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Notes: Abstract The histological and enzymatic effects of single-dose irradiation of 7 Gray (Gy) versus fractionated irradiation of 5 × 2 Gy on the suppression of heterotopic ossification were examined over a period of 60 days in adult male Wistar rats (n = 57). The standardized osteogenesis model system in rats [9, 10, 11, 16, 19] was used for this purpose. The course of developing ossifications was documented quantitatively and qualitatively by means of quantitative computed tomography/osteodensitometry and digital luminescence radiography. Assessment of the activities of the enzymes alkaline and acid phosphatase throughout the experiment as well as characterization of the isoenzyme of alkaline phosphatase (AP) in connection with histological observations displayed a metaplasia of the ingrowing connective tissue into bone-typical cells during osteoinduction. Thus, the increase of AP is the first sign of a functional transformation of mesenchymal stem cells into chondroid bone cells. The increase in the acid phosphatase level with a maximum of acitivity between the 15th and 30th day (according to the respective treatment group) is highly suggestive of a remodeling process paralleling incipient chondroclast and osteoclast activity. In the animal groups undergoing irradiation, the above-mentioned increase of enzymes occurred after a delay. Furthermore, the maximum values observed were lower than those in the group not undergoing irradiation. Both findings were more manifest in the animal group which underwent 5 × 2 Gy of radiation than in the group which underwent single-dose irradiation of 7 Gy. Radiation suppresses matrix-induced osteogenesis. The histological and enzymatic course of this process was unchanged in the animals which did not undergo irradiation. However, it was quantitatively reduced and accompanied by a retardation of osteogenesis. Both effects were again reduced with fractionated irradiation of 5 × 2 Gy, which is theoretically dose-equivalent to a 1 × 7 Gy application. Histological examinations revealed damage to the migratory, proliferating mesenchymal stem cell population by irradiation doses which had relatively small effects on preosteoblasts, osteoblasts, chondroblasts and other specialized cell forms. Therefore, it may be concluded that the smaller degree of heterotopic ossification in the irradiated groups was due to damage of and a decrease in the number of mesenchymal stem cells at the implant site. Our results stress the necessity of instituting postoperative irradiation therapy as early as possible to prevent heterotopic ossification. In view of experimentally proven better effects, fractionated irradiation has to be preferred to a dose-equivalent single-dose radiation, especially considering the fewer side-effects noted with fractionated irradiation.

Notes: Abstract Arthroscopy of the wrist is a helpful diagnostic procedure in cases of painful problems that cannot be diagnosed by clinical and radiological examination. Arthroscopy of the wrist was done in 32 patients, who could not be diagnosed by clinical and radiological examination. During arthroscopy, lesions of the fibrocartilaginous disc and of the cartilage, synovitis of the joint capsule, scaphoidlunate dissociations and a loose body were detected. As a result of arthroscopic findings, 10 operative procedures were necessary. Resection of a torn disc, local synovectomy, reconstruction of the torn scaphoid-lunate ligament and removal of a loose body were done by open arthrotomy (8 patients). In 2 patients shaving of chondral ulcers on the radial joint surface was performed, which obviated the need for an explorative arthrotomy. Arthroscopy is a simple method that enables new diagnostic possibilities in rare but difficult cases of posttraumatic pain of the wrist.