Preclinical evaluation of a fully threaded biodegradable magnesium alloy headless compression screw for enhanced fixation in small bones

Abstract

Background Biodegradable magnesium (Mg) alloys have attracted attention as alternatives to conventional metallic implants; however, their clinical applicability to fully threaded headless compression (HC) screws has been scarcely investigated. Methods In this study, a fully threaded biodegradable Mg alloy HC screw was developed, and its mechanical performance, biological safety, and in vivo degradation behavior were systematically evaluated. Mechanical properties were assessed according to ASTM standards and compared with clinically used titanium (Ti) alloy and poly-L-lactic acid/hydroxyapatite (PLLA/HA) screws. Biological safety was evaluated in accordance with ISO 10993 and in compliance with Good Laboratory Practice. In vivo degradation behavior was investigated using a rabbit distal femoral condyle model. Results The Mg alloy HC screw demonstrated superior torsional strength compared with PLLA/HA screws and comparable insertion performance, along with enhanced fixation strength, compared with Ti alloy screws. No cytotoxicity, sensitization, or intracutaneous reactivity was observed. Although transient gas cavity formation was observed during the early implantation period, it progressively diminished over time and did not adversely affect bone formation or implant stability. Conclusion These findings indicate that the developed Mg alloy HC screw exhibits favorable mechanical performance, biocompatibility, and in vivo degradation. This study provides preclinical evidence supporting its potential clinical translation, particularly in eliminating the need for secondary implant removal surgery. The translational potential of this article This article focuses on the preclinical evaluation of a fully threaded Mg-alloy HC screw developed to improve fixation performance for small bone fractures. The results of this study have significant clinical potential for the fully threaded design of biodegradable Mg alloy implants in fracture treatment.