Purpose: Fresh frozen intervertebral disc allograft transplantation has been reported to be a viable treatment option for advanced degenerative disc diseases, but rapid degeneration of the postoperative allograft was found. Loss of nutrient supply is believed to be the most likely inducer because the disc allografts have to endure in an ischaemic environment until the nutrient pathway is re-established. The aim of this study was to focus on the revascularisation of the disc allograft after transplantation in goats.
Methods: Twenty male goats were used in this study. Intervertebral disc allograft transplantation was performed at L4/L5. Groups of five goats were killed at 1.5, 6 and 12 m postoperatively, respectively. The transplanted segments were harvested, fixed, sagittally cut and decalcified for H&E staining and immunochemistry to observe the blood vessel formation at the endplates, anterior outer annulus, posterior outer annulus, inner annulus and the nucleus. The blood vessel density and the sectional vessel area were measured.
Results: Blood vessels were first found in the marrow space of the bony endplate and the outer annulus at 1.5 month postoperatively. Then, they were able to penetrate to reach the cartilaginous endplate and the inner annulus after 6 months. Interestingly, the endplate area possessed the most abundant blood vessels, with the highest level of vessel density and area at the final follow-up. None of these newly formed vessels invaded the nucleus during the observation period.
Conclusions: Revascularisation of the postoperative disc allograft has been determined, but its pattern was different from that in adult normal discs, suggesting that the typical nutrient diffusion pattern may be affected after transplantation.
Keywords: Allograft; Blood vessels; Intervertebral disc; Revascularisation; Transplantation.