluate the biocompatibility of silk and PGA scaffolds as an artificial ligament to an ACL reconstruction. The scaffold for the artificial ligament was braided / knitted silk or PGA thread. The mechanical properties, cell growth, and subcutaneous tissue reactions were determined for both types of scaffolds. The breaking load of the PGA scaffold was double that of the sericin removed silk scaffold (SRSS). However, the initial attachment and growth of human ACL cells on the SRSS was superior to the PGA scaffold. In addition, the immune response was significantly higher on the PGA scaffold after 72 h (p<0.05) compared with the sericin removed silk scaffold by T lymphocyte and mononuclear cells (MNCs) in vitro cultures. In vivo, the ACL scaffold made from silk or PGA were implanted in the subcutaneous layer in rats and harvested 1 week later. A histological evaluation of the scaffolds explants revealed the presence of monocytes in the SRSS, and an absence of giant cells in all cases. An inflammatory tissue reaction was more conspicuous around the silk scaffold containing sericin and even more around the PGA scaffold compared with SRSS. These results support the conclusion that a properly prepared SRSS, aside from providing benefits in terms of biocompatibility both in vitro and in vivo, can provide suitable scaffolds for the support of ACL cell growth. These results suggest that a SRSS for ACL repair can overcome the current limitations with the PGA scaffold. And SRSS is biocompatible, and the in vitro T cell and MNCs culture model showed inflammatory responses that were comparable to those observed in vivo.

The Otto Aufranc Award: Enhanced Biocompatibility of Stainless Steel Implants by Titanium Coating and Microarc Oxidation

BackgroundStainless steel is one of the most widely used biomaterials for internal fixation devices, but is not used in cementless arthroplasty implants because a stable oxide layer essential for biocompatibility cannot be formed on the surface. We applied a Ti electron beam coating, to form oxide layer on the stainless steel surface. To form a thicker oxide layer, we used a microarc oxidation process on the surface of Ti coated stainless steel. Modification of the surface using Ti electron beam coating and microarc oxidation could improve the ability of stainless steel implants to osseointegrate.Questions/purposesThe ability of cells to adhere to grit-blasted, titanium-coated, microarc-oxidated stainless steel inxa0vitro was compared with that of two different types of surface modifications, machined and titanium-coated, and microarc-oxidated.MethodsWe performed energy-dispersive x-ray spectroscopy and scanning electron microscopy investigations to assess the chemical composition and structure of the stainless steel surfaces and cell morphology. The biologic responses of an osteoblastlike cell line (SaOS-2) were examined by measuring proliferation (cell proliferation assay), differentiation (alkaline phosphatase activity), and attraction ability (cell migration assay).ResultsCell proliferation, alkaline phosphatase activity, migration, and adhesion were increased in the grit-blasted, titanium-coated, microarc-oxidated group compared to the two other groups. Osteoblastlike cells on the grit-blasted, titanium-coated, microarc-oxidated surface were strongly adhered, and proliferated well compared to those on the other surfaces.ConclusionsThe surface modifications we used (grit blasting, titanium coating, microarc oxidation) enhanced the biocompatibility (proliferation and migration of osteoblastlike cells) of stainless steel.Clinical RelevanceThis process is not unique to stainless steel; it can be applied to many metals to improve their biocompatibility, thus allowing a broad range of materials to be used for cementless implants.

Postoperative Mortality and Factors Related to Mortality After Bipolar Hemiarthroplasty in Patients With Femoral Neck Fractures

The purpose of this study was to determine the mortality rate and factors related to mortality in elderly patients with acute and monotraumatic femoral neck fractures. This study included 241 patients with femoral neck fractures after bipolar hemiarthroplasty. We analyzed the mortality rate and the relationship between postoperative mortality and risk factors, such as age, sex, body mass index, the time to surgery, and the Society of Anesthesiologists score. The postoperative mortality rate 1 and 3 years after surgery was 11.2% and 19.5%, respectively. There proved to be a relationship between postoperative mortality and age, the time to surgery, and the Society of Anesthesiologists score. We recommend that surgery should not be delayed, and caution should be exercised for the high-risk group patients.

In vitro effects of mussel-inspired polydopamine coating on Ti6Al4V alloy

Mussel adhesion phenomena in nature have inspired the integration of inorganic hydroxyapatite (HA) crystals within versatile materials. One example is the simple, aqueous, two-step functionalization approach, called polydopamine-assisted hydroxyapatite formation (pHAF), which consists of the chemical activation of material surfaces via polydopamine coating and the growth of hydroxyapatite in a simulated body fluid (SBF). For this study, we anticipated that such a polydopamine coating on the surface of titanium (Ti) alloy would improve the ability of cementless stems to osseointegrate. We compared the in vitro ability of cells to adhere to polydopamine-coated Ti alloy and machined Ti alloy. We performed energy-dispersive x-ray spectroscopy (EDS) and scanning electron microscopy (SEM) investigations to assess the structure and morphology of the surfaces. Biological and morphological responses to osteoblast cell lines (MC3T-E1) were then examined by measuring cell proliferation, cell differentiation (alkaline phosphatase (ALP) activity), and actin filament formation. Real-time polymerase chain reaction (PCR) was used to analyze gene expression for osteocalcin, osteonectin, and osteoprotegerin. Cell proliferation and ALP activity in the polydopamine-coated Ti alloy did not differ statistically compared to the other group. The polydopamine-coated Ti alloy exhibited better apatite formation ability than the untreated alloy, as evidenced by apatite formation after SBF immersion for 10 days. Molecular biological analysis did not differ statistically between the groups. The surface modification of the Ti alloy by coating with polydopamine did not change the biological properties of the Ti alloy. This may make some difficulties for osteogenesis signaling for the cells.