## Fracture Healing Phases: Inflammatory vs. Reparative ### Phase Comparison | Feature | Inflammatory Phase | Reparative (Callus) Phase | Remodeling Phase | |---------|-------------------|--------------------------|------------------| | **Duration** | 0–3 weeks | 3–12 weeks | Months to years | | **Dominant cells** | Neutrophils, macrophages, RBCs | Fibroblasts, osteoblasts, chondrocytes | Osteocytes, osteoclasts | | **Tissue type** | Blood clot, granulation tissue | Woven bone, cartilage (soft callus → hard callus) | Lamellar bone, cortical remodeling | | **Vascularity** | Hemorrhage, edema | Neovascularization | Normalized | | **Radiographic appearance** | Fracture line visible, no callus | Callus bridging fracture site | Callus resorption, cortical restoration | ### Key Point: **The inflammatory phase is characterized by a cellular infiltrate dominated by polymorphonuclear leukocytes (neutrophils) and macrophages, with minimal osteogenic activity.** This phase is essential for debridement of dead tissue and release of growth factors, but does NOT produce new bone. ### Clinical Pearl: **The transition from inflammatory to reparative phase occurs around 3 weeks post-fracture.** At this point, the fracture site shifts from a hemorrhagic/inflammatory milieu to an osteogenic environment where fibroblasts and osteoblasts proliferate and begin laying down woven bone (soft callus formation). ### High-Yield: **Neutrophils and macrophages = inflammatory phase; fibroblasts and osteoblasts = reparative phase.** This is the single most reliable discriminator on exams. ### Mnemonic: **INFLAMATORY = INFlammatory cells (Neutrophils, macrophages); REPAIR = REPair cells (fibroblasts, osteoblasts).** [cite:Rockwood & Green's Fractures in Adults Ch 1] 
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.