Bone Mineral Density and Clinical Outcome after Ankle Fracture.

Background: No gold standard exists for bone mineral density (BMD) measurement of the ankle. This study aimed to determine the correlation between bone density using Hounsfield units (HU) based on computed tomography (CT) and BMD using dual energy X-ray absorptiometry (DXA) as well as to evaluate the correlation between HU and clinical outcome of ankle fracture.

Methods: Fifty-one patients aged ≥65 years who underwent surgical treatment for trimalleolus or bimalleolus ankle fractures were included. The HU were measured at the distal tibia metaphyseal region approximately 1 cm proximal to the plafond on the axial images of preoperative CT. BMD was measured using DXA within one year before the injury. The clinical outcome was evaluated according to the Foot and Ankle Outcome Score (FAOS).

Results: Although the HU of an osteoporosis group was lower than that of a non-osteoporosis group, we observed no significant difference between the two groups. The mean HU significantly correlated with the lumbar and total lumbar spine BMD using DXA. Increased HU significantly correlated with improved clinical outcomes in three of five FAOS subscales: symptoms, pain, activity of daily living (ADL), and quality of life (QOL). In a linear regression analysis adjusted for age and body mass index, increased HU significantly correlated with improved clinical outcomes in three of five FAOS subscales: symptoms, pain, ADL, and QOL.

Conclusions: The correlations between bone density using HU and BMD and those between HU and the clinical outcome were confirmed in ankle fractures. The HU of preoperative CT might provide valuable information for predicting postoperative clinical outcomes.