| PART Ⅰ: A Preliminary Study on the Establishment of Early-onset Scoliosis Animal Model via Growth Intervention of Neurocentral Synchondrosis in Immature LandraceBackground Early-onset scoliosis(EOS)refers to scoliosis that presents in children aged less than 5 years,characterized by rapid curve progression and thoracic insufficiency,which requires early intervention.However,currently available treatment measures for EOS,including growing rod technique and vertical expandable prosthetic titanium rib,remain to be ineffective to control the rotation of vertebrae,probably resulting in curve progression and pulmonary function deterioration.Therefore,it is imperative to create a scoliosis model with growth property similar to human EOS,and further to develop a novel non-fusion correction technique for EOS in this model.Neurocentral synchondrosis(NCS),a three-dimension cartilage located at the junction of the vertebral body and the pedicle,is believed to contribute to the growth of both the vertebral body and the posterior arch.As demonstrated in previous studies,disturbance of unilateral NCS could lead to remarkable vertebral rotation,suggesting that asymmetric growth of NCS might be not only one of the initiating factors of EOS development,but one of the main contributing factors to curve progression as well.Objective To establish a landrace scoliosis model similar to human EOS by way of producing vertebral rotation via unilaterally inserting pedicle screws through NCS;Methods Ten immature landrace(3 weeks old)were used to model EOS animal.Six immature landrace were assigned to an experiment group,and four in sham operation group.In the experimental group,transpedicular screw placed across the NCS in thoracolumbar vertebra region.In the sham operation group,four animals received a sham operation without pedicle screw fixation.Scoliosis models was evaluated by the scoliotic deformity and vertebral rotation for a 3-month period with CT examination monthly.Results One immature landrace in surgical group suffered neurological deficit and thus excluded from the current study.There were no significant difference in weight and body length between the two groups(P>0.05).The surgical group demonstrated scoliotic deformity of 10.5°±3.20° at one month after pedicle screw inserction,and then increased to 23.1°±7.03° at 2 months,and 31.4°±6.51° at the time point of three months.Also,the vertebral rotation were significantly increased during the observed periods.No scoliotic changes were observed in the sham operation group.Conclusion Intervention of NCS growth can directly result to vertebral rotation and scoliotic changes,without the damages to thoracic cage,which is more consistent with the growth characteristics of EOS.PART Ⅱ:Incidence,Risk Factors,and Evolution of Proximal Junctional Kyphosis after Posterior Long-segment Spinal Fusin in Young Children with Congenital ScoliosisBackground PJK is an undesired postoperative complication observed in the sagittal plane following instrumentation and fusion for spinal deformities.PJK is well recognized in adults and adolescents after surgery for scoliosis and/or kyphosis.According to the literature,the incidence of PJK is reported to be 26%~39% for adults and 8.1%~46% for adolescents.The variance in PJK incidence might be related to differences in case pathology,proximal instrumentation type,criteria for defining PJK,and duration of follow-up.Moreover,the risk factors for PJK in adult populations include high body mass index(BMI),poor bone quality,older age,fusion to the sacrum,thoracoplasty,overcorrection of sagittal balance,larger preoperative thoracic kyphosis.PJK is also seen upon clinical observation in a substantial portion of children younger than 10 years.But young children usually differ from these patients in terms of patient characteristics and disease pathogenesis.Previous studies mainly focused on PJK in young children treated with growing rods or the vertical expandable prosthetic titanium rib technique.There are very few reports concentrating on PJK in young children with CS exclusively treated with posterior long-segment spinal fusion.Objective To investigate the incidence,risk factors and evolution of proximal junctional kyphosis(PJK)in young children who underwent posterior long-segment spinal fusion.Methods This study included young children who had undergone posterior long-segment spinal fusion between 2008 and 2013 at a single institution.The inclusion criteria were as follows:(1)age at surgery 10 years or younger;(2)congenital scoliosis;(3)posterior instrumented fusion at least four motion segments;(4)upper instrumented vertebra(UIV)localized between T1 and T12;(5)a minimum follow-up of 2 years with complete radiographs.Patients were excluded for any of the following criteria:(1)syndromic scoliosis;(2)previous history of spinal surgery;(3)screw malpositioning at UIV.All patients were followed up for more than 24 months.Radiographic measurements were made preoperatively and throughout the follow-up period.From sagittal images,the following values were obtained: proximal junctional angle,sagittal vertical axis,pelvic incidence,thoracic kyphosis,lumbar lordosis,and segmental kyphosisResults The mean age at surgery was 4.5 years(range,3~10 years)and the average follow-up was 48.8 months.Twenty-one(18.6%)patients experienced PJK.PJK was identified within 3 months after