Strain shielding in distal radius after wrist arthroplasty with a current generation implant: An in vitro analysis

Abstract

A systematic review of peer reviewed articles has shown that the main cause for wrist arthroplasty revision is carpal and radial prosthetic loosening and instability. To improve arthroplasty outcomes, successive generations of implants have been developed over time. The problem with the current generation of implants is the lack of long-term outcomes data. The aim of the present work was to test the hypothesis that the current generation Maestro WRS implant has a stress, strain and stability behaviour which may be associated with a reduced risk of long-term radial component loosening. This study was performed using synthetic radii to experimentally predict the cortex strain behaviour and implant stability considering different load conditions for both intact and implanted conditions. Finite element models were developed to assess the structural behaviour of cancellous-bone and bone-cement, these models were validated against experimentally measured cortex strains. Measured cortex strains showed a significant reduction between intact and implanted states. Cancellous bone adjacent to the radial body component suffers a two to threefold strain reduction, comparing with the intact condition, while along the radial stem, in the axial direction, a strain increase was observed. It is concluded that the use of contemporary Maestro WRS implant changes the biomechanical behaviour of the radius and is associated with a potential risk of bone resorption by stress-shielding in the distal radius region for wrist loads in the range of daily activities.

The optimal strategy for 3D‐printed uncemented endoprosthesis for the bone defect reconstruction of the distal radius, based on biomechanical analysis and retrospective cohort study

“…A dorsal surgical approach was employed for tumor the displacement values gradually decreased from the distal to the proximal end part of the radius (Figure 4E). These results were similar to those of previous studies, 22,26 which demonstrated the reliability of the finite element models in our study. concentrated at the endoprosthetic stem, with maximum stress at the stem base.…”

“…After the contact setting was completed, 100 N (60 + 40 N) compression and stretching forces were loaded onto the scaphoid and lunate surfaces in the radial axis direction, respectively. To simulate palmar flexion and dorsiflexion, a 25 N compression force, at angles of 45°and 30°, respectively, was loaded onto the scaphoid and lunate surfaces [20][21][22] (Figure 2). The stress distribution and displacement of the normal and prosthetic reconstruction models were observed and analyzed using ANSYS analysis and calculations.…”

My personal experience with arthroplasties in the hand and wrist over the past four decades

“…Neither could we find evidence of infection or rheumatoid activity being involved. Recent biomechanical investigations using finite element models on the radial component of a wrist prosthesis implanted in synthetic bones indicate that stress shielding may be a factor (Completo et al., 2017), but PPO remains an unsolved problem.…”

Long-term outcomes of the Universal 2 total wrist replacement: revision and loosening at 10 years and beyond

“…In reality the implant may still remain stable if bony fixation is sufficient in the other zones, so subsidence is not universally seen (Boeckstyns and Herzberg, 2014; Boeckstyns et al., 2014). Although polyethylene reaction is our suspected reason for the loosening, other factors such as stress shielding can contribute to bone resorption (Completo et al., 2017). Similar patterns of osteolysis have also been seen in total wrist implants that do not contain a polyethene bearing (Reigstad et al., 2017), confirming there are multiple potential causes.…”