Abstract: BACKGROUND: Patients with severe lumbar degenerative disease may have their bone mineral density incorrectly raised by dual-energy X-ray absorptiometry. While lumbar cancellous bone Hounsfield unit value can assist dual-energy X-ray absorptiometry in reducing osteoporosis misdiagnosis.  
OBJECTIVE: To identify osteoporosis in woman patients with lumbar degenerative diseases using lumbar CT scans.
METHODS: Bone mineral density test results and lumbar CT data of 192 women patients who were treated at the Department of Spine Surgery, Sixth Affiliated Hospital of Xinjiang Medical University were retrospectively reviewed. All patients were divided into a degeneration group (n=107) and a control group (n=85) according to the criteria of severity of vertebral degeneration as assessed on CT of the lumbar spine. The CT value of axial cancellous bone of L1 vertebral body was measured in the two groups. The T score and bone mineral density of the hip and L2-L4 were recorded. According to previously published studies, osteoporosis was diagnosed at L1 vertebral CT values ≤110. The prevalence of osteoporosis diagnosed by dual-energy X-ray absorptiometry and CT values was compared between the two groups.  
RESULTS AND CONCLUSION:  (1) CT values were significantly and positively correlated with T scores and mean bone mineral density of the L2-L4 vertebrae in both groups (P < 0.001), while the correlation was higher in the control group. (2) Lumbar T scores and bone mineral density values were significantly higher in the degeneration group than those in the control group (P < 0.05) and CT values were significantly lower in the degeneration group than that in the control group (P = 0.001). Hip T scores and bone mineral density were not significantly different in the two groups. (3) The prevalence of osteoporosis diagnosed by CT thresholds was higher in all patients than that diagnosed by T values (51.0% and 42.7%). (4) The prevalence of osteoporosis diagnosed by CT values was as high as 23.6% in the 110 patients diagnosed with non-osteoporosis by dual energy X-ray absorptiometry in both groups, and was higher in the degeneration group than that in the control group (31.7% and 14.0%, respectively). (5) The prevalence of missed osteoporosis was as high as 38.6% (27/70) of non-osteoporosis patients diagnosed by dual-energy X-ray absorptiometry of the lumbar spine in the degeneration group compared to 19.6% (11/56) in the control group. (6) It is concluded that osteoporosis is common in female patients with lumbar degenerative diseases aged ≥50 years. Measurement of lumbar cancellous bone CT values may be a useful complementary method for diagnosing osteoporosis in patients with lumbar degenerative diseases, especially in patients with severe degenerative lumbar degenerative diseases where more missed osteoporosis patients can be identified.

Key words: osteoporosis, lumbar degenerative disease, lumbar CT value, dual-energy X-ray absorptiometry, bone mineral density