surgery in 19 cases(90.5%),and the most common type was ligamentous failure.In comparison with the non-PJK group,the PJK group showed greater preoperative thoracic kyphosis(TK)(45.9° vs.37.3°,P=0.027),longer fusion levels(6.6 vs.5.4,P < 0.01),and greater segmental kyphosis(SK)change(30.1° vs.11.2°,P=0.002).Both a change in SK greater than 30° and a preoperative TK greater than 40° were independent risk factors associated with PJK.In the PJK group,the average PJA increased from 7.3° to 19.7° at 3 months postoperatively,but significantly decreased to 18.9° at final follow up.Eight patient received brace treatment,and no patients required revision surgery.Conclusion Despite the incidence of PJK in 18.6% of young children undergoing posterior longsegment spinal fusion,no significant deterioration of PJA were found till the last follow-up.PJK mainly occurs within 3 months postoperatively and its risk factors include e preoperative hyperkyphosis,over-correction of kyphosis,and ligamentous failure.Early detection and active management may be helpful for minimizing the progression of PJK.PART Ⅲ:Adding Satellite Rods to Standard Two-Rod Construct: An Effective Technique to Improve Surgical Outcomes and Preventing Proximal Junctional Kyphosis in Posterior-Only Correction of Scheuermann KyphosisBackground The surgical treatment of Scheuermann kyphosis(SK)used to involve anterior release and posterior fusion.But the addition of anterior release did not significantly alter the rate of correction.Thus,with the goal of lessening surgical trauma,intraoperative blood loss and perioperative complications,a posterior-only procedure consisting of Ponte osteotomy and posterior instrumentation and fusion has been widely accepted as the standard procedure for SK correction for recent years.Multi-level Ponte osteotomies have been proved to improve the spinal flexibility,shorten the posterior spinal column and open the disc anteriorly.However,the Ponte osteotomy combined with posterior instrumentation with a standard 2-rods constract(2-RC)did not significantly improve the rate of correction.Furthermore,some undesired complications may also be encountered after surgery,including implant failure,correction loss and junctional kyphosis either proximal or distal to the fusion.Objective To compare the surgical results after the use of a complex of 2-rod construct plus bilateral satellite rods(S-RC)versus a standard 2-rod construct(2-RC)across osteotomy sites in a matched-cohort with Scheuermann kyphosis(SK).Methods Between 2009 and 2014,patients with SK undergoing posterior-only correction employed the Ponte osteotomy procedure were reviewed.The inclusion criteria were as follows:(1)The diagnosis of SK was based on radiological criteria(at least 3 consecutive vertebral bodies with a minimum of 5° wedging)with additional findings(endplate irregularities,Schmorl’s nodes);(2)Posterior-only procedure with multiple segmental Ponte osteotomies and pedicle-screw instrumentation;(3)At least 24 months of follow-up.Patients with any other spinal abnormality in addition to SK in the sagittal alignment(eg,spondylolysis,spondylolisthesis),coronal deformity(Cobb angle>20° in the coronal plane),or with previous spinal trauma or surgery were excluded from the study.During the study period,there were two surgical techniques employed in correction surgery.Finally,twenty-two consecutive patients with S-RC were identified in this study.During the same period,patients who had undergone posterior correction of SK with 2-RC were randomly selected andmatched as controls to the S-RC groupbased on age at surgery(within 3 years),apex(thoracic or thoracolumbar kyphosis)and magnitude(within 10°)of kyphosis.Thus,a total of 22 control patients with a 2-RC were identified and appropriately matched to 22 consecutive patients with an S-RC.Comparisons were made with regards to deformity magnitude,correction results,complications and clinical outcomes between the two groups.Results No significant difference was found between groups in preoperative patient’s factors(age,gender,and apex,magnitude of kyphosis and SRS-22 scores)and surgical factors(blood loss,operation time,osteotomy levels and fused levels).As for kyphosis magnitude,the S-RC group averaged 73.1°±12.4° before surgery and corrected to 32.3°±8.7° after surgery,while the 2-RC group averaged 71.2°±14.1° before surgery and corrected to 38.4°±7.9° after surgery.In contrast to the 2-RC group,the S-RC group had higher correction rate(55.4% vs.46.2%,P<0.01)and less correction loss(1.0° vs 2.4°,P<0.01)during the follow-up.After surgery and at the latest follow-up,the S-RC group reported higher improvement of back pain and more satisfactory reponse to the surgery than the 2-RC group(P<0.05).There were 1 case with wound problems in each group,and no cases were detected with pseudarthrosis or implant failure in either group.No difference was observed in the incidence of distal junctional kyphosis between 2-RC group(2 of 22)and S-RC group(1 of 22)(P>0.05),but proximal junctional kyphosis was more frequently seen in 2-RC group(7 of 22)than S-RC group(1 of 22)(P<0.05).Conclusion As a safe and simple method,the use of S-RC is effective in providing increased stability across multiple Ponte osteotomy levels,improving correction rate as well as preventing proximal junctional kyphosis. |
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