70 year old Caucasian male presents for an initial DXA scan (National Osteoporosis Foundation and ISCD recommend routine DXA scans in all males over 70, Osteoporosis Society of Canada recommends DXA scanning in all males over age 65). He is 70” tall and weighs 157 pounds, BMI = 22.5. He has no history of insufficiency fractures.
Question: Why does this patient have an elevated BMD (note Z-score = +2.7 at L2) and why is there significant variability between vertebrae (T-score at L2 almost 3 S.D. greater than L1 and the T-score at L3 almost 2 S.D. greater than L4)?