Poly L, DL‐lactic acid, and composite poly l, DL‐lactic acid/β‐tricalcium phosphate‐based bioabsorbable interference screw

Abstract

There has been a growing interest in the use of bioabsorbable polymers in interference screws for knee ligament reconstruction surgeries. This interest is driven by virtue of the relevant properties exhibited by these polymers. Among such essential properties include excellent biocompatibility and bioabsorption, good integration between graft/bone, in addition to the ease they offer when it comes to surgical revision. This article seeks to report the results obtained from the study aimed at the development of a bioabsorbable interference screw produced by the injection molding process with two distinct polymeric materials: PLDL poly(L,DL‐Lactic acid) and a composite PLDL + 30 wt% TCP (β‐tricalcium phosphate). Finite element analysis (FEA) was used for the development of the screw design. The mechanical strength of the screws was evaluated, where the maximum torque to break was found to surpass the insertion torque by 136% in PLDL material and by 190% in PLDL+TCP. The mean values of pullout force obtained for PLDL and PLDL+TCP were 1635 N and 809 N, respectively. An in vitro degradation test performed over a period of 180 days helped to assess the mechanical behavior during degradation and facilitated the comparison of the screws based on specific application requirements. The composite material (PLDL+TCP) exhibited a faster degradation process, with 88% loss of mechanical resistance following 180 days of degradation compared with 55% observed in the PLDL material. The results show that the addition of bioactive ceramic TCP contributed toward raising the initial mechanical resistance and acceleration during the process of degradation. POLYM. COMPOS., 40:2197–2207, 2019. © 2018 Society of Plastics Engineers