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[Comparison of primary trapezometacarpal cup fixation using mechanical tests]
K Bruyère Garnier1, R Dumas, C Rumelhart
1Laboratoire de Mécanique des Solides INSA, Bât. 304, 20, Avenue A. Einstein, 69621 Villeurbanne, France.
Chirurgie De La Main
|April 9, 2001
Summary
The "with crown" trapeziometacarpal prosthesis cup demonstrated superior fixation strength in both bending and torsion tests compared to other designs. This enhanced stability is attributed to its equatorial over-thickness, improving press-fit fixation.
Area of Science:
- Orthopedic biomechanics
- Implant design and fixation
Background:
- Optimizing primary fixation of the Arpe (Biomet Merck) trapeziometacarpal prosthesis is crucial for implant success.
- Several cup geometries, including those with slots, blades, and a crown, were investigated to improve fixation.
Purpose of the Study:
- To compare the mechanical strengths of different trapeziometacarpal prosthesis cup geometries for primary fixation.
- To evaluate the efficacy of novel designs against the standard Arpe cup fixation.
Main Methods:
- Mechanical testing of prototype cups (with slots, bladed, with crown) in lamb cancellous bone.
- Assessment of primary fixation strength in both torsion and bending using torque measurements.
Main Results:
- The "with crown" cup exhibited superior bending strength (mean pull-out torque Cbending = 0.89 Nm).
- The Arpe cup's fixation was insufficient in torsion, while the "with crown" cup showed the highest torsion strength (mean unsealing torque Ctorsion = 0.83 Nm).
Conclusions:
- Equatorial over-thickness in "bladed" and "with crown" cups enhances both bending and torsion strength via press-fit.
- Modifying the Arpe cup fixation to a "crown" design significantly improves its torsion stability.