Osseointegration and mechanical stability of pyrocarbon and titanium hand implants in a load-bearing in vivo model for small joint arthroplasty.
OBJECTIVE
To test the mechanical stability and histologic osseointegration under load-bearing conditions of 2 different materials, pyrocarbon (Py) and titanium (Ti), in a rabbit model.


METHODS
Proximal interphalangeal implants (9 Ti, 8 Py) were placed into rabbit knees and the animals were killed after 3 months. Subsidence was assessed by monthly x-rays. Mechanical stability was measured with a nondestructive pullout test. Implant osseointegration was evaluated by an analysis of the relative implant-calcified bone contact surface on microradiographs and by a histomorphometric analysis of the percentage of bone and connective tissue contact with the implant surface. Histologic examination included assessment of bone apposition on the basis of fluorochromes.


RESULTS
Subsidence was found in all 8 Py implants but in none of the Ti group. All 9 Ti implants were mechanically stable; all 8 Py implants were loose. A significantly higher implant-bone contact was found for the Ti group compared with the Py group. Bone apposition increased with time and was highest for the Ti implants 6 weeks after implantation.


CONCLUSIONS
In the rabbit model osseointegration of implants was highly dependent on the material. A reliable osseointegration was found for Ti implants. For Py implants no osseointegration or implant stability was achieved. For use of small joints of the hand we therefore recommend Ti-based implants.
Daecke
Wolfgang
W
Department of Orthopaedic Surgery, University of Heidelberg, Heidelberg, Germany. wolfgang.daecke@ok.uni-heidelberg.de
Veyel
Katrin
K
Wieloch
Peter
P
Jung
Martin
M
Lorenz
Helga
H
Martini
Abdul-Kader
AK
D000818:Animals; D050806:Arthroplasty, Replacement, Finger / Q000295:instrumentation*; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D002244:Carbon; D003238:Connective Tissue / Q000473:pathology; D007595:Joint Prosthesis; D007719:Knee Joint / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D008422:Materials Testing; D023421:Models, Animal; D016348:Osseointegration; D011474:Prosthesis Design; D011817:Rabbits; D011859:Radiography; D016059:Range of Motion, Articular; D014025:Titanium; D016474:Weight-Bearing
C009139:pyrolytic carbon; D002244:Carbon; D014025:Titanium