Autologous growth factors versus autogenous graft for anterior cervical interbody fusion: an in vivo caprine model.

Object: Using an in vivo caprine model, authors in this study compared the efficacy of autologous growth factors (AGFs) with autogenous graft for anterior cervical interbody arthrodesis.

Methods: Fourteen skeletally mature Nubian goats were used in this study and followed up for a period of 16 weeks postoperatively. Anterior cervical interbody arthrodesis was performed at the C3-4 and C5-6 vertebral levels. Four interbody treatment groups (7 animals in each group) were equally randomized among the 28 arthrodesis sites: Group 1, autograft alone; Group 2, autograft + cervical cage; Group 3, AGFs + cervical cage; and Group 4, autograft + anterior cervical plate. Groups 1 and 4 served as operative controls. Autologous growth factors were obtained preoperatively from venous blood and were ultra-concentrated. Following the 16-week survival period, interbody fusion success was evaluated based on radiographic, biomechanical, and histological analyses.

Results: All goats survived surgery without incidence of vascular or infectious complications. Radiographic analysis by 3 independent observers indicated fusion rates ranging from 9 (43%) of 21 in the autograft-alone and autograft + cage groups to 12 (57%) of 21 in the autograft + anterior plate group. The sample size was not large enough to detect any statistical significance in these observed differences. Biomechanical testing revealed statistical differences (p < 0.05) between all treatments and the nonoperative controls under axial rotation and flexion and extension loading. Although the AGF + cage and autograft-alone treatments appeared to be statistically different from the intact spine during lateral bending, larger variances and smaller relative differences precluded a determination of statistical significance. Histomorphometric analysis of bone formation within the predefined fusion zone indicated quantities of bone within the interbody cage ranging from 21.3 +/- 14.7% for the AGF + cage group to 34.5 +/- 9.9% for the autograft-alone group.

Conclusions: The results indicated no differences in biomechanical findings among the treatment groups and comparable levels of trabecular bone formation within the fusion site between specimens treated with autogenous bone and those filled with the ultra-concentrated AGF extract. In addition, interbody cage treatments appeared to maintain disc space height better than autograft-alone treatments.