Persistent mineralisation defects in the medial malleolus after resorption of Mg implants for fracture fixation: lateral comparison with the unfractured side

Introduction: Bioresorbable implants ought to provide stability for fracture healing and resorb thereafter, rendering implant removal obsolete. We follow up on our long-term results of the first in human study in 5 patients with medial malleolus fractures treated with bioresorbable magnesium screws. The study is a comparison of the implantation site with the corresponding contralateral part as well as implant resorption and assessment of the implantation site of 9 implants in 5 patients with HRpQCT (high resolution peripheral quantitative computed tomography).

Methods: Isolated bimalleolar or trimalleolar ankle fractures were surgically treated with bioresorbable screws (Magnesium 99.1%, Calcium 0.45%, Zinc 0.45%). 20 patients were assessed clinically and HRpQCT scans were performed after at least 2.5 years in 5 patients. The implantation site was compared to the contralateral ankle. Evaluations included total volume, bone volume, and volume of the trabeculae-free space.

Results: All patients showed clinical evidence of fracture healing already twelve weeks after the surgery without clinical complications, full weight bearing and absence of pain in the fractured ankle. All observed implants were resorbed for the most part after 2.5 years. Persistent mineralization defects at the surgical site were recorded at all implantation sites studied, with apparent secondary enlargements of the drilling channel in patients with low bone mineral density. The trabeculae-free cavities were 596.1 mm³ in mean size (239.2 –1109.1mm³), with a screw volume before implantation of 243.3 mm³.

Discussion: Bioresorbable magnesium screws for fracture fixation provide satisfactory fracture healing and clinical outcome after one year. Surgical removal is not necessary. We provide long-term results in paired patient investigations. Especially in patients with decreased bone mineral density, the dynamic of implant resorption needs to be studied further.

Keywords: ankle fracture, bioresorbable implant, magnesium screw, HRpQCT

Korrespondenzadresse: Ines Fößl, Medizinische Universität Graz, Universitätsklinik für Innere Medizin, Abteilung für Endokrinologie und Diabetologie, Stiftingtalstraße 24, 8010 Graz, Austria, E-Mail: [e-mail]

Publication History

Article published online:
13 March 2024