The Effects of Human Amniotic Fluid and Different Bone Grafts on Vertebral Fusion in an Experimental Rat Model

OBJECTIVE The high risk of nonunion represents a challenge in vertebral surgery, thus stimulating new strategies to improve fusion rates. We investigated the effect of 2 different bone grafts and amniotic fluid application on radiologically and histologically evaluated vertebral fusion in an experimental rat model. MATERIALS AND METHODS Forty-eight 24-week-old Sprague Dawley rats were included and assigned into 1 of 4 groups: allograft group, allograft plus human amniotic fluid group, demineralized bone matrix (DBM) group, or DBM plus human amniotic fluid group. After decortication and L4-L6 spinal fusion, study treatments were applied. Fusion in each rat was examined radiologically and histologically 8 weeks after the intervention. RESULTS The group that received only allograft had better radiologic scores (median = 3.5; range = 3-4) when compared with the group that received only DBM (median = 2; range = 1-4) (P = 0.002); however, histologic scores did not differ. When amniotic fluid was added to the grafting, allograft-based treatments performed better than DBM-based treatments both on radiologic (median = 4; range = 3-4 vs median = 3; range = 3-4; P = 0.003) and histologic (median = 7; range = 6-7 vs median = 5; range = 3-6; P < 0.001) evaluation. Addition of amniotic fluid did not result in better outcomes in the rats that received DBM-based treatments but based on histologic evaluation, rats that received allograft-based treatments benefited from this application. CONCLUSIONS Amniotic fluid seems to have an enhancing effect on posterior spinal fusion, particularly when combined with allograft.