Background/Purpose: To validate ultrasound (US) for measuring cartilage thickness, by evaluating cartilage thickness on cadaver specimens of metacarpophalangeal (MCP) joints by US and conventional measurement. To correlate cartilage thickness measured by US with joint space narrowing (JSN) and joint space width (JSW) as assessed on conventional radiographs in MCP joints of patients with rheumatoid arthritis (RA).
Methods: Forty-three consecutive patients with RA were evaluated by US at our outpatient clinic. Bilateral MCP joints of 35 consecutive patients, who had hand x-rays taken within the last 12 months and additionally cadaver specimens of MCP 2-5 joints (n=12) were assessed by ultrasonography and histology. The cartilage layer of the metacarpal heads and proximal phalangeal bases of digits 2-5 were assessed bilaterally using a 15 Mhz linear transducer (GE Logic E9) from dorsal longitudinal and transverse views in midline, with the joints in 90° flexion. Cartilage thickness was measured in mm with an integrated caliper on static images. Both JSW and JSN were evaluated on conventional posterior-anterior radiographs. JSW was quantified as the shortest distance between the subchondral bone plates along the force-bearing axis of the joint using a standard measurement tool of the applied picture archiving and communication system; while JSN was evaluated using the van der Heijde modified Sharp scoring method (vdHS). Ankylosed or luxated joints were not included. Metacarpal cartilage thickness (MCT) of cadaver MCP joints was evaluated using a stereoscopic magnifying loupe and digitised image software. Cartilage thickness was correlated with x-ray findings using Spearman’s or Pearson’s correlation. Intra- and interobserver reliability of US and agreement between US and anatomic measurement were assessed by estimating the intraclass correlation coefficient (ICC).
Results: Agreement (ICC) between US and anatomic measurement of MCT on cadaver specimens of MCP joints (n=12) was 0.62 while the smallest detectable difference was 0.028 mm. Intra- and interobserver reliability of the US measurement of MCT in patients was 0.77 and 0.62 respectively. In the clinical group mean age was 63.1±11.3 years, mean disease duration was 10.6±7.8 years, mean CDAI was 7.76±7.1; 82.9% were female and 54.1% were rheumatoid factor positive. US measurement of MCT of MCP 2-5 in patients was 0.38+/-0,17 mm. MCT of individual joints of the left and right hand correlated with individual MCP JSN (r=-0.799 and -0.702, respectively; p<0.01) and individual MCP JSW (r=0.588 and 0.401, respectively; p<0.01). The sum score of MCS for MCP joint 2-5 correlated with total MCP JSW (r=0.771, p<0.01), total JSN (r=-0.412, p<0.05), sum erosion score of the vdHS (r=-0.500, p<0.01) and the total vdHS (r=-0.576, p<0.01). No significant correlation was found between phalangeal cartilage thickness and JSN.
Conclusion: Both JSW and JSN by radiography indeed represent cartilage thickness at least in MCP joints. US is a validated tool for measuring MCT. When radiographic scoring is not available, US measurement of MCT might be a feasible alternative to depict cartilage damage in patients with RA. Phalangeal cartilage thickness has no added value beyond the measurement of MCT.
Disclosure:
P. Mandl,
None;
G. Supp,
None;
G. Baksa,
None;
D. Aletaha,
None;
R. Kurucz,
None;
D. Niedermayer,
None;
H. Radner,
None;
P. Studenic,
None;
P. V. Balint,
None;
J. S. Smolen,
None.
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ACR Meeting Abstracts - https://acrabstracts.org/abstract/relationship-between-radiographic-joint-space-narrowing-sonographic-cartilage-thickness-and-anatomy-in-rheumatoid-arthritis-and-control-joints/