Characteristics and outcomes of interprosthetic versus periprosthetic femur fractures.

OBJECTIVES

The purpose of this study was to compare demographics, treatments, and outcomes of interprosthetic (IPFFs) and periprosthetic femur fractures (PPFFs). IPFFs were hypothesized to occur in older patients and have higher rates of reoperation, implant failure, and mortality.

METHODS

This was a retrospective cohort at a Level 1 trauma center analyzing adults with PPFFs/IPFFs from 2012-2024. Patients with < 30 days follow-up were excluded. Patient characteristics, treatments, and complications were compared between IPFFs and PPFFs.

RESULTS

276 patients with 30 IPFFs and 246 PPFFs were included. IPFFs were older (74y v 69y p=.035), more commonly osteoporotic (33% v 11% p<.001), and more commonly current (17% v 14%) or former smokers (7% v 0% p<.001). IPFFs presented with 29 total hip (THA) and knee (TKA) arthroplasties and one THA and unicompartmental knee arthroplasty. PPFFs presented with 130 fractures around THAs and 116 fractures around TKAs. IPFFs more commonly presented with unstable prostheses (40% v 21% p=.017). Of the seven IPFFs treated with nail-plate hybrid constructs (NPCs), six (86%) were immediately weightbearing as tolerated (WBAT). Of the 23 IPFFs not treated with NPCs, 9 (39%) were immediately WBAT (p=.031). IPFFs had more blood loss (811mL v 513mL p=.016). The mortality rate was 15% in IPFFs and 4% in PPFFs (p=.02). IPFFs had higher rates of implant failure (23% v 7% p=.004) and superficial infection (15% v 4% p=.013). Of the seven IPFFs treated with NPCs, there were no implant failures, while 7/23 (30%) IPFFs treated with other techniques failed (p=.09).

CONCLUSIONS

IPFFs were older, more commonly osteoporotic, more likely to be smokers, and more often had unstable prostheses at presentation than PPFFs. While treatments were similar, the rate of mortality, implant failure and superficial infection was higher in IPFFs. NPCs may allow for earlier weightbearing but their long-term effects regarding outcomes and stability require further investigation in prospective studies.

LEVEL OF EVIDENCE: III.