Degradative and mechanical properties of a novel resorbable plating system during a 3-year follow-up in vivo and in vitro

Abstract

We tested the tissue reactions and mechanical strength of a novel biodegradable craniomaxillofacial plating system, Inion CPS, in the course of degradation. Plates and screws composed of L-lactide, D-lactide and trimethylene carbonate were implanted to the mandible and dorsal subcutis of 12 sheep. The animals were sacrificed at 6-156 weeks. Histological evaluation was done using paraffin and methylmetacrylate techniques. Degradative and mechanical properties during the follow-up were measured both of in vivo and in vitro implants. In light microscopy, the in vivo implant material began to fragment at 52 weeks and could not be detected at 104 weeks. No significant foreign body reactions were seen in the mandibles. The dorsal subcutis disclosed mild reactions, which were, however, not of clinical significance. The implants in vitro maintained their entire mass for 26 weeks and lost 63-80% of the mass by week 104. The inherent viscosity of the implants in vitro and in vivo diminished uniformly. The screws retained their shear strength for 12-16 weeks. The plates maintained their tensile strength for at least 6 weeks. The maximum capacity of the plates in 3-point bending tests diminished gradually by 87% in 26 weeks. In conclusion, the plates and screws examined maintain adequate strength for the healing period of a bone fracture or osteotomy, producing no harmful foreign body reactions.

Delayed Foreign-body Reaction to Absorbable Implants in Metacarpal Fracture Treatment

“…In animal models, these implants showed normal inflammatory sequelae [22,25]. Similarly, the incidence of foreign-body reactions was extremely low in some clinical applications, including maxillofacial surgery [20,21,33] and in a series of pediatric patients [23].…”

“…Third-generation implants composed of trimethylene carbonate, L-lactide, and D, L-lactide displayed improved strength and slow degradation rates (2-4 years). These were designed to overcome the problems of rapidly diminishing strength and frequent foreign-body reactions [22,23,25]. However, the prolonged degradation rate of new implants has raised further concerns.…”

“…A major concern is whether these materials actually diminish adverse soft tissue reactions or whether the reactions simply are postponed to a later time ? These bioabsorbable implants have been studied extensively in vitro and in animal models [22,25], but only few short-term studies were conducted in humans [20,33].…”

Biomechanical in vitro evaluation of the effect of cyclic loading on the postoperative fixation stability and degradation of a biodegradable ankle plate

“…The copolymer material softens in 6 to 12 months and degrades completely by 24 months without any harmful inflammatory or foreign body reactions. 25 Sjöblom et al 24 conducted a biomechanical human cadaver study to compare the initial strength of the ankle plate to two conventional, clinically proven metallic ankle fracture fixation methods (fixation with hemicerclage wire and metal plate fixation). No significant difference was found between the biodegradable and metal fixation methods, suggesting that the biodegradable ankle plate provides sufficient initial fixation strength for the treatment of lateral malleolus fractures.…”

“…[31][32][33][34][35] In some studies, the degradation was evaluated in vivo. 25,[36][37][38][39][40] Although in vivo conditions are ideal to create degradation, it is extremely difficult to control loading conditions in animal models. Accordingly, animal models often lack clinical relevance because loading is uncontrolled and does not properly simulate the corresponding loading conditions in humans.…”