Tibial cortical thickness: A dependable tool for assessing osteoporosis in the absence of dual energy X-ray absorptiopmetry.

BACKGROUND AND OBJECTIVE

Bone mineral density measurements with absorptiometry dual-energy X-ray absorptiometry (DXA) is the gold standard for diagnosing low bone mass and risk for fragility fractures. DXA is not available at every center, and physicians require an alternative method of diagnosis before referring patients. We conducted this study to assess and compare total cortical thickness (TCT) and its relation to the T score by DXA and its correlation-ship in the diagnosis of osteoporosis.

PATIENTS AND METHODS

Total cortical thickness was carried out in 50 Saudi Arabian females ≥ 45 years with DXA scans and 25 patients with age of ≤ 35 years whose radiographs of the upper tibia were available for analysis. Postero-medial cortical thickness of the tibia was measured 13 cm from the joint line and an average was calculated. The average T score of the spine and the hip was taken. A comparison was made between age, T score, and the TCT. Inter cortical distance (ICD) was measured and compared in both groups. Data were analyzed for predictive value for diagnosis of osteopenia and osteoporosis.

RESULTS

There was a significant association between the T score and the TCT and age. As the age advanced the T score and TCT was very low (<0.05, 95% confidence interval [CI] <0.2). Forty patients were osteopenic and 10 osteoporotic. The T score in the former was - 1.33 ± 0.71 and the later was - 3.22 ± 0.56 (P < 0.0001 95% CI: <-1.67) and the TCT was 0.655 ± 0.06 versus 0.51 ± 0.05 (P < 0.0001 95% CI: <-0.17). In women ≤35 years the average TCT was 0.804 ± 0.155 cm and IMD was 3.34 ± 0.45 cm.

CONCLUSIONS

We conclude that if TCT is less than the threshold value of ≤ 0.5 cm, patients should be referred for further investigations with DXA. We believe that further studies are needed to confirm our findings and in areas where DXA is not available, based on the TCT measurement anti-osteoporotic therapy could be initiated when other risk factors for osteoporosis is present.