Rigid Fixation of the Spinal Column Improves Scaffold Alignment and Prevents Scoliosis in the Transected Rat Spinal Cord

Study Design. A controlled study to evaluate a new technique for spinal rod fixation after spinal cord injury in rats. Alignment of implanted tissue-engineered scaffolds was assessed radiographically and by magnetic resonance imaging. Objective. To evaluate the stability of implanted scaffolds and the extent of kyphoscoliotic deformities after spinal fixation. Summary of Background Data. Biodegradable scaffolds provide an excellent platform for the quantitative assessment of cellular and molecular factors that promote regeneration within the transected cord. Successful delivery of scaffolds to the damaged cord can be hampered by malalignment following transplantation, which in turn, hinders the assessment of neural regeneration. Methods. Radio-opaque barium sulfate-impregnated poly-lactic-co-glycolic acid scaffolds were implanted into spinal transection injuries in adult rats. Spinal fixation was performed in one group of animals using a metal rod fixed to the spinous processes above and below the site of injury, while the control group received no fixation. Radiographic morphometry was performed after 2 and 4 weeks, and 3-dimensional magnetic resonance microscopy analysis 4 weeks after surgery. Results. Over the course of 4 weeks, progressive scoliosis was evident in the unfixed group, where a Cobb angle of 8.13 degrees +/- 2.03 degrees was measured. The fixed group demonstrated significantly less scoliosis, with a Cobb angle measurement of 1.89 +/- 0.75 degrees (P = 0.0004). Similarly, a trend for less kyphosis was evident in the fixed group (7.33 +/- 1.68 degrees) compared with the unfixed group (10.13 +/- 1.46 degrees). Quantitative measurements of the degree of malalignment of the scaffolds were also significantly less in the fixed group (5 +/- 1.23 degrees) compared with the unfixed group (11 +/- 2.82 degrees) (P = 0.0143). Conclusion. Radio-opaque barium sulfate allows for visualization of scaffolds in vivo using radiographic analysis. Spinal fixation was shown to prevent scoliosis, reduce kyphosis, and reduce scaffold malalignment within the transected rat spinal cord. Using a highly optimized model will increase the potential for finding a therapy for restoring function to the injured cord.