this is, at present, the technique preferred for bone-mass evaluation to enable the diagnosis of osteoporosis, prediction of fracture risk and follow-up monitoring. The technique uses X-Rays of two different energies, which allow the subtraction of soft tissue absorption and the estimate of calcium content of the bone. When projected onto a surface this gives a parameter called Bone Mineral Density (BMD g/cm²), from which Bone Mineral Content (BMC, g/cm³) may be inferred. In general, measurement at a particular site provides a more accurate estimate of fracture risk for that site. Since the most clinically relevant osteoporotic fractures occur in the spine and in the hip, the most frequently measured sites are the lumbar spine and proximal femur. However, there are a number of technical limitations to the application of DXA to diagnosis. For example, the presence of osteomalacia will underestimate total bone matrix because of decreased bone mineralisation while, on the other hand, osteoarthrosis or osteoarthritis of the spine or hip will contribute to density but not to skeletal-strength [2]. In the latter case, the specific site involved must be excluded from the analysis; at least two lumbar vertebrae must be evaluated so that the densitometry result may be considered reasonably accurate. For this reason, femoral densitometric evaluation is probably preferable after the age of 65. Recently some software has been developed to enable DXA to measure, not only BMD, but also some of the geometrical parameters related to bone strength, such as HSA (hip structure analysis) and TBS (Trabecular Bone Score). TBS processes the degree of inhomogeneity of the spinal densitometry scan, thus providing indirect information regarding trabecular microarchitecture. Although this device has been approved by the FDA, its everyday use in clinical practice is still limited.

this technique, because it is able to separate the trabecular BMD from the cortical BMD, permits total and local volumetric BMD (g/cm³) measurements at both vertebrae and femur levels. However, this method exposes patients to high radiation dose levels (about 100 μSv). As a technique, DXA is usually preferred to QCT because of its accuracy, shorter scan times, more stable calibration, lower radiation dose and lower costs.

This technique provides two parameters (speed and attenuation) which are indirect indicators of bone mass and structural integrity; it is used mainly to carry out measurements in two sites, the phalanges and the calcaneus. It has been demonstrated that ultrasound parameters are capable of predicting risk of osteoporotic fractures (femoral and vertebral) no less accurately than lumbar or femoral DXA, both in post-menopausal women and in men, but this technique does not provide direct bone-density measurements. Discordant results between ultrasonographic and DXA evaluations are neither surprising nor infrequent and they do not necessarily indicate an error, but rather, that the QUS parameters are independent predictors of fracture risk influenced by other characteristics of the bone tissue. However, this does mean that QUS cannot be used for the diagnoses of osteoporosis based on WHO criteria. QUS can be useful when it is not possible to estimate a lumbar or femoral BMD with DXA and may be recommended for epidemiological investigations and first-level screening, considering its relatively low cost, easy transportability and absence of radiation.

Risk factors for falls include history of fracture/falls, dizziness and orthostatic hypotension visual impairment, gait deficits, urinary incontinence, chronic musculoskeletal pain, depression, functional and cognitive impairment, low body mass index, female sex, erectile dysfunction (in male adults), and people aged over 80 [19]. Some of these factors are modifiable: reduced visual acuity can be corrected, medication that may diminish awareness and/or balance can be reduced or stopped and modifications to the home environment can be performed (slippery floors can be corrected, mats can be fixed or removed, lighting improved, handrails placed in bathrooms etc.) [20]. A programme of exercises may prevent falls by improving confidence and coordination and by preserving muscle strength but there is no consensus around the most suitable programme for the ‘oldest old’ [20, 21].

Vitamin D is involved in the intestinal absorption of calcium and phosphorus and is necessary for the mineralisation of bone and the maintenance of muscle, but it also has numerous beneficial effects on other organs. Most Vitamin D is synthesised in the skin during exposure to the sun but, as this capacity is reduced in older people, they produce lower amounts of vitamin D; moreover, they also tend to expose their skin less than younger adults. Thus, the majority of older people suffer from hypovitaminosis D [22]. Threshold values for vitamin D are presented below in Table 3.3. Several trials have demonstrated lower fracture risk in patients having a plasma concentration of 25-hydroxy-vitamin D (25-OH-D) of at least 60 nmol/L compared to those having levels below 30 nmol/L [23]. Moreover, there is growing evidence that vitamin D supplementation has beneficial effects on other systems, in addition to the skeleton. It has been demonstrated that improvement of 25-OH-D levels leads to a lower incidence of falls in older people; other trials have demonstrated that vitamin D supplementation is associated with a reduction in all-cause mortality [24]. The Recommended Nutrient Intakes (RNI) are 800 IU of vitamin D per day in men and women over 50 [2]. Intakes of at least 800 IU of vitamin D can be recommended in the general management of patients with osteoporosis, especially in patients receiving bone protective therapy [25]. Considering that hypovitaminosis D is epidemic among the elderly, there is probably no strong necessity to measure circulating levels of 25-OH-D in patients with high fracture risk [22]. Vitamin D supplementation should start as soon as possible, and it should precede the administration of any drug used to treat osteoporosis [25]. Since the inactive form of vitamin D (cholecalciferol) is stored in fat tissue, it is sensible to saturate the stores with repeated small loading doses and then to continue with maintenance doses.