Abstracts Posters SICOT-SOF meeting Gothenburg 2010 _2_

Poster
Topic: Arthroplasty - Hip
Abstract number: 26565
INFLUENCE OF THE FIXATION LENGTH ON MICROMOTION OF FEMORAL HIP
REVISION IMPLANTS: AN EXPERIMENTAL STUDY
Robert SOUFFRANT, Martin ELLENRIEDER, Daniel KLUESS, Wolfram
MITTELMEIER, Rainer BADER
Orthopädische Klinik und Poliklinik Universität Rostock, Rostock (GERMANY)
Revision surgery of femoral hip endoprostheses is on the rise due to decreasing
primary implantation ages and current demographic changes. Long term results
depend on the level of secondary stability of the implant, which by itself depends on a
sufficient primary stability and bony reaction after surgery. Aim of this study was to
evaluate the influence of bone defects on micromotions in the bone-implant interface
of a modular revision hip stem by means of experiments. Five composite femora
(Sawbones, Sweden) were implanted with modular hip revision implants (Restoration
Modular, Stryker Orthopaedics, Duisburg) embedded and attached to a servo
hydraulic testing machine. A sinusoidal axial cyclic load of 1000 N, oriented
according to the information of Bergmann et al., was applied to the implant with a
frequency of 1 Hz (R = 0.1). Micromotions were measured by a mechanical testing
device with 4 degrees of freedom using LVDTs. Load was applied in 3 x 500 cycles
while the relative motion between implant and surrounding bone was measured.
Seven reproducible bone defects, three according to the classification of Paprosky
and four total bone resections at different heights, were generated successively and
micromotions were measured during 3 x 500 cycles for each defect.Observed
micromotion kept below the bony integration threshold of 150 µm, while the motion
fraction associated to implant migration increased with decreasing fixation length.
Even though composite femora offer the opportunity of repeatable and reproducible
experiments by means of geometry and bone material, results need validation with
human samples.
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