비글견의 하악골절모델에서 생분해성 마그네슘 기반 판과 나사의 생체적합성 및 효율성

Abstract

Background

Trauma involving bone are very common and occur six million bone fracture each year in the United States. These fractures are caused by a variety of causes such as birth defect, osteoporosis, osteomyelitis, MRONJ (Medication related osteonecrosis of the jaw) and, most commonly, trauma. As the population ages and the number of medically compromised patients increases, the rate of pathologic bone fracture is expected to be increased in the future. For this reason, fracture treatment remains an important clinical focus in bone tissue engineering. Fracture treatments often require internal fixation. Plates and screws are used for alignment and stabilization of bone fragments. Largely, two kind of internal bone fixation devices have been used such as metallic and polymeric substances. Internal anchors made of permanent metal are associated with numerous long-term complications and may require removal. Polymeric materials are biodegradable and need not be removed, but are known to have poorer mechanical quality than metals.

Unlike permanent metals and resorbable polymers, degradable magnesium alloys can provide an ideal balance of degradation and strength. Recent investigations of magnesium alloys in vivo have highlighted their potential as bone fixation materials.

Purpose

A biodegradable magnesium alloy system has been developed as a substitute for conventional plates and screws made of titanium or absorbable polymer. However, previous studies were limited to small animal experiments using screws or wires. In this study, human standard-sized degradable magnesium devices were evaluated by using the mandible fracture model of beagles. Device degradation, fracture healing, and new bone formation were assessed.

Method and Materials

The biodegradable magnesium alloy plate products are evaluated using biological safety / efficacy in large animals. Among large animals, beagle, in which the masticatory and oral conditions are similar to those of humans, is routinely selected as an experiment related to CMF implants and other dental materials. The hydrogen gas generation and decomposition behavior around the plates were evaluated for the fracture site on the mandibular right mandible. Micro CT images were performed 5 times at 4 weeks interval (1, 4, 8, 12, 16 weeks) immediately after implantation. Bone and tissue volumes were calculated using CT analyzing software. Histology was performed after sacrifice. Local response and biocompatibility were evaluated.

Result and Discussion

The biodegradable magnesium plates used in this study were found to be a positive result in histological and pre-clinical evaluation after 16 weeks of CT and after sacrifice. Particularly, additional bone formation in the surgery site was found when it compared to the control site, and hydrogen gas pocket formation as a result of plate decomposition was observed in one animal. However, all dogs underwent normal healing process. Further study is recommended to confirm that bone deposition is more prevalent in comparison with the control site before the prototype is applied to humans, and how to control hydrogen production at the early stage of surgery.