Advances in noninvasive bone measurement

Several noninvasive measurement methods are used for evaluation of metabolic disease. Single-photon (125I) scans of the peripheral skeleton are useful in some diseases but are ineffective in osteoporosis (even on the distal radius or os calcis) because they cannot predict spinal or femoral density. Also, peripheral measurements show high percentages of false negatives, that is many patients with fractures have normal peripheral density. Dual-photon (153Gd) scans of the spine, femur, and total skeleton are precise and accurate (2% error) and provide direct measurements of bone strength at fracture sites. This gives the best discrimination of abnormality and the most sensitive monitoring. Quantitative computed computed tomography (QCT) allows measurement of the spine but not the critical proximal femur area. QCT has a large accuracy error because (a) the limited area measured (under 5 cm3) fails to represent the total vertebral body, (b) technical errors, and (c) variable fat and osteoid influence the results.

Radial and spinal bone mineral density in a patient population

Density of the radius (by single-photon absorptiometry) and the spine (by dual-photon absorptiometry) was measured in 281 normal young women and in a large heterogeneous group of 1,622 consecutive female patients. Both spinal and radial density were useful measurements when performed on patients with medical indications; spine and radius densities in these patients averaged 10-20% below those of age-matched controls. However, patients younger than 60 years of age had deficits of spine density that were twice as large as those in the radius, and twice as many of these patients had spinal osteopenia, compared with those with radial osteopenia. After age 70, loss of density in the radius approximated that in the spine and the prevalence of osteopenia was similar at both sites. The poorer sensitivity of the radius measurement reflected the fact that it did not predict spine density. The standard error of the estimate was 0.12 gm/cm2 in normal subjects and 0.15 gm/cm2 in patients. At any given radial density, the spinal density of patients averaged 0.18 gm/cm2 (15-20%) below that in normal subjects. Predictions of spinal density from body weight were as accurate as predictions from radial density. Preferential spinal osteopenia occurring without radial osteopenia precluded radial densitometry as a screening method for individuals with osteoporosis before age 60. However, measurement of the radius was more effective than body weight for defining groups at risk, even though the radius did not reliably predict individual spine density. A radius shaft density less than 0.55 gm/cm2 occurring with a body weight less than 55 kg was associated with a high prevalence of spinal osteopenia.

Bone density of the radius, spine, and proximal femur in osteoporosis

Bone mineral density (BMD) was measured in 140 normal young women (aged 20 to 39 years) and in 423 consecutive women over age 40 referred for evaluation of osteoporosis. Lumbar spine and proximal femur BMD was measured using dual-photon absorptiometry (153Gd), whereas the radius shaft measurement used single-photon absorptiometry (125I). There were 324 older women with no fractures, of which 278 aged 60 to 80 years served as age-matched controls. There were 99 women with fractures including 32 with vertebral and 22 with hip fractures. Subsequently, another 25 women with hip fractures had BMD measured in another laboratory; their mean BMD was within 2% of that of the original series. The mean age in both the nonfracture and fracture groups was 70 +/- 5 years. The BMD in the age-matched controls was 20% to 25% below that of normal young women for the radius, spine, and femur, but the Ward's triangle region of the femur showed even greater loss (35%). The mean BMD at all sites in the crush fracture cases was about 10% to 15% below that of age-matched controls. Spinal abnormality was best discriminated by spine and femoral measurements (Z score about 0.9). In women with hip fractures, the BMD was 10% below that of age-matched controls for the radius and the spine, and the BMD for the femoral sites was about 25% to 30% below that of age-matched control (Z score about 1.6). Femoral densities gave the best discrimination of hip fracture cases and even reflected spinal osteopenia. In contrast, neither the spine nor the radius reflected the full extent of femoral osteopenia in hip fracture.

Spine and femur density using dual-photon absorptiometry in US white women

Bone mineral density (BMD) of the spine (n = 892) and femur (n = 634) was measured using dual-photon absorptiometry in normal white women from seven diverse locations. The same model commercial scanner with a 153Gd source was used in all locations (SD = 1.3% among locations). There was not an age-associated decrease of spinal BMD during young adulthood (20-40 years); the correlation of age and femoral BMD in this period was low but significant (r = -0.21). There was a narrow range of intra-population variation at all ages (10-12%). The cross-sectional data showed an average diminution of about 20% in the spine and 25% in the femur between 40 and 70 years of age, followed by a continued but slower, decrease of density in older women. Adjustment of values for height and weight was called for mainly at extremes of body size.

Sleep parameters after surgery for obstructive sleep apnea

Obstructive sleep apnea (OSA) is a disorder that is frequently treated surgically. Few reports in the literature give objective reports of the effect of such treatment on polysomnographic parameters before and after treatment, although symptomatic improvement is common. This article reviews total sleep time (TST) spent in apnea, number of apneic episodes per hour or sleep apnea index (SAI), and oxygen desaturations in such patients treated with tracheostomy, uvulopalatopharyngoplasty (UPP), and combinations of these. Although improvement is noted in these parameters after UPP, this is not as impressive as some reports in the literature indicate. Our suggested indications for this type of surgery are discussed.