Abstract
Aims: Optimisation of femoral stem load transfer potentially encourages new bone growth. The effect of increasing the taper angle of a highly polished double tapered stem on stability and hoop strain is investigated.
Methods: An in-vitro model femur was instrumented at 3 levels with 10 strain gauges, proximally (channel 1–4), mid taper level (channel 5–8) and distally (channel 9–10). Under controlled conditions surgical Simplex P cement (Stryker Howmedica Osteonics) was prepared and introduced into the canal of the model femur. The Exeter (Stryker Howmedica Osteonics) stem with centraliser was inserted using a standardised technique. The cementation process was repeated 5 times for each stem. The mantle and stem were subjected to cyclic loading at 1 Hz to 0.5kN using an Instron 8511 servohydraulic materials testing machine. The subsidence of the stem and hoop strains generated were recorded. Each experiment was repeated 6 times.
Results: The average subsidence of all the stems was 0.2mm with a standard deviation varying between 0.1 and 0.2. All the stems showed similar patterns of loading, with no significant difference.
Conclusions: The results suggest that within a purely cemented environment the taper angle of the stem used is irrelevant with regard to the hoop strain and the stability of the construct. The authors therefore suggest that size of stem does not matter.
Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
