How Much Protection Does a Collar Provide? Assessing Risk of Early Periprosthetic Femur Fractures Following THA in Elderly Patients

Periprosthetic fractures (PPF) account for approximately 25% of early revisions following total hip arthroplasty (THA). Cemented femoral fixation is associated with a lower risk of PPF, and collared-cementless stems may reduce the risk as well. The objective of this study was to compare early PPF rates between cemented, collared-cementless and non-collared cementless stems in elderly patients.A consecutive series of 11,522 primary THAs performed between 2016 and 2021 at our institution in patients greater than 65 years of age was identified. Stem types used were categorized as cemented, collared-cementless, or non-collared cementless. Patients undergoing THA who had. cemented stems were older, more commonly women, and more likely to have a posterior approach. To reduce confounding of patient characteristics, we matched patients in the 3 stem categories according to age, sex, and body mass index (BMI). This generated 3 groups (cemented, collared-cementless and non-collared cementless) consisting of 936 patients per group. Mean age of these 2,808 patients was 73 years (range, 66 to 92), mean BMI was 27 (range, 17 to 45), and 67% were women. Logistic regressions were used to evaluate risk factors for early PPF. In the entire cohort of primary THA in elderly patients there were 85 early PPF (0.7%) over the study period.Non-collared cementless stems were associated with increased risk of early PPF (Odds Ratio: 3.11; P=0.03) compared to collared-cementless stems. There were no early PPF in the matched cemented cohort, six early PPF in the matched collared-cementless cohort, and 16 early PPF in the matched non-collared cementless cohort (0 vs 0.64 vs 1.71%, P < 0.001).In this large series of patients greater than 65 years of age undergoing primary THA, cemented stem fixation had the lowest incidence of early PPF, but collared-cementless femoral stems had a nearly three-fold decrease in risk for early PPF compared to non-collared cementless femoral stems.