Bone mineral density and low bone mass in severely burned patients: A retrospective cohort study

Introduction: Severe burns can alter bone metabolism through different mechanisms. Despite prior published studies describing the association between burns and a decrease in bone mineral density (BMD), no clinical guidelines currently exist recommending the systematic evaluation of bone health in patients after severe burns. This study aims to describe the BMD of individuals with severe burn injuries and healthy controls and determine the frequency of low-to-normal bone mass (LNBM) and BMD below the expected range for age (BEA). Materials and methods: We conducted a retrospective cohort of patients with either severe thermal or electrical burns and healthy controls paired by gender and age. We performed a dual-energy X-ray absorptiometry at least 90 days after the burn and collected data from each patient's clinical evaluation and clinical file. Results: A total of 77 patients (64 men and 13 women) and their paired controls were included in the study (age [mean +/- standard deviation, SD]: 30.37 +/- 8.66 years). Patients participated in the study an average of 315 +/- 438 days after their burn. The BMD (grs/cm(2)) in total hip burned vs controls was: 0.998 +/- 0.135 vs 1.059 +/- 0.12 (p = 0.004); femoral neck 0.876 +/- 0.121 vs 0.915 +/- 0.097 (p = 0.031), spine 0.977 +/- 0.127 vs 1.003 +/- 0.076 (p = 0.132).The Z-scores for total hip were 0.06 +/- 1.05 vs 0.41 +/- 0.80 (p = 0.002); for neck-0.39 +/- 0.89 vs-0.01 +/- 0.77 (p = 0.005); and for spine-0.75 +/- 1.11 vs-0.32 +/- 0.73 (p = 0.005). The proportion of subjects with BMD BEA in burns vs controls was 5.2 vs 1.2% (p = 0.05) in total hip, 3.9 vs 0% (p = 0.045) in the neck, and 18.2 vs 1.2% (p = 0.001) in the spine. The logistic regression model found-in burn patients vs controls-an OR of 9.83 for BMD BEA (CI 95%: 2.17-44.45, p = 003), OR = 4.05 for electrical burns (CI 95%: 1.72-20.89, p = 004) and OR = 15.16 for thermal burns (CI 95%: 2.91-79.00, p = 001). The model also found an OR = 2.48 for LNBM (CI 95%: 1.25-4.93, p = 0.009). The burn variables associated with BMD BEA at any site in the patients were BMI >25 Kg/m(2) with an OR = 0.180 (CI 95%: 0.046-0.710, p = 0.014); and the lower limb amputation with an OR = 7.33 (CI 95%; 1.12-48.33, p = 0.038). Five burn patients had a fragility fracture. Conclusion: BMD was significantly lower in severely burned patients than in controls, and the proportion BMD BEA cases was significantly higher in the burn patient sample. Severe burns are a strong independent predictor of bone loss, and this risk is maintained for an extended period after the burn.