Measurement of bone by dual-photon absorptiometry (DPA) and dual-energy X-ray absorptiometry (DEXA)

Bone densitometry is essential for (a) confirming a diagnosis of osteoporosis, (b) determining the degree of osteopenia and risk of fracture, and (c) monitoring the response of bone to therapeutic agents. Fracture risk at specific axial fracture sites (spine, proximal femur), is associated directly with bone mineral density (BMD) at these sites. ROC analysis demonstrates that the diagnostic sensitivity of spine and femur BMD for spine and/or femur fracture is substantially superior to BMD of appendicular sites in the immediate postmenopausal period. Femoral neck BMD affords high diagnostic sensitivity for proximal femur fracture even in the elderly. Recent prospective studies have shown that bone densitometry can predict future fractures in postmenopausal women. Conventional DPA with 153Gd provides high accuracy for total body, spine, and femur BMD with adequate clinical precision of 1%, 2% and 3%, respectively. Dual-energy x-ray absorptiometry (DEXA), using either switched kVp or by k-edge filtering, offers better precision; typically the precision error is halved. The higher flux available from x-ray sources provides other advantages over DPA, including: improved spatial resolution (2 vs 4 mm), reduced radiation exposure (1 vs 2 mrem), and decreased scan times (3 to 10X). Improved DPA systems, with automatic gain stabilization to minimize drift, could offer clinical precision comparable to DEXA but the scan time and spatial resolution remain as before. Both DPA and DEXA allow detection of therapeutic efficacy in individual patients over the first year or two of therapy.     

Techniques of exposure for the stiff total knee

Primary and revision total knee arthroplasty have become common orthopaedic procedures. The operating surgeon, at times, may be faced with a difficult surgical case due to soft tissue contractures or bone deformities. A review of multiple surgical techniques using soft tissue releases and osteotomies are presented including their potential complications. Although these techniques are aimed at the atypical operative case, the operating surgeon may utilize them for ‘routine’ exposures as well. Importance is focused on the functional integrity of the knee extensor mechanism.     

Total body bone mineral in vivo by dual photon absorptiometry. II. Accuracy

We investigated the accuracy of total body mineral (TBBM) measured by dual photon absorptiometry (1 Ci 153Gd source, 44 and 100 KeV) using skeletons, soft tissue equivalent materials and whole cadaver extremities. The accuracy was assessed on five skeletons (r = 0.99, SEE = 1.5%). The influence of the soft tissue composition on the TBBM measurement was investigated in the same five skeletons. They were scanned in a 16 cm thickness of ethanol solutions of different concentration (0, 20, 40, 60, 80, 100% ethanol) and only a 2% difference (non-significant) was found between measuring 100% ethanol and 100% water. Furthermore, seven whole cadaver extremities were scanned before and after removal of the soft tissues (r = 0.995, SEE = 6.3%). The slope was not different from one and the intercept not different from zero. Equipment at the University of Wisconsin, Madison, and at Glostrup Hospital, Denmark, was compared by measuring the same healthy subjects and skeletons on both scanners. The Glostrup and Madison TBBM values correlated well (r = 0.99, SEE = 5.8%) and the intercept (345 Glostrup arbitrary units) was not significantly different from zero (P greater than 0.05). The TBBM results were calibrated into total body calcium (TBCa) and no significant difference was found between Glostrup and Madison TBCa values (P greater than 0.20).     

新生儿复苏培训项目十年回顾

每年约2000万新生儿出生的中国，鼓励一对夫妻只生一个孩子，随着国民经济迅速发展，生活水平不断提高，每一个新生儿的健康都受到家庭及社会的高度关注。1991年中国要儿死亡率为50．2‰，1998年降至33．3‰，地区性差别很大，贫困地区最高可达56‰，一些条件较好的城市低至7．5‰。围产医学界公认围产窒息为要儿患病及死亡的首要原因，如合并早产、严重肺、脑疾病等后果更为严重。