The potential role of protease systems in hemophilic arthropathy.

Hemophilic arthropathy (HA) is characterized by joint damage following recurrent joint bleeds frequently observed in patients affected by the clotting disorder hemophilia. Joint bleeds or hemarthroses trigger inflammation in the synovial tissue, which promotes damage to the articular cartilage. The plasminogen activation system is integral to fibrinolysis, and the urokinase plasminogen activator, or uPA in particular, is strongly upregulated following hemarthroses. uPA is a serine protease that catalyzes the production of plasmin, a broad-spectrum protease that can degrade fibrin as well as proteins of the joint extracellular matrix and cartilage. Both uPA and plasmin are able to proteolytically generate active forms of matrix metalloproteinases (MMPs). The MMPs are a family of >20 proteases that are secreted as inactive proenzymes and are activated extracellularly. MMPs are involved in the degradation of all types of collagen and proteoglycans that constitute the extracellular matrix, which provides structural support to articular cartilage. The MMPs have an established role in joint destruction following rheumatoid arthritis (RA). They degrade cartilage and bone, indirectly promoting angiogenesis. MMPs are also implicated in the pathology of osteoarthritis (OA), characterized by degradation of the cartilage matrix that precipitates joint damage and deformity. HA shares a number of overlapping pathological characteristics with RA and OA. Here we discuss how the plasminogen activation system and MMPs might exacerbate joint damage in HA, lending insight into novel possible therapeutic targets to reduce the comorbidity of hemophilia.

MR of the cauda equina.

To define the anatomy of the cauda equina nerve roots by MR imaging, the lower spine of 14 normal volunteers was imaged using a high-field surface-coil technique. A total of 56 sagittal and 56 axial MR sections (eight selected slices from each case) were correlated with undistorted anatomic sections from cadaver spine specimens, and the visualization of the nerve roots was assessed. In addition, MR images of three patients with infiltrating or seeding tumors affecting the cauda equina were analyzed. Seventy-eight percent of the MR sections from normal cases clearly showed the anatomy of the cauda equina nerve roots. The nerve roots were fairly shown in 17% of the sections; and false findings (presumably caused by CSF pulsation) were observed in the remaining 5%. Coronal imaging provided excellent anatomic views of the nerve roots within the intervertebral foramina. Morphologic alterations in the pathologic cases were correctly shown when both T1- and T2-weighted imaging were used. In conclusion, MR proved efficient in viewing the cauda equina region.

Three-dimensional computed tomography in maxillofacial trauma.

Roentgenographic evaluation of maxillofacial trauma is an integral component in the management of the acutely injured patient. Recent developments in computerized software permit three-dimensional computed tomographic (CT) reconstructions of complex anatomic parts. Five examples of complex maxillofacial trauma were demonstrated by conventional plain films, followed by two-dimensional and three-dimensional CT. Three-dimensional CT vividly demonstrates spatial relationships not easily conceptualized by present modalities.

Magnetic resonance imaging of the temporomandibular joint meniscus.

This report describes early experience with magnetic resonance imaging (MRI) of the temporomandibular joint meniscus in which surface coil technology was used. The results suggest remarkable imaging capabilities and speed with noninvasive methods.