[Three dimensional ultrasound volumetric assessment of the synovial fluid in the ankle and hindfoot: Technique and normative data].

PURPOSE: Since synovial fluid is an important marker of disease, we performed three-dimensional ultrasound volumetric measurements of synovial fluid to provide baseline normative data.

MATERIALS AND METHODS: Volume data were acquired using a 7-10 MHz three dimensional ultrasound probe on 40 ankles in 20 volunteers (25-61 years). Amounts of fluid were assessed in the ankle joint recesses, bursae and tendon sheaths. Images were acquired in the sagittal plane and were reconstructed in three orthogonal planes; transverse, sagittal and coronal. Fluid volumes were calculated from the volume data set using the manual planimetric method.

RESULTS: Fluid in tendon sheaths was most common about the peroneals, and unlike prior MRI results, was less common around the flexors. In the flexors, fluid was most common around the flexor hallucis longus tendon, less common around posterior tibial tendon, and rare around fleksor digitorum longus tendon. In the extensors, fluid was less common but, when present, of greater volume, especially around the extensor hallucis longus tendon. Fluid was most common around the anterior tibial tendon and rare around the extensor digitorum longus tendon. Sparse fluid was seen in the majority of retrocalcaneal bursae. Fluid in the anterior ankle recess was quite common. Visualization of fluid in the posterior ankle recess was infrequent.

CONCLUSION: Three-dimensional ultrasound permits measurement of fluid volume in the normal ankle/hindfoot; normative data are provided.