Cervical spine fusion with bioabsorbable cages

Area of Science:

• Biomaterials Science
• Orthopedic Surgery
• Spinal Fusion Research

Background:

• Conventional spinal instrumentation poses risks like hardware complications and stress shielding.
• Bioabsorbable devices offer a potential alternative to permanent spinal implants.
• Long-term effects of traditional implants necessitate investigation into biodegradable options.

Purpose of the Study:

• To evaluate the efficacy of a bioabsorbable interbody fusion device in a goat cervical spine model.
• To compare different compositions of poly(L-lactide-co-D,L-lactide)/polyglycolic acid (PLDLLA/PGA) cages.
• To assess the fusion rates and inflammatory response associated with these novel implants.

Main Methods:

• A pilot study involving 42 goats undergoing two-level anterior cervical discectomy and fusion.
• Utilized cage implants made of 70:30 PLDLLA/PGA and 85:15 PLDLLA/PGA, filled with autograft or recombinant human bone morphogenetic protein-2 (rhBMP-2).
• Histological, radiographic, and physical evaluations were performed at 3, 6, and 12 months post-surgery.

Main Results:

• The 85:15 PLDLLA/PGA cages showed rapid absorption, limiting functional utility.
• The 70:30 PLDLLA/PGA cages demonstrated comparable fusion to autograft when filled with autograft.
• Cages composed of 70:30 PLDLLA/PGA combined with rhBMP-2 achieved 63% histologically confirmed fusion with increased bone content and stability at 6 months.
• Minimal inflammatory response and no significant absorption of 70:30 PLDLLA/PGA cages were observed at 6 months.

Conclusions:

• The 85:15 PLDLLA/PGA cages are absorbed too rapidly for functional use in this model.
• The 70:30 PLDLLA/PGA cages are a viable alternative to autograft, particularly when combined with rhBMP-2.
• Further biomechanical testing and longer follow-up are warranted to fully assess the long-term behavior of 70:30 PLDLLA/PGA cages.