# Bone defects in knee revision arthroplasty—a therapy-oriented classification

## TL;DR

This paper introduces a reliable classification system for bone defects in knee revision surgeries to improve preoperative planning and intraoperative guidance.

## Contribution

The paper presents the Knee Defect Classification (KDC), a new, reliable, and reproducible system for assessing bone defects in knee revision arthroplasty.

## Key findings

- The KDC showed good agreement between preoperative and intraoperative assessments (Cohen's kappa of 0.79).
- Inter-rater reliability for femoral and tibial defects was in the good agreement range (Fleiss kappa of 0.71).
- Intra-rater reliability was also good (Cohen's kappa of 0.78).

## Abstract

The complex field of revision knee arthroplasty displays a lack of standardized, intuitive pre- and intraoperative assessment of bone defects. In clinical practice revision surgeries are a common sight presenting with increasingly complex cases of bone loss and ligamentary dysfunction. To address these issues the Knee Defect Classification (KDC) is introduced to offer a reliable, reproducible and an intuitive classification system with a clear therapeutic guideline.

Reliability was evaluated through comparison between intraoperative findings and preoperative gradings of 218 patients. To account for reproducibility inter- and intra-rater agreement was assessed.

The mean agreement between intraoperative and radiographic grading of femoral and tibial defects was evaluated with a Cohens kappa of 0.79, representing a good agreement. For interrater reliability a mean Fleiss kappa of 0.71 could be evaluated for femoral and tibial defects falling into the good agreement range. In the subgroup analysis femoral defects presented with a Fleiss kappa of 0.652 ± 0.026 (good agreement), while tibial defects presented with a Fleiss kappa of 0.768 ± 0.024 (good agreement). For intrarater reliability a mean Cohens kappa was evaluated at 0.78 indicating good agreement.

The KDC is a reliable and reproducible classification system. Through its structured design it facilitates intuitive use and allows for consistent preoperative planning and intraoperative guidance. A therapeutic algorithm is provided based on a review of the literature in combination with expert opinion.