Influence of steel implant surface microtopography on soft and hard tissue integration

The experimental study of tissue integration into porous titanium implants

INTRODUCTION

Due to a lack of uniform shapes and sizes of bone defects in hip and knee joint pathology, their fixing could benefit from using individually manufactured 3D-printed highly porous titanium implants. The objective of this study was to evaluate the extent of bone and muscle tissue integration into porous titanium implants manufactured using additive technology.

MATERIALS AND METHODS

Porous and non-porous titanium plates were implanted into the latissimus dorsi muscle and tibia of 9 rabbits. On days 1, 60 and 90 animals were examined with x-rays. On day 60 histological tests were carried out. On day 90 the tensile strength at the implant-tissue interface was tested.

RESULTS

Histological analysis of muscle samples with porous titanium implants showed integration of connective tissue and blood vessels into the pores. Bone defect analysis demonstrated bone ingrowth into the pores of titanium with a minimal amount of fibrous tissue. The tensile strength of the muscular tissue attachment to the porous titanium was 28 (22-30) N which was higher than that of the control group 8.5 (5-11) N. Bone tissue attachment strength was 148 (140-152) N in the experimental group versus 118 (84-122) N in the control group.

CONCLUSIONS

Using additive technology in manufacturing 3D-printed highly porous titanium implants improves bone and muscle integration compared with the non-porous material of the control group. This could be a promising approach to bone defect repair in revision and reconstruction surgery.

Biocompatibility and Osseointegration of Calcium Phosphate-Coated and Non-Coated Titanium Implants with Various Porosities

The aim of the investigation was to study the influence of pore size and the presence of a biologically active calcium phosphate coating in porous 3D printed titanium implants on the process of integration with the bone tissue.

Materials and Methods

Samples of cylindrical implants with three different pore diameters (100, 200, and 400 μm) were fabricated from titanium powder on the Arcam 3D printer (Sweden) using electron beam melting technology. A calcium phosphate coating with a thickness of 20±4 μm was applied to some of the products by microarc oxidation. Cytotoxicity of the implants was determined in vitro on human dermal fibroblast cultures. The samples were implanted in the femoral bones of 36 rabbits in vivo. The animals were divided into 6 groups according to the bone implant samples. The prepared samples and peri-implant tissues were studied on days 90 and 180 after implantation using scanning electron microscopy and histological methods.

Results

All samples under study were found to be non-toxic and well biocompatible with the bone tissue. There were revealed no differences between coated and non-coated implants of 100 and 200 μm pore diameters in terms of their histological structure, intensity of vascularization in the early stages, and bone formation in the later stages. Samples with pore diameters of 100 and 200 μm were easily removed from the bone tissue, the depth of bone growth into the pores of the implant was lower than in the samples with pore diameter of 400 μm (p<0.001). There were differences between coated and non-coated samples of 400 μm pore diameter, which was expressed in a more intensive osseointegration of samples with calcium phosphate coating (p<0.05).

Conclusion

The optimal surface characteristics of the material for repairing bone defects are a pore diameter of 400 μm and the presence of a calcium phosphate coating.

Strategies for improving antimicrobial properties of stainless steel

In this review, strategies for improving the antimicrobial properties of stainless steel (SS) are presented. The main focus given is to present current strategies for surface modification of SS, which alter surface characteristics in terms of surface chemistry, topography and wettability/surface charge, without influencing the bulk attributes of the material. As SS exhibits excellent mechanical properties and satisfactory biocompatibility, it is one of the most frequently used materials in medical applications. It is widely used as a material for fabricating orthopedic prosthesis, cardiovascular stents/valves and recently also for three dimensional (3D) printing of custom made implants. Despite its good mechanical properties, SS lacks desired biofunctionality, which makes it prone to bacterial adhesion and biofilm formation. Due to increased resistance of bacteria to antibiotics, it is imperative to achieve antibacterial properties of implants. Thus, many different approaches were proposed and are discussed herein. Emphasis is given on novel approaches based on treatment with highly reactive plasma, which may alter SS topography, chemistry and wettability under appropriate treatment conditions. This review aims to present and critically discuss different approaches and propose novel possibilities for surface modification of SS by using highly reactive gaseous plasma in order to obtain a desired biological response.