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2. Reparative Phase (1-6 Weeks)
o The hematoma is gradually replaced by granulation tissue, which serves as a
scaffold for new bone formation.
o Soft Callus Formation: Fibroblasts and chondroblasts infiltrate the fracture site
and produce collagen and cartilage, forming a fibrocartilaginous soft callus.
o Hard Callus Formation: Osteoblasts begin depositing woven bone, transitioning
the callus into a hard, mineralized structure. This phase is influenced by adequate
mechanical stability and sufficient vascular supply.
o Radiographic evidence of a healing callus typically appears within 3-6 weeks.
3. Remodeling Phase (6 Weeks – Several Months/Years)
o Woven Bone to Lamellar Bone Transition: Osteoclasts resorb immature woven
bone while osteoblasts lay down organized lamellar bone.
o Bone Strength Restoration: The newly formed bone is remodeled according to
mechanical stresses via Wolff’s Law, where bone adapts to the loads under which
it is placed.
o This phase continues for months to years depending on the individual’s metabolic
activity, age, and overall health.

Factors Influencing Bone Healing

Bone healing is a dynamic process influenced by intrinsic and extrinsic factors that can
accelerate or delay recovery.

Biological Factors

• Age: Younger individuals have a higher osteogenic potential and shorter healing times.
• Genetic Factors: Certain genetic conditions (e.g., osteogenesis imperfecta) may impair
bone formation.
• Systemic Conditions: Chronic diseases such as diabetes, osteoporosis, and rheumatoid
arthritis can negatively impact bone metabolism.

Mechanical Factors

• Stability of Fixation: Proper immobilization (casts, splints, internal fixation) enhances
healing by minimizing micromotion.
• Weight-Bearing Status: Controlled loading can stimulate osteogenesis, while excessive
early weight-bearing may disrupt callus formation.
• Fracture Gap: Large gaps between bone fragments may lead to nonunion or fibrous
tissue formation instead of bone healing.

Environmental and Lifestyle Factors

• Nutrition: Calcium, phosphorus, vitamin D, and protein are essential for optimal bone
healing.
• Smoking: Nicotine and other toxins impair angiogenesis and osteoblastic function,
increasing the risk of delayed union.