gms | German Medical Science

Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2019)

22. - 25.10.2019, Berlin

Biomechanical study of femoral stem in hinged knee prosthesis

Meeting Abstract

Suche in Medline nach

  • presenting/speaker Federica Armaroli - BEAMS Department, Université Libre de Bruxelles, Bruxelles, Belgium
  • Bernardo Innocenti - BEAMS Department, Université Libre de Bruxelles, Bruxelles, Belgium

Deutscher Kongress für Orthopädie und Unfallchirurgie (DKOU 2019). Berlin, 22.-25.10.2019. Düsseldorf: German Medical Science GMS Publishing House; 2019. DocIN39-452

doi: 10.3205/19dkou720, urn:nbn:de:0183-19dkou7206

Veröffentlicht: 22. Oktober 2019

© 2019 Armaroli et al.
Dieser Artikel ist ein Open-Access-Artikel und steht unter den Lizenzbedingungen der Creative Commons Attribution 4.0 License (Namensnennung). Lizenz-Angaben siehe http://creativecommons.org/licenses/by/4.0/.


Gliederung

Text

Objectives: Achieving adequate fixation is a key prerequisite in hinged total knee arthroplasty and several stem solutions are available on the market. However, no evidence-based biomechanical guidelines are currently available to determine the appropriate stem length, and whether or not to use cemented femoral stems in hinged revision total knee arthroplasty (TKA).

Therefore, the objective of this study was to compare bone stresses and implant micromotions when cemented or cementless stems are used. Moreover, the effect of different femoral stem lengths was also investigated using a validated finite element analysis.

Methods: The model is based on a previously validated finite element model (Innocenti B et al J Arthroplasty 29:1491-1498, 2014). The bone geometries were obtained by 3D reconstruction from CT images of a patient. The 3D geometries of a LINK Endo-Model rotating hinged TKA (Waldemar LINK GmbH) were generated starting from industrial design provided by the manufacturer.

Four stem lengths (50, 95, 120 and 160mm) and two types of fixation (cemented or press fit) were examined. A further configuration, in which no stem was implanted, was also analyzed as control.

Physiological and osteoporotic bone properties were also investigated.

The bone stresses distribution in several regions of interest were analyzed at 0 and 90° of flexion under physiological load condition. Similar to previous study, in all the models the femoral head was considered fixed and the force was applied on the distal tibia (El-Zayat et al. Arch Orthop Traum Surg 136:1741-1752, 2016).

Results and conclusion: Medium and maximum compressive and Von Mises stresses were extracted along the femoral length for each configuration. In general, the presence of the cement helps to reduce the peak stresses in each region of the bone (up to 62%). A longer stem induces higher stresses compared to a short stem at both flexion angles (max increment up to 350% in press-fit stem). Micromotions were higher when a small cementless stem was adopted; longer stems guarantee a better fixation; however, a small cemented stem is already sufficient to reduce implant micromotions (up to 62%). The absence of stem induces higher stress and micromotions (especially at 90°of flexion), therefore this situation should be avoided.

These considerations can be made for both the physiological and the osteoporotic femur, even if the configurations with the osteoporotic femur show greater stress values on the bone (up to 30%).

Therefore, if surgeons need to select a femoral stem in a hinged TKA, aiming to good stability and lower bone stress, according to this study, the preferable option is a small cemented stem.