A 35-year-old male presents with a closed fracture of the femur sustained 3 weeks ago. Radiographs show early callus formation bridging the fracture site. Which of the following is NOT a characteristic feature of the stage of fracture healing occurring at this time point?

Question

Accepted Answer

B. Complete resorption of the fracture hematoma and formation of a rigid bony bridge. ## Fracture Healing Stages — Timeline and Features

Fracture healing progresses through four overlapping stages:

### Stage 1: Inflammatory Phase (0–3 weeks)
- Fracture hematoma forms immediately
- Inflammatory cells (neutrophils, macrophages) infiltrate
- Angiogenesis begins
- Fibrocartilaginous callus starts forming
- **Duration: Overlaps with early callus formation**

### Stage 2: Soft Callus Formation (1–4 weeks)
- **Key feature at 3 weeks: This is the primary stage occurring**
- Hyaline cartilage and fibrocartilage replace the hematoma
- Woven bone (immature, non-lamellar) begins to form
- Osteoblasts and chondroblasts proliferate from periosteum and endosteum
- Angiogenesis and neovascularization are active
- **Callus is NOT yet rigid — still cartilaginous**

### Stage 3: Hard Callus Formation (3–12 weeks)
- Cartilaginous callus is gradually replaced by woven bone
- Rigid bony bridge forms
- Fracture becomes mechanically stable

### Stage 4: Remodeling Phase (Months to years)
- Woven bone is replaced by lamellar bone
- Hematoma is completely resorbed
- Medullary canal is restored

**Key Point:** At 3 weeks, the fracture is in the **soft callus stage**. The hematoma is being replaced, not completely resorbed. A rigid bony bridge does NOT yet exist — that occurs in the hard callus stage (weeks 3–12).

**High-Yield:** The **soft callus is cartilaginous and NOT rigid**. Complete resorption of hematoma and formation of a rigid bony bridge are features of the **hard callus stage**, which occurs AFTER 3 weeks.

**Clinical Pearl:** Radiographically, at 3 weeks you see early callus bridging the fracture, but the callus is still mostly cartilaginous. Mechanical testing would show the fracture is still weak — it gains strength progressively as woven bone replaces cartilage.

Answer

A. Proliferation of osteoblasts and chondroblasts from the periosteum and endosteum

Answer

C. Angiogenesis and neovascularization of the fracture hematoma

Answer

D. Replacement of fibrin clot with hyaline cartilage and woven bone

A 35-year-old male presents with a closed fracture of the femur sustained 3 weeks ago. Radiographs show early callus formation bridging the fracture site. Which of the following is NOT a characteristic feature of the stage of fracture healing occurring at this time point?

Explanation

Fracture Healing Stages — Timeline and Features

Stage 1: Inflammatory Phase (0–3 weeks)

Stage 2: Soft Callus Formation (1–4 weeks)

Stage 3: Hard Callus Formation (3–12 weeks)

Stage 4: Remodeling Phase (Months to years)

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