Fluid collection within the synovial sheath of the tendon of the flexor hallus longus muscle in the tarsal joint of rats: an anatomic variant detectable with magnetic resonance imaging

Abstract

Magnetic resonance (MR) images of the right tarsal joint of 22 normal male Han:Wistar rats were acquired using a 4.7 T magnet. An intermediate-high signal area associated with the tendon of the flexor hallus longus muscle was noticed in three rats on T2-weighted images. These areas appeared as an intermediate-high signal on lightly T2-weighted images, but appeared as an iso-signal to muscle structure on proton density weighted images. Histology preparations showed that such areas were caused by a sizable fluid collection within the synovial sheath of the tendon of the flexor hallus longus muscle, with all other joint structures appearing normal. This anatomic variant could be potentially regarded as a lesion on T2-weighted MR images, such as inflamed tissue with oedema, especially when the spatial resolution and/or signal-to-noise ratio are not optimal.

Some aspects of rat femorotibial joint microanatomy as demonstrated by high-resolution magnetic resonance imaging

“…To date, MRI tomographic knowledge of rodent joint anatomy and pathology is limited (Tessier et al 2003, Wang & Westwood 2006. Indeed, knowledge accumulated for human clinical MRI has been translated into understanding of MRI of animal joints (Banfield & Morrison 2000).…”

Pitfalls in interpreting rat knee joint magnetic resonance images and their histological correlation

“…To date, MRI tomographic knowledge of laboratory animal skeletal anatomy and pathology remains limited (4,11,12). In the meantime, radiologists are increasingly getting involved in animal-based experimental research using modern imaging techniques, as projects leaders or being asked to help interpret imaging findings (7, 13Á15).…”

In vivo three-dimensional magnetic resonance imaging of rat knee osteoarthritis model induced using meniscal transection

“…Animal models of biomechanically induced OA include anterior cruciate ligament transection in dogs, lateral meniscectomy in sheep, partial meniscectomy in rabbits, meniscectomy in guinea pigs and rats, and cruciate ligament transection in rats [1] , [2] , [3] , [4] , [5] , [6] , [7] , [8] . High resolution MRI can noninvasively demonstrate the detailed anatomy and pathological changes, including progression and regression of joint changes of bone, cartilage, synovium, fascia, muscles, and other soft tissues [9] , [10] , [11] , [12] , [13] . MRI has also been used to assess therapeutic effects in animal models, allowing paired comparisons, and increasing statistical power of experiments, and reducing the amount of animal usage [14] , [15] , [16] .…”