Quantitative screening of engineered implants in a long bone defect model in rabbits

Area of Science:

• Biomaterials Science
• Orthopedic Surgery
• Regenerative Medicine

Background:

• Standardized long bone defect model in rabbits for quantitative comparison of bone healing.
• Evaluation of engineered biological implants for bone regeneration.

Purpose of the Study:

• To compare the bone healing performance of hydroxyapatite (HA), titanium (Ti), and a polymer-bioceramic composite (PH70alphaTCP) scaffolds.
• To assess the impact of rabbit periosteal cells (RPCs) on scaffold-mediated bone healing and mechanical functionality.

Main Methods:

• Porous cylindrical scaffolds (6-20 mm, 70% porosity) made of HA, Ti, and PH70alphaTCP were implanted into standardized 2 cm rabbit tibial defects.
• Scaffolds were tested with and without RPCs (20 x 10^6) cultured in a bioreactor.
• Bone formation and healing were assessed using X-rays and histomorphometry over 10 weeks.

Main Results:

• New bone formation observed at 3 weeks; bone corticalization in most animals by 10 weeks.
• HA and Ti scaffolds demonstrated osteoconductive properties, with 10-25% bone volume.
• PH70alphaTCP scaffolds did not integrate bone but did not inhibit callus formation.
• HA scaffolds seeded with RPCs significantly enhanced long bone mechanical functionality (308% max energy, 155% max angle increase vs. controls).

Conclusions:

• Ti and HA scaffolds are osteoconductive, promoting bone ingrowth.
• RPC-seeded HA scaffolds significantly improve mechanical properties of healed bone defects.
• The novel PH70alphaTCP composite requires further modification for bone integration.