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[Mechanical changes in the femur induced by a joint prosthesis. Comparative extensometric studies]
J Delecrin1, J Royer, N Passuty
1Service de chirurgie orthopédique, Hôpital Saint-Jacques, Nantes.
Chirurgie; Memoires De L'Academie De Chirurgie
|January 1, 1991
Summary
This study compared titanium femur prostheses, finding screwed implants stiffened bone most. Cement-free and collar-free cemented prostheses showed similar, minimal effects on femur deformation.
Area of Science:
- Orthopedic biomechanics
- Biomaterials science
- Surgical implant technology
Background:
- Femoral implant biomechanics are critical for successful total hip arthroplasty.
- Understanding in-vivo stress distribution is essential for optimizing implant design and longevity.
- Previous studies have not comprehensively compared various titanium prosthesis designs on the same femur.
Purpose of the Study:
- To compare the relative in-vitro deformations of a single fresh femur before and after sequential implantation of different titanium prostheses.
- To evaluate the biomechanical impact of cement-free, cemented (with and without collar), and screwed prosthesis designs.
- To assess the influence of metaphyseal endocortical support and the 'collar effect' on femoral mechanics.
Main Methods:
- Electrical extensometry was used to measure 56 deformation paths on a fresh human femur.
- A specialized loading device ensured consistent external stress and torsion application across all tests.
- Prostheses were successively implanted: cement-free with metaphyseal support, cemented (with/without collar), and screwed titanium implants.
Main Results:
- The screwed titanium prosthesis significantly increased the stiffness of the proximal femur.
- Cement-free and collar-free cemented prostheses exhibited very similar deformation patterns.
- The 'collar effect' demonstrated a minimal incidence even under optimal implantation conditions.
- Metaphyseal endocortical support in cement-free implants enhanced primary anchorage and promoted secondary osteogenesis.
Conclusions:
- Prosthesis design critically influences proximal femur biomechanics, with screwed implants inducing the greatest stiffening.
- Cement-free designs with adequate metaphyseal support offer promising biomechanical stability and potential for osseointegration.
- The study provides novel insights into in-vitro femoral deformation under various titanium implant types, informing future implant development.