Introduction

Osteoporosis (OP) is probably the most common metabolic disorder of the musculoskeletal system, affecting more than 200 million people (Whitcroft & Stevenson, 1992). Because the sequelae of OP, namely hip, vertebral, and distal radial fractures, result in considerable morbidity and mortality, OP has become a significant healthcare problem.

OP, a disorder of both cortical (compact) and trabecular (cancellous) bone, is characterized by a paucity of qualitatively normal bone. It is thought to be due to increased bone resorption rather than deficient bone formation (Aguado et al., 1997). Although advanced stages of OP are frequently detected by radiography, plain radiography is insensitive to early and intermediate stages of OP. Twenty-five to 50% of bone loss must occur before radiographic detection is possible (Resnick & Niwayama, 1998). Furthermore, plain radiographs are unable to precisely quantify OP. Thus plain radiography's role is primarily to distinguish OP from osteomalacia and other etiologies of OP, and to assess the progression and sequelae of OP.

Quantification of osteoporosis

Well-established techniques allowing quantification of bone mineral density include X-ray absorptiometry, photon absorptiometry, and quantitative computerized tomography. More recently, ultrasound and magnetic resonance imaging have also demonstrated some utility in assessment of bone mineral density.

X-ray absorptiometry employs an X-ray source to determine bone mineral density in the spine and peripheral skeleton.