Investigation of early surface delamination observed in retrieved heat-pressed tibial inserts.
The objective was to examine possible reasons for delamination observed in tibial inserts of the porous-coated anatomic (PCA) knee replacement. To date, 33 PCA inserts have been forwarded to the authors' labs. Of these 33, 52% showed severe delamination within four years of implantation. Visual, structural, and mechanical analyses were conducted and data compared on the heat-pressed PCA type and the common machined inserts. Twenty inserts of the two different types were examined. Visual data using polarized light microscopy showed the presence of a surface layer separated from the middle region of the heat-pressed inserts by a line of demarcation 250-580 microns beneath the articulating surface. This anomaly was not observed in machined inserts. Structural analysis showed the new heat-pressed inserts had increased crystallinity in the surface layer when compared to new machined inserts. The retrieved heat-pressed inserts showed increased crystallinity in the surface and middle regions. There was a slight increase in surface crystallinity in the retrieved machined inserts. Microhardness data showed that there was an increased hardness associated with the crystallinity seen on the heat-pressed inserts. Orthopedic surgeons should be aware of early delamination and surface failure in heat-pressed inserts.
Bloebaum
R D
RD
Bone and Joint Research Labs, VA Medical Center, Salt Lake City, Utah 84148.
Nelson
K
K
Dorr
L D
LD
Hofmann
A A
AA
Lyman
D J
DJ
D006244:Hardness; D006358:Hot Temperature; D006801:Humans; D007720:Knee Prosthesis; D011095:Polyethylenes; D011474:Prosthesis Design; D011475:Prosthesis Failure; D013977:Tibia; D013997:Time Factors
D011095:Polyethylenes