Local Bone Density of Preoperative CT: A Predictor of Clinically Significant Shortening and Varus Collapse of Well-Reduced Geriatric Intertrochanteric Hip Fractures

INTRODUCTION: Intertrochanteric (IT) fractures are the most common geriatric hip fracture, with early fixation failure contributing to high morbidity and mortality. Lower bone density, as measured by Hounsfield units (HU) from CT scans, is predictive of various long bone fractures and fracture fixation failure, although its role in IT fractures is less well described. We aimed to assess the association between local bone density and radiographic outcomes after cephalomedullary nail (CMN) fixation of well-reduced geriatric IT fractures, hypothesizing that lower HU measurements are associated with increased rates of clinically significant shortening and varus collapse. METHODS: We retrospectively reviewed patients older than 60 years with low-energy IT fractures treated with a long or short CMN between 2017 and 2024 at a single institution. Fractures with varus malreduction or tip apex distance >25 mm were excluded. Radiographs were assessed postoperatively and at 6 to 24-week follow-up to evaluate for shortening and change in the neck-shaft angle. Hounsfield unit measurements of the proximal femur were obtained from injury CT scans. Two-sample t-tests, simple linear regression, and multivariate logistic regression were used to analyze the relationship between HU and shortening/varus collapse. RESULTS: Among 103 patients (74 women, 29 men; mean age 79.3 ± 9.8 years), the mean local bone density was 193.3 ± 63.4 HU. Patients with clinically significant shortening or varus collapse (n = 38) had significantly lower HU than those without (n = 65) (160.9 vs. 212.3 HU, P < 0.0001). HU was independently associated with shortening/varus collapse (OR 0.98, P < 0.01) and negatively correlated with magnitude of shortening (R2 = 0.091, P < 0.01). An exploratory threshold of 150 HU significantly predicted shortening. CONCLUSIONS: Lower local bone density predicts shortening/varus collapse after CMN fixation of well-reduced geriatric IT fractures, despite optimization of modifiable surgical factors. An exploratory threshold of 150 HU may identify patients at risk of shortening within 24 weeks postoperatively.