Measurement of bone mineral density is possible with standard radiographs: a study involving total knee replacement.
BACKGROUND
Measured bone density correlates well with the mechanical properties of the bone. Our objective was to evaluate optical densitometry as a method of measuring the periprosthetic bone density of the tibial platform in total knee replacement using serial dual-energy X-ray absorptiometry (DXA) as the reference test.


METHODS
30 patients who underwent a cemented total knee replacement were followed up for over 2 years. Standard radiographs of the knee were obtained at 12 and 24 months. These were photographed with a digital camera and enhanced with image processing software. A DXA scan was performed at the same time as the reference method. 3 regions of interest were defined under the tibial plateau (medial, lateral and stem positions).


RESULTS
After 24 months of follow-up there was a significant decrease in density in the 3 regions, both with the optical and DXA methods. The concordance between methods was studied using Bland and Altman plots, Cronbach's alpha and intraclass correlation coefficients resulted in values from 0.72 to 0.87, depending on the region and the follow-up time.


CONCLUSIONS
Quantification of optical density values with a standardized measurement system on conventional radiographs is a reliable and efficient method of determining the bone mineral density.
Department of Orthopaedic Surgery and Clinical Research Unit, Hospital San Agustin, Avilés, School of Medicine, University of Oviedo, Spain. dhernandezv@meditex.es
Daniel
D
Hernandez-Vaquero
Manuel Angel
MA
Garcia-Sandoval
Jose Manuel
JM
Fernandez-Carreira
Abelardo
A
Suarez-Vázquez
Domingo
D
Perez-Hernández
D015502:Absorptiometry, Photon / Q000379:methods; D000368:Aged; D019645:Arthroplasty, Replacement, Knee; D015519:Bone Density; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007719:Knee Joint / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged