Jasper Van Tiel MD, Presenter: Nothing to Disclose

Michiel Siebelt MD, Abstract Co-Author: Nothing to Disclose

Max Reijman, Abstract Co-Author: Nothing to Disclose

Koen Bos, Abstract Co-Author: Nothing to Disclose

Erwin Waarsing, Abstract Co-Author: Nothing to Disclose

Jan Verhaar, Abstract Co-Author: Nothing to Disclose

Gabriel P. Krestin MD, PhD, Abstract Co-Author: Consultant, General Electric Company Research Grant, General Electric Company Research Grant, Bayer AG Research Grant, Siemens AG Speakers Bureau Siemens AG

Harrie Weinans, Abstract Co-Author: Nothing to Disclose

Edwin H.G. Oei MD, PhD, Abstract Co-Author: Nothing to Disclose

Recently, the ability of CT arthrography (CTa) to quantitatively measure knee cartilage composition in terms of its sulphated glycosaminoglycan (sGAG) content has been demonstrated in an ex-vivo study using human cadaveric knee joints. Since a validation study comparing in-vivo acquired CTa outcomes against ex-vivo reference standards for cartilage composition has not yet been performed, the aim of the present study was to perform such a validation in humans with knee OA.

We included 12 knee OA patients (Kellgren and Lawrence grade 2-4) who underwent CTa one month before total knee replacement (TKR). Mean X-ray attenuation values were calculated in 6 regions of interest (ROI) of the articular cartilage (medial and lateral weight-bearing femoral condyles and tibial plateaus and non- weight-bearing cartilage of the condyles). All cartilage ROIs were harvested during TKR and rescanned with contrast-enhanced microCT (CE-μCT). Mean CE-μCT X-ray attenuation values served as surrogate reference standard for cartilage sGAG content since it has been shown to accurately measure sGAG. We analyzed the correlation between mean CTa X-ray attenuation and mean CE-μCT X-ray attenuation with linear regression.

Mean X-ray attenuation values of the different ROIs ranged from 115 to 455 Hounsfield Units. Outcomes of CTa had a strong correlation with reference CE-μCT X-ray attenuation, representing sGAG content of articular cartilage, in the femoral (r= 0.76; p< 0.0001; r^2= 0.58), in the tibial (r= 0.77; p< 0.0001; r^2= 0.59) and in the tibiofemoral cartilage (r= 0.76; p= 0.0001; r^2= 0.57) (figure 1).

Our results suggest that CTa can accurately measure sGAG content of articular cartilage in human knee joints in-vivo. The coefficient of determination, however, is only moderate and therefore CTa outcomes are likely to be also influenced by other composites of cartilage, e.g. collagen. Despite the use of intra-articular contrast agent and ionizing radiation, CTa might become a relatively cheap and quick alternative to MRI based techniques to quantitatively measure cartilage composition in patients with contra-indications for MRI.  

CT arthrography can accurately measure cartilage sulphated glycosaminoglycan content in human knee joints in-vivo and might become a cheap and fast alternative to similar MRI based techniques 

Van Tiel, J, Siebelt, M, Reijman, M, Bos, K, Waarsing, E, Verhaar, J, Krestin, G, Weinans, H, Oei, E, Quantitative CT Arthrography of the Human Knee to Measure Cartilage Biochemical Composition: Results of an In-Vivo Validation Study Against Ex-Vivo Reference Standards .  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14014407.html