Abstract
Due to their high stiffness, metal femoral implants in total knee arthroplasty may cause stress shielding of the peri-prosthetic bone, which can lead to loss of bone stock. Using a polymer (PEEK) femoral implant reduces the stiffness mismatch between implant and bone, and therefore has the potential to decrease strain shielding. The goal of the current study was to evaluate this potential benefit of PEEK femoral components in cadaveric experiments. Cadaveric femurs were loaded in a materials testing device, while a 3-D digital image correlation set-up captured strains on the surface of the intact femurs and femurs implanted with PEEK and CoCr components. These experimental results were used to validate specimen-specific finite element models, which subsequently were used to assess the effect of metal and PEEK femoral components on the bone strain energy density. The finite element models showed strain maps that were highly comparable to the experimental measurements. The PEEK implant increased strain energy density, relative to the preoperative bone and compared to CoCr. This was most pronounced in the regions directly under the implant and near load contact sites. These data confirm the hypothesis that a PEEK femoral implant can reduce peri-prosthetic stress shielding.
Highlights
Total knee arthroplasty is one of the most successful interventions in orthopaedic surgery for treatment of patients suffering from degenerative knee joints, with impressive survival rates [AOANJRR, 2019]
The effect of a polyetheretherketone (PEEK) femoral total knee arthroplasty TKA component was studied in computational analyses
The load applicator for one pair of implanted femurs was slightly undersized, which was resolved by moving the load applicator to ensure optimal lateral seating, where digital image correlation (DIC) data was being recorded
Summary
Total knee arthroplasty is one of the most successful interventions in orthopaedic surgery for treatment of patients suffering from degenerative knee joints, with impressive survival rates [AOANJRR, 2019]. There is still a small number of cases that require revision for aseptic loosening, which is why there is an ongoing drive for development of new implant systems and materials Before clinical introduction, these new systems should be subjected to extensive pre-clinical evaluation to determine its potential benefits and risks. The effect of a polyetheretherketone (PEEK) femoral total knee arthroplasty TKA component was studied in computational analyses (de Ruiter et al, 2017a, 2017b). Those studies demonstrated that a PEEK knee implant may improve the periprosthetic bone remodelling stimulus. Both the computational and in vitro studies confirmed the hypothesis that a more compliant material can distribute forces more physiologically than when using a stiff metal implant
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