Bone tissue engineering for spine fusion: an experimental study on ectopic and orthotopic implants in rats.

Alternatives to the use of autologous bone as a bone graft in spine surgery are needed. The purpose of this study was to examine tissue-engineered bone constructs in comparison with control scaffolds without cells in a posterior spinal implantation model in rats. Syngeneic bone marrow cells were cultured in the presence of bone differentiation factors and seeded on porous hydroxyapatite particles. Seven rats underwent a posterior surgical approach, in which scaffolds with (five rats) or without cells (two rats) were placed on both sides of the lumbar spine. In addition, separate scaffolds were inserted intramuscularly and subcutaneously during the surgical procedure. After 4 weeks, all rats were killed and examined radiographically, by manual palpation of the excised spine and histologically for signs of bone formation or spine fusion. All rats that received cell-seeded scaffolds showed newly formed bone in all three locations, whereas none of the locations in the control rats showed bone formation. The results of this study support the concept of developing tissue-engineering techniques in posterior spine fusion as an alternative to autologous bone.