[Effect of Staple on Growth Rate of Vertebral Growth Plates in Goat Scoliosis].

OBJECTIVE:To further investigate the possible mechanism of the correction of scoliosis with Staple by quantifying the effect of Staple on growth rate of vertebral growth plates in goat scoliosis. METHODS:Experimental scoliosis was created in 10 juvenile female goats by using unilateral pedicle screws asymmetric tethering. After 8-10 weeks, goats were divided randomly into Staple treated group (n=5) and control group (n=5). All tethers were removed in both groups and Staple group underwent anterior vertebral stapling with 4-5 shape memory alloy Staples along the convexity of the maximal curvature after posterior tether being removed. All goats were observed for an additional 8-13 weeks, the Cobb angle were measured to observe the correction of scoliosis. The fluorochromes Oxytetracycline and Calcein were administered respectively 18 and 3 days before death to label the ossifying front under the growth plates. Superior intervertebral disc of apical vertebra and two adjacent growth plates were completely harvested in all goats. All specimens were embedded with polymethyl methacrylate and sliced undecalcified. The growth rates of the vertebral growth plates were calculated by measuring the distance between the two fluorescent lines with fluorescence microscope. RESULTS:Nine (5 in Staple treated group and 4 in control group) of 10 tethered goats had progressive scoliotic curves of significant magnitude after 8-10 weeks of tethering. In Staple treated group, the Cobb angles were (34.8 +/- 12.4) degrees at the instant after treatment, and (15.6 +/- 11.7) degrees 8-13 weeks after treatment; showing statistically significant difference (P < 0.05). In the control group, the Cobb angles were (49.3 +/- 18.0) degrees at the instant after treatment, and (49.0 +/- 17.6) degrees 8-13 weeks after treatment; showing no statistically significant difference (P > 0.05). In Staple treated group, the growth rate of growth plate in the concavity (3.27 +/- 0.96) microm/d was higher than that in convexity (1.84 +/- 0.52) microm/d (P < 0.05), while the growth rate of the concavity did not differ significantly from that of the convexity in control group (P > 0.05). CONCLUSION:Staple can significantly alter the growth rates of two sides of vertebrae in scoliosis with the growth rate of concavity exceeding the one of convexity, which results in correction of deformity.