Radiological signs of degradation and soft-tissue response to Mg–2Zn–2Ga and titanium implants in vivo

Background. The clinical potential of magnesium implants depends on their degradation behavior and the response of surrounding tissues. For Mg–2Zn–2Ga, the correspondence between radiological and morphological changes in a paired subcutaneous model with a titanium control has not been adequately studied.

Aim. To compare MSCT signs of Mg–2Zn–2Ga degradation and gas formation with the morphological response of soft tissues relative to titanium at 1–11 weeks.

Materials and methods. The study was performed on 20 male Wistar rats. Discs measuring 7 mm in diameter and 4 mm in thickness were implanted subcutaneously over the scapulae of each animal: Mg–2Zn–2Ga on the left and titanium on the right. At weeks 1, 2, 3, 4, and 11 (four animals per time point), MSCT, macroscopic assessment, and histological examination of both implantation sites were performed.

Results. At week 1, a gas cavity was detected around Mg–2Zn–2Ga, and a slight reduction in radiodensity was observed. At weeks 2–4, radiological changes became more apparent; by week 4, the magnesium specimen was visually smaller than the stable titanium implant. At week 11, a residual gas cavity and reduced radiodensity and dimensions of Mg–2Zn–2Ga persisted. Histologically, the early cavity with a thin fibrous capsule and lymphohistiocytic infiltration was followed by a cellular rim and multiple cavities with fragmentation of adjacent muscle fibers; occasional foreign-body giant cells were detected by week 11. Orderly connective-tissue organization predominated around titanium. Crepitus over the magnesium implant was observed in 3 of 20 animals (15 %).

Conclusion. Comparison of MSCT and histology revealed a concordant time course of Mg–2Zn–2Ga degradation signs and surrounding tissue remodeling that differed from the response to titanium. Early changes developed at weeks 2–4 and persisted at week 11. These time points and features may be used in subsequent quantitative preclinical assessment.

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