Why are dexascan only taken of hips and lumbar spine?

[lotl]

Why is bone density scan carried out on just spine and hips rather than area where an osteoporotic break is suspected? A recent bone scan showed that my T score had Changed from -2.7 to -0.5 in the seven years I had been treated wIth ibandronic acid. Having had a complex shoulder fracture my consultant said it was an osteoporotic fracture. How can he know this without the evidence of a dexascan of the shoulder?