Deltoid tuberosity index for proximal humerus fracture: reliability and a predictor of systemic osteoporosis in an Asian population.

Hypothesis and Background: Fragility fracture of the proximal humerus is a common occurrence. Current literature suggests that poor local bone density is a significant predictor of surgical fixation failure. The deltoid tuberosity index (DTI) is a simple radiographic tool that strongly correlates with local humeral bone mineral density (BMD), aiding surgical planning to consider adjuncts or arthroplasty. However, there is a lack of data in the reliability of assessment of DTI, as well as its correlation to systemic osteoporosis. Our study investigates the reliability of DTI as a predictor of systemic osteoporosis.
Methods: A retrospective cohort of patients with proximal humeral fracture (PHF) treated at a trauma center in Singapore from August 2017 to July 2018 were recruited. Four raters at different levels of varying clinical seniority measured DTI using shoulder radiographs. The dual-energy x-ray absorptiometry (DEXA) BMD scan of the hip and lumbar spine was used to diagnose osteoporosis. Area under the receiver operating characteristic curve analysis was calculated to study the diagnostic utility of DTI for predicting the risk of osteoporosis.
Results: Our study sample had 87 patients comprising 18 men and 69 women, mainly of Chinese ethnicity (84%), and with a mean age of 69.7 years (standard deviation 9.52, range 39-92). For assessment of DTI, there was good intrarater reliability among 4 raters (correlation coefficient range 0.805-0.843) and excellent interrater reliability between all raters (intraclass correlation coefficient 0.898, 95% confidence interval [CI] 0.784-0.950, P < .001). Based on the BMD, 55.2% (n = 48) had osteoporosis, with a T score <2.5. The highest correlation of DTI to BMD was with femoral neck density at 0.580. The DTI cutoff of 1.6 had the highest combined sensitivity and false positive rate, with areas under the curve of 0.682 (95% CI 0.564-0.799) for the overall population and 0.706 (95% CI 0.569-0.842) for patients aged <75 years.
Conclusion: The DTI is a simple and reliable tool and has a strong applicability in clinical practice to enhance preoperative planning in the surgical fixation of PHF. DTI with a cutoff of 1.6 may help prompt clinicians to initiate workup and thus manage underlying osteoporosis.
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