Investigation of stress shielding around the Stryker Omnifit and Exeter periprosthetic hip implants using an irreversible thermodynamic‐based model

Abstract

This study investigates stress shielding by predicting bone density around two different implants following total hip arthroplasty using a new thermodynamic-based model for bone remodeling. This model is based on chemical kinetics and irreversible thermodynamics in which bone is treated as a self-organizing system capable of exchanging matter, energy, and entropy with its surroundings. Unlike the previous works in which mechanical loading is regarded as the only stimulus for bone remodeling, this model establishes a coupling between mechanical loading and the chemical reactions involved in the process of bone remodeling. This model is incorporated into the finite element software ANSYS by means of a macro to investigate stress shielding around two different implants: Stryker Omnifit and Exeter periprosthetic hip stems. The results of the simulation showing bone density reductions of 17% in Gruen zone 1 and 27% in Gruen zones 7 around the Omnifit hip stem agree well with dual-energy X-ray absorptiometry (DEXA) measurements reported in the literature. On the other hand, the Exeter implant is found to result in more severe resorption in the proximal femur. This is consistent with clinical studies, which report a higher survivorship rate for HA-coated Omnifit hip stems.

Effect of bisphosphonates in preventing femoral periprosthetic bone resorption after primary cementless total hip arthroplasty: a meta-analysis

“…After THA, the stress shielding will cause significant decrease in load bearing in zones 1, 2, 3, 6, and 7. However, the load bearing in zone 5 does not change apparently [ 26 , 27 ]. In our study, the pooling results at 3 months after surgery indicated the BMD of the bisphosphonates group was all significantly higher than that of the control group except zone 5.…”

“…In our study, the pooling results at 3 months after surgery indicated the BMD of the bisphosphonates group was all significantly higher than that of the control group except zone 5. The reason for this phenomenon might be that the bone resorption due to stress shielding was significantly suppressed by bisphosphonates in most zones; however, stress shielding is not apparent in zone 5, which limits the antiresorptive efficacy of bisphosphonates [ 26 , 27 ]. As the accumulation of bone formation, no difference was detected in zone 5 at 6 and 12 month after surgery.…”

Cell-based approaches to the engineering of vascularized bone tissue

“…Attempts to modify the surfaces of implants with bioceramics and mineralized coatings have shown some success, but these surface conditioning techniques can lead to decreased durability of the device (5). Local stress shielding caused by metallic implants can also lead to a reduction in bone density and can require revision surgeries (6). Vascularization of regions supported by metallic implants is also limited (5).…”

Effects of femoral bone defect morphology on initial polished tapered stem stability in massive defect model: a biomechanical study

“…In the case of a distally extended defect, the tensile stress in the anterior region due to internal rotation may be absorbed at the bone defect region and not transmitted to the anterior part of the femur. Such imbalance of the stress distribution may cause stress shielding of the anterior proximal bone, resulting in bone fragility [16, 17]. The quality of periprosthetic bone determines the risk of periprosthetic fracture [7], and a high incidence of early periprosthetic fractures is associated with polished tapered stems [8, 18–20].…”