A Classification of Extra-articular Distal Radius Fractures With Associated Injuries.

Abstract

To develop a classification system for extra-articular distal radius fractures (DRFs) integrating radiographic parameters of instability, ulnar fractures, distal radioulnar (DRU) joint disruption, and carpal involvement and to evaluate its reliability. A multicenter study across three university-affiliated orthopedic centers identified 1,239 extra-articular DRFs from 3,784 radiographs. Radiographic features were categorized into four domains: (1) DRF instability (radial inclination <15°, radial height loss ≥5 mm, dorsal angulation >15° in dorsally displaced fractures or volar tilt >15° in volarly displaced fractures, or metaphyseal comminution); (2) distal ulnar fractures (simple vs comminuted); (3) DRU joint disruption (bony vs soft tissue); and (4) carpal involvement. A hierarchical classification system with four types and eight subtypes was developed: Type I (isolated DRFs: IA stable, IB unstable), type II (ulnar fracture: IIA simple, IIB comminuted), type III (DRU joint disruption: IIIA bony, IIIB soft tissue), and type IV (carpal involvement: IVA isolated, IVB with DRU joint disruption). Reliability was assessed using a stratified random sample of 80 cases (10 per subtype) independently reviewed by six trained observers (two per center). Reliability was determined using Cohen's kappa with 95% confidence intervals. Reliability testing of the classification system across centers demonstrated mean k values ranging from 0.81 to 0.88 for Type I (IA and IB), Type IIA (simple ulnar), and Type IIIA (bony DRU joint) subtypes and mean k values ranging from 0.75 to 0.79 for Types IIB (comminuted ulnar), IIIB (soft tissue DRU joint), IVA (carpal only), and IVB (carpal + DRU joint). This classification system provides reliable and reproducible classification of extra-articular DRFs with meaningful inter- and intraobserver reliability across all fracture types. This proposed classification may improve comparability across studies and assist in clinical management and evidence synthesis for extra-articular DRFs.