Fracture Risk Assessment Tool Scores and Radiographical Bone Measurements in Total Hip Arthroplasty Patients.

Background: Osteoporosis is a major risk factor for periprosthetic fractures (PPFx) in total hip arthroplasty (THA) patients but is not routinely screened for in this population. Given the availability of hip x-rays and preoperative screenings, Fracture Risk Assessment Tool (FRAX) scores and radiographic bone measurements are potentially promising, novel risk stratification tools. This study aims to characterize FRAX scores and radiographic bone measurements in THA and PPFx patients.

Methods: A retrospective chart review for demographic variables and FRAX scores was performed on 250 THA and 40 PPFx patients. Radiographic bone measurements including cortical thicknesses (both antero-posterior [AP] and lateral), canal to calcar ratio, canal flare index, and Dorr classifications were obtained from preoperative x-rays. Correlation between FRAX scores and radiographic bone measurements was investigated with linear regressions. FRAX scores and radiographic bone measurements were compared between the THA and PPFx patients. Multivariate logistic regressions were used to identify factors predicting PPFx.

Results: FRAX scores were significantly correlated with both AP (P < .001) and lateral (P = .007) cortical thicknesses. Compared to THA patients, those with PPFx had significantly higher FRAX scores (P = .003) and lower AP cortical thickness (P = .005). Multivariate logistic regressions demonstrated that FRAX major osteoporotic fracture risk score and AP cortical thickness were independent predictors of PPFx (P = .001 and .024, respectively).

Conclusion: Cortical thicknesses are good proxy measurements of osteoporosis-related fracture risk in THA patients. In addition, both major and AP cortical thickness indices are promising tools for identifying patients who are at a high risk of PPFx in the THA population.