Recombinant human bone morphogenetic protein-4 (rhBMP-4) enhanced posterior spinal fusion without decortication

Area of Science:

• Orthopedics
• Regenerative Medicine
• Biomaterials

Background:

• Posterior spinal fusion success can be limited by insufficient decortication, potentially reducing osteoprogenitor stem cells.
• Recombinant human bone morphogenetic protein-4 (rhBMP-4) has shown potential in inducing bone formation from mesenchymal cells.

Purpose of the Study:

• To investigate the molecular enhancement of posterior spinal fusion using site-specific application of rhBMP-4.
• To evaluate the efficacy of rhBMP-4 with or without surgical decortication in a rabbit model.

Main Methods:

• Eighteen adult rabbits underwent L5-L6 posterior intertransverse process spinal fusion, with one side decorticated and the other not.
• Animals were randomized into three groups using hydroxyapatite-tricalcium phosphate (HA-TCP) ceramic blocks with 0, 125, or 5 µg of rhBMP-4.
• Fusion was assessed via X-ray, microradiography, and histomorphology at 7 weeks.

Main Results:

• No fusion occurred in the absence of rhBMP-4, regardless of decortication.
• Low-dose rhBMP-4 resulted in 33% fusion in un-decorticated sites and 50% in decorticated sites.
• High-dose rhBMP-4 achieved 100% complete bony fusion in both decorticated and un-decorticated sites.

Conclusions:

• rhBMP-4 effectively enhances posterior spinal fusion by inducing osteogenic differentiation of non-marrow derived mesenchymal cells.
• Surgical decortication is not essential for achieving high fusion rates when using high-dose rhBMP-4.
• rhBMP-4 represents a promising molecular approach to improve spinal fusion outcomes.