Inter-subject variability effects on the primary stability of a short cementless femoral stem.
This paper is concerned with the primary stability of the Furlong Evolution(®) cementless short stem across a spectrum of patient morphology. A computational tool is developed that automatically selects and positions the most suitable stem from an implant system made of a total of 48 collarless stems to best match a 3D model based on a library of CT femur scans (75 males and 34 females). Finite Element contact models of reconstructed hips, subjected to physiologically-based boundary constraints and peak loads of walking mode, were simulated using a coefficient of friction of 0.4 and an interference-fit of 50 μm. Maximum and average implant micromotions across the subpopulation were predicted to be 100±7 μm and 7±5 μm with ranges [15 μm, 350 μm] and [1 μm, 25 μm], respectively. The computed percentage of implant area with micromotions greater than reported critical values of 50 μm, 100 μm and 150 μm never exceeded 14%, 8% and 7%, respectively. To explore the possible correlations between anatomy and implant performance, response surface models for micromotion metrics were constructed. Detailed morphological analyses were conducted and a clear nonlinear decreasing trend was observed between implant average micromotion and both the metaphyseal canal flare indices and average densities in Gruen zones. The present study demonstrates that the primary stability and tolerance of the short stem to variability in patient anatomy were high, reducing the need for patient stratification. In addition, the developed tool could be utilised to support implant design and planning of femoral reconstructive surgery.
Bioengineering Science Research Group, FEE, 5/3019, University of Southampton, Southampton SO17 1BJ, UK. Electronic address: mtb@soton.ac.uk.
Mamadou T
MT
Bah
Bioengineering Science Research Group, FEE, 5/3019, University of Southampton, Southampton SO17 1BJ, UK.
Junfen
J
Shi
Bioengineering Science Research Group, FEE, 5/3019, University of Southampton, Southampton SO17 1BJ, UK.
Markus O
MO
Heller
CETIM, Pôle Fatigue des Composants Mécaniques, 52, avenue Félix Louat - 60304 SENLIS Cedex, France.
Yanneck
Y
Suchier
CETIM, Pôle Fatigue des Composants Mécaniques, 52, avenue Félix Louat - 60304 SENLIS Cedex, France.
Fabien
F
Lefebvre
Simpleware Ltd., Bradninch Hall, Castle Street, Exeter, EX4 3PL, UK.
Philippe
P
Young
Southampton University Hospitals NHS Trust, Tremona Road, Southampton SO16 6YD, UK.
Leonard
L
King
Southampton University Hospitals NHS Trust, Tremona Road, Southampton SO16 6YD, UK.
Doug G
DG
Dunlop
JRI Orthopaedics Ltd., 18 Churchill Way, 35A Business Park, Chapeltown, Sheffield S35 2PY, UK.
Mick
M
Boettcher
JRI Orthopaedics Ltd., 18 Churchill Way, 35A Business Park, Chapeltown, Sheffield S35 2PY, UK.
Edward
E
Draper
Bioengineering Science Research Group, FEE, 5/3019, University of Southampton, Southampton SO17 1BJ, UK.
Martin
M
Browne
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D001696:Biomechanical Phenomena / Q000502:physiology; D003198:Computer Simulation; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging*; D020342:Finite Element Analysis; D006621:Hip Joint / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D006622:Hip Prosthesis / Q000592:standards*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D015588:Observer Variation; D014057:Tomography, X-Ray Computed
Inter-subject variability; Primary stability; Short stem