The Effects Of Auto-guided Growth Rod System On The Spine Growth In Young Pigs

Purposes The aim of this study was to evaluate the efficacy and feasibility of implantation a Auto-guided growing rod system(AGGRS) in a porcine model.Description of Technique The “Auto-guided growing rod system” is a growth guidance system that can slide along with the natural growth of the spine. The “Auto-guided growing rod system” is a central tandem growing rod, Sliding titanium rod inside growth sleeve. This can avoid the surrounding soft tissue impediment to the sliding rod, thereby improving sliding efficiency.Methods Twelve four-month-old pigs were randomly divided into an experimental group(n=8) and a sham group(n=4). Animals in experimental group, we made a single midline incision from the upper thoracic to the upper lumbar spine(T6-T7 to T14-L1) and exposed the T6-L1 bilateral lamina. Pedicle screws were placed anatomically in the center of those vertebral(T6, T7, T13, T14, L1) pedicles bilaterally. The growing rod were placed between T8 to L1. Whereas ones in the sham group were just expose the T6-L1 bilateral lamina. On the day of surgery, and 6 and 12 weeks postoperation, all young pigs accepted the spinal X tablets. Spinal growth height was assessed by vertebral unit height(VUH) measurements on X tablets. In addition, spinal magnetic resonance image(MRI) was used to evaluate the degenerative degree of intervertebral disc. All experiment datas analyzed by SPSS22.0 statistical software. When P<0.05 were considered significant.Results Throughout 3-month follow-up, In the experimental group, one pig died immediately after operation and one young pig find internal fixation loosening through spinal X ray after 6 weeks of operation, unfinished experiment. Therefore, there have 10 pigs finished experiment. The average VUH of T6-7 segment of the pigs in the EG and SG were increased by 4.14 mm and 5.33 mm, respectively. Similarly, the mean VUH of T8-13 segment of the animals in EG and SG was increased by 10.96 mm and 12.88 mm, and the average VUH of T14-L1 segment increased by 8.88 mm and 14.19 mm. The average length of T8-T13 segment of the pigs in the EG and SG were increased by 65.74 mm and 77.31 mm, respectively. The experimental group un-fixed segment(T8-T13) and the control group relative segment length ratio is 85%. The average sliding length of the growing rod was 65.76 mm. As shown in the MRI, in the slide section, the disc height is good, the signaling were bright. While the signal of the fixed segment(T6-T7, T14-L1) was confusion, and the disc growing were significantly inhibited.Conclusions It was feasible to implanted AGGRS in porcine animal model. The AGGRS was effectively fixed and allowed for continued growth in spine without repetitive surgical lengthening.