The neurocentral vertebral cartilage: anatomy, physiology and physiopathology

Genetics and pathogenesis of scoliosis

Background

Scoliosis is defined as a lateral spine curvature of at least 10° with vertebral rotation, as seen on a posterior-anterior radiograph, often accompanied by reduced thoracic kyphosis. Scoliosis affects all age groups: idiopathic scoliosis is the most common spinal disorder in children and adolescents, while adult degenerative scoliosis typically affects individuals over fifty. In the United States, approximately 3 million new cases of scoliosis are diagnosed annually, with a predicted increase in part due to global aging. Despite its prevalence, the etiopathogenesis of scoliosis remains unclear.

Methods

This comprehensive review analyzes the literature on the etiopathogenetic evidence for both idiopathic and adult degenerative scoliosis. PubMed and Google Scholar databases were searched for studies on the genetic factors and etiopathogenetic mechanisms of scoliosis development and progression, with the search limited to articles in English.

Results

For idiopathic scoliosis, genetic factors are categorized into three groups: genes associated with susceptibility, disease progression, and both. We identify gene groups related to different biological processes and explore multifaceted pathogenesis of idiopathic scoliosis, including evolutionary adaptations to bipedalism and developmental and homeostatic spinal aberrations. For adult degenerative scoliosis, we segregate genetic and pathogenic evidence into categories of angiogenesis and inflammation, extracellular matrix degradation, neural associations, and hormonal influences. Finally, we compare findings in idiopathic scoliosis and adult degenerative scoliosis, discuss current limitations in scoliosis research, propose a new model for scoliosis etiopathogenesis, and highlight promising areas for future studies.

Conclusions

Scoliosis is a complex, multifaceted disease with largely enigmatic origins and mechanisms of progression, keeping it under continuous scientific scrutiny.

Digital anatomical features of morphological development in C2-C7 neurocentral synchondrosis in children aged 1-6 years: a retrospective study of CT images

BACKGROUND

With the continuous improvement of diagnosis and treatment technology for cervical spine-related diseases in children at home and abroad, the demand for exploring the developmental anatomy and function of children's cervical spine of different ages is increasing. So the aim of this study was to investigate the changes of anatomical indicators in neurocentral synchondrosis (NCS) of C2-C7 with age and the developmental characteristics of different vertebrae in children aged 1-6 years old.

METHOD

A retrospective collection of 160 cases of normal cervical spine CT images of children aged 1-6 years old in provincial tertiary hospitals, according to the age group of 1-year-old into 6 groups. The original data of continuously scanned cervical spine tomography images were imported into Mimics16.0 software, under the two-dimensional image window, selected the measurement tool under the Measurements toolbar to measure and statistically analyzed the anatomical indicators such as cross diameter, sagittal diameter, height, perimeter and area of NCS in the C2-C7 segment of the cervical spine on the coronal plane and cross-section.

RESULTS

There was no significant difference in the anatomical indexes of cervical spine NCS in children compared with the left and right sides of the same vertebrae (P > 0.05). The same cervical spine generally had differences between the age groups of 1-4 years old and 5-6 years old (P < 0.05).The transverse diameter and circumference gradually decreased with age; the sagittal diameter and height showed a slight increase trend; there was a maximum area at 2 years of age. In different cervical vertebrae of the same age group, the NCS values of C3, C4, and C5 varied greatly, which showed that the ossification process of cervical cartilage was faster than that at the upper and lower ends. There were obvious differences between C2 and the rest of the cervical vertebral segments' NCS ossification process. C7 was also very different from the rest of the cervical vertebrae segments, presumably more similar to the thoracic spine.

CONCLUSIONS

The anatomical indexes of C2-C7 NCS in children have obvious developmental regularities at different ages, and there are also regularities between cervical segments.

Closure of the neuro-central synchondrosis and other physes in foal cervical spines

BACKGROUND

The neuro-central synchondrosis (NCS) is a physis responsible for the growth of the dorsal third of the vertebral body and neural arches. When the NCS of pigs is tethered to model scoliosis, stenosis also ensues. It is necessary to describe the NCS for future evaluation of its potential role in equine spinal cord compression and ataxia (wobbler syndrome).

OBJECTIVES

To describe the NCS, including when it and other physes closed in computed tomographic (CT) scans of the cervical spine of foals, due to its potential role in vertebral stenosis.

STUDY DESIGN

Post-mortem cohort study.

METHODS

The cervical spine of 35 cases, comprising both sexes and miscellaneous breeds from 153 gestational days to 438 days old, was examined with CT and physes scored from 6: fully open to 0: fully closed. The dorsal physis, physis of the dens and mid-NCS were scored separately, whereas the cranial and caudal NCS portions were scored together with the respective cranial and caudal vertebral body physes.

RESULTS

The NCS was a pair of thin physes located in a predominantly dorsal plane between the vertebral body and neural arches. The mid-NCS was closed in C1 from 115 days of age, and in C2-C7 from 38 days of age. The dorsal physis closed later than the NCS in C1, and earlier than the NCS in C2-C7. The dens physis was closed from 227 days of age. The cranial and caudal physes were closing, but not closed from different ages in the different vertebrae of the oldest cases.

MAIN LIMITATIONS

Hospital population.

CONCLUSIONS

The NCS was a thin physis that contributed mainly to height-wise growth, but also width- and length-wise growth of the vertebral body and neural arches. The mid-NCS was closed in all cervical vertebrae from 115 days of age. The NCS warrants further investigation in the pathogenesis of vertebral stenosis.

