Efficiency of 3D Implants with Bioactive Properties for Treatment of Extensive Bone Defects: Experimental Study

Abstract

Background. The problem of replacing extensive bone defects remains relevant. The use of implant structures with bioactive properties can stimulate osteogenesis, which will improve the final treatment result.The aim of the study. In an in vivo experiment, to study the possibility of replacing an extensive defect in the bone diaphysis with a personal bioactive cellular 3D implant and evaluate the long-term results of its use.Materials and Methods. In an in vivo experiment, adult large mongrel dogs (n = 8) were modeled with an extensive segmental defect of the tibial diaphysis measuring 4 cm. The defect was replaced with a cellular bioactive 3D implant made of titanium alloy Ti6Al4V, manufactured using the additive technology. The diameter of the cells was 1.5 mm on average. The walls of the implant had pores of 100– 300 μm in size. The inner and outer surfaces were coated with a calcium phosphate layer formed by micro-arc oxidation. The primary fixation was provided with the Ilizarov apparatus. In the early postoperative period, antibiotic prophylaxis with broad-spectrum drugs was performed. Clinical, X-ray, histological and statistical methods were used to analyze the results. The main control points were considered: the end of external fixation with the Ilizarov apparatus, after 180 days and 1 year after the termination of external fixation.Results. During the experiment, the death of animals and complications were not observed. The spatial location of the implant was preserved. The formation of a strong bone-implantation block occurred 37.2±6.3 days after the operation. During this period, the external fixation apparatus was dismantled. Osseointegration was provided under conditions of sufficient primary mechanical stability, due to the cellular structure of the implant, the presence of pores on its walls, and the osteoinductive properties of the applied calcium phosphate coating. The achieved degree of osseointegration persisted in long-term periods (6 months and 1 year after the termination of external fixation). The osteoinductive properties of the calcium phosphate coating were confirmed by the expression of osteopontin cells at all stages of the experiment. Outflow of Ca and P from bone fragments was not observed. An elastic sheath was formed on the surface of the implant, similar in structure to the periosteum. The implant cells were filled with a well-vascularized bone substrate. In the projection of the intermediate zone, compact bone tissue was formed, and in the projection of the medullary canal — reticulofibrous bone marrow. This indicates the possibility of organotypic remodeling of bone structures inside the implant.Conclusion. The results of the study showed the effectiveness of using a bioactive cellular 3D implant to replace an extensive defect in the shaft of the bone. The architectonics and osteoinductive properties of the implant surface contributed to the formation of complete osseointegration in a short time, while maintaining the achieved result in long-term periods.

Biocompatible implants in orthopedics: bone tissue engineering

“…Products from PCL with the inclusion of hydroxyapatite (from 10 to 50 wt %) were studied in the treatment of fractures of long bones in animals, treatment of bone defects and experimental limb lengthening. Experimental studies revealed a high biological activity of this new type of intraosseous implants: pH of the environment remained at the level of 6-7, bone union of tibial fractures occurred within 1 month, external fixation index for limb lengthening did not exceed 20 days/cm in monofocal procedures [98]. CONCLUSION Thus, ceramic polymer composites are commercially available nowadays for treatment purposes.…”

“…However, the main shortcoming of ceramics is its fragility. Therefore, bioinert metals and alloys with a calcium phosphate coating can be used for fabrication of orthopedic devices for the musculoskeletal system, which experiences significant mechanical loads [37][38][39][40]. The coating provides biological compatibility and expressed biological activity in the formation of bone tissue around the metal.…”

“…1. Development of joint prosthetic devices, the bearing metal part of which is covered with ceramics for the purpose of osteoinduction and formation of an extensive bone coupling that ensures reliable contact of the metal with the bone tissue over the maximum area, thus eliminating the failure of fixing the elements of the joint on the bone for many years [37,40].…”

“…Such a coating is designed to induce reparative osteogenesis around the implant, thereby contributing to the filling of extensive bone defects. The coupling created in this way around the implant provides optimal conditions for consolidation of bone fractures or nonunion, the formation of a distraction regenerate [40].…”