| Part I:A preliminary study on a new growing rod system in an immature swine modelBackground:Treatment of early-onset scoliosis(EOS)in childhood is still a challenge to surgeon.Nonfusion techniques,such as growing rods,were developed to postpone or avoid the fusion procedure and maintain the development of vital organs such as heart and lung.Although growing rods have well-accepted efficacy in controlling the deformity of a growing spine,they also have a high rate of complications.Therefore,a novel system of growing rod is urgently wanted to improve surgical outcome of early-onset scoliosis,minimizing the surgical trauma and reducing surgery-related complications.Objective:The objective of this study is to mainly investigate the efficacy and safety of new growing rod system in an immature swine model.And to evaluate its effect on the spinal disc degeneration and vertebral potential growth as well.Methods:12 immature swine(age:10 weeks old;weight:8-12 kg)were used in this study.They were randomly assigned to an experiment group(new growing rod system)and control group(traditional growing rod system).Dual growing rod were implanted to fix low thoracic and lumbar spine.They underwent lengthening procedure at 4-week intervals with a total of 12 weeks observation period.Radiographs,magnetic resonance image,and computed tomographic scan of the spine were obtained to evaluate the fixation,rod extension,and spine degeneration.Results:One swine in traditional growing rod group encountered deep wound infection and thus was excluded from analysis.Of the remaining 11 swine,all animals successfully underwent 12 weeks observation with 3 times of lengthening procedure.No new growing rod complications were observed.In new growing rod group,the average operative time was 12.1 ±3.1 min and the average length of incision was 1.1± 0.2 cm,which were significantly lower than that of the traditional growth group(P<0.001).New growing rod was extend by 40.08 mm(range,30.1-46.83 mm)and spine segments within the instruments grew by 17.42%(range:13.77-21.67%)in 12 weeks.Traditional growing rod was extend by 43.62 mm(range,38.84-46.28 mm)and spine segments within the instruments grew by 18.69%(range:15.97-20.03%)in 12 weeks.There was no statistical difference between two groups(P>0.05).Besides,there was no statistically significant difference between the two groups in vertebral body and intervertebral disc height(P>0.05).In new growing rod group,axial spinal computed tomographic scan demonstrated normal facets within the instrumented segments.Magnetic resonance imaging showed normal disc within the instrumented segments.Motion of the instrumented spinal segments was conserved.Conclusion:The new growing rod system can be safe and effective in immature swine,reserve potential growth ability of the spine,with less surgical trauma compared with the traditional growing rod.The new growing rod system well conserved the motion ability of the instrumented spinal segments,as well as the spinal disc within the instrumented segments.Part Ⅱ:Radiological characteristics and its clinical relevance on congenital scoliosis associated with split cord malformationBackground:Split cord malformation(SCM)is a rare form of closed neural tube defect which often associated with congenital scoliosis(CS).Type I SCM is defined as two hemicords,each within a separate dural tube separated by a bony spur,while type II SCM is defined as two hemicords within a single dural tube separated by a fibrous septum.Vertebrae,ribs,and spinal cord are anatomically adjacent structures,and their close relationships are clinically important for planning better corrective surgical approach.Furthermore,the nature history of split cord malformation(SCM)is still unclear.Baseline the characteristics of bony spur and its relationship with the spinal deformity can be used to help early identify those patients with higher neurological risk and improve surgical strategy.Objective:To identify the radiographic characteristics and its clinical relevance in surgical patients with congenital scoliosis and split cord malformation.Methods:A total of consecutive 266 patients with CS and SCM underwent surgical treatment at our hospital between May 2000 and December 2015 was retrospectively identified.There were 190 female and 76 male patients,with a mean age of 14.2 years(3-39 yr).Each patient received examinations of an entire spine magnetic resonance imaging(MRI)and computerized tomography(CT)to evaluate the type and location of SCM.According to Pang’s classification for SCM,all patients were divided into Type I group and Type Ⅱ group.The demographic distribution and radiographic data were collected to investigate the characteristics of spine curve,vertebral,rib,and intraspinal anomalies.Of them,85 consecutive type-I SCM patients were identified to investigate the characteristics of spine curve and bony spur.There were 22 male and 63 female patients with an average age of 13.9 years at surgery.They were divided into two groups according to their neurological status(intact or deficit).The location of bony spur relative to the apex of scoliosis were evaluated by MRI and CT of whole spine.The length and thickness of bony spur was also measured.Besides,in order to quantify the asymmetric splitting of the spinal cord,the diameter of hemicords were both measured on the axial MRI scans.Results:There were 104 patients(39.1%)in Type I group and 162 patients(60.9%)in Type Ⅱ group.SCM was most commonly found in the lower thoracic and lumbar regions.The mean length of the septum in Type I SCM was significantly shorter than Type II SCM(2.7 vs.5.2 segments).Patients in Type I group had a higher proportion of kyphotic deformity(22.1%).The vertebral deformities were simple in only 16.5%and multiple in 83.5%of 266 cases.Patients in Type I group presented higher prevalence of multiple(90.4%)and extensive(5.1 segments)malformation of vertebrae.In addition,hypertrophic lamina and bulbous spinous processes were more frequent in Type I group(29.7%),even developing into the "volcano-shape" deformities.Rib anomalies occurred in 62.8%of all patients and 46.1%of them were complex anomalies.The overall prevalence of other intraspinal anomalies was 42.9%.The most common coexisting intraspinal anomalies was syringomyelia(30.5%).Furthermore,there were 52 patients(61.2%)in Group A(intact)and 33 patients(38.8%)in Group B(deficit).No significant differences were found in the demographic distribution,curve magnitude,and length of bony spur between two groups.In Group A,the location of bony spur relative to the apex of major curve were:proximal 13(25%),distal 28(53.8%),centered 11(21.2%).While,in Group B,the relationships were:proximal 7(21.2%),distal 8(24.2%),centered 18(54.5%).There were statistically significant difference of the location of bony spurs between two groups(χ2 = 10.898,P= 0.004).In addition,patients in Group B had a higher proportion of kyphotic deformity(42.4%).Furthermore,the ratio of the diameter of hemicords(concave/convex)were statistically different between two groups(0.98 vs.0.87,p=0.045).Conclusion:The current study,with the largest cohort to date,demonstrated that patients with CS and coexisting SCM presented high prevalence of multiple vertebral deformities,rib and intraspinal anomalies.Especially in those with Type I SCM,they developed into more complicated and extensive vertebral anomalies,even "volcano-shape" deformities in the posterior elements of spine.The neurological status in patients with CS and type-I SCM may have a close relationship with their bony spur’s location relative to spinal deformity.When bony spurs occur at the apex of scoliosis,it have a higher risk of developing neurological deficits,especially in cases with kyphotic deformity.Besides,the neurological deficits in these patients may also attribute to the asymmetric splitting of the spinal cord. |
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