A modelling approach demonstrating micromechanical changes in the tibial cemented interface due to in vivo service

Abstract

Post-operative changes in trabecular bone morphology at the cement-bone interface can vary depending on time in service. This study aims to investigate how micromotion and bone strains change at the tibial bone-cement interface before and after cementation. This work discusses whether the morphology of the post-mortem interface can be explained by studying changes in these mechanical quantities. Three post-mortem cement-bone interface specimens showing varying levels of bone resorption (minimal, extensive and intermediate) were selected for this study Using image segmentation techniques, masks of the post-mortem bone were dilated to fill up the mould spaces in the cement to obtain the immediately post-operative situation. Finite element (FE) models of the post-mortem and post-operative situation were created from these segmentation masks. Subsequent removal of the cement layer resulted in the pre-operative situation. FE micromotion and bone strains were analyzed for the interdigitated trabecular bone. For all specimens micromotion increased from the post-operative to the post-mortem models (distally, in specimen 1: 0.1 to 0.5 μm; specimen 2: 0.2 to 0.8 μm; specimen 3: 0.27 to 1.62 μm). Similarly bone strains were shown to increase from post-operative to post-mortem (distally, in specimen 1: −185 to −389 με; specimen 2: −170 to −824 με; specimen 3: −216 to −1024 με). Post-mortem interdigitated bone was found to be strain shielded in comparison with supporting bone indicating that failure of bone would occur distal to the interface. These results indicate that stress shielding of interdigitated trabeculae is a plausible explanation for resorption patterns observed in post-mortem specimens.

Finite element study on the micromechanics of cement-augmented proximal femoral nail anti-rotation (PFNA) for intertrochanteric fracture treatment

“…Previously, researchers utilized the FEM to observe cement-trabeculae interactions and quantify the strain shielding of cement at the trabecular scale, using lab-prepared or post-mortem-retrieved samples from the cement-trabeculae interface in total knee arthroplasty 20 – 25 . However, these interface samples introduce inherent limitations or errors into the analysis.…”

“…First, the demanding nature of modelling cement–bone interface limits the number of specimens that can be tested, validated, and modelled. Second, micro- and macro-gaps between the cement and trabeculae have frequently been discovered 20 , 26 , 27 , and there is room for improvement in terms of accuracy in mechanical analysis. Third, in order to investigate pre- and postoperative differentiation in osteolysis accurately, it is necessary to manually fill the cavity that are time-consuming 20 .…”

“…Second, micro- and macro-gaps between the cement and trabeculae have frequently been discovered 20 , 26 , 27 , and there is room for improvement in terms of accuracy in mechanical analysis. Third, in order to investigate pre- and postoperative differentiation in osteolysis accurately, it is necessary to manually fill the cavity that are time-consuming 20 . Fourth, when utilizing micro-computed tomography (micro-CT) scanning for investigation purposes, there is a significant overlap between the global thresholds of trabeculae and bone cement 26 , 28 ; investigators have to manually segment the cement layer and trabeculae, which could potentially introduce additional artificial interference by unintentionally altering the original structure of trabeculae.…”

Study of Mechanical Behavior in Epiphyseal Fracture Treated by Reduction and Cement Injection: No Immediate Post-Operative Weight-Bearing but Only Passive and Active Mobilization Should be Advised

“…An improved DIC method (Heaviside-based DIC) was developed and used on bone tissue to compensate for these limitations ( Valle et al, 2015 ). In addition, finite element methods were used recently to study the microdamage in the bone distribution in the cancellous bone and bone interface ( Tozzi et al, 2012 ; Srinivasan et al, 2017 ). However, no works so far have reported on the mechanical understanding of the bone–cement interface in the field of traumatology.…”

First Biomimetic Fixation for Resurfacing Arthroplasty: Investigation in Swine of a Prototype Partial Knee Endoprosthesis

“…In the case of partial knee RA endoprostheses, the components are commonly secured with cement and drill holes are made in the femoral condyle to accommodate the two pegs used to stabilize the implant. Extensive cement penetration into the periprosthetic bone causes remodeling and resorption of the bone surrounding the cement [11]. The appearance of peripheral radiolucent lines (RLLs) under the component, defined as intervals between the cement and the bone, is a frequent occurrence and is associated with the preparation of the bone surface [12].…”