Osteochondrosis and other lesions in all intervertebral, articular process and rib joints from occiput to sacrum in pigs with poor back conformation, and relationship to juvenile kyphosis

Background

Computed tomography (CT) is used to evaluate body composition and limb osteochondrosis in selection of breeding boars. Pigs also develop heritably predisposed abnormal curvature of the spine including juvenile kyphosis. It has been suggested that osteochondrosis-like changes cause vertebral wedging and kyphosis, both of which are identifiable by CT. The aim of the current study was to examine the spine from occiput to sacrum to map changes and evaluate relationships, especially whether osteochondrosis caused juvenile kyphosis, in which case CT could be used in selection against it. Whole-body CT scans were collected retrospectively from 37 Landrace or Duroc boars with poor back conformation scores. Spine curvature and vertebral shape were evaluated, and all inter-vertebral, articular process and rib joints from the occiput to the sacrum were assessed for osteochondrosis and other lesions.

Results

Twenty-seven of the 37 (73%) pigs had normal spine curvature, whereas 10/37 (27%) pigs had abnormal curvature and all of them had wedge vertebrae. The 37 pigs had 875 focal lesions in articular process and rib joints, 98.5% of which represented stages of osteochondrosis. Five of the 37 pigs had focal lesions in other parts of vertebrae, mainly consisting of vertebral body osteochondrosis. The 10 pigs with abnormal curvature had 21 wedge vertebrae, comprising 10 vertebrae without focal lesions, six ventral wedge vertebrae with ventral osteochondrosis lesions and five dorsal wedge vertebrae with lesions in the neuro-central synchondrosis, articular process or rib joints.

Conclusions

Computed tomography was suited for identification of wedge vertebrae, and kyphosis was due to ventral wedge vertebrae compatible with heritably predisposed vertebral body osteochondrosis. Articular process and rib joint osteochondrosis may represent incidental findings in wedge vertebrae. The role of the neuro-central synchondrosis in the pathogenesis of vertebral wedging warrants further investigation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12917-021-03091-6.

Rationale, design, and methods of a randomized, controlled, open-label clinical trial with open-label extension to investigate the safety of vosoritide in infants, and young children with achondroplasia at risk of requiring cervicomedullary decompression surgery

Achondroplasia causes narrowing of the foramen magnum and the spinal canal leading to increased mortality due to cervicomedullary compression in infants and significant morbidity due to spinal stenosis later in adulthood. Vosoritide is a C-natriuretic peptide analogue that has been shown to improve endochondral ossification in children with achondroplasia. The objective of this trial is to evaluate the safety of vosoritide and whether vosoritide can improve the growth of the foramen magnum and spinal canal in children that may require decompression surgery. An Achondroplasia Foramen Magnum Score will be used to identify infants at risk of requiring decompression surgery. This is a 2-year open label randomized controlled trial of vosoritide in infants with achondroplasia ages 0 to ≤12 months. Approximately 20 infants will be randomized 1:1 to either open label once daily subcutaneous vosoritide combined with standard of care or standard of care alone. The primary and secondary aims of the study are to evaluate the safety and efficacy of vosoritide in children with cervicomedullary compression at risk of requiring decompression surgery. The trial will be carried out in specialized skeletal dysplasia treatment centers with well established multidisciplinary care pathways and standardized approaches to the neurosurgical management of cervicomedually compression. After 2 years, infants randomized to standard of care alone will be eligible to switch to vosoritide plus standard of care for an additional 3 years. This pioneering trial hopes to address the important question as to whether treatment with vosoritide at an early age in infants at risk of requiring cervicomedullary decompression surgery is safe, and can improve growth at the foramen magnum and spinal canal alleviating stenosis. This in turn may reduce compression of surrounding structures including the neuraxis and spinal cord, which could alleviate future morbidity and mortality.Trial registrations: ClinicalTrials.gov, NCT04554940; EudraCT number, 2020-001055-40.

A pilot study of influence of pedicle screw instrumentation on immature vertebra: a minimal 5-year follow-up in children younger than 5 years

OBJECTIVE

Concerns remain over the influence of pedicle screw instrumentation on the growth potential of an immature spine. Previous studies have reported discrepancies between animal experiments and clinical studies. The authors' objective was to explore the influence of pedicle screw instrumentation on the growth of an immature spine at a very young age.

METHODS

Individuals who met the authors' criteria were included. Anteroposterior diameter of the vertebral body; pedicle length on both sides; and anteroposterior diameter, transverse diameter, and area of the spinal canal were measured on CT images before surgery and at the final follow-up. Parameters of instrumented vertebrae and adjacent noninstrumented vertebrae were compared. The growth value and growth percentage of each parameter were calculated. Subgroup comparisons were made in thoracic vertebrae and lumbar vertebrae. Statistical analyses were performed.

RESULTS

Thirteen patients with a congenital spinal deformity were included in the study. The average age at surgery was 3.4 (range 2-5) years, and the average follow-up was 7.2 (range 5-11) years. Osteotomy and short instrumentation with pedicle screws were performed in each case. A total of 69 segments were measured, including 43 instrumented vertebrae and 26 immediately adjacent noninstrumented vertebrae. Significant increases in all parameters were noted at the final follow-up. In instrumented vertebrae, growth of the pedicle length and the anteroposterior diameter and area of the spinal canal increased significantly, while growth of the anteroposterior diameter of the vertebral body decreased significantly compared with noninstrumented vertebrae. Similar results were noted in the lumbar region. The shape-change phenomenon was found in noninstrumented vertebrae but was not apparent in instrumented vertebrae.

CONCLUSIONS

Pedicle screw instrumentation may slow down growth of the vertebral body, indirectly speed up growth of the spinal canal, and hinder the shape-change phenomenon of the lumbar spinal canal. However, the influences were quite slight, and significant development did occur in instrumented vertebrae. Therefore, pedicle screw instrumentation may not have much effect on the growth of immature vertebrae in children younger than 5 years.

Effect of neurocentral cartilage destruction on spinal growth in immature rabbits

Objective

This study was performed to observe the effect of neurocentral cartilage (NCC) destruction on spinal growth in immature rabbits.

Methods

The NCC of the lumbar vertebrae of 24 4-week-old female rabbits was destroyed through posterolateral and anterior approaches, and three-dimensional computed tomography examinations were performed 3 months after the procedure.

