The effects of Modic-III change on the osseointegration in cervical disc prosthesis: an experimental study in caprine models.

OBJECTIVE

To quantitatively investigate the effects of Modic-III changes on the porous bone ingrowth at the interface of cervical disc prosthesis using caprine models.

METHODS

The Modic-III changes were induced at C3-4 level in eight goats by discectomy, followed by the implantation of cervical disc prostheses, while another eight goats served as a control group. Computed tomography (CT) and X-rays of cervical spine were performed intraoperatively and postoperatively at verify implant placement. The vertebral specimens were examined by micro-CT for histomorphometric quantification, including bone volume fraction (BV/TV), trabecular number (Tb.N), trabecular thickness (Tb.Th). Methylene-blue/acid fuchsin staining, standard hematoxylin and eosin staining, and Masson staining were used for histologic evaluation. Immunohistochemical staining, including osteocalcin (OCN), alkaline phosphate (ALP), and runt-related transcription factor 2 (RUNX2), were also conducted.

RESULTS

All goats were followed for a period of 6 months after prosthesis implantation. The rate of prosthesis complications in experimental group was significantly higher than that in control group (37.5% vs. 12.5%, P = 0.046). The histomorphometric parameters of experimental group, including BV/TV, Tb.N, Tb.Th, and bone ingrowth percentage were significantly lower than those of control group. The histologic sections of control group showed the excellent bone ingrowth and close contact between bone and prosthesis interface. By contrast, in experimental group, plenty of interfacial gaps were filled up with abundant fibrous tissue. The immunohistochemical sections of control group demonstrated the bone trabecula was surrounded by numerous osteoblasts, compared with the clear and smooth bone trabecula margin surrounded by few osteoblasts in experimental group. Moreover, the experimental group had significantly lower integrated optical density values of OCN, ALP, and RUNX2 staining.

CONCLUSION

The Modic-III changes significantly impaired the osseointegration of artificial cervical disc in caprine models by reducing the number of osteoblasts, BV/TV, Tb.N, Tb.Th, bone ingrowth percentage and down-regulating the expression levels of ALP, Osteocalcin, and Runx-2, possibly leading to more occurrence of prosthesis complications.