To evaluate the efficacy of the sleeve type guide growth rod sliding automatically with the growth of piglet spine.

Fourteen 4-month-old piglets were randomly divided into growth rod group (n=8) and control group (n=6). Animals in growth rod group were implanted with the sleeve type guide growth rod system through the small incision of the tho-racodorsal. Whereas ones in control group were just expose the bilateral lamina. On the day of surgery, 6 and 12 weeks of postop-eration, all piglets accepted the spinal X-ray examination. Measured the mean height of T₈, T₉ vertebral bodies, the average height of T_7-8, T_8-9, T_9-10 discs and the mean length of the rods through X-ray film. Spinal MRI was measured 3 months after the operation. The morphological changes of the plate were observed after HE staining. The morphological changes of the nucleus pulposus cells were observed and the thickness of the growth plate and the length of the growth bar were measured.

Two piglets of growth rod group did not complete the experiment, 1 piglet died of aspiration due to anesthesia resuscitation, and 1 piglet had in-fection after operation. The average height of T₈, T₉ vertebral bodies of the piglets in the growth rod group on the day after surgery and 3 months after operation was 18.26±3.26 mm and 27.15±4.18 mm, respectively, and the difference was statistically significant (F=16.868, P=0.002). Similarly, the mean height of T_7-8, T_8-9, T_9-10 discs of the piglets in growth rod group on the day after surgery and 3 months of postoperation was 1.79±0.24 mm and 2.14±0.23 mm, respectively, and the difference was statistically significant(F=6.455, P=0.029). The average height of T₈, T₉ vertebral bodies in the control group on the day after surgery and 3 months after operation was 17.86±3.50 mm and 28.63±4.45 mm, respectively, and the difference was statistically significant (F=21.654, P=0.001). Similarly, the mean height of T_7-8, T_8-9, T_9-10 discs in control group at the day after surgery and 3 months of postoperation was 1.78±0.27 mm and 2.17±0.30 mm, respectively, the difference was statistically significant (F=5.928, P=0.035). There was no statistically significant difference in average height between T₈ and T₉ vertebral bodies in growth rod group and the control group at 3 months after operation (F=0.352, P=0.566). Similarly, There was no statistically significant difference in average height of T_7-8、T_8-9、T_9-10 discs in growth rod group and the control group at 3 months after operation (F=0.053, P=0.823). The average sliding length of the growth rod in growth rod was 65.74 mm. Furthermore, growth plate chondrocytes and nucleus pulposus cells in EG and SG, all showed that the cells were arranged in order, the cell volume was large, the shape was round and the cytoplasm was rich. Simultaneously, there was no significant difference between the two groups in growth plate chondrocytes (P>0.05).

The sleeve type guiding growing rod can automatically slip to extend due to the driving force of young pig’s spine growth, without obvious effects on the normal growth of piglet's spine.

Scoliosis; Orthopedic fixation devices; Internal fixators