Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Labmayr, V.
The Use of Magnesium-based Bioresorbable Screws in the Surgical Treatment of Fractures
Doktoratsstudium der Medizinischen Wissenschaft; Humanmedizin; [ Dissertation ] Medizinische Universität Graz; 2024. pp. 141
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- Autor*innen der Med Uni Graz:
- Betreuer*innen:
- Holweg Patrick
- Obermayer-Pietsch Barbara
- Puchwein Paul
- Altmetrics:
- Abstract:
- Background: In a pilot study, the magnesium-based screw ZX00 demonstrated successful healing of medial malleolar fractures while gradually resorbing. The proof of concept and excellent 1-year outcomes generated interest beyond the first year. This study reports the clinical outcomes after 2½ years and investigates the changes in bone microarchitecture following the resorption of ZX00, as well as after the removal of conventional implants around the ankle joint. Methods: All imaging data from the pilot study involving ZX00 screws for medial malleolar fractures were analyzed. The initial study included 20 adults who received either one or two ZX00 screws (most commonly two) for medial malleolar fracture fixation. Each 3.5 mm ZX00 screw had a volume of 243.3 mm³. In cases of combined injuries, conventional fibulo-tibial positioning screws were used for syndesmotic instability (n=9), and conventional plates/screws were applied for additional fractures (n=14). Fibulo-tibial positioning screws were removed after 6–8 weeks, while plates/screws were removed based on patient preference or discomfort (n=8). Two cases were lost to follow-up or excluded. Clinical follow-up and radiographs for the remaining 18 patients extended to an average of 2½ years post-ZX00 implantation. Of these, 15 patients underwent CT scans at an average of 3½ years post-implantation, including six cases with high-resolution CTs (HR-CTs) conducted between 2 and 3 years. CT scans were analyzed for changes in bone microarchitecture following ZX00 resorption. HR-CTs specifically evaluated ZX00 traces and enabled volumetric measurements of trabecular voids at the former ZX00 implantation sites. Lastly, the cohort comprised eleven patients with CT scans after hardware removal, allowing the evaluation of implantation sites of conventional implants (n=12). Results: At around 2½ years, there were no clinical complications, and patients remained pain-free. The radiographs revealed no visibility of ZX00 screws in 94% (17 of 18) of cases. Additionally, bone texture at the ZX00 implantation site was rated as homogeneous in 83% (15 of 18) of cases and slightly inhomogeneous in 17% (3 of 18). CT scans demonstrated sclerotic voids in the trabecular bone following ZX00 resorption in 100% (15 cases) after approximately 3½ years. Among the six HR-CTs conducted between 2 and 3 years, one case showed complete ZX00 screw resorption, while five cases exhibited tiny, irregularly shaped ZX00 traces. The trabecular void volumes measured in HR-CT were 596.2 ± 275.7 mm³. The CTs after conventional hardware removal showed sclerotic screw holes in the trabecular bone, both following the removal of fibulo-tibial positioning screws (6-8 weeks implant residence) and plates/screws (approximately 1½ years). Discussion: The clinical outcomes confirm the success of the intervention with ZX00 screws, demonstrating true bioresorbability with near-complete resorption 2 to 3 years post-implantation. Radiographs show an increasingly homogeneous bone texture at the ZX00 implantation sites over time, reflecting remodeling and strengthening of adjacent trabecular bone, a phenomenon also observed after conventional screw removal. However, CT and HR-CT scans reveal the full extent of structural changes following ZX00 screw resorption, including voids that differ in size from those associated with conventional screws. This underscores the need for advanced imaging techniques when assessing bioresorbable implants.