Quantitative Bone Mineral Assessment at the Forearm: A Review

Abstract

Bone mineral density and geometric properties of the human forearm can be measured to determine the amount of bone or bone loss at the scanning site and to predict the risk of forearm fractures. These forearm measurements are also used to estimate bone mass at remote anatomical locations and thereby estimate the risk for spine, hip and other fractures. The peripheral location of the human forearm, with its relatively small amount of surrounding soft tissue, improves the accuracy and the precision of bone mass measurement and has made this site an early choice for the assessment of a subject's bone mineral status. Furthermore, the anatomy of the human radius enables the examination of both cortical and cancellous bone. This review describes the procedures for non-invasive bone assessment at peripheral sites including some of the more recently developed systems dedicated to assessment of the distal radius. The accuracy, precision and normative values they provide are presented. Responses to different forms of therapies as well as the ability to discriminate or predict osteoporotic fractures are also assessed. Low radiation dose, comfortable and fast handling, moderate cost, and a strong association with the risk of non-spine fractures, promote the use of forearm scanning as a widely applied screening procedure for the detection of generalised osteoporotic bone loss. However, a higher accuracy of fracture risk prediction at the spine or at the hip can be achieved by a direct bone density measurement at these sites. The monitoring of treatment at the distal forearm appears to require a longer follow-up time due to its decreased responsiveness compared with such highly trabecular load-bearing sites as the spine and the proximal femur.

Novel ultrasonic bone densitometry based on two longitudinal waves: significant correlation with pQCT measurement values and age-related changes in trabecular bone density, cortical thickness, and elastic modulus of trabecular bone in a normal Japanese population

“…The percent coefficient of variation of TBD with the LD-100 system was also similar to that with pQCT reported in the literature [4,25]. The measurement sites adopted by the LD-100 and pQCT systems were slightly different, although on the same radius of the subjects.…”

“…As mentioned in Materials and methods, the measurement site for the LD-100 system (the nearest point to the distal 5.5% point of the radius for both TBD and CoTh) was chosen to select a perpendicular incidence site for the ultrasonic beam and to avoid interference waves overlapping with the transmitted signal. On the other hand, the measurement site used for the pQCT system is well accepted as 4% of the forearm length proximal to the distal end of the radius for TBD and the mid-radial 20% site for CoTh, adopting the area of high mineral content and trabecular bone percentage for the former and the area with a relatively round shape of the cross-section of the radius, permitting the application of the circular ring model, for the latter [25,[27][28][29][30][31]. In the present study, a highly significant correlation was found between the LD-100 and pQCT measurement values in TBD and CoTh, suggesting that evaluation of the bone status, at least the bone status of the forearm, can be similarly evaluated at positions used by both systems.…”

“…pQCT measurements Peripheral quantitative computed tomography measurements were performed in 52 subjects ages 36-85 years, on the non-dominant forearm at a distance 4% of the forearm length proximal to the distal end of the radius for TBD and at the mid-radial 20% site for CoTh [25], using single 2.5-mm thick slice pQCT (XCT-960 Stratec, Medizintechnik, Pforzheim, Germany).…”

The impact of accurate positioning on measurements made by peripheral QCT in the distal radius

“…b Showing the trabecular BMD difference between section 1 and section 2 at baseline (mg/cm 3 ). c Showing the total BMD difference between section 1 and section 2 at baseline (mg/cm 3 ) large, up to 40 mm 2 over the very small distance of 1.2 mm. The magnitude of decrease in CSA between the distal end and diaphysis of the radius has been measured in cadaver studies [4] and in small clinical studies of adolescents and adults [5,6].…”

“…There are three common sites of measurement for pQCT at the radius [3]: the 4% distal site and the 50% or 66% midshaft site. In adults, measurements of cross-sectional area (CSA), bone mineral content (BMC) and volumetric BMD (BMD) at the distal forearm are made at 4% of the forearm length, proximal to the distal medial articular surface of the radius.…”