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Objectives and questions: Cementless total hip arthroplasty’s (THA) success relies on its primary mechanical stability and secondary biological fixation, which can be assessed by specific exams like dual-energy x-ray absorptiometry (DEXA) or computed tomography (CT) scan. Here we retrospectively evaluate the bone adaptation of a cementless primary THA using a validated image analysis tool and plain radiographs.

Material and methods: Patients who received a cementless THA from September 2020 to July 2022 were included in the study. Clinical scores and X-rays were prospectively collected. Relative Bone Density (RBD) was calculated for each patient, using Rossler validated method with Image-J software, to assess bone density changes after THA.

Results: 155 patients with mean 56.4-year-old (range 31–84) were followed-up for 38.5 months. Harris Hip Score was 92.2 at the latest follow-up. Radiographically, all the cups were positioned in the Lewinnek safe zone. Five cups showed non-progressive radiolucent lines. RBD showed a significant decrease in Gruen zone 1, while the percentage difference int the other zones ranged from -9% to +4%. In the cohort there were 4 intraoperative fractures treated with cerclage wires. One patient had a superficial infection, and another one had a deep infection.

Discussion and conclusions: In conclusion, the ability of a cementless THA has been confirmed as well as the possibility to evaluate accurately the bone-implant interface using plain radiographs.