Low vertebral CT Hounsfield units: a risk factor for new osteoporotic vertebral fractures after the treatment of percutaneous kyphoplasty

PURPOSES: To identify the characteristics of the vertebral HU in the elderly patient with new osteoporosis vertebral compression fractures (OVCF) after treatment of percutaneous kyphoplasty (PKP), which may help us to preliminarily evaluate the risk of a new OVCF after the treatment of PKP. METHODS: We retrospectively analyzed the patients who received PKP treatments in our hospital to find out the patients suffered new OVCFs after the treatment of PKP and set an age-, sex-, first fracture vertebrae-, surgical segment-, and comorbidity-matched control group without new fractures. We measured the axial and sagittal L1-HU values to compare their differences. RESULTS: There were 32 patients who suffered new OVCFs and received another PKP surgery in our department. In the study group, the average L1 sagittal and axial HU values were 46.17 ± 21.31 HU and 47.77 ± 22.38 HU, and they had no statistical difference (P > 0.05). For the control group, the average L1 sagittal and axial HU values were 75.69 ± 29.72 HU and 80.23 ± 30.26 HU, and their difference was not significant (P > 0.05). No matter from the axial or sagittal evaluation, the L1 HU value in the study group was significantly lower than that in the control group (P < 0.001). The AUC of using the L1 axial HU value to differentiate patients with new fractures from controls was 0.85 while the sagittal one was 0.82. In axial (and sagittal) evaluation, the cutoff value (adjusted to the multiple of five) had high specificity of 90% or high sensitivity of 90% to identify patients with new fractures of 45 HU and 75 HU (50 HU and 75 HU), respectively. CONCLUSIONS: The lower the vertebral HU value is, the more likely the patients suffer new OVCFs after PKP treatment.