Article
Stress shielding effect after total hip arthroplasty varies between combinations of stem design and stiffness – a comparing biomechanical finite elements analysis
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Authors
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Rene Burchard
- Kreisklinikum Siegen, Klinik für Unfallchirurgie und Orthopädie, Siegen, Germany
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Christian Soost
- Institut für Statistik und Ökonometrie, Universität Siegen, Siegen, Germany
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Jan Adriaan Graw
- Klinik für Anästhesiologie, Charité-Universitätsmedizin, Berlin Institute of Health (BIH), Berlin, Germany
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Jan Schmitt
- Klinik für Orthopädie und Unfallchirurgie, Klinikum Wetzlar, Wetzlar, Germany
| Published: | November 6, 2018 |
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Outline
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Objectives: Total hip arthroplasty (THA) is one of the most important milestones in orthopaedic surgery. Because of the demographic trend with increasing numbers of THAss, surgeons are also challenged by an increasing number of complex revision procedures. The goal to preserve as much bone stock as possible during THA resulted in new implant designs. Multiple approaches have been made to design a femoral component for THA with a physiological behaviour close to a native femur. The main objective of this study was to compare different combinations of designs and biomechanical properties of THA-prostheses and their impact on stress-shielding of the periprosthetic bone using virtual hip stem implantation.
Methods: Virtual implantation of different stem designs (straight standard stem, straight short stem, and anatomical short stem) was performed with a finite elements software. A geometrical matrix for each stem was generated based on in vivo data from computer tomography. A double layer hip stem with a titanium shell and a bone-marrow-like core was developed. To evaluate the impact of the different stem-designs on periprosthetic bone structure, a classic strain analysis for each combination of stem-type and stem-stiffness was performed.
Results and conclusion: With reduction of stem-stiffness less stress shielding was induced in the medial bone regions. In contrast to the anatomical short-stem, the other stem-types showed a lower strain gain in the lateral regions. In all stem types, a clear reduction of a strain-reducing stress-shielding appeared only in proximal medial bone regions. Implantation of an anatomical short-stem prosthesis together with a small titanium shell provided the most physiological strain-loading effect (Figure 1). [Fig. 1]
A combination of a short and anatomically designed stem with a low stiffness might provide the most physiological strain transfer during THA. The biomechanical properties of the femoral component should be considered as a multifactorial function including design and stiffness. Further research with translational approaches into clinical application is needed to understand the impact of hip stem function on bone remodelling processes and to find the optimal stem with a minimal stress-shielding effect.
