The foot and ankle are commonly involved in a range of arthritides that affect the joints, bones, and soft tissues. Accurate plain film interpretation can often aid the diagnosis and monitor disease progression and treatment response. Ultrasound and MRI afford superior depiction of the soft tissues, and advances over recent years have centered on early detection of synovitis, enabling earlier diagnosis and treatment. Advantages and disadvantages of the imaging techniques of radiography, multidetector computed tomography, ultrasound, and MRI are discussed, as is optimization of these modalities for the assessment of the anatomically complex joints of the foot and ankle. Diagnostic features enabling differentiation between rheumatoid arthritis, seronegative spondyloarthropathies, osteoarthritis, gout, crystal deposition disease, pigmented villonodular synovitis, Charcot arthropathy, septic arthritis, synovial osteochondromatosis, hemophilia, and reflex sympathetic dystrophy are also reviewed.
Deep-seated, low-grade lipomatous lesions detected on imaging often cause uncertainty for diagnosis and treatment. Confidently distinguishing lipomas from well-differentiated liposarcomas is often not possible on imaging. The approach to management of such lesions varies widely between institutions. Applying an evidenced-based approach set around published literature that clearly highlights how criteria such as lesion size, location, age and imaging features can be used to predict the risk of well-differentiated liposarcomas and subsequent de-differentiation would seem sensible. Our aim is to review the literature and produce a unified, evidence-based guideline that will be a useful tool for managing these lesions.
An intraosseous pneumatocyst is an unusual cause of gas in a vertebral body and is rarely reported in the thoracic spine. We report the evolution of thoracic spine pneumatocysts, one that enlarged rapidly with resorption of fluid and one that resolved. A 65-year-old female with lower back and left leg pain underwent MRI of the lumbar spine, which demonstrated a well-defined lesion in a T10 vertebral body of low-signal on T(1) and T(2) weighted imaging. CT confirmed this as a gas-containing cyst. Review of previous imaging showed that this lesion had initially contained fluid and had expanded rapidly over 14 months. It also showed smaller pneumatocysts, which had resolved. The variable natural history and imaging features of pneumatocysts make them an important differential diagnosis of an intravertebral lesion. Their aetiology is not known, but previous case reports suggest that they can occur spontaneously or in association with vacuum phenomenon in adjacent discs or facet joints. Previous reports have observed that they can fill with granulation tissue or fluid, and the case we report demonstrates that this fluid can be resorbed and that the pneumatocyst can undergo rapid enlargement. A pneumatocyst is a differential diagnosis for an expanding intravertebral lesion of indeterminate MRI characteristics. The diagnosis can be made with CT if the lesion is gas or gas and fluid filled.
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