Influence of preoperative mechanical bone quality and bone mineral density on aseptic loosening of total hip arthroplasty after seven years.
OBJECTIVE
To test mechanical bone quality and bone mineral density of the femoral head at the day of implantation as indicators for femoral prosthesis loosening.


METHODS
Mechanical bone quality of a femoral head slice was assessed by destructive compression testing combined with bone mineral density measurements using peripheral quantitative computed tomography. Fourteen patients with walking pains were attainable for a radiographical follow-up mean 7.1 years after implantation.


RESULTS
Radiolucent lines along the stem were evident in 11 of 14 femurs, most of them seen in Gruen zones 7, 6, 1, 3, 14, and showed strong correlations to preoperative bone strength (r=-0.80; P<0.001) and axial stiffness (r=-0.75; P=0.002), yet not to bone mineral density (r=-0.67; P=0.009). Slight varus deviations <3 degrees were noted in six femurs. Preoperative strength was reduced in this femurs to 54% (P=0.006), and stiffness to 61% (P=0.038), while bone mineral density did not differ significantly.


CONCLUSIONS
Femoral prosthesis loosening after seven years can be predicted by mechanical bone quality of the femoral head at the time of implantation. Bone mineral density measurements may also indicate future stem loosening but have to interpreted carefully, keeping in mind a poorer predictive value.


CONCLUSIONS
Indications and choice of type of hip arthroplasty should be balanced in osteoporotic bones in particular. While preoperative bone mineral density measurement allows the prediction of mechanical bone quality, its relevance in predicting failure in arthroplasty treatment remains unclear.
Krischak
Gert D
GD
Department of Traumatology, Hand and Reconstructive Surgery, University of Ulm, Steinhoevelstrasse 9, D-89075 Ulm, Germany. gert.krischak@medizin.uni-ulm.de
Wachter
Nikolaus J
NJ
Zabel
Tanja
T
Suger
Gebhard
G
Beck
Alexander
A
Kinzl
Lothar
L
Claes
Lutz E
LE
Augat
Peter
P
D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D001696:Biomechanical Phenomena; D015519:Bone Density; D005270:Femur Head / Q000503:physiopathology*; D006801:Humans; D008875:Middle Aged; D011237:Predictive Value of Tests; D011475:Prosthesis Failure