Background Accurate detection of bone erosions in RA patients is important both for clinical studies and practice. US has been demonstrated to be more sensitive than x rays for detecting erosions.(1)Yet there are certain limitations: acoustic window (sesamoids, osteophytes), anatomical pitfalls (vessel channels, grooves, normal irregularities). Thus, further US studies on standardization are needed.
Objectives To evaluate by PDUS physiological cortical breaks of metacarpophalangeal joints (MCPJ) and proximal interphalangeal joints (PIPJ) in HI to investigate whether their localization correlates with erosive lesions in RA.
Methods MCPJ and PIPJ of both hands of 43 HI (without history of inflammatory joint disease) and 40 RA patients were examined by PDUS (ESAOTE MyLab 70, Genoa Italy) at palmar, dorsal and lateral side (MCP2+5). Width and depth were assessed longitudinally and transversally. Cortical break was defined as a defect in cortical lining detectable in 2 perpendicular planes (2). Physiological and abnormal breaks were defined according to the examiner. Moreover, MCP 2-5 and PIPJ 2-4 of the clinically more affected hands of 27 (17 for PIP) RA patients and of the dominant hands of 20 (8 for PIP) HI were scanned in μCT. Prevalence, sensitivity (Se) and specificity (Sp) of breaks in PDUS and μCT were recorded and compared.
Results By PDUS a total of 731 scans were made in PIP and 1118 in MCP in HI, and 680 in PIP and 1040 in MCPJ in RA. 24 PIP and 80 MCPJ were additionally evaluated by μCT in HI, and 51 PIP and 108 MCP respectively in RA. By PDUS, in HI, 226/1118 breaks (20%) were detected in MCP and 115/731 (16%) in PIP. 222 (98%) of MCP breaks (61% palmar) and 100% of PIP (98.5% palmar) were considered physiological. In RA 255/1040 (25%) breaks were detected in MCP by PDUS, 143 (14%) physiological (64% palmar) and 112 (11%) pathological (i.e. erosions) (51% lateral); and 90/680 (13%) breaks were detected in PIP, 66 (10%) normal (100% palmar) and 24 (3.5%) abnormal (100% dorsal). All physiological breaks were considered vessel channels. Specificity of PDUS for detecting and defining normal/abnormal breaks was very good. Table 1 shows mean values of abnormal breaks, tab. 2 Se and Sp.
Conclusions US allows the exact location and discrimination between bone erosions and physiological breaks in cortical bone. Both US and μCT could identify predilection sides for nutritive vessels.
Wakefield RJ et al. The value of sonography in the detection of bone erosions in patients with rheumatoid arthritis: a comparison with conventional radiography. Arthritis Rheum. 2000 Dec;43(12):2762-70.
Wakefield RJ et al. Musculoskeletal ultrasound including definitions for ultrasonographic pathology. J Rheumatol. 2005 Dec;32(12):2485-7.
Disclosure of Interest None Declared
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