Abstract
Trabecular materials show great promise for soft-tissue attachment to prosthetic implants. Results with Tantalum have been very encouraging, however, it remains unclear if this in-growth is secondary to the specific metal or its generic structure,. If structure, is there a specific tolerance with respect to porosity and pore size? In a canine model, bulk blocks of porous alumina ceramic were shown to be completely ingrown by four weeks. The type material was not a factor, and effect of pore size revealed that there is a wide tolerance in facilitating in-growth with the larger pores having the greatest attachment strength (p=0.004).
This study examines the in-vivo soft tissue in-growth potential of porous alumina ceramic and the effect of three distinct pore size ranges on this process.
Alumina ceramic implants of fixed porosity (~ 85%) were designed in three pore size ranges (100–200, 250–400 and 600–800 μM). Using an established canine model, six implants (two of each type) were implanted in the dorsal subcutaneous tissues of tweleve mature canines and examined histologically and mechanically at four, eight and sixteen weeks with respect to type, amount and strength of soft tissue in-growth.
Soft tissue in-growth was grossly evident in all implants at each time interval, and in each pore size. Microscopic examination revealed neo-vascularized in-growth throughout the implant, without evidence of inflammation or foreign body reaction. Numerous blood vessels were visible at the implant interface and within the porous alumina ceramic structure. With peel testing, the weakest attachment strength was with the small pore size with no differences between the medium and large pore sizes. An increase of attachment strength in each pore size was observed over time.
This study suggests that architecture of porous structures in general, and not the type of material used, confers the biologic activity and that there is a wide tolerance for pore size in facilitating this process in soft tissue in-growth. Further study of other inert foam structures will be useful in further defining the assets and limitations of this genre of trabecular materials as a whole.
Funding: Stryker Orthopaedics, Mahwah, NJ
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Correspondence should be addressed to Cynthia Vezina, Communications Manager, COA, 4150-360 Ste. Catherine St. West, Westmount, QC H3Z 2Y5, Canada
