Abstract
BackgroundFeatures of new bone formation (NBF) are common in tophaceous gout. The aim of this project was to develop a plain radiographic scoring system for NBF in gout.MethodsInformed by a literature review, scoring systems were tested in 80 individual 1st and 5th metatarsophalangeal joints. Plain radiography scores were compared with computed tomography (CT) measurements of the same joints. The best-performing scoring system was then tested in paired sets of hand and foot radiographs obtained over 2 years from an additional 25 patients. Inter-reader reproducibility was assessed using intraclass correlation coefficients (ICC). NBF scores were correlated with plain radiographic erosion scores (using the gout-modified Sharp-van der Heijde system).ResultsFollowing a series of structured reviews of plain radiographs and scoring exercises, a semi-quantitative scoring system for sclerosis and spur was developed. In the individual joint analysis, the inter-observer ICC (95% CI) was 0.84 (0.76–0.89) for sclerosis and 0.81 (0.72–0.87) for spur. Plain radiographic sclerosis and spur scores correlated with CT measurements (r = 0.65–0.74, P < 0.001 for all analyses). For the hand and foot radiograph sets, the inter-observer ICC (95% CI) was 0.94 (0.90–0.98) for sclerosis score and 0.76 (0.65–0.84) for spur score. Sclerosis and spur scores correlated highly with plain radiographic erosion scores (r = 0.87 and 0.71 respectively), but not with change in erosion scores over 2 years (r = −0.04–0.15).ConclusionA semi-quantitative plain radiographic scoring method for the assessment of NBF in gout is feasible, valid, and reproducible. This method may facilitate consistent measurement of NBF in gout.
Highlights
Features of new bone formation such as sclerosis and spurs are common on plain radiography in tophaceous gout [1]
Published definitions of new bone formation features in gout were used in this project [1]: ankylosis—fusion of the bones of a joint, with trabeculae crossing the joint space; osteophyte— bone projection arising along the joint margin and associated with cartilage; periosteal new bone formation—bone proliferation arising from the periosteum; sclerosis—increased density of medullary or subcortical bone; and spur—a sharp spicule of dense bone proliferation extending at an acute angle from the cortex
Literature review of scoring systems There were 840 papers identified, reporting 86 unique scoring systems for new bone formation (Supplementary Fig. S1). These scoring systems were applicable to a range of musculoskeletal conditions including osteoarthritis (n = 61 scoring systems), spondyloarthropathies (n = 16), diffuse idiopathic skeletal hyperostosis (n = 2), heterotopic ossification (n = 2), rheumatoid arthritis (n = 2), psoriatic arthritis (n = 1), slipped capital femoral epiphysis (n = 1), and juvenile idiopathic arthritis (n = 1)
Summary
Features of new bone formation such as sclerosis and spurs are common on plain radiography in tophaceous gout [1]. There have been some reports of reparative processes with increased new bone formation in response to intensive urate-lowering therapy [3, 4], it is not possible to systematically quantify these changes at present, due to the lack of a validated scoring method. The aim of this project was to develop a plain radiographic scoring system for new bone formation in patients with gout. Features of new bone formation (NBF) are common in tophaceous gout The aim of this project was to develop a plain radiographic scoring system for NBF in gout
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