Floating knee: A new prognostic classification.

Introduction: Usually ipsilateral fractures of the femur and tibia are not compatible with good results and require surgery. The unsatisfactory results are more likely due to complex patterns of fractures, compromised soft tissue, associated ligament injuries, and concomitant vital organ injuries. There are many classifications to describe this type of fracture but none of them is a prognostic classification. The aim of this study is to validate our classification according to prognostic terms.

Methods: This retrospective study encloses patients accepted with a diagnosis of floating knee between January 1st 2014 and December 31th 2020. A total of 372 patients met the inclusion criteria, but only 168 patients were selected for the final review. We have reclassified the 168 patients into three classifications: according to our alphanumeric; according to the Fraser classification; according to Letts and Ran. Our classification is divided into 5 macro categories in increasing order of severity, and considering fracture site, and exposure status. The Tau B Kendall and Cohen's Kappa was used to statistically evaluate the prognostic value, reliability and reproducibility of our classification versus Fraser Classification, Letts and Ran Classification in the prognosis of these injuries.

Results: The statistical results showed that classifiying patient into macro category and sub-category it is possible to have a prognostic correlation with functional results. Noteworthy, floating knee is a complex injury with poor results.

Conclusion: The floating knee is not only the bone lesion but is above all the lesion of the soft tissues and the extensor apparatus that allow the correct functionality of the knee. These lesions do not always have favorable outcome, with respect to the nonseverity of the lesion as in Fraser's classification. Furthermore, on average these patients are subjected to an average of 6 surgical interventions; in some cases we have assisted to 23 surgical procedures. This study proved that this new classification system is prognostic, reliable and reproducible.