# Challenging the myth: comparing early complications of native and periprosthetic distal femur fractures. The role of implant stability

## TL;DR

This study compares the treatment outcomes of native and periprosthetic distal femur fractures, finding that periprosthetic fractures are not necessarily more complex or problematic than native ones.

## Contribution

The study directly compares periprosthetic and native distal femur fractures using the Lewis–Rorabeck classification to assess implant stability and early complications.

## Key findings

- Periprosthetic fractures had lower complication rates compared to native fractures.
- Lewis–Rorabeck Type III fractures required more revision surgeries and had longer time to surgery.
- No significant differences were found in mobility or hospital stay between native and periprosthetic fractures.

## Abstract

Periprosthetic distal femur fractures are often considered more complex and morbid than native distal femur fractures, yet few studies directly compare them. This study aimed to compare patient characteristics, treatment strategies, and early complications between native and periprosthetic distal femur fractures using the Lewis–Rorabeck classification.

We retrospectively analyzed 152 patients treated surgically for distal femur fractures at a level I trauma center. Cases included native fractures (n = 90) and periprosthetic distal femur fractures (n = 62), further divided into Lewis–Rorabeck Type I/II (n = 49) and Type III (n = 13). Demographics, comorbidities, surgical details, and in-hospital complications were assessed. We conducted a multivariate analysis comparing native fractures with Lewis–Rorabeck Type I/II fractures, as well as comparing Type I/II with Type III fractures.

Patients with periprosthetic fractures were older and had higher BMI than those with native fractures (p < 0.001). Multivariate analysis showed no significant differences in surgery duration, mortality, mobility at discharge, transfusion needs, or revision rates between native distal femur fractures (AO/OTA Type A) and Lewis–Rorabeck Type I/II. The complication rate was significantly lower in the periprosthetic group (p = 0.029). Lewis–Rorabeck Type III fractures showed significantly longer time to surgery (p = 0.015) and revision surgery was performed more frequently compared to Lewis–Rorabeck Type I/II fractures. However, no differences were observed in early postoperative complications, mobility at discharge, or length of hospital stay.

This study directly compares periprosthetic distal femur fractures stratified by implant stability to native distal femur fractures. The findings challenge the perception that periprosthetic fractures are universally more difficult to treat. Periprosthetic fractures achieve results comparable to native fractures. The increased complexity of Lewis–Rorabeck Type III fractures is reflected in prolonged time to surgery and an increased need for revision surgery.

The online version contains supplementary material available at 10.1007/s00402-025-06173-4.