Evaluation of the mechanical properties of orthopedic screw made from bovine cortical bones

Allogeneic cortical bone screws offer a promising alternative to traditional metallic orthopedic screws, primarily due to their potential for improved biocompatibility and osteointegration. However, earlier designs of these biological implants faced significant challenges, including antigenicity, inconsistent mechanical properties, limited bioactivity, and inadequate fixation performance—factors that restricted their clinical adoption. This study addresses these issues through two key innovations: a redesigned screw shape and an optimized processing method for the allogeneic cortical bone material. The new fabrication process involves decellularization of cortical bone to eliminate antigenic components while preserving its mechanical strength. A novel screw geometry was developed to increase surface area and enhance bone-implant interaction. The redesigned shape was aimed at optimizing stress distribution and promoting superior osteointegration. To evaluate the mechanical performance, Stress Transfer Parameters (STP) were measured for both conventional and redesigned screws. For the first thread (α), the STP of redesigned bovine, titanium, and stainless-steel screws were 0.361, 0.145, and 0.136 respectively, compared to 0.116, 0.110, and 0.013 for their conventional counterparts. For the remaining engaged threads (β), the redesigned screws recorded STP values of 0.658, 0.546, and 0.510, significantly outperforming the conventional designs, which had values of 0.128, 0.039, and 0.029 respectively. The results confirm that the redesigned allogeneic cortical bone screws exhibit superior mechanical stability and improved osteointegration. This advancement in both material processing and screw design represents a significant step toward more effective, reliable, and biocompatible orthopedic implants.