Sonographic measurements of low-echoic synovial area in the dorsal aspect of metatarsophalangeal joints in healthy subjects.

INTRODUCTION

Assessment of synovitis in the metatarsophalangeal (MTP) joints with ultrasound has been shown to improve the accuracy of assessment of rheumatoid arthritis (RA). However, the presence of intraarticular low-echoic synovial area (LESA) in the MTP joints in healthy subjects complicates the sonographic assessment of these joints.

METHOD: Healthy subjects with no arthritic symptoms in their MTP joints were recruited. All subjects completed a questionnaire and underwent physical examination and sonographic assessment. LESAs in the dorsal aspect of all MTP joints were measured in the longitudinal view.

RESULTS

One thousand non-arthritic MTP joints in 100 healthy subjects (female 73, mean age 41.0 years old) were evaluated. Measurable LESAs were identified in all joints assessed. Mean length of LESA in each of the 1st-5th MTP joints was 17.8, 13.9, 11.9, 10.6, and 9.2 mm, respectively, whereas mean thickness was 2.4, 2.4, 1.8, 1.2, and 0.8 mm, respectively. Multivariate linear regression models identified the difference between 1st and 5th MTP joints as the most independently influential factor on the measurement of LESA.

CONCLUSIONS

Our data provide the normal reference values for the measurements of LESA in Japanese, which should be taken into consideration when the synovitis in MTP joints is evaluated with ultrasound.