Biomechanical considerations in the design of patient-specific fixation plates for the distal radius

Abstract

Use of patient-specific fixation plates is promising in corrective osteotomy of the distal radius. So far, custom plates were mostly shaped to closely fit onto the bone surface and ensure accurate positioning of bone segments, however, without considering the biomechanical needs for bone healing. In this study, we investigated how custom plates can be optimized to stimulate callus formation under daily loading conditions. We calculated implant stress distributions, axial screw forces, and interfragmentary strains via finite element analysis (FEA) and compared these parameters for a corrective distal radius osteotomy model fixated by standard and custom plates. We then evaluated these parameters in a modified custom plate design with alternative screw configuration, plate size, and thickness on 5 radii models. Compared to initial design, in the modified custom plate, the maximum stress was reduced, especially under torsional load (− 31%). Under bending load, implants with 1.9-mm thickness induced an average strain (median = 2.14%, IQR = 0.2) in the recommended range (2–10%) to promote callus formation. Optimizing the plate shape, width, and thickness in order to keep the fixation stable while guaranteeing sufficient strain to enhance callus formation can be considered as a design criteria for future, less invasive, custom distal radius plates. Graphical abstract ᅟ

Application of 3D-Printed Orthopedic Cast for the Treatment of Forearm Fractures: Finite Element Analysis and Comparative Clinical Assessment

“…The region nearby the proximal side of the cast was fixed. For the setting of axial load, some previous studies used 100 N load or 1 Nm bending moment [ 21 , 22 ], but in this study, a larger load was applied to evaluate the immobilization performance of the cast. A compression load with 400 N was exerted on the palm along anterior to posterior (AP), posterior to anterior (PA), medial to lateral (ML), and lateral to medial (LM) directions to mimic different mechanical scenarios.…”

Patient-specific plate for navigation and fixation of the distal radius: a case series

“…Changing the screw diameter from 2.4 to 3.5 mm resolved this issue. In a parallel study [ 42 ], we investigated implant stress distributions and compared these in custom and standard distal radius plates. Under mechanical load, the highest stress levels were observed at the boundary of the plate and the screws, i.e., exactly at the location where the screws broke in our patients.…”

“…Under mechanical load, the highest stress levels were observed at the boundary of the plate and the screws, i.e., exactly at the location where the screws broke in our patients. Since custom plates are more rigid than standard anatomical plates [ 42 ], the stress level at the plate-screw boundary is higher, which may explain plastic deformation and breaking of screws at a lower load. Fatigue due to repetitive stress could very well be the causative mechanism that led to screw breakage, exactly at the location that we saw in these three patients.…”

Holistic Approach in Designing the Personalized Bone Scaffold: The Case of Reconstruction of Large Missing Piece of Mandible Caused by Congenital Anatomic Anomaly

“…In most of the papers, which are related to the topic of personalized human bone implants, the personalization is about the adaptation of the geometry of endoprostheses [ 14 ] or fixation elements (plates, [ 15 ]) to the geometry of the injured bone. There are many papers reporting on conducted analyses and simulations of mechanical behaviour of the bone [ 16 ] or corresponding endoprosthesis and fixation elements or their assembly [ 17 ] performed by the finite element method. However, there is almost no reported research in which a FEM analysis is performed to adapt the geometry of the implant structure to provide targeted deformations that would affect tissue recovery, i.e., stimulating the ossification process.…”