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

Area of Science:

• Orthopedic Surgery
• Biomedical Engineering
• Radiology

Background:

• Periprosthetic fractures (PPFs) are a significant complication of total hip arthroplasty (THA), increasing patient morbidity and healthcare costs.
• Femoral stem design, specifically the presence of a collar, is hypothesized to improve axial stability and reduce micromotion, potentially mitigating PPF risk.

Purpose of the Study:

• To compare the incidence of PPFs and other clinical outcomes between collared and non-collared femoral stems in cementless THA.
• To evaluate the biomechanical effects of collared versus non-collared stems on alignment and subsidence.

Main Methods:

• Retrospective cohort study of 618 patients undergoing cementless THA.
• Patients were divided into collared (n=308) and non-collared (n=310) femoral stem groups.
• Analysis included baseline demographics, comorbidities, fixation, stem alignment, PPF classification (Vancouver system), and radiological evaluation (Gruen zones).

Main Results:

• The collared stem group exhibited a significantly lower PPF incidence (0.97% vs. 3.87%, p=0.033) and reduced stem subsidence (0.54 mm vs. 0.83 mm, p<0.001).
• Collared stems were associated with improved neutral alignment, fewer varus/valgus alignments, and less cortical hypertrophy.
• Reactive lines were more frequent with collared stems, and hospital stay was marginally longer, with no difference in early complications.

Conclusions:

• Collared cementless femoral stems demonstrate a significantly lower risk of PPFs and reduced subsidence compared to non-collared stems.
• These findings support the biomechanical advantage of collared stems in primary THA, leading to improved alignment and stability.