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Micromotion of plasma spray versus grit-blasted radial head prosthetic stem surfaces
Cholawish Chanlalit1, James S Fitzsimmons, Dave R Shukla
1Department of Orthopedics, Faculty of Medicine, HRH Princess Maha Chakri Sirindhorn Medical Center, Srinakhrinwirot University, Bangkok, Thailand.
Background:
Initial stability of a textured surface prosthetic stem is necessary for bone in-growth. Surfaces currently used for radial head prostheses include titanium plasma spray and grit-blasted titanium.
Hypothesis:
Plasma spray radial head prosthetic stems are less dependent than grit-blasted stems on a tight press fit. Good initial press-fit stability, with acceptable micro-motion, can be achieved with a greater range of stem sizes using a plasma spray than grit-blasted surface.
Methods:
Paired cadaveric radii were implanted with plasma spray or grit-blasted radial head prosthetic stems. Micromotion at the stem tip was measured under circumstances simulating eccentric loads.
Results:
Micromotion in the plasma spray (PS) stems (49 ± 37) μm was not better than that in the grit-blasted (GB) stems (28 ± 10) μm (P = .13). Micromotion of less than 100 μm was measured in all 12 GB stems that were maximum or 1 mm less than maximum size, versus 5/6, and 4/6 PS stems, respectively.
Discussion:
Micromotion in plasma spray prosthetic radial head stems was not better than that seen in grit-blasted stems, contrary to our initial hypothesis.
Conclusion:
Grit-blasted prosthetic radial head stems confer initial press-fit stability that is as good as, or slightly better than, corresponding plasma spray stems. Acceptable amounts of micromotion can be achieved with 2 grit-blasted stem sizes and probably with 2 plasma spray stem sizes.