Results

Scoliosis was successfully induced in all rabbits of both the anterior and posterolateral approach groups. The scoliosis exceeded 10 degrees in three rabbits, which exhibited coronal scoliosis of the spine, unequal length and thickness of the bilateral pedicles, and rotation of the vertebrae. Scoliosis was not observed in the control group.

Conclusions

Destruction of the unilateral NCC in immature rabbits can induce structural scoliosis, similar to the pathological features of human scoliosis. The Cobb angles are similar after NCC destruction by a posterolateral approach and under direct vision via the anterior approach.

Biomechanical simulations of costo-vertebral and anterior vertebral body tethers for the fusionless treatment of pediatric scoliosis

Compression-based fusionless tethers are an alternative to conventional surgical treatments of pediatric scoliosis. Anterior approaches place an anterior (ANT) tether on the anterolateral convexity of the deformed spine to modify growth. Posterior, or costo-vertebral (CV), approaches have not been assessed for biomechanical and corrective effectiveness. The objective was to biomechanically assess CV and ANT tethers using six patient-specific, finite element models of adolescent scoliotic patients (11.9 ± 0.7 years, Cobb 34° ± 10°). A validated algorithm simulated the growth and Hueter-Volkmann growth modulation over a period of 2 years with the CV and ANT tethers at two initial tensions (100, 200 N). The models without tethering also simulated deformity progression with Cobb angle increasing from 34° to 56°, axial rotation 11° to 13°, and kyphosis 28° to 32° (mean values). With the CV tether, the Cobb angle was reduced to 27° and 20° for tensions of 100 and 200 N, respectively, kyphosis to 21° and 19°, and no change in axial rotation. With the ANT tether, Cobb was reduced to 32° and 9° for 100 and 200 N, respectively, kyphosis unchanged, and axial rotation to 3° and 0°. While the CV tether mildly corrected the coronal curve over a 2-year growth period, it had sagittal lordosing effect, particularly with increasing initial axial rotation (>15°). The ANT tether achieved coronal correction, maintained kyphosis, and reduced the axial rotation, but over-correction was simulated at higher initial tensions. This biomechanical study captured the differences between a CV and ANT tether and indicated the variability arising from the patient-specific characteristics. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:254-264, 2018.

Does pedicle screw fixation under age 5 cause spinal canal narrowing? A CT study with minimum 5 years follow-up

PURPOSE

The aim of this retrospective study was to evaluate the changes in the vertebral body and spinal canal area in a group of patients who had pedicle screw fixation under age 5 for the treatment of congenital spinal deformity at least 5 year follow-up.

METHODS

11 patients who had been operated due to spinal deformity under age 5 with who had a CT examination at least 5 years after the initial operation were included in the study. All patients underwent hemivertebrectomy and transpedicular fixation procedures at an average age of 3.18 years (range 2-5 years). All had preoperative CT to evaluate the congenital deformities. Measurements were done at the instrumented vertebrae as well as the un-instrumented ones above and below them to evaluate; vertebral body parameters, pedicle parameters and spinal canal area of upper instrumented vertebra (UIV), lower instrumented vertebra (LIV), upper adjacent un-instrumented vertebra and lower adjacent un-instrumented vertebra.

RESULTS

The average follow-up was 7.2 (range 5-12) years. Six of the patients were over age 10 during the final CT examination while 5 were at age 7. Female-to male ratio was 8-3. Measurement of all the parameters in 22 instrumented and 22 non-instrumented segments showed a proportional increase rather than a decrease at each segment. The percentage of canal area growth at UIV and LIV was 21 and 17.5 %, respectively.

CONCLUSION

Pedicle screw instrumentation has no adverse effect on further spinal body, pedicle and canal growth and does not result in iatrogenic spinal canal stenosis.

Surgical outcomes by age at the time of surgery in the treatment of congenital scoliosis in children under age 10 years

BACKGROUND CONTEXT

There is little information regarding the surgical outcomes with regard to the timing of surgery in children under age 10 years for congenital scoliosis with a long-term follow-up.

PURPOSE

The purpose of this study was to compare the surgical outcomes for congenital scoliosis in children 6 years or older but less than 10 years of age.

STUDY DESIGN

This is a retrospective study.

PATIENT SAMPLE

Eighteen congenital scoliosis patients under age 10 years at the time of surgery were treated by posterior hemivertebra resection and bilateral pedicle screw fixation.

OUTCOME MEASURES

Outcome measures are radiological outcomes (plain radiographs and computed tomography) and complications.

METHODS

Eighteen congenital scoliosis patients (n=18) under age 10 years at the time of surgery were treated by posterior hemivertebra resection and bilateral pedicle screw fixation. These cases were retrospectively studied and had a minimum of 7-year follow-up. We assigned patients into two groups: Group 1 (n=9) patients who had surgery before 6 years of age and Group 2 (n=9) those who had surgery after 6 years of age.

RESULTS

The groups were not found to be statistically different in operative time, blood loss, and follow-up period. In the Group 1, the mean Cobb angle of the main curve was 32.4° before surgery, 6.4° after surgery, and 9.1° at last follow-up. In the Group 2, the mean Cobb angle of the main curve was 36.5° before surgery, 10.4° after surgery, and 14.5° at last follow-up. There was significantly better deformity correction of main curve immediate postoperatively and at last follow-up in Group 1. No significant difference was observed in growth rate of the vertebral body and spinal canal parameters comparing the two groups at the vertebra with or without screws. There was no crankshaft phenomena, no clinical or radiographic features suggestive of spinal stenosis during follow-up, and no major vascular or neurological complications related to the pedicle screws in either group.

CONCLUSIONS

In congenital scoliosis patients, posterior hemivertebra resection after pedicle screw fixation before the age of 6 years had significantly better deformity correction and did not cause a negative effect on the growth of vertebral body or spinal canal compared with the group treated after 6 years of age. Therefore, early surgical correction of a congenital hemivertebra in children under 6 years of age, before structural changes occur, effectively achieves a more satisfactory correction without causing iatrogenic spinal stenosis or neurologic complications compared with children older than 6 years but under 10 years of age.

