Our aim was to determine the precision of the measurements of bone mineral density (BMD) by dual-energy x-ray absorptiometry in the proximal femur before and after implantation of an uncemented implant, with particular regard to the significance of retro- and prospective studies. We examined 60 patients to determine the difference in preoperative BMD between osteoarthritic and healthy hips. The results showed a preoperative BMD of the affected hip which was lower by a mean of 4% and by a maximum of 9% compared with the opposite side. In addition, measurements were made in the operated hip before and at ten days after operation to determine the effect of the implantation of an uncemented custom-made femoral stem. The mean increase in the BMD was 8% and the maximum was 24%. Previous retrospective studies have reported a marked loss of BMD on the operated side. The precision of double measurements using a special foot jig showed a modified coefficient of variation of 0.6% for the non-operated side in 15 patients and of 0.6% for the operated femur in 20 patients. The effect of rotation on the precision of the measurements after implantation of an uncemented femoral stem was determined in ten explanted femora and for the operated side in ten patients at 10 degrees rotation and in 20 patients at 30 degrees rotation. Rotation within 30 degrees influenced the precision in studies in vivo and in vitro by a mean of 3% and in single cases in up to 60%. Precise prediction of the degree of loss of BMD is thus only possible in prospective cross-sectional measurements, since the effect of the difference in preoperative BMD, as well as the apparent increase in BMD after implantation of an uncemented stem, is not known from retrospective studies. The DEXA method is a reliable procedure for determining periprosthetic BMD when positioning and rotation are strictly controlled.

Our aim was to determine the precision of the measurements of bone mineral density (BMD) by dual-energy x-ray absorptiometry in the proximal femur before and after implantation of an uncemented implant, with particular regard to the significance of retro-and prospective studies.We examined 60 patients to determine the difference in preoperative BMD between osteoarthritic and healthy hips. The results showed a preoperative BMD of the affected hip which was lower by a mean of 4% and by a maximum of 9% compared with the opposite side. In addition, measurements were made in the operated hip before and at ten days after operation to determine the effect of the implantation of an uncemented custom-made femoral stem. The mean increase in the BMD was 8% and the maximum was 24%. Previous retrospective studies have reported a marked loss of BMD on the operated side.The precision of double measurements using a special foot jig showed a modified coefficient of variation of 0.6% for the non-operated side in 15 patients and of 0.6% for the operated femur in 20 patients.The effect of rotation on the precision of the measurements after implantation of an uncemented femoral stem was determined in ten explanted femora and for the operated side in ten patients at 10°r otation and in 20 patients at 30° rotation. Rotation within 30° influenced the precision in studies in vivo and in vitro by a mean of 3% and in single cases in up to 60%.Precise prediction of the degree of loss of BMD is thus only possible in prospective cross-sectional measurements, since the effect of the difference in preoperative BMD, as well as the apparent increase in BMD after implantation of an uncemented stem, is not known from retrospective studies. The DEXA method is a reliable procedure for determining periprosthetic BMD when positioning and rotation are strictly controlled. J Bone Joint Surg [Br] 2000;82-B:1065-71. Received 8 January 1999; Accepted after revision 27 August 1999Measurements of the bone mineral density (BMD) of the proximal femur after arthroplasty of the hip have been made for a number of years, mainly in retrospective studies [1][2][3][4][5] in which a reduction of up to 50% has been observed compared with the non-operated side. Prospective studies could not predict a reduction in BMD by this amount. The maximum reduction of BMD two years after arthroplasty was 38% compared with the immediate postoperative density of the operated femur. 6-10 Direct comparison of retroand prospective studies is not possible since the implant time of the prostheses is markedly different and it has not been possible to identify the degree to which the BMD of both femora differ because of individual differences, and the effect of implantation of an uncemented stem. 11We have compared the preoperative with the immediate postoperative BMD and examined the effect of implantation. The method of measurement and the influence of rotation in vitro and in vivo after implantation of an uncemented custom-made femoral stem were compared with those in standard uncemente...

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A s part of the infection control response to the SARS-CoV-2 pandemic, several measures are necessary during exercise testing in Sports Medicine which all aim at preventing risk to our patients and colleagues and contribute generally to the reduction of contact required in the public sector. This article serves as a Guideline for action, describing the contents and implementation of these measures. Basically, the public and hospital-specific guidelines must be adhered to on site. Due to the developing status of knowledge concerning this new disease, these recommendations may be valid only for a short period. They will be revised as things develop or by 01.08.2020 at the latest. SARS-CoV-2 is one member of the species SARS-associated corona viruses, it is a contained RNA virus with an unsegmented genome (monopartite), i. e. only a single nucleic acid molecule (here RNA) surrounded by a capsid. It is sensitive to disinfectants and physical measures like heating and drying.The main transmission of SARS-CoV-2 is by droplets arising from coughing and sneezing and contracted by the person opposite via the mucosae of the nose, mouth and possibly the eyes; contact infections are also possible.Exercise leads to increased ventilation of the test person and to the release of droplets, aerosol and sweat. Sweat does not contain corona viruses. Studies to date on SARS-CoV-2 show that mechanically-generated aerosols contain SARS-CoV-2 viruses. Thus transmission in ambient air or on surfaces appears to be possible (2,6). But the fact that viruses are present does not permit a conclusion that contagion occurs. The main route of transmission is by droplet. Whether transmission via aerosols is also possible has not yet been convincingly demonstrated. It does not, at least, appear to be a major mode of transmission. The Robert Koch-Institut (RKI) points out, however, that these studies do not present the usual modes of transmission. In a commentary by the U. S. National Academies of Sciences in early April 2020, it is assumed that transmission via exhalation of SARS-CoV-2 is possible (4). The RKI cites two other studies (1, 5) in which the ambient air around COVID-19 patients with considerable virus burden in the respiratory tract was examined, but no proof of SARS-CoV-2 was found.According to the RKI (Status 16.4.2020), it is not yet possible to definitively estimate the risk of transmission of SARS-CoV-2 via the exhaled breath of infected persons. The RKI concludes that "transmission of SARS-CoV-2 via aerosols in normal social dealings cannot be ruled out".

The therapeutic strategy for patients with osteoarthritis of the knee should be reconsidered to include less expensive therapeutic sport measures. Anglo-american and Scandinavian studies support this statement. Overuse and pain can be avoided by precise and low-dose strength training. Objective and reproducible measurements in the patients are essential to make individual training possible.