Radiographic morphometry of the osteoporotic femur: Comparison with densitometry

Object: To determine the accuracy of radiographic morphometry i.e. grading of osteoporosis on plain x-rays of femur (Singh index) compared with bone densitometry by dual energy x-ray absorptiometry (DEXA) in post menopausal females.Design: Comparative, analytical study.Duration & Place of Study: From May 2004 to June 2005 at Radiology Department, Dow University of Health Sciences (DUHS), and Civil Hospital Karachi (CHK) in collaboration with Osteoporosis Diagnostic Clinic, Karachi.Patients and Methods: Post menopausal females referred for evaluation of clinically suspected osteoporosis by both plain x-rays and DEXA were included in the study. Those with history of previous trauma or radiation, other systemic disease with bony component, advanced degenerative disease, metastatic disease and bony metallic implants or prosthesis, were excluded A standardized system of grading skeletal osteoporosis on plain x-rays offemur/pelvis (Singh index grades 1- 6) was exercised Bone mineral density and T-score were determined on DEXA. Sensitivity and specificity of each assessed was determined against the gold standard T-score.Results: There were 98 patients in all with mean age of 59+/- 6.5 years and mean post menopausal interval of9. 66+/- 6.52 years. The predominant distribution was, 26.5% in grade 6 and 31% in grade 3. Nineteen had normal T-score (\u3e-1), 49 were osteopenic (I\u27- score between -1.00 and -2.5) and 30 were osteoporotic with T-score below -2.5. For grade 3 and below, the sensitivity and specificity of Singh index (S1)were 55% and 84% respectively. For S1grades 4 and above, the values were 44% and 97 % respectively.Conclusion: Singh index or radiographic morphometry grading of osteoporosis isfairly accurate for advanced osteoporosis with high specificity. The sensitivity is low requiring use of bone densitometry for early detection