Ultrasonic bone assessment: "the time has come".

Bone is unique in its ability to maintain its strength in the presence of constant turnover. It has been established that there is gradual and relatively complete removal and replacement with new bone several times in a lifetime. The reparative pattern is constantly changing in order to maintain strength and is influenced by changes in general health, the presence of disease, and the degree of physical activity. To date, no method has been developed to measure the nature of lifetime changes in patterns during childhood and throughout older age [1]. Often the first indication that a problem exists is the occurrence of a fragility fracture, which is often associated with a high degree of morbidity and mortality. Fracture risk is dependent on the strength of bone as well as other factors including tendency to fall. This latter aspect may be related to poor balance and eyesight, or to environmental obstacles like stray wires, defective pavements, and edges on carpeting [2]. Inherent strength of bone depends upon a host of multi-factorial components. Dual-energy X-ray absorptiometry (DXA), which measures the mass of the mineralized matrix at a given site (e.g., hip, spine, forearm) is currently the accepted indicator used to assess bone strength. It has been shown that bone mass has about the same predictive value for fracture as blood pressure has for stroke [3]. Stages of bone turnover have been studied by analysis of biochemical markers as bone is removed and reformed [4]. But there is as yet no reliable clinical method to assess the status of the internal trabecular structure of bone which normally contributes significantly to strength. Notwithstanding the fact that X-ray densitometry is reasonably effective in bone mass assessment, osteoporosis remains one of the most prevalent undiagnosed and under-diagnosed diseases in the world today [5]. Among the reasons for this is that densitometry (i.e., DXA) is not a standard tool in a primary care physician's office. It does not lend itself to routine screening because of expense, inconvenience, and reticence concerning X-ray exposure, particularly in young adults and children. It is estimated that approximately 20% of women with osteoporosis have unrecognized or untreated conditions that are capable of causing absorption of bone (“secondary osteoporosis”) [6]. These may include thyroid, parathyroid, gastrointestinal disease, may be drug related or associated with a whole host of other possibilities [6]. Similarly for example, in adolescents and children, bone loss may be associated with metabolic conditions including hypogonadism, malnutrition, bulimia, and medication [7]. The ability to screen the quality of bone at any age would be expected to serve as preventive medicine by uncovering unrecognized causes and permit treatment of these conditions as well as to institute early appropriate therapy for osteoporosis.