Strength–Durability Correlation of Osteosynthesis Devices Made by 3D Layer Manufacturing

Abstract

To develop orthopedic implants that are optimized for each patient’s needs or skeletal structure (custom-made implants), evaluations of the bending strength, bending stiffness, and durability of various types of conventional osteosynthesis devices have become important. Four-point bending tests and compression bending tests of osteosynthesis devices (bone plates, intramedullary nail rods, spinal rods, compression hip screws (CHSs), short femoral nails, and metaphyseal plates) were carried out to measure their bending stiffness, bending strength, and durability. The bending stiffness of bone plates, intramedullary nails, spinal rods, CHSs, short femoral nails, and metaphyseal plates increased with increasing bending strength. The durability limit of various types of osteosynthesis devices linearly increased with increasing bending strength. The relationship (durability limit at 106 cycles) = 0.67 × (bending strength) (N·m) (R2 = 0.85) was obtained by regression. The relationship for the highly biocompatible Ti-15Zr-4Nb-4Ta alloy was also linear. The mechanical strength and ductility of specimens that were cut from various osteosynthesis devices were excellent and their microstructures consisted of fine structures, which were considered to be related to the excellent durability. These results are expected to be useful for the development of implants suitable for the skeletal structure of patients using three-dimensional (3D) layer manufacturing technologies.

Mechanical, Histological, and Scanning Electron Microscopy Study of the Effect of Mixed-Acid and Heat Treatment on Additive-Manufactured Titanium Plates on Bonding to the Bone Surface

“…The development of fully customized artificial restorations to repair bone defects has been reported in recent years, expanding the scope of treatment in the fields of bone reconstruction, ossification, and rehabilitation [ 25 , 26 ]. Ti is also considered one of the biorepair materials due to its high bioaffinity.…”

Development of Orthopedic Implants with Highly Biocompatible Ti Alloys

“…This slope of 0.67 is close to the ratio of the fatigue strength to the tensile strength of the raw metals. The relationship for the highly biocompatible Ti-15Zr-4Nb alloy is also linear [17].…”

“…M-N curves (maximum bending moment vs. number of cycles to failure on logarithmic scale) of osteosynthesis devices are measured for the compression bending and four-point bending durability tests [17]. The maximum bending moments (M) are calculated as M = L  P m for the compression bending durability test and M=h P m /2 for the four-point bending durability test, where P m is the maximum cyclic load (N) in the compression bending durability or four-point bending test.…”

Characteristics of the Mg-Zn-Ca-Gd Alloy after Mechanical Alloying

“…Since their mechanical properties are similar to those of a human bone, this makes them a perfect solution for biodegradable fracture fixtures [5]. This is particularly important as the bone growth, and therefore the regrowth as well, is at least partially connected with the mechanical properties of the osseous tissue [6][7][8][9]. It is hypothesized to be caused by microscopic damage stimulating bone adaptation, as explained by Wolff's law, i.e., if higher mechanical load on a certain bone is present, then, the bone will adapt and remodel itself to be stronger in order to resist said load accordingly.…”