DOS Kongressen 2014 ·
121
Evaluation of peri-implant bone mineral density
changes after femoral osseointegrated prosthesis
surgery
Rehne Lessmann Hansen, Peter Holmberg Jørgensen, Kjeld Søballe,
Klaus Kjær Petersen, Maiken Stilling
Department of orthopaedic research, University Hospital of Aarhus;
Department of orthopaedic surgery, University Hospital of Aarhus
Background:
Trans-femoral amputees have reduced bone mineral density
(BMD) in the residual femur, hip and ipsilateral pelvis. Insertion of an osseointe-
grated (OI) prosthesis may affect the BMD additionally.
Purpose / Aim of Study:
To study the effects of unloading/loading and stress
shielding after OI-prosthesis surgery.
Materials and Methods:
20 patients (13 males) mean age 48 (range 30-66)
years, were operated with an OI femoral implant in two stages. DXA scans were
performed at baseline and at intervals of 3, 6, 9, 12, 18 months postopera-
tively. The first 9 months partial weight bearing (PW) was allowed, and after
9 months full weight bearing (FW) was encouraged. The femoral peri- implant
bone was evaluated in 3 regions of interest (ROIs), proximally (Rp), medially
(Rm) and laterally (Rl) to OI implant.
Findings / Results:
From baseline to 18 months follow-up total peri-pros-
thetic BMD was unchanged (p=0.44). However, during PW periprosthetic BMD
decreased (p=0.005) 25% and during FW BMD increased (p=0.04) 17%. All 3
periprosthetic ROIs had a decrease in BMD (p<0.0007) during the PW rehabili-
tation period of 30%, 20% and 24% for Rp, Rm and Rl, respectively. During FW
rehabilitation BMD increased (p<0.04) in Rp 19% and in Rm 14%, whereas the
BMD in Rl was similar (p=0.06). However, baseline values were not reached at
18 months.
Conclusions:
Unloading, or less than full weight bearing, in the first 9 months
after IO implantation causes pronounced stress-shielding and peri-implant BMD
loss. Increased or full loading between 9 and 18 months increases BMD, but not
to baseline values. Patients will be followed to investigate if direct femoral bone
loading from the OI implant will result in continued BMD increase of the peri-
implant bone.
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