Periosteal Cells for Lumbar Segmental Fusion
Failure rate for lumbar fusion is ten to fifteen percent. Because it takes months for the bone to incorporate to complete fusion, there is interest in finding materials that could hasten and improve the fusion rate in the lumbar spine. The present accepted surgical procedure involves transpedicular stabilization and placement of autologous bone graft material in the disc space within two titanium cages. Autologous bone is harvested from the iliac crest. The authors compared the success of this surgical procedure with subjects who underwent fusion with bone from the tibia combined with engineered tissue. The engineered tissue was called fibrin/polyglactin-poly-p-dioxanone, PGLA-PPD fleece.

Twenty-four subjects were studied, 11 in the control group using iliac crest bone, 13 in the study group using periosteal bone cells from the tibia within PGLA-PPD fleece. There was less pain associated with tibial periosteal harvesting than with iliac crest cancellous bone harvesting. However, iliac crest bone harvesting is done at the same time as the fusion, where as surgery for harvesting of the periosteal bone cells must take place weeks prior to lumbar fusion.

The subjects in the study group had tibial periosteal bone harvested 10 weeks prior to lumbar surgery. Venous blood was also taken for cell culture. The bone cells were digested and cultured for six to eight weeks. They were then embedded in a fibrin gel. They were then placed on resorbable carrier fleece made of PGLA and PPD. This material was then placed in the titanium cages in the intervetebral space. The same hardware, screws and rods were used for fixation in the study group as the control group. All of the subjects underwent fusion at L4-5 or L5-S1, except one subject had fusion at L5-6.

All of the subjects were mobilized in physical therapy the day following surgery. None were given a back brace or support. The subjects were evaluated by dynamic radiographs and computed tomographic reconstructions at three, six, nine, and 12 months after surgery.

According to dynamic radiographs, at the three month interval, none of the control group were fused, and one of the study group subjects had evidence of fusion. However, at six months, 63.6 percent of the study group demonstrated fusions and 20 percent in the control group. At nine months, 90.9 percent of the study subjects demonstrated fusion compared to 40 percent of the control group. At 12 months, 90.9 percent of the study subjects and 80 percent of the control group demonstrated fusion. CT demonstrated earlier fusion in the study group as well, but a lower overall fusion rate at 12 months for each group.

Periosteal cells appear to be a viable substitute for harvesting iliac crest bone in spinal fusion surgery. Periosteal cells impregnated in polymer fleece appear to have advantages in terms of earlier consolidation of bone than iliac crest bone. The authors suggest that this technique be approved for lumbar fusion surgery.
M. Putzier, et al. Periosteal cells compared with autologous cancellous bone in lumbar segmental fusion. Journal of Neurosurgery:Spine June 2008. Volume 8, number 6. Pp. 536-543.