New Diagnostic and Monitoring Method for Osteoporosis

Background

Bone is a composite formed by the mineralization of an organic matrix (largely collagen type I) by the deposition and growth of a carbonated calcium phosphate mineral (bio apatite), highly resembling hydroxy-apatite, Ca₁₀(PO₄)₆(OH)₂, within the matrix. Bioapatite provides the biomechanical properties needed for body support and movement, enabling it also to withstand stresses. Failure of mineralization of newly formed or bone remodeling results in an excess of unmineralized bone matrix (called osteoid tissue) comprising the clinical entity of osteomalacia. Main causative mechanisms are vitamin D deficiency and phosphate depletion (Mundy, 1995). In contrary, the decrease in the amount of normally mineralized bone and the disturbance in bone micro architecture (which increases the risk of fractures occurring in the absence of trauma or in response to trivial trauma) are known as osteoporosis (Melton, 1998). Some clinicians use the generic term osteopenia, which describes decreased mineralized bone mass with no reference in particular bone pathology responsible for the decrease in bone mineral density (Mundy, 1995). Osteopenia may be due to osteomalacia, primary hyperparathyroidism or malignant diseases, all of which may cause generalized bone loss.

Bone Mineral Density (BMD) is recognized as the most important single determinant of fracture risk in populations with bone disease (Cumings, 1990, 1993). Accordingly, measurement of bone density is currently the mainstay for the diagnosis and monitoring of osteoporosis, osteomalacia or osteopenia in general. However, many other skeletal and extraskeletal factors and conditions may influence the risk of developing a fracture, as in particular, a hip fracture (Cumings, 1995). Therefore, the ability of bone to withstand traumatic insults is the result of both the amount of mineralized tissue per unit of volume (density), and many other factors that are commonly referred to as bone quality. Loss of trabecular connectivity is considered one of the critical factors that weaken bone strength in osteoporosis (Parfitt, 1987). Although data are still limited, this architectural abnormality may independently constitute an important factor for predicting fracture risk (Kleerekoper, 1985).