Collared Femoral Stems Have Lower Risk of Postoperative PPFs After THA: A Retrospective Cohort Study

Periprosthetic fractures (PPFs) remain a serious complication following total hip arthroplasty (THA), contributing to increased morbidity and healthcare costs. Femoral stem design, particularly the presence of a collar, has been hypothesized to enhance axial stability and reduce micromotion, potentially lowering the risk of PPFs. This retrospective cohort study aimed to compare outcomes between collared and non-collared femoral stems in cementless THA.

We retrospectively analyzed 618 patients who underwent cementless THA between January 2014 and December 2024. Patients were stratified into two groups based on femoral stem design: collared (n = 308) and non-collared (n = 310). Baseline demographics, comorbidities (Charlson Comorbidity Index), fixation method, stem alignment, and complications were recorded. Periprosthetic fractures were classified using the Vancouver system, and radiological findings were evaluated across Gruen zones. Follow-up outcomes included stem subsidence, alignment, and radiographic changes.

The collared stem group showed a significantly lower incidence of PPFs (0.97% vs. 3.87%, p = 0.033) and reduced stem subsidence (0.54 mm vs. 0.83 mm, p < 0.001). Radiographic analysis demonstrated improved neutral alignment (p < 0.001), fewer varus (p = 0.009) and valgus alignments (p = 0.021), and less cortical hypertrophy (p = 0.021) in collared stems. Reactive lines were more frequent in the collared group (p = 0.003). Hospital stay was marginally longer in this group (p = 0.012), with no significant difference in early complications.

Collared cementless femoral stems are associated with improved alignment, less subsidence, and a significantly lower risk of PPFs, supporting their biomechanical advantage in primary THA.