DXA vs QCT: in vitro and in vivo studies.

The aim of this study was to evaluate the discrepancy between bone mineral density (BMD) results when using dual X-ray absorptiometry and quantitative computed tomography both in vitro and in vivo. Using these two techniques, we found that the T-score densitometric index values were discrepant in the BMD qualitative evaluation, which can affect the diagnosis of osteopenia or osteoporosis, thus we propose its modification.

[The hyperostotic knee]. / Il ginocchio iperostosico.

Diffuse idiopathic skeletal hyperostosis (DISH) is a disorder characterized by bone proliferation of spinal and extraspinal structures. Frequently, extraspinal manifestations may occur before the involvement of the spine. These alterations are so common and characteristic that they should be included in the diagnostic criteria for DISH. The patella is one of the most commonly involved sites. The knee of 48 patients affected by DISH, according to Resnick's diagnostic criteria, were subjected to systematic, radiographic and xerographic studies. The most characteristic radiographic patterns are: thickening of the anterior margin of the patella (81.1%); ossifying enthesopathy of supero-anterior margin of patella (68.7%); periosteal new bone formation on the tibial insertion of the cruciate ligaments (47.8%); presence of fabella (41.%); presence of megafabella (22.9%), which may come near the posterior profile of the femur. Changes are usually symmetrical in DISH: entheseal abnormalities mostly involve the antero-superior margin of the patella, whereas in osteoarthritis, osteophytes are found on the postero-superior margin. In the lateral view enthesophytes at the bone attachment of the cruciate ligaments are oriented inside the joint space; on the contrary, osteophytes are always oriented outside the joint space. Radiographic manifestations of the fabella are similar to those observed in osteoarthritis, and so they cannot be utilized in the differential diagnosis of these diseases.