Heterotopic bone formation about the hip undergoes endochondral ossification: a rabbit model

Area of Science:

• Orthopedic Surgery
• Regenerative Medicine
• Skeletal Biology

Background:

• Heterotopic ossification (HO) frequently complicates hip surgery and trauma, impairing function.
• Existing animal models often use exogenous agents, not reflecting trauma-induced HO.
• A need exists for models that mimic human HO post-trauma.

Purpose of the Study:

• To characterize the histological progression of heterotopic bone formation.
• To establish an animal model that recapitulates human HO without induction agents.
• To understand the cellular mechanisms of trauma-induced HO.

Main Methods:

• A rabbit model with intramedullary femur instrumentation and gluteal muscle crush injury was used.
• 30 animals underwent bilateral procedures without osteogenic stimulants.
• Histological grading of tissue maturation was performed at 10 time points (1 day–26 weeks).

Main Results:

• Heterotopic bone reliably formed de novo in the model.
• The ossification pathway consistently followed endochondral ossification.
• Immature woven bone and chondroid elements were observed with mature bone.

Conclusions:

• HO occurs predictably in this trauma-mimicking animal model.
• The process consistently follows endochondral ossification.
• This model provides a basis for investigating HO mitigation strategies.