Posterior hemivertebra resection and short segment fusion with pedicle screw fixation for congenital scoliosis in children younger than 10 years: greater than 7-year follow-up

STUDY DESIGN

A retrospective study.

OBJECTIVE

To evaluate the surgical outcomes of posterior hemivertebra resection and short segment fusion with segmental pedicle screw fixation in congenital scoliosis in children younger than 10 years.

SUMMARY OF BACKGROUND DATA

This is the first long-term follow-up on surgical outcomes of posterior hemivertebra resection and short segment fusion using segmental pedicle screw fixation in children younger than 10 years with congenital scoliosis.

METHODS

Patients with congenital scoliosis (n = 18) younger than 10 years at the time of the surgery were treated by posterior hemivertebra resection and bilateral pedicle screw fixation. The mean age at the time of surgery was 6.6 years (range, 2.6-9.8 yr). They were retrospectively studied with a mean follow-up of 11.4 years (range, 7.1-17.3 yr).

RESULTS

The mean Cobb angle of the main curve was 34.4° before surgery, 8.6° after surgery, and 12.9° at last follow-up. In the compensatory cranial curve, the preoperative Cobb angle of 14.5° was corrected to 5.9° postoperatively and was 8.4° at last follow-up. In the compensatory caudal curve, the preoperative Cobb angle of 17.4° improved to 4° postoperatively and 6.6° at last follow-up. There were no crankshaft phenomena and no clinical and radiographical features suggestive of spinal stenosis during follow-up. There were no major vascular or neurological complications related to the pedicle screws.

CONCLUSION

Posterior hemivertebra resection after pedicle screw fixation in congenital scoliosis is a safe and effective procedure that can achieve rigid fixation and deformity correction and restore spinal balance. This study showed that early posterior hemivertebra resection of congenital scoliosis before structural changes occur above or below can reduce fusion length, prevent curve progression, and effectively achieve a more satisfactory correction without hazardous iatrogenic spinal stenosis, crankshaft phenomena, or neurological complications.

LEVEL OF EVIDENCE

3.

Biomechanical simulation and analysis of scoliosis correction using a fusionless intravertebral epiphyseal device

STUDY DESIGN

Computer simulations to analyze the biomechanics of a novel compression-based fusionless device (hemistaple) that does not cross the disc for the treatment of adolescent idiopathic scoliosis.

OBJECTIVE

To biomechanically model, simulate, and analyze the hemistaple action using a human finite element model (FEM).

SUMMARY OF BACKGROUND DATA

A new fusionless growth sparing instrumentation device (hemistaple), which locally compresses the growth plate without spanning the disc, was previously developed and successively tested on different animal models.

METHODS

Patient-specific FEMs of the spine, rib cage, and pelvis were built using radiographs of 10 scoliotic adolescents (11.7 ± 0.9 yr; Cobb thoracic: 35° ± 7°, lumbar: 24° ± 6°). A validated algorithm allowed simulating the growth (0.8-1.1 mm/yr/vertebra) and growth modulation process (Hueter-Volkmann principle) during a period of 2 years. Four instrumentation configurations on the convex curves were individually simulated (Config 1: 5 thoracic vertebrae with hemistaples on superior endplates; Config 2: same as Config 1 with hemistaples on both endplates; Config 3: same as Config 1 + 4 lumbar vertebrae; Config 4: same as Config 2 + 4 lumbar vertebrae).

RESULTS

Without hemistaples, on average the thoracic and lumbar Cobb angles, respectively, progressed from 35° to 56° and 24° to 30°, whereas the vertebral wedging at curve apices progressed from 5° to 12°. With the hemistaple Config 1, the Cobb angles progressed but were limited to 42° and 26°, whereas the wedging ended at 8°. With Config 3, Cobb and wedging were kept nearly constant (38°, 21°, 7°). With hemistaples on both endplates (Config 2, Config 4), the Cobb and wedging were all reduced (thoracic Cobb for Config 2 and 4: 24° and 15°; lumbar Cobb: 21° and 11°; wedging: 2° and 1°).

CONCLUSION

This study suggests that the hemistaple has the biomechanical potential to control the scoliosis progression and highlights the importance of the instrumentation configuration to correct the spinal deformities. It biomechanically supports the new fusionless device concept as an alternative for the early treatment of idiopathic scoliosis.

LEVEL OF EVIDENCE

5.

Effect of dual screws across the vertebral neurocentral synchondrosis on spinal canal development in an immature spine: a porcine model

BACKGROUND

Questions remain as to the effect of pedicle screws on spinal canal development in young children. The purpose of this study was to determine the effects of unilateral placement of dual screws across the neurocentral synchondrosis on spinal canal development as assessed with histological analysis and measurement of the canal dimensions in an immature pig model.

METHOD

Twenty-seven one-month-old pigs were assigned to two groups on the basis of the surgical approach used to place unilateral double screws that did or did not cross the neurocentral synchondrosis. In one group, sixteen pigs underwent a posterior approach from T7 to T14 and were divided into four subgroups: no screws (without screw fixation), short screws (dual pedicle screws that did not cross the neurocentral synchondrosis), long screws (dual pedicle screws that crossed the neurocentral synchondrosis), and screw removal (long dual pedicle screws that were removed at six weeks postoperatively). In the other group, eleven pigs underwent an anterior approach, with double vertebral body screws placed via thoracotomy. These animals were divided into two subgroups: short screws (dual vertebral body screws that did not cross the neurocentral synchondrosis) and long screws (dual vertebral screws that crossed the neurocentral synchondrosis). All animals were killed at seventeen weeks. The total area, width, and depth of the spinal canal were measured on axial computed tomography (CT) images. Quantitative histological analysis was performed to measure the rate of neurocentral synchondrosis closure.

