Abstract
The increasing incidence of trauma in medicine brings with it new demands on the materials used for the surgical treatment of bone fractures. Titanium, its alloys, and steel are used worldwide in the treatment of skeletal injuries. These metallic materials, although inert, are often removed after the injured bone has healed. The second-stage procedure—the removal of the plates and screws—can overwhelm patients and overload healthcare systems. The development of suitable absorbable metallic materials would help us to overcome these issues. In this experimental study, we analyzed an extruded Zn-0.8Mg-0.2Sr (wt.%) alloy on a rabbit model. From this alloy we developed screws which were implanted into the rabbit tibia. After 120, 240, and 360 days, we tested the toxicity at the site of implantation and also within the vital organs: the liver, kidneys, and brain. The results were compared with a control group, implanted with a Ti-based screw and sacrificed after 360 days. The samples were analyzed using X-ray, micro-CT, and a scanning electron microscope. Chemical analysis revealed only small concentrations of zinc, strontium, and magnesium in the liver, kidneys, and brain. Histologically, the alloy was verified to possess very good biocompatibility after 360 days, without any signs of toxicity at the site of implantation. We did not observe raised levels of Sr, Zn, or Mg in any of the vital organs when compared with the Ti group at 360 days. The material was found to slowly degrade in vivo, forming solid corrosion products on its surface.
Highlights
Age-related fractures in the USA are projected to increase from 2.1 million in 2005 to over 3 million fractures in 2025 [1]
The architecture and cytomorphological characteristics of the parenchymatous organs did not show any regressive changes that might be related to absorbable metal alloys being used
Massive hepatic steatosis occurred a total of three times: once in the rabbit with the experimental alloy screw euthanized 360 days after implantation, and twice in the control rabbits with Ti-based screws (Figure 11k)
Summary
Age-related fractures in the USA are projected to increase from 2.1 million in 2005 to over 3 million fractures in 2025 [1]. To remove a non-absorbable metallic implant, the patients are forced to undergo a second surgical procedure—doubling the number of operations required. This significantly prolongs the convalescence period and increases the costs connected with the healthcare. Absorbable, or biodegradable implants are able to degrade in the organism after fulfilling their mission, which makes the second surgical procedure unnecessary. This means that application of absorbable implants is connected with an increased comfort of patient life, and with significant economical savings [2]
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