Vj. Hetherington et al., MECHANICAL AND HISTOLOGICAL FIXATION OF HYDROXYLAPATITE-COATED PYROLYTIC CARBON AND TITANIUM-ALLOY IMPLANTS - A REPORT OF SHORT-TERM RESULTS, Journal of applied biomaterials, 6(4), 1995, pp. 243-248
Historically, pyrolytic carbon has been a material for cardiovascular
applications, but it has several properties suited for orthopedic uses
as well. Pyrolytic carbon has an elastic modulus similar to bone and
is highly fatigue resistant, but has not been used in orthopedics beca
use of poor fixation to bone. Plasma sprayed hydroxylapatite (HA) has
significantly improved the bonding of bone to titanium alloy implants.
The effect of plasma-sprayed HA on pyrolytic carbon implants was inve
stigated in this study. Cylindrical samples were implanted through a s
ingle cortex in Beagle femurs. The animals were sacrificed after 8 wee
ks, and a mechanical push-out test was performed on the implants immed
iately after explantation. Samples were microradiographed, stained for
histology, and examined histomorphometrically. Interface strength for
each type of implant was calculated. Pyrolytic carbon showed almost n
o attachment strength with an average strength value of 1.59 MPa. HA-c
oated pyrolytic carbon (8.71 MPa) yielded the same interfacial strengt
h as HA-coated titanium (8.71 MPa). Histology revealed that bone was i
n direct apposition to all implants, both HA coated and noncoated. Fai
lures occurred between the core material and the coating, or within th
e coating, but not at the bone/HA interface. Histomorphometry results
confirmed that the two types of HA-coated implants had more bone appos
ition than the uncoated pyrolytic carbon implants. It was concluded th
at a plasma sprayed HA coating significantly improves the bone fixatio
n of pyrolytic carbon. (C) 1995 John Wiley & Sons, Inc.