Validity of joint space width measurements in hand osteoarthritis

To investigate the validity of joint space width (JSW) measurements in millimeters (mm) in hand osteoarthritis (OA) patients by comparison to controls, grading of joint space narrowing (JSN), and clinical features.

Hand radiographs of 235 hand OA patients (mean age 65 years, 83% women) and 471 controls were used. JSW was measured with semi-automated image analysis software in the distal, proximal interphalangeal and metacarpal joints (DIPJs, PIPJs and MCPJs). JSN (grade 0-3) was assessed using the osteoarthritis research society international (OARSI) atlas. Associations between the two methods and clinical determinants (presence of pain, nodes and/or erosions, decreased mobility) were assessed using Generalized Estimating Equations with adjustments for age, sex, body mass index (BMI) and mean width of proximal phalanx.

JSW was measured in 5631 joints with a mean JSW of 0.98 mm (standard deviation (SD) 0.21), being the smallest for DIPJs (0.70 (SD 0.25)) and largest for MCPJs (1.40 (SD 0.25)). The JSN=0 group had a mean JSW of 1.28 mm (SD 0.34), the JSN=3 group 0.17 mm (SD 0.23). Controls had larger JSW than hand OA patients (P-value<0.001). In hand OA, females had smaller JSW than men (β -0.08, (95% confidence interval (95% CI) -0.15 to -0.01)) and lower JSW was associated with the presence of pain, nodes, erosions and decreased mobility (adjusted β -0.21 (95% CI -0.27, -0.16), -0.37 (-0.40, -0.34), -0.61 (-0.68, -0.54) and -0.46 (-0.68, -0.24) respectively). These associations were similar for JSN in grades.

In hand OA the quantitative JSW measurement is a valid method to measure joint space and shows a good relation with clinical features.