Importance of lateral spine view in DEXA bone densitometry

Aim: Bone Mineral Density (BMD) measurement is an invaluable technique for assessing fracture risk in suspected cases of osteoporosis. The routine procedure includes AP spine and hip views. But quite often there are discordant results between them, bone mineral concentration (BMC) in the AP spine appears higher than hip. Our study was done to establish the importance of lateral spine view. The lateral view would provide better scope to draw the ROI perfectly and so BMC would be more accurately measured. Materials and Methods: In a prospective study a total of 60 consecutive patients (48F, 12M) were evaluated for bone densitometric measurements. The age group was 35 - 80 years (Mean 59 years). None of the patients received estrogen, biphosphonates or steroid therapy. Bone density of the hip and lumbar spine were measured with Norland XR 36. The T-score, which measures the difference between patient's BMD and young-normal was computed and age-matched Z-score were calculated. X-ray correlation was also done in most of the cases. Results: When we analyzed the femoral neck values, 30 cases were osteoporotic and 23 were osteopenic whereas according to AP spine views only 20 were osteoporotic and 30 were osteopenic. So, clearly a significant number of patients having osteoporosis were interpreted as osteopenia (P<0.05). When the lateral views were considered the bone mineral concentrations more closely matched with femoral neck values (P>0.05). But in the same vertebra there were significant differences (P<0.05) of BMC measured with AP and lateral views. Conclusion: The lateral view can exclude the posterior element of the vertebra as well as the aorta anteriorly, where a high incidence of calcified atherosclerotic plaques are present. AP view includes these drawbacks resulting in falsely higher BMC. Lateral spine view can eliminate these problems and so it provides an important role in BMD measurements. The authors recommend that it should be included in routine practice