Matthias Lerch1, Henning Windhagen2, Agnes-Elisabeth Kurtz3, Stefan Budde4, Bernd-Arno Behrens5, Anas Bouguecha6, Amer Almohallami7. 1. Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries Straße 1-7, 30625 Hannover, Germany. Electronic address: Matthias.lerch@diakovere.de. 2. Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries Straße 1-7, 30625 Hannover, Germany. Electronic address: henning.windhagen@diakovere.de. 3. Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries Straße 1-7, 30625 Hannover, Germany. Electronic address: agneselisabeth.kurtz@diakovere.de. 4. Department of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borries Straße 1-7, 30625 Hannover, Germany. Electronic address: stefan.budde@diakovere.de. 5. Institute of Forming Technology and Machines, Leibniz University Hannover, An der Universität 2, 30823 Garbsen, Germany. Electronic address: behrens@ifum.uni-hannover.de. 6. Institute of Forming Technology and Machines, Leibniz University Hannover, An der Universität 2, 30823 Garbsen, Germany; Laboratory La2MP, ENIS, National school of engineering in Gafsa, Sfax, Tunisia. 7. Institute of Forming Technology and Machines, Leibniz University Hannover, An der Universität 2, 30823 Garbsen, Germany; PROFIL Verbindungstechnik GmbH & Co. KG, Otto-Hahn-Strasse 22-24, 61381 Friedrichsdorf, Germany.
Abstract
BACKGROUND: We applied a previously established and validated numerical model to a novel short-stemmed implant for a 'pre-launch' investigation. METHODS: The implant system consists of two different implant geometries for valgus/varus-positioned proximal femurs with differences in volume distribution, head/neck angle, and calcar alignment. The aim of the design was to achieve a better adaption to the anatomic conditions, resulting in a favourable load transfer. The implant type G showed the best fit to our model, but both stem geometries were implanted; the implant type B was used to compute an 'imperfection scenario'. FINDINGS: Apparent bone density decreased by 4.3% in the entire femur with the implant type G, and by 12.3% with the implant type B. Bone mass loss was pronounced in the proximal calcar region. Apparent bone density increased at the lateral cortical ring and in the minor trochanter. The apparent bone density in the imperfection scenario was very similar to that of a straight stem, indicating a distal load transfer. INTERPRETATION: No adverse effects of the A2 short-stemmed implant system on bone remodeling could be detected. The overall bone density reduction was acceptable, and wedge fixation was not observed, indicating that there was no distal load transfer. The simulation of an incongruous implant indicates the sensitivity of our model in response to modifications of implant positioning. Correct implant selection and positioning is crucial when using the A2 system.
BACKGROUND: We applied a previously established and validated numerical model to a novel short-stemmed implant for a 'pre-launch' investigation. METHODS: The implant system consists of two different implant geometries for valgus/varus-positioned proximal femurs with differences in volume distribution, head/neck angle, and calcar alignment. The aim of the design was to achieve a better adaption to the anatomic conditions, resulting in a favourable load transfer. The implant type G showed the best fit to our model, but both stem geometries were implanted; the implant type B was used to compute an 'imperfection scenario'. FINDINGS: Apparent bone density decreased by 4.3% in the entire femur with the implant type G, and by 12.3% with the implant type B. Bone mass loss was pronounced in the proximal calcar region. Apparent bone density increased at the lateral cortical ring and in the minor trochanter. The apparent bone density in the imperfection scenario was very similar to that of a straight stem, indicating a distal load transfer. INTERPRETATION: No adverse effects of the A2 short-stemmed implant system on bone remodeling could be detected. The overall bone density reduction was acceptable, and wedge fixation was not observed, indicating that there was no distal load transfer. The simulation of an incongruous implant indicates the sensitivity of our model in response to modifications of implant positioning. Correct implant selection and positioning is crucial when using the A2 system.
Authors: Philippe Favre; Ghislain Maquer; Adam Henderson; Daniel Hertig; Daniel Ciric; Jeffrey E Bischoff Journal: Ann Biomed Eng Date: 2021-05-10 Impact factor: 3.934