Relationship of bone erosion with the urate and soft tissue components of the tophus in gout: a dual energy computed tomography study.
Imaging and pathology studies have established a close relationship between tophus and bone erosion in gout. The tophus is an organized structure consisting of urate crystals and chronic inflammatory tissue. The aim of this work was to examine the relationship between bone erosion and each component of the tophus.



Plain radiographs and dual energy CT scans of the feet were prospectively obtained from 92 people with tophaceous gout. The 10 MTP joints were scored for erosion score, tophus urate and soft tissue volume. Data were analysed using generalized estimating equations and mediation analysis.



Tophus was visualized in 80.2% of all joints with radiographic (XR) erosion [odds ratio (OR) = 7.1 (95% CI: 4.8, 10.6)] and urate was visualized in 78.6% of all joints with XR erosion [OR = 6.6 (95% CI: 4.7, 9.3)]. In mediation analysis, tophus urate volume and soft tissue volume were directly associated with XR erosion score. About a third of the association of the tophus urate volume with XR erosion score was indirectly mediated through the strong association between tophus urate volume and tophus soft tissue volume.



Urate and soft tissue components of the tophus are strongly and independently associated with bone erosion in gout.
Bone and Joint Research Group, Department of Medicine.
Mark
M
Sapsford
Bone and Joint Research Group, Department of Medicine.
Gregory D
GD
Gamble
Bone and Joint Research Group, Department of Medicine.
Opetaia
O
Aati
Bone and Joint Research Group, Department of Medicine.
Julie
J
Knight
Bone and Joint Research Group, Department of Medicine.
Anne
A
Horne
Department of Anatomy with Radiology, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand.
Anthony J
AJ
Doyle
Bone and Joint Research Group, Department of Medicine n.dalbeth@auckland.ac.nz.
Nicola
N
Dalbeth
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001862:Bone Resorption / Q000000981:diagnostic imaging*; D005260:Female; D033023:Foot Joints / Q000000981:diagnostic imaging*; D006073:Gout / Q000000981:diagnostic imaging*; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D011859:Radiography; D014057:Tomography, X-Ray Computed; D014527:Uric Acid; D055815:Young Adult
D014527:Uric Acid
computed tomography; dual energy computed tomography; erosion; gout; imaging; urate