RESULTS

Use of unilateral double pedicle screws across the neurocentral synchondrosis through a posterior approach resulted in 97% neurocentral synchondrosis closure with a 20% decrease in the canal area and a 15% decrease in the canal depth. Use of unilateral double vertebral body screws across the neurocentral synchondrosis through an anterior approach resulted in 71% neurocentral synchondrosis closure with a 15% decrease in the canal area and an 8% decrease in the canal width.

CONCLUSIONS

Unilateral double pedicle screws crossing the neurocentral synchondrosis adversely affected spinal canal growth in immature pigs.

CLINICAL RELEVANCE

Pedicle screws should be used with caution in very young children, and a delay in surgical treatment until they are older should be considered.

X-Ray assessment of the effect of pedicle screw on vertebra and spinal canal growth in children before the age of 7 years

PURPOSE

To determine the reliability of pedicle screws placed in children younger than 7 years of age, and to evaluate the effect of pedicle screw insertion on further growth of the vertebra and spinal canal.

METHODS

A retrospective study of 35 consecutive patients through Jan 2003-Dec 2010 for congenital scoliosis in <7 years children was performed at one spine center. Patients undergoing pedicle screw instrumentation of at least two levels, which had been followed-up for at least 24 months were included. Measurements were performed in instrumented and adjacent non-instrumented levels. The effect of pedicle screw insertion on further growth was evaluated.

RESULTS

The average age at surgery was 4.4 year (53 months, range, 23-84 months). 190 segments in 35 patients met the inclusion criteria. 77 segments had no screws and 113 had at least one screw. There was a significant difference between the pre-operative and final follow-up values of the measurement of spinal canal and vertebral body parameters (P < 0.001). No significant difference existed between growth rates of vertebral bodies and the sagittal diameters of spinal canal with or without screws. The growth rates of vertebral bodies in lumbar spine were higher than in thoracic spine in both instrumented and adjacent groups.

CONCLUSION

Pedicle screw instrumentation does not cause a retardation effect on the development of vertebral bodies and the spinal canal in children at an early age. It is a safe and reliable procedure to achieve a stable fixation.

Quantitative analysis of the closure pattern of the neurocentral junction as related to preexistent rotation in the normal immature spine

BACKGROUND CONTEXT

The normal spine is not a symmetrical structure. In recent studies, we demonstrated the presence of an axial rotational pattern that is similar to what is seen in the most prevalent curve patterns in idiopathic scoliosis at different ages. This suggests that if the spine starts to decompensate into scoliosis, it follows this preexistent rotational pattern. In scoliosis, the neurocentral junctions (NCJs) close asymmetrically, which leads to a different pedicle morphology in the convexity and concavity of the curve. The present study aimed to establish at which age the NCJ closes in different regions of the spine, whether it closes asymmetrically in the nonscoliotic spine as well and whether the closure pattern is related to the earlier demonstrated preexistent rotation.

PURPOSE

To evaluate the closure pattern and surface area of the left and right NCJs throughout the normal immature spine in relation to the preexistent spinal rotation at different ages.

STUDY DESIGN

Retrospective cohort study using a systematic, semiautomatic analysis.

PATIENT SAMPLE

Computed tomography (CT) scans of the thorax and abdomen of 199 nonscoliotic children (0-16 years old) were systemically analyzed. CT scans had been obtained for several reasons unrelated to this study, for example, recurrent respiratory infections, malignant disease (not involving the spine), or work up before bone marrow transplantation. Scans were categorized according to the criteria of the Scoliosis Research Society into infantile (0-3 years old), juvenile (4-9 years old), and adolescent (10-16 years old) age cohorts.

OUTCOME MEASURES

Closure, absolute surface area, and the angle between the longitudinal axis of the left and right NCJ and preexistent vertebral rotation at each spinal level.

METHODS

Transverse CT slices were systemically analyzed for closure and asymmetry of the absolute area of 4,992 NCJs from spinal levels T2-L5. The outcome measures were analyzed semiautomatically using custom-made software developed at our institution (ImageXplorer; Image Sciences Institute). Inter- and intraobserver reliabilities were calculated.

RESULTS

For all subjects, the entire thoracic area was available. Complete scans down to L5 of the lumbar spine were available in 43 cases. Closure of the NCJs was first observed in the lumbar spine, then in the high thoracic spine, and finally in the mid- and low thoracic spine. Closure occurred asymmetrically, left-right predominance depended on the age. In the mid- and low thoracic spine, the surface areas of the right NCJs were larger at the infantile age, whereas at the juvenile age the areas of the left NCJs were larger. This corresponded to the spine's preexistent rotation. Rotation of the high thoracic vertebrae was to the left in all age cohorts. Rotation in the mid- and low thoracic spine was to the left in the infantile cohort but reversed to the right in the juveniles and even more so in the adolescents. The lumbar spine was rotated to the left at the infantile age and not significantly rotated at the juvenile and adolescent ages. Orientation of the NCJs in relation to the vertebraes' longitudinal axis was symmetrical, not dependent on age, and more transverse at the midthoracic levels than at other spinal levels.

CONCLUSIONS

This study focuses on the asymmetry and the regional pattern of closure of the NCJs at different ages. It suggests that preexistent rotation of the spine is related to the asymmetrical closure of the NCJs. Whether the asymmetry is the cause of or is caused by the preexistent rotation cannot be derived from this study.

The effect of pedicle screw insertion at a young age on pedicle and canal development

STUDY DESIGN

A longitudinal case study.

OBJECTIVE

To determine whether pedicle screws placed in an immature spine exert effect on the continued growth of the vertebral body.

SUMMARY OF BACKGROUND DATA

Pedicle screws have revolutionized surgical treatment of spinal deformities by allowing a mode of secure fixation that provides consistently better correction rates in adults and adolescents. In the young child, however, the trajectory of pedicle screws takes them through an open physis: the neurocentral cartilage. There exists little information regarding the possible effect of pedicle screws inserted at a young age on further development of the spine and the spinal canal.

