DOS Kongressen 2014 ·
131
Micromotion Induced Osteolysis in a Sheep Hip
Arthroplasty Model
Thomas Jakobsen, Søren Kold , Jørgen Baas , Kjeld Søballe, Ole Rahbek
Ortopædkir. Forskningslab., Aarhus Universitets Hospital; Ortopædkir. afd.,
Aalborg Universitets Hospital; Ortopædkir. Afd. , Aarhus Universitets Hospital;
Ortopæd. Afd., Aarhus Universitets Hospital
Background:
Aseptic implant loosening might occur when peri-prosthetic bone
anchorage is replaced by a fibrous membrane. It could be that the first step
in the osteolytic cascade is micromotion-induced formation of a fibrous mem-
brane around the implant.
Purpose / Aim of Study:
The aim of this study was to investigate whether
implants subjected to micromotion would be able to induce bone resorption and
formation of a fibrous membrane without the presence of wear-debris par-
ticles.
Materials and Methods:
One micromotion implant (T12) were inserted into
one of the medial femoral condyle in ten sheep. The micromotion device con-
sists of an anchor bearing a PMMA implant and a PE plug. The 7.5 mm PMMA
implant is placed exact-fit into a 7.5 mm bone cavity. During each gait cycle
the PE plug will transfer load through the anchor and make the PMMA implant
axially piston 0.5 mm. After 12 weeks of observation the bone specimens were
harvested and a post- mortem control implant (T0) was inserted into the con-
tra-lateral medial femoral condyle. Each specimen were embedded and cut for
histomorphometrical analysis.
Findings / Results:
Histomorphometrical evaluation showed that the T12
implant surface was covered by fibrous tissue (93% for T12 vs. 0% for T0, p
<0.001). The control implants were covered by lamellar bone (91% for T0 vs.
4 % for T12, p < 0.001). No difference was found with respect to the volume
fraction of lamellar bone in a 1 mm zone around the implants (57% for T12 vs.
48% for T0, p = 0.2).
Conclusions:
This study indicates that micromotion alone is sufficient to induce
osteolysis and a fibrous membrane around an implant.
78.
