Pre-operative bone mineral density is a predictive factor for excellent early patient-reported outcome measures in cementless total hip arthroplasty using a proximally fixed anatomic stem. A prospective study at two year minimum follow-up.

Abstract

The goal of the study was to analyze the impact of the pre-operative bone mineral density on the patients' reported outcomes at two year minimum follow-up of cementless THA using a proximally fixed anatomic stem. A prospective study included all patients who underwent a cementless THA using a specific proximally fixed anatomic stem and a 3D preoperative CT scan-based planning. The bone mineral density (BMD) of the metaphyseal cancellous bone was computed in a volume (of 1mm thick and of 1cm2 surface) at the level of the calcar 10mm above the top of the lesser trochanter. Patients were assessed at two year follow-up using self-administered auto-questionnaires corresponding to the modified Harris (mHHS), the Oxford (OHS), and the Forgotten Hip (FHS) scores. A multiple linear regression statistical analysis was performed to assess the link between the mHHS, the age, body mass index (BMI), BMD, gender, and ASA grade. Fifty patients were included (29 men, 21 women), with an average age of 62 ± 12years and an average BMI of 27 ± 5kg/m2. At two year follow-up, on multivariate analysis, excellent mHHS (≥ 90%) was significantly associated with only two parameters: a BMI ≤ 25kg /m2 with an odd ratio OR = 10 (CI95% [2.1-48.3], p = 0.004) and a BMD ≥ 72mg/cm3 with an odd ratio OR = 4.87 (CI95% [1.2-18.6], p = 0.02). The short-term PROMs after cementless THA are impacted by pre-operative cancellous bone density. However, the BMI remains the most influential parameter on the clinical outcomes.