METHODS

Patients undergoing pedicle screw instrumentation of at least 2 levels before the age of 5 years (60 mo) for the first time for any diagnosis and who had been followed for at least 24 months were included. Measurements were performed in instrumented and adjacent noninstrumented levels without visible deformity in pre- and postoperative cross-sectional images and compared using statistical methods.

RESULTS

Ninety segments in 15 patients met the inclusion criteria (average age at instrumentation 46.3 mo [range, 29-60 mo]). Forty segments had no screws and 50 had at least 1 screw. Pedicle length and vertebral body diameter had significantly increased in both groups, whereas spinal canal parameters did not change significantly. No significant difference was observed between the growth rates in levels with or without screws in pedicle length, vertebral body diameter, or spinal canal parameters (anterior-posterior and interpedicular diameters, and area).

CONCLUSION

Pedicle screw instrumentation performed before the age of 5 years does not cause a negative effect on the growth of pedicles, the transverse plane of the vertebral body, or the spinal canal. It can be safely performed in the treatment of deformity in this age group.

Histology-based morphology of the neurocentral synchondrosis in Alligator mississippiensis (Archosauria, Crocodylia)

Morphology of the neurocentral synchondroses--thin cartilaginous layers between centra and neural arches--are documented in the extant crocodilian, Alligator mississippiensis (Archosauria, Crocodylia). Examination of dry skeletons demonstrates that neurocentral suture closure occurs in very late postnatal ontogeny (after reaching sexual maturity and/or body size ca. 40% from the upper range). Before sexual maturity (body length (BL) ≥ ca. 1.80 m), completely fused centra and neural arches are restricted to the caudal vertebral series. In contrast, the presacral vertebrae often remain unfused throughout postnatal ontogeny, retaining open sutures in very mature individuals (BL ≥ 2.80 m). These unfused centra and neural arches are structurally supported by the relatively large surface area of the neurocentral junctions, which results from primarily horizontal (mediolateral) increases with strong positive allometry. Cleared and stained specimens show that the cartilaginous neurocentral synchondrosis starts to form after approximately 40 embryonic days. Histological examination of the neurocentral junction in dorsal and anterior caudal vertebrae of six individuals (BL = 0.28-3.12 m) shows : (1) neurocentral fusion is the result of endochondral ossification of the neurocentral synchondrosis, (2) the neurocentral synchondrosis exhibits bipolar organization of three types of cartilaginous cells, and (3) complex neurocentral sutures (i.e., curved, zigzagged, and/or interdigitated boundaries) come from clumping of bone cells of the neural arches and centra into the neurocentral synchondrosis. The last two morphological features can be advantageous for delaying neurocentral fusion, which seems to be unique in crocodilians and possibly their close relatives, including nonavian dinosaurs and other Mesozoic archosaurs.

Vertebral growth modulation by hemicircumferential electrocoagulation: an experimental study in pigs

INTRODUCTION

This experimental study in pigs was aimed at evaluating spinal growth disorders after partial arrest of the vertebral epiphyseal plates (EP) and neurocentral cartilages (NCC). Unilateral and multisegmental single or combined lesions of the physeal structures were performed by electrocoagulation throughout a video-assisted thoracoscopical approach.

MATERIALS AND METHODS

Thirty 4-week-old domestic pigs (mean weight 16 kg) were included in the experiments. The superior and inferior epiphyseal plates of T5 to T9 vertebra were damaged in ten animals by hemicircumferential electrocoagulation (group I). In other ten pigs (group II), right NCC at the same T5-T9 levels were damaged. Ten other animals underwent combined lesions of the ipsilateral hemiepiphyseal plates and NCC at the T5-T9 levels. A total of 26 animals could be evaluated after 12 weeks of follow-up using conventional X-rays, CT scans and histology.

RESULTS

The pigs with hemicircumferential EP damage developed very slight concave non-structured scoliotic deformities without vertebral rotation.(mean 12° Cobb; range10-16°). Some of the damaged vertebra showed a marked wedgening with unilateral development alteration of the vertebral body, including the adjacent discs The animals with damage of the NCC developed mild scoliotic curves (mean 19° Cobb; range 16-24°) with convexity opposite to the damaged side and loss of physiological kyphosis. The injured segments showed an asymmetric growth with hypoplasia of the pedicle and costovertebral joints at the damaged side. The pigs undergoing combined EP and NCC lesions developed minimal non-structured curves, ranging from 10 to 12° Cobb. In these animals there was a lack of growth of a vertebral hemibody and disc hypoplasia at the damaged segments. Both damage of the NCC and the EP affect the height of the vertebral body. No spinal stenosis was found in any case. In most cases, the adjacent superior and inferior vertebral EP to damaged segments had a compensatory growth that maintained the straight spinal shape.

CONCLUSIONS

In summary, unilateral direct lesion of the EP by hemicircumferential thoracoscopic electrocoagulation modifies vertebral growth, but is not able to induce true scoliostic curves in pigs. Only animals with damaged NCC developed mild scoliotic curves of lordotic type. This work rediscovers and emphasizes the decisive role of the neurocentral cartilage in the ethiopatogeny of idiopathic scoliosis.

Prospective study of the effect of pedicle screw placement on development of the immature vertebra in an in vivo porcine model

INTRODUCTION

There is increasing awareness of the need for pedicle screw constructs in the treatment of spinal deformities in very young children. However, the long-term effects of pedicle screws on the immature spine are still unclear. We used a porcine model to analyze the morphological changes of the spinal canal and vertebral body in response to the placement of pedicle screws.

METHODS

13 newborn pigs were operated on. Each pig received a single pedicle screw at the L2 level. After a tenfold increase in body weight (7 months later), the symmetry of the spinal canal and vertebral body was measured on CT scans of the investigational (L2) and control (L3) levels in terms of the angulations of the instrumented and non-instrumented halves of the vertebral body and spinal canal.

