DOS 2017

DOS Kongressen 2017 ·

Low Preoperative BMD is Related to High Migration of

Tibia Components in Uncemented TKA – 92 patients in a

combined DEXA- and RSA-study with two-year follow-

up.

Mikkel Rathsach Andersen, Nikolaj S. Winther, Thomas Lind, Henrik M. Schrøder,

Michael Mørk Petersen

Ortopædkirurgisk afd., Rigshospitalet, Hvidovre Hospital; Ortopædkirurgisk

afd., Rigshospitalet; Ortopædkirurgisk afd., Rigshospitalet; Ortopædkirurgisk

afd., Næstved Sygehus; Ortopædkirurgisk afd., Rigshospitalet

Background:

The fixation of uncemented tibia components in Total Knee Ar-

throplasty (TKA) may rely on the bone quality of the tibia, however, no previous

studies have shown convincing objective proof of this.

Purpose / Aim of Study:

To investigate the possible relation between preop-

erative bone quality and fixation of uncemented tibia components in TKA.

Materials and Methods:

We performed 2 year follow up of 92 patients who

underwent TKA surgery with an uncmented tibia component. Bone mineral

density (BMD) (g/cm2) of the tibia host bone was measured preoperatively

using dual energy X-ray absorbtiometry (DEXA). The proximal tibia was di-

vided in to two regions of interest (ROI) in the part of the tibia bone where

the components were implanted. Radiostereometric analysis was performed

postoperatively and after 3, 6, 12 and 24 months. Primary the outcome was

Maximum Total Point Motion (MTPM) (mm). Statistics: Regression analysis was

performed to evaluate the relation between preoperative BMD and MTPM.

Findings / Results:

We found low preoperative BMD in ROI1 to be signifi-

cantly related to high MTPM at all follow-ups: After 3 months (R2 = 20%,

PBMD=0.017), 6 months (R2=29%, PBMD=0.003), 12 months (R2=33%,

PBMD=0.001) and 24 months (R2=27%, PBMD=0.001). We also found a

significant relation for low BMD in ROI2 and high MTPM: 3 months (R2=19%,

PBMD=0.042), 6 months (R2=28%, PBMD=0.04), 12 months (R2=32%,

PBMD=0.004) and 24 months (R2=24%, PBMD=0.005).

Conclusions:

Low preoperative BMD in the tibia is related to high MTPM. Thus,

high migration of uncemented tibia components is to be expected in patients

with poor bone quality. High component migration is relevant as it has been

shown to predict aseptic loosening.

No conflicts of interest reported