Bone status in rheumatoid arthritis assessed at peripheral sites by three different quantitative ultrasound devices.

Rheumatoid arthritis (RA) is characterized by periarticular and generalized loss of bone mass. Quantitative ultrasound (QUS) has been introduced as a method for the assessment of bone status and fracture risk. In this cross-sectional study bone status was assessed by QUS at different peripheral sites in 27 women with RA (mean disease duration 15 years) and in 36 healthy women matched for age, height and weight. Speed of sound (SOS, m/s), broadband ultrasound attenuation (BUA, dB/MHz) and stiffness of the calcaneus were assessed by a Lunar Achilles device. Amplitude-dependent SOS (Ad-SOS, m/s) of the second to fifth phalanx was measured by a DBM Sonic 1200, and SOS of the distal forearm and third phalanx was measured by a Omnisense multisite scanner. Bone mass (g/cm2 or g) of the hip, spine, distal forearm and total body was measured by dual-energy X-ray absorptiometry. QUS values were significantly reduced in RA at most sites ( p<0.005-0.001), but between-group differences were small, and large overlaps between the groups were noticed. After correction for bone mass, the observed differences remained statistically significant for the calcaneus and distal radius ( p<0.05). Independent associations between ultrasound measures and markers of disease activity were not demonstrated. In conclusion, bone status as assessed by QUS was compromised in RA, but whether ultrasound transmission may serve as a marker of disease progression and fracture risk in the individual patient remains to be clarified in prospective studies.

Effects of silicone breast prostheses on the assessment of body composition by dual-energy X-ray absorptiometry.

We examined the influence of silicone breast prostheses on body composition as assessed by dual-energy X-ray absorptiometry (DXA). Eighteen women were measured with and without a pair of silicone breast prostheses placed on the upper part of the trunk simulating endogenous implants. Bone area, bone mineral content (BMC), areal bone mineral density (BMD), lean tissue mass (LTM) and fat tissue mass (FTM) of the total body and of the subregions of the body, i.e. the head, trunk, arms and legs, were measured by a Norland XR-36 DXA scanner. After application of the silicone prostheses, bone area, BMC and BMD of the total body significantly increased by an average of 3.7, 6.6 and 3.4% (P<0.0001), respectively. Total body LTM and FTM were not affected. In the trunk region, changes were more pronounced. Trunk BMC, for example, was overestimated by 17.9% (P<0. 0001). The prostheses also influenced measurements of truncal soft tissue composition, with a small but statistically significant overestimation of both LTM (1.1%) and FTM (2.1%) (P<0.05). No changes in bone mass and soft tissue composition were seen in the head, arms and legs. Activation of a high-density detection software utility provided by the manufacturer had no influence on any of the measurements. We conclude that silicone breast prostheses affect the assessment of body composition by DXA.

Influence of orthopaedic metal and high-density detection on body composition as assessed by dual-energy X-ray absorptiometry.

We examined the influence of orthopaedic material and computerized high-density detection (HDD) on analysis of bone mass and soft tissue composition performed by dual-energy X-ray absorptiometry (DXA). Measurements of total and regional bone area, bone mineral content (BMC), areal bone mineral density (BMD), lean tissue mass (LTM) and fat tissue mass (FTM) were made using a Norland XR-26 DXA scanner with dynamically changing samarium filtration. Twenty-one subjects who were free of metal implants were measured without and with a Biomet femoral prosthesis (titanium) placed on the proximal part of the femoral region. Twenty-one women with an endogenous prosthesis in the proximal femur were measured once. Analyses of tissue composition were performed without and with HDD using software provided by the manufacturer. Measurements were considerably affected by exogenous metal with overestimation of LTM and underestimation of FTM and bone area. BMC and BMD were over- or underestimated depending on the anatomical region. Enabling the HDD mode, values of bone area and tissue mass came closer to the expected values (-metal/-HDD) but were in general still significantly different from these. For the total body, the following significant changes were found after application of metal (+metal/-HDD vs. +metal/+HDD, mean values): bone area -19.8% vs. -6.9%, BMC +1.1% vs. -2.1%, BMD +26.5% vs. +4.7%, LTM +12.4% vs. +3.7%, FTM -15.8% vs. -7.0%. A similar pattern of change in tissue composition and bone area was found for the subregions of the body. Changes in tissue composition after HDD were similar in subjects with exogenous and endogenous metal, indicating that the experimental model was appropriate. In conclusion, measurements of tissue composition were substantially influenced by orthopaedic metal. HDD partly corrected for the artefacts induced by the metal.

Early changes in muscle strength after total knee arthroplasty. A 6-month follow-up of 30 knees.

We studied 30 patients with arthrosis in one knee operated on with a cemented (n 26) or an uncemented total knee arthroplasty (TKA) (n 4). Full weight-bearing from the first postoperative day was allowed in all patients, and they received standard postoperative physiotherapy. 1 week prior to surgery, and after 3 and 6 months, isokinetic and isometric muscle strength in both legs were measured, using a Cybex 6000 dynamometer. Isokinetic tests showed a bilateral, significant, and progressive increase (30-53%) in flexor muscle strength most pronounced in the operated legs. Isokinetic extensor strength increased significantly (14-18%) in the operated legs, while in the contralateral legs, a limited increase was found. Isometric flexion strength significantly decreased in the operated knees (17%). Isometric extension strength showed a temporary decrease at 3 months, which returned to the preoperative level. No significant change in isometric strength was observed in the contralateral legs. The knee pain during the muscle strength measurements decreased significantly from the preoperative level, which may indicate that the substantial pain relief within 3 months after a TKA is an important factor for evaluation of muscle strength.

Mechanism of aminoglycoside resistance in Danish Staphylococcus aureus strains during the years 1979-1987.

A total of 49 gentamicin-resistant strains of Staphylococcus aureus isolated from blood (n = 26) or from other sites (n = 23) during the years 1979 to 1987 were evaluated for the presence of aminoglycoside-inactivating enzymes on the basis of minimum inhibitory concentrations measured by agar dilution as well as inhibition zone diameters determined by disc diffusion. Enzymatic activity was caused by AAC (6')III/APH (2") in 45 strains, and by AAC (6')III/APH (2") + APH (3') in four strains. No changes in the distribution of enzymatic activity were observed during the eight years.