RESULTS

After 7 months, the normalised vertebral body angle had reduced on the non-screw side and increased on the screw side, indicating asymmetry in vertebral body growth in the axial plane. The difference was significant (p = 0.009). However, there was no significant difference between the screw and non-screw sides for the spinal canal angles at the L2 level at either the intraoperative or 7-month follow-up assessment (each p > 0.05).

CONCLUSIONS

Pedicle screws in the immature porcine spine have a significant effect on the development of the vertebral body. However, in the present study, no corresponding alteration of the morphology of the spinal canal was observed. Our results provide further support for the existing arguments in favour of pedicle screws when weighing up the many factors to be considered in creating a treatment plan for early onset scoliosis.

Neurocentral synchondrosis screws to create and correct experimental deformity: a pilot study

BACKGROUND

Unilateral pedicle screw epiphysiodesis of the neurocentral synchondrosis (NCS) can produce asymmetric growth of the synchondrosis to create scoliosis in an immature animal model.

QUESTIONS/PURPOSES

We asked whether a preexisting experimentally created scoliosis could be limited and corrected by modulating the growth of the faster-growing NCS by a similar method.

METHODS

Nine 1-month-old pigs were assigned to each of three groups: (1) a sham group in which three animals received a sham operation but without a pedicle screw fixation; (2) an experimental group with double right pedicle screws placed across the NCS from T7 to T14 (scoliosis-untreated); and (3) an experimental group treated in the same way except a second set of double pedicle screws was placed in the left pedicles 6 weeks after the screws were placed on the right (scoliosis-treated). All animals were euthanized at 17 weeks, and radiographs and axial CT images of the spine were obtained.

RESULTS

A scoliotic curve was not seen in any of the animals in the sham group, in three of three in the scoliosis-untreated group with an average of 34°, and in three of three in the scoliosis-treated group with an average of 20°. In comparison to the scoliosis-untreated group, the second set of pedicle screws produced a 41% correction of the scoliosis.

CONCLUSIONS

We found the pedicle screw inhibited the overgrowth of the NCS to prevent further curve progression and obtained some correction of the deformity. The NCS screw epiphysiodesis can create and reverse scoliosis in an immature pig model.

Morphometric analysis of neurocentral synchondrosis using magnetic resonance imaging in the normal skeletally immature spine

STUDY DESIGN

Morphometric analysis of the neurocentral synchondrosis (NCS) using magnetic resonance imaging in the normal infantile and juvenile patients.

OBJECTIVES

To assess the developmental stages of the neurocentral synchondrosis (NCS) by determining the age at which closure of the NCS occurs at specific levels of the spine and to evaluate whether symmetric growth of the NCS occurs during the different developmental stages in normal immature spine.

SUMMARY OF BACKGROUND DATA

The function and developmental stage of the NCS are controversial because of a lack of agreement on the exact age of closure. To date, most authors believe that the NCS is actively open at a very early age, but the reported age of closure of the NCS varies from age 3 to 16 years. This various closure age of the NCS has resulted in some confusion about the role of the NCS in the normal spinal growth or the development of spinal deformity.

METHODS

A total of 34 normal pediatric patients who had axial magnetic resonance images from first thoracic vertebra to fifth lumbar vertebra were assigned into following 3 groups: infantile group (n = 11), 0 to 3 years of age; juvenile-young group (n = 16), 4 to 7 years of age; and juvenile-old group (n = 7), 8 to 10 years of age. T2-weighted axial magnetic resonance images were used to analyze the NCS developmental stages using a custom 6-point scale (0: actively open with 0% closure; 5: 100% NCS closure). For the stage 0 closure NCS, the width and thickness of the NCS were measured.

RESULTS

The NCS was actively open without closure for all less than 4-year-old patients at all levels. The NCS had approximate 75% closure in the lumbar region at 4 years of age while the thoracic NCS remained nearly open. After 5 years of age, the middle-lower thoracic NCS began to close with closure rate less than 25%. At the 10 years of age, the NCS in the lumbar region had near 100% closure, whereas the thoracic NCS demonstrated approximate 50% closure. For the NCS without closure, the average width and thickness were 7.6 x 1.3 mm on the left and 7.9 x 1.3 mm on the right, which was not significantly different. For the NCS with closure, the left and right NCS closure rates were not significantly different.

CONCLUSION

The NCS developmental stage is age- and vertebral level-dependent. The NCS closes from the lumbar and proximal thoracic spine to the middle-distal thoracic spine and times from very early juvenile to the adolescent. The NCS symmetry bilaterally occurred not only during the active open, but also the long closure period. The NCS symmetric open and/or closure may be important to maintain the normal spine alignment.

Aetiology of idiopathic scoliosis: current concepts

The aetiology of the three-dimensional spinal deformity of idiopathic scoliosis (IS) is unknown. Progressive adolescent idiopathic scoliosis (AIS) that mainly affects girls is generally attributed to relative anterior spinal overgrowth from a mechanical mechanism (torsion) during the adolescent growth spurt. Established biological risk factors to AIS are growth velocity and potential residual spinal growth assessed by maturity indicators. Spine slenderness and ectomorphy in girls are thought to be risk factors for AIS. Claimed biomechanical susceptibilities are (1) a fixed lordotic area and hypokyphosis and (2) concave periapical rib overgrowth. MRI has revealed neuroanatomical abnormalities in approximately 20% of younger children with IS. A neuromuscular cause for AIS is probable but not established. Possible susceptibilities to AIS in tissues relate to muscles, ligaments, discs, skeletal proportions and asymmetries, the latter also affecting soft tissues (e.g. dermatoglyphics). AIS is generally considered to be multi-factorial in origin. The many anomalies detected, particularly left-right asymmetries, have led to spatiotemporal aetiologic concepts involving chronomics and the genome altered by nurture without the necessity for a disease process. Genetic susceptibilities defined in twins are being evaluated in family studies; polymorphisms in the oestrogen receptor gene are associated with curve severity. A neurodevelopmental concept is outlined for the aetiology of progressive AIS. This concept involves lipid peroxidation and, if substantiated, has initial therapeutic potential by dietary anti-oxidants. Growth saltations have not been evaluated in IS.

