Predicting Contralateral Second Hip Fracture Risk Within 5 Years of First Hip Fracture: A New Risk Tool to Guide Patient/Family Counseling and Bone Health Treatment.

Objective: To develop a stratification tool to identify hip fracture patients at risk for second contralateral hip fracture and mortality within 5 years of an index fracture, and to assess the cost-effectiveness of prophylactic fixation in high-risk/low-mortality patients.

Methods: Design: Retrospective prognostic cohort study.

Setting: Single academic system with 2 Level 1 Trauma Centers, 1 orthopedic specialty hospital, and 1 tertiary care hospital.

Patient selection criteria: Patients who were 60 years or older with OTA 31A/B hip fractures from low-energy mechanisms between 11/1/2014 and 11/31/2023 with ≥5 years follow-up or until death were included.

Outcome measures and comparisons: The study included four phases: (1) identifying factors associated with second hip fracture within 5 years; (2) using multivariate logistic regression to generate models predicting 5-year second hip fracture (vs. FRAX) and mortality risk; (3) creating a "risk matrix" to identify candidates for prophylactic fixation using Youden's Index which determined cutoff points encompassing the maximum sensitivity and specificity for each risk equation and were used to define a value-based target group; (4) cost analysis comparing standard vs. prophylactic care in high-risk/low-mortality patients.

Results: Of 426 patients (mean age 80.25 years, 73.4% female), 78 sustained second hip fractures (mean interval: 594 days). Predictors included higher FRAX score (p=0.004), dementia (p<.001), ICU stay (p=0.014), discharge to subacute care (p<.001), and 90-day readmission (p=0.011). Logistic regression predicted 5-year second fracture risk (AUC 0.742 vs. FRAX 0.617, p=0.012) and 5-year mortality (AUC 0.723). The risk matrix used cutoff points of 18.2% (mortality) and 38.2% (second fracture) to define a value-based target group (n=26; 13 experienced second fracture). Cost analysis showed prophylactic fixation of all 26 patients ($781,508) would save $353,067 compared to treating the 13 who fractured again ($1,134,575).

Conclusions: A novel matrix was developed that accurately predicted 5-year second hip fracture and mortality risk. Prophylactic fixation in low-mortality, high-risk patients may reduce costs and prevent future fractures. [Tool available: https://sttgmacom.wpcomstaging.com/predicting-risk-of-second-hip-fractures/].

Level of evidence: Level III Diagnostic.