A New Porous Tantalum Biomaterial: Experimental Studies
Michael
Tanzer,M.D.,F.R.C.S.(C) Director Orthopaedic Group Associate Professor, Department of Surgery McGill University Montreal, Quebec Conventional
metallic porous materials are best suited for use as coatings on implants
since they do not readily have the required mechanical and processing
characteristics which would allow them to be used as bulk structural
materials for implants, bone augmentation, or substitutes for bone
graft. A
new porous biomaterial made of tantalum has recently been developed for
potential application in reconstructive orthopaedics. The material has an unusually high and
interconnecting porosity with a very regular pore shape and size. It can be made into complex shapes and
used either as bulk implant or as a surfacing coating. Our laboratory studies have demonstrated
that porous tantalum filled rapidly with new bone in a canine transcortical
model. The majority of the available
porosity was bone ingrown by eight weeks after surgery. The healing of new bone into porous
tantalum was comparable to bone healing within empty drill holes. New bone formed in apposition to the
tantalum struts: apposition increased with postoperative time. At 16 and 52 weeks, Haversian canals were
seen within the pores. Because of its
high volume porosity, more bone formed at the interface compared with other
porous materials. This resulted in a
faster rate of development of high fixation strength. In
a canine acetabular cup model, bone ingrowth was maximized by six weeks with
little change at twelve and twenty-four weeks. Bone often formed to the maximum depth within the pores, up to
the compression-molded polyethylene.
Gap healing in the dome region was common. The density of bone ingrowth was comparable to surrounding
acetabular trabecular bone. This porous tantalum biomaterial has desirable characteristics for bone ingrowth. Further studies are warranted to ascertain its potential for clinical reconstructive orthopaedics.
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