PRECISION OF SONOGRAPHIC MEASUREMENT OF ARTICULAR-CARTILAGE - INTEROBSERVER AND INTRAOBSERVER ANALYSIS

Objective. To establish the precision of sonographic measurement of th e thickness of the articular cartilage of the hip and knee in children . Design. The precision was assessed by evaluating the intra- and inte robserver variations in sonographic measurements. Patients. A total of 65 healthy children were in the study. The articular cartilage of the right hip and knee of 40 subjects (mean age 10.3 years, range 4-16.9 years) was evaluated in masked fashion by two observers to assess the interobserver variability. The articular cartilage of the right hip an d knee of 25 children (mean age 10.1 years, range 6.2-15.5 years) was examined twice by the same observer to assess the intraobserver variab ility. Results and conclusions. Discrepancies between repeated measure ments were expressed as data differences. The ''limits of agreement'' of data differences, i.e. the mean +2 SD and the mean -2 SD, ranged fr om -0.26 to +0.22 mm and from -0.56 to +0.48 mm for the interobserver analysis of the femoral head cartilage (FHC) and femoral condylar cart ilage (FCC), respectively. The ''limits of agreement'' for the intraob server analysis ranged from -0.16 to +0.15 mm and from -0.51 to +0.41 mm for the FHC and the FCC, respectively. The overall precision of the sonographic measurements was satisfactory. When used for determinatio n of skeletal age, sonographic assessment of FHC thickness resulted in under/overestimation of skeletal age by about 7.5 months. In conclusi on, sonographic measurement of articular cartilage is precise enough t o be used in clinical practice.