title: Measuring finger joint cartilage by ultrasound as a promising alternative to conventional radiograph imaging.
abstract: OBJECTIVE
  To evaluate the reliability and validity of a novel ultrasound (US) imaging method to measure metacarpophalangeal (MCP) and proximal interphalangeal (PIP) finger joint cartilage.
  
  
  METHODS
  We examined 48 patients with rheumatoid arthritis (RA), 18 patients with osteoarthritis (OA), 24 patients with unclassified arthritis of the finger joints, and 34 healthy volunteers. The proximal cartilage layer of MCP and PIP joints for fingers 2-5 was bilaterally visualized from a posterior view, with joints in approximately 90 degrees flexion. Cartilage thickness was measured with integrated tools on static images. External validity was assessed by measuring radiologic joint space width (JSW) and a numeric joint space narrowing (JSN) score in patients with RA.
  
  
  RESULTS
  Precise measurement was possible for 97.5% of MCP and 94.2% of PIP joints. Intraclass correlation coefficients for bilateral total joint US scores were 0.844 (95% confidence interval [95% CI] 0.648-0.935) for interobserver comparisons and 0.928 (95% CI 0.826-0.971) for intraobserver comparisons (using different US devices). The US score correlated with JSN for both hands (adjusted R(2) = 0.513, P < 0.001) and JSW of the same finger joints (adjusted R(2) = 0.635, P < 0.001). Reduced cartilage shown by US allowed discrimination of early symptomatic OA versus early RA and healthy joints. In patients with RA, US scores correlated with duration of treatment-resistant, progressive RA.
  
  
  CONCLUSIONS
  The US method of direct visualization and quantification of cartilage in MCP and PIP joints is objective, reliable, valid, and can be useful for diagnostic purposes in patients with arthritis.
authors.affiliation: University Hospital Berne, Inselspital, Berne, Switzerland. burkhard.moeller@insel.ch
authors.forename: Burkhard
authors.initials: B
authors.lastname: Möller
authors.forename: Harald
authors.initials: H
authors.lastname: Bonel
authors.forename: Marianne
authors.initials: M
authors.lastname: Rotzetter
authors.forename: Peter M
authors.initials: PM
authors.lastname: Villiger
authors.forename: Hans-Rudolf
authors.initials: HR
authors.lastname: Ziswiler