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• Medications: Corticosteroids, NSAIDs, and bisphosphonates can negatively affect bone
remodeling by inhibiting osteoblast activity.

Primary vs. Secondary Bone Healing

Primary Bone Healing (Direct Healing)

• Occurs when rigid internal fixation (e.g., plates and screws) is used, eliminating
micromotion at the fracture site.
• No callus formation is observed; healing occurs through direct osteonal remodeling.
• Requires absolute stability and is common in surgical fixation of fractures.

Secondary Bone Healing (Indirect Healing)

• The most common type of healing, involving callus formation.
• Requires relative stability, such as in casting or external fixation.
• More resistant to mechanical stress and typically follows the natural phases of
inflammation, repair, and remodeling.

Complications of Impaired Bone Healing

When the normal bone healing process is disrupted, it can lead to complications that may require
additional medical or surgical intervention.

1. Delayed Union
o The fracture takes longer than expected to heal.
o Causes: Poor blood supply, inadequate immobilization, infection, or systemic
conditions.
o Treatment: Extended immobilization, bone stimulators, or revision surgery.
2. Nonunion
o The fracture fails to heal, often resulting in persistent pain and instability.
o Types:
▪ Atrophic Nonunion: Lack of biological activity, requiring bone grafting.
▪ Hypertrophic Nonunion: Excessive callus formation, indicating
instability rather than biological failure.
o Treatment: Surgical intervention with bone grafting or fixation revision.
3. Malunion
o The bone heals in an improper position, leading to functional impairment.
o Causes: Poor initial alignment, inadequate immobilization, or early weight-
bearing.
o Treatment: Osteotomy and realignment through surgical correction.
4. Avascular Necrosis (AVN)
o Loss of blood supply leads to bone tissue death, commonly affecting the femoral
head, scaphoid, or talus.
o Risk Factors: High-energy trauma, corticosteroid use, and alcohol abuse.