Comparison of the resorbable magnesium . alloys LAE442 und MgCa0.8 concerning their mechanical properties, their progress of degradation and the bone‐implant‐contact after 12 months implantation duration in a rabbit model

Abstract

Extruded implants (2.5 mm x 25 mm) of the resorbable magnesium alloys MgCa0.8 and LAE442 were implanted into the marrow cavity of both tibiae of 10 New Zealand White rabbits. The animals were in a good general condition over the whole experimental period and showed no signs of lameness. Radiographic examinations could not reveal any generation of gas. The endosteal based bone adhesion to the implant surface was evaluated by l-computed tomography of the right tibia. 53 % of the evaluated slices of the alloy LAE442 showed an adherence of trabecular bone. MgCa0.8 showed trabeculae (38 %), bone clasps (13 %) and -rings (9 %) that covered the whole implant surface. Beside the weight and volume loss, the cross sectional area of the implants were measured to investigate the progress of degradation. Implants of the MgCa0.8 group showed an average loss of more than half of the original implant area (2.18 mm 2 AE 1.03). In contrast LAE442 implants degraded very regularly (4.7 mm 2 AE 0.07). Weight and volume measurements revealed a volume loss of 64.13 % AE 15.92 in the MgCa0.8 group and a lesser volume loss of 45.63 % AE 0.89 in the LAE442. The mechanical properties were tested by a three point bending test. It showed a decrease of the maximal force of 71.2 % AE 2.88 for LAE442 implants and of 85.6 % for MgCa0.8 implants, each compared to the initial condition.Key words: magnesium, long term study, resorbable implants, three point bending, rabbit Stranggepresste Implantate (2,5 mm x 25 mm) der resorbierbaren Magnesiumlegierungen MgCa0,8 und LAE442 wurden in die Markhöhlen beider Tibiae von 10 New Zealand White Kaninchen implantiert. Die Tiere wiesen über den gesamten Versuchszeitraum ein gutes Allgemeinbefinden auf und zeigten keine Lahmheiten. Röntgenologisch konnte keine Gasbildung festgestellt werden. Mit Hilfe von l-computertomographischen Untersuchungen der rechten Tibiae wurde das Knochenanwachsverhalten vom Endost ausgehend an die Implantatoberfläche beurteilt. 53 % der ausgewerteten Schnittbilder der Legierung LAE442 zeigten ein Anhaften trabekulären Knochens an die Implantatoberfläche. Bei MgCa0,8 wurden Trabekel (38 %), Knochenspangen (13 %) und -ringe (9 %), die der gesamten Oberfläche des Implantates auflagen, detektiert. Zur Ermittlung des Degradationsgrades wurde neben der Ermittlung des Gewichts-und Volumenverlustes die Querschnittsfläche der Implantate vermessen. Die Implantate der MgCa0,8-Gruppe hatten im Mittel mehr als die Hälfte der ursprünglichen Implantatfläche verloren (2,18 mm 2 AE 1,03). Die LAE442-Implantate waren hingegen sehr regelmäßig degradiert (4,7 mm 2 AE 0,07). Die Gewichtsmessung und Volumenbestimmung ergab innerhalb der MgCa0,8-Gruppen einen Volumenverlust von 64,13 % AE 15,92. Die Gruppe LAE442 zeigte einen geringeren mittleren Volumenverlust von 45,63 % AE 0,89. Die mechanischen Eigenschaften wurden im Dreipunktbiegeversuch geprüft und ergaben bei LAE442 einen Abfall der maximalen Kraft von 71,2 % AE 2,88, bei MgCa0,8 von 85,6 % im Vergleich zum Initialzustand.

Assessment of Cellular Reactions to Magnesium as Implant Material in Comparison to Titanium and to Glyconate Using the Mouse Tail Model

“…A high corrosion rate results in gas formation and a rapid loss of mechanical strength [12] . In vivo models are essential for evaluating magnesium alloys as an implant material, because in vivo and in vitro corrosion rates can differ to a large extent [3,13] .…”

Comparative in vitro study and biomechanical testing of two different magnesium alloys

“…1,25 Several studies have investigated the properties and corrosion behavior of binary magnesium-calcium alloys. 13,14,18,19,[26][27][28][29][30] The addition of calcium provides solid solution strengthening and contributes to grain refinement owing to grain boundary strengthening. 1 It was observed that the addition of calcium above the solubility limit of approximately 1.34 wt% Ca enhanced the corrosion rate.…”

“…18 Previous studies have demonstrated good biocompatibility of MgCa0.8 in vivo. 13,28 The production of high amounts of gas in a short time due to high corrosion rates is undesirable for clinical applications. The accumulation of gas associated with MgCa0.8 implants was mild to moderate in vivo, with no harmful effects toward the animal.…”

Magnesium Alloys as Promising Degradable Implant Materials in Orthopaedic Research

“…In general anaesthesia, a hole was drilled into the tibial plateau and the implant was inserted. The detailed operation procedure is described elsewhere (Thomann et al, 2009). Radiographs of two planes were taken immediately after surgery (Fig.…”

“…In µ-computed tomography, samples were analysed with a slice sickness of 36µm and a scanning time of 1s. An evaluation of endosteal and periosteal bone remodeling as well as bone adhesion on the implant material was done with a semi quantitative scoring system (Krause et al, 2010; Thomann et al, 2009) (Fig. 2).…”