A collar is a protective factor against early periprosthetic fracture for cementless stems in total hip arthroplasty : a multivariate analysis in a single-centre cohort of 1,623 total hip arthroplasties.

Periprosthetic fractures (PPFs) are a significant complication in total hip arthroplasty (THA), with their incidence varying from 0.1% to 5.2% in registries. The use of a collared femoral stem may reduce the risk of PPF by enhancing the distribution of load and the stability of the implant. The aim of this study was to compare the effect of collared versus collarless stems on the incidence of PPFs in a large cohort of patients. This retrospective study involved all primary THAs performed in a single centre between 1 January 2010 and 31 December 2020. Of the 2,182 THAs performed in 1,767 patients, 559 in 447 patients were excluded for the following reasons: having cemented stems, patients with a femoral neck fracture, dysplasia of the hip, or an oncological indication for surgery. A total of 1,623 THAs in 1,320 patients were included. The data which were collected included the patients' demographics, the surgical approach, the implant characteristics, and the incidence of PPF. Univariate and multivariate analyses were conducted using the Bursac's logistic regression model considering factors such as sex, age, BMI, surgical approach, and the presence of a collar. There were nine PPFs within 90 days of surgery: five in the collared stem group (0.4%) and four in the collarless stem group (1.6%). Multivariate analysis revealed that the presence of a collar was the only significant independent predictive factor of a reduced rate of PPFs (p = 0.048). Other factors such as sex, age, BMI, and surgical approach did not show significant correlations. The collared stem was a protective factor against early femoral PPF when cementless stems were used in primary THA. These results support the preference for collared versus collarless cementless stems, particularly in patients who are at a high risk of PPF, to enhance the initial stabilty of the stem and reduce complications.