DOS Kongressen 2014 ·
129
Inhibition of Micromotion induced Osteolysis in a
Sheep Hip Arthroplasty Model
Thomas Jakobsen, Søren Kold , Juan Shiguetomi-Medina , Jørgen Baas,
Kjeld Søballe, Ole Rahbek
Ortopædkir. Forskningslab., Aarhus Universitets Hospital; Ortopædkir. afd.,
Aalborg Universitets Hospital; Ortopædkir. Forskningslab, Aarhus Universitets
Hospital; Ortopæd. Afd., Aarhus Universitets Hospital
Background:
Aseptic loosening is the leading indication for revision surgery of a
total hip replacement. It has previously been shown that early micromotion of a
total hip replacement is associated with early aseptic loosening. One way to re-
duce the impact of the early micromotion on implant fixation could be with the
use of bisphosphonates (BP). These compounds are strong inhibitors of bone
resorption.
Purpose / Aim of Study:
The aim of this study was to investigate whether
local treatment with BP would reduce bone resorption around an experimental
implant subjected to micromotion.
Materials and Methods:
One micromotion implant were inserted into each
medial femoral condyle in ten sheep. The micromotion device consists 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 pis-
ton 0.5 mm. During surgery one of the femoral condyles were locally treated
with 0.8 mg zoledronic acid. The other condyle served as control. Bone-implant
specimens were harvested after 12 weeks of observation. Each specimen were
embedded and vertically cut for histomorphometrical analysis.
Findings / Results:
Histological evaluation showed a fibrous capsule around
both the control and BP implants. Histomorphometrical analysis showed that
97% of the surface on both control and BP implants were covered by fibrous tis-
sue (p=0.7). However, the BP was able to preserve bone in a 1 mm zone around
the implants (66% bone volume fraction for BP vs. 57% bone volume fraction
for control, p = 0.02).
Conclusions:
This study indicates that local treatment with BP can not prevent
the formation of a fibrous capsule around an implant subjected to micromotion.
However, BP is able to reduce resorption of peri-prosthetic bone.
76.
