Incidence and risk factors of intraoperative periprosthetic femoral fractures during primary total hip arthroplasty: 218,423 cases reported to the Norwegian Arthroplasty Register between 1987 and 2020

Abstract

Background and purpose: Intraoperative periprosthetic femoral fractures (IPFFs) can occur during primary total hip arthroplasty (THA). We describe the incidence of IPFFs during THA in Norway and estimate potential risk factors that could be associated with IPFF Patients and methods - Data from the Norwegian Arthoplasty Register (1987-2020) was used: 2,268 IPFFs from 218,423 primary THAs in 172,598 patients. The following factors were analyzed: sex, age, diagnosis, previous operation on the same hip, surgical approach, and stem fixation technique. Association of these factors with IPFF risk was assessed using multivariable Poisson regression.

Results: IPFF occurred during 2,268 operations with an incidence of 1.0% among all primary THAs. The risk of IPFF was associated with female sex (relative risk 1.8; 99% CI 1.5-2.1), age 80-90 years and age over 90 years (compared with age 60-70 years: 1.3; CI 1.0-1.6 and 2.6; CI 1.6-4.3, respectively), non-osteoarthritis diagnoses (2.2; CI 1.9-2.6), previous surgery to the same hip (1.8; CI 1.5-2.2), lateral approach (compared with the posterior approach: 1.5; CI 1.1-2.0), and cementless stem fixation (2.7; CI 2.0-3.6).

Interpretation: Surgeons should be aware of the factors associated with an increased risk of IPFF: female sex, age above 80 years, non-osteoarthritis diagnoses, and previous surgery to the same hip. Cemented stem fixation and posterior approach should be favored in high-risk patients, such as elderly women.

Figure 1

Categorization process of perioperative complications in 218,423 THAs registered in the Norwegian Arthroplasty Registry from 1987 to 2020. THA = total hip arthroplasty; IPFF = intraoperative periprosthetic femoral fracture.

Figure 2

A directed acyclic graph (DAG) showing the theoretical pathways from the potential risk factors of interest—previous surgery, sex, age, diagnosis, fixation technique, surgical approach—to the outcome of interest, intraoperative periprosthetic femoral fracture (IPFF). The minimum set of required confounder adjustments varied between the risk factors of interest, operation year age and sex. An unbiased estimate of the association of diagnosis on the risk of IPFF required adjusting for operation year, sex, and age, whilst previous surgery also had to be adjusted for diagnosis. Confounders on the effect of surgical approach were operation year and previous surgery. Finally, for an unbiased estimate of the effect of fixation technique on the risk of IPFF, operation year, age, sex, previous surgery, and diagnosis had to be adjusted for.

Figure 3

Annual incidence of intraoperative periprosthetic femoral fracture (IPFF) from 1987 to 2020. There were 218,423 total hip arthroplasties without missing data on perioperative complications. Error zone represent 99% confidence intervals.

Figure 4

Type of stem fixation (cemented or cementless) for different age groups during the study period. Based on 216,317 total hip arthroplasties with available information on stem-fixation technique.

Figure 5

Nonlinear relationship between age and probability of IPFF based on 210,256 total hip arthroplasties without missing data. Figures A and C are adjusted for operation year, whilst B and D are adjusted for all the studied potential risk factors of IPFF. For A–B, no stratification, and C–D, stratified on sex. Adjustment variables were set to the following fixed levels: cementation type = cemented; previous operation = no; sex = female; diagnosis = osteoarthritis; and operation year group = 2016–2020. IPFF = intraoperative periprosthetic femoral fracture.