Development of the D-FLLIP classification for ipsilateral floating hip and knee injuries

Introduction: Ipsilateral “floating lower limb” (FLL)—coexisting pelvic/acetabular, femoral, and tibial fractures—presents rare, high-energy trauma with complex limb-threat physiology. A standardized diagnostic framework could improve early triage and operative sequencing. Objective: To develop and preliminarily evaluate the Diagnostic Floating Lower Limb Ipsilateral Protocol (D-FLLIP) as an ordinal severity classification and early decision-support tool for FLL. Methods: Retrospective, single-center case series at a tertiary trauma referral hospital (January 2018–December 2023); n=28 consecutive patients meeting FLL criteria. Study design characteristics: retrospective, informal, single-center, consecutive, exposure-based sampling (clinical); Level of evidence IV. Patients were graded I–V with D-FLLIP from itemized domains (pelvis, femur, tibia, and soft-tissue/high-risk features). Primary analyses used Kruskal–Wallis and Fisher’s exact/χ² to compare variables across grades. An exploratory univariable logistic regression assessed discrimination of an acute-complication composite (ICU stay >0 days, amputation, early wound infection