Relatively lower body mass index is associated with an excess of severe truncal asymmetry in healthy adolescents: Do white adipose tissue, leptin, hypothalamus and sympathetic nervous system influence truncal growth asymmetry?

BACKGROUND

In healthy adolescents normal back shape asymmetry, here termed truncal asymmetry (TA), is evaluated by higher and lower subsets of BMI. The study was initiated after research on girls with adolescent idiopathic scoliosis (AIS) showed that higher and lower BMI subsets discriminated patterns of skeletal maturation and asymmetry unexplained by existing theories of pathogenesis leading to a new interpretation which has therapeutic implications (double neuro-osseous theory).

METHODS

5953 adolescents age 11-17 years (boys 2939, girls 3014) were examined in a school screening program in two standard positions, standing forward bending (FB) and sitting FB. The sitting FB position is thought to reveal intrinsic TA free from back humps induced by any leg-length inequality. TA was measured in both positions using a Pruijs scoliometer as angle of trunk inclinations (ATIs) across the back at each of three spinal regions, thoracic, thoracolumbar and lumbar. Abnormality of ATIs was defined as being outside 2 standard deviations for each age group, gender, position and spinal region, and termed severe TA.

RESULTS

In the sitting FB position after correcting for age,relatively lower BMIs are statistically associated with a greater number of severe TAs than with relatively higher BMIs in both girls (thoracolumbar region) and boys (thoracolumbar and lumbar regions).The relative frequency of severe TAs is significantly higher in girls than boys for each of the right thoracic (56.76%) and thoracolumbar (58.82%) regions (p = 0.006, 0.006, respectively). After correcting for age, smaller BMIs are associated with more severe TAs in boys and girls.

DISCUSSION

BMI is a surrogate measure for body fat and circulating leptin levels. The finding that girls with relatively lower BMI have significantly later menarche, and a significant excess of TAs, suggests a relation to energy homeostasis through the hypothalamus. The hypothesis we suggest for the pathogenesis of severe TA in girls and boys has the same mechanism as that proposed recently for AIS girls, namely: severe TAs are initiated by a genetically-determined selectively increased hypothalamic sensitivity (up-regulation, i.e. increased sensitivity) to leptin with asymmetry as an adverse response to stress (hormesis), mediated bilaterally mainly to the growing trunk via the sympathetic nervous system (leptin-hypothalamic-sympathetic nervous system (LHS) concept). The putative autonomic dysfunction is thought to be increased by any lower circulating leptin levels associated with relatively lower BMIs. Sympathetic nervous system activation with asymmetry leads to asymmetries in ribs and/or vertebrae producing severe TA when beyond the capacity of postural mechanisms of the somatic nervous system to control the shape distortion of the trunk. A test of this hypothesis testing skin sympathetic responses, as in the Rett syndrome, is suggested.

The effect of pedicle screw insertion through the neurocentral cartilage on the growth of immature canine vertebra

OBJECTIVE

To explore the influence of pedicle screw insertion through the neurocentral cartilage (NCC) on the development of vertebrae and spinal canal in an animal experiment.

METHODS

Sixteen dogs were randomly assigned to three groups: in group 1, posterior muscles at the surgery site were dissected; in group 2, the pedicles were drilled through the NCC by screws; in group 3, screws were placed in the pedicles through the NCC. Vertebrae of T8, T10, T12, L2, L4 and L6 were studied with the average data of the adjacent two vertebrae serving as controls. Spiral computerized tomography (CT) was used to assess the morphologic parameters of studied vertebrae and their controls. Measurements were made by an independent radiologist on the first post-operative day and 3 months after operation. Paired Student's t-tests of studied vertebrae and their controls were performed to evaluate the effect of pedicle screw insertion.

RESULTS

In group 3, 3 months after operation the area, transverse diameter and anterior-posterior diameter of the vertebral canal and length of pedicle of studied vertebrae were significantly smaller than those of control vertebrae (P < 0.05). There were no significant differences in morphologic parameters between the studied vertebrae and the control vertebrae in groups 1 and 2 (P > 0.05).

CONCLUSION

(i) Pedicle screw placement has a significant impact on the growth of the canine vertebra canal, and may lead to iatrogenic spinal stenosis, but their placement has no significant effect on the vertebral bodies; and (ii) the NCC can repair itself automatically. Drilling pedicle bone through the NCC with a screw and then removing the screw has no obvious impact on the growth of vertebrae.

The pathogenesis of adolescent idiopathic scoliosis: review of the literature

STUDY DESIGN

Review of the literature on the pathogenesis of adolescent idiopathic scoliosis (AIS).

OBJECTIVE

To discuss the different theories that have appeared on this subject.

SUMMARY OF BACKGROUND DATA

The pathogenesis of AIS, a condition exclusive to humans, has been the subject of many studies. Over the years, practically every structure of the body has been mentioned in the pathogenesis of AIS; however, the cause of this spinal deformity remains little understood. The pathogenesis of this condition is termed multifactorial.

METHODS

PubMed and Google Scholar electronic databases were searched focused on parameters concerning the pathogenesis of adolescent idiopathic scoliosis. The search was limited to the English language.

RESULTS

No single causative factor for the development of idiopathic scoliosis has been identified, it is thus termed multifactorial. AIS is a complex genetic disorder. The fully erect posture, which is unique to humans, seems to be a prerequisite for the development of AIS.

CONCLUSION

Although any or all of the mentioned factors in this review may play a certain role in the initiation and progression of AIS at a certain stage, the presented material suggests that in the observed deformation, genetics, and the unique mechanics of the fully upright human spine play a decisive role.

Unilateral pedicle screw epiphysiodesis of the neurocentral synchondrosis. Production of idiopathic-like scoliