Background: Over the last decade, the development of new and alternative materials in trauma care using bioresorbable metals has increased, concentrating mainly on magnesium (Mg) alloys. Our research group has dedicated itself to finding ideal indications for magnesium alloys in trauma surgery. Aim: Magnesium (Mg)-based biodegradable screws for medial malleolar fracture reduction were investigated in this prospective cohort study. Our bioabsorbable Mg-based screws are composed of pure Mg alloyed with zinc and calcium (0.45 wt% zinc (Zn) and 0.45 wt% calcium (Ca); ZX00). Visual analog scale (VAS) and the presence of complications (adverse events) during 3.5 years of follow-up were used to evaluate the clinical outcomes. The functional outcome were analyzed through the AOFAS foot score. Furthermore, implant degradation was studied in 11 patients with computed tomography after 3.5 years. Results: The mean follow-up was 3.5 years. The 12-weeks-results with successful fracture healing in all 20 patients had already been published (Bone Joint Res. 2020-08). No adverse events or breakage of screws were observed. All ankle fractures were reduced, and a complete consolidation of all fractures was achieved after 12 weeks. At the final follow-up examination after 3.5 years, the mean AOFAS score was 93±6.1 points. Implant remnants were assessed by the CT after 3.5 years at 22 implantation sides. At 15 (68%) screw implantation sides, the screws had been completely degraded without any visible remnants. At 7 implantation sides (32%), the range of visible remnants seen at single CT slides ranged from 2% to 21%. Conclusion: After 3.5 year of follow-up, no adverse events and excellent clinical and functional outcomes were reported. In the CT investigation an almost complete degradation of the implants was proved. Mg-based bioresorbable screws seem to be an excellent and safe alternative compared to titanium screws while avoiding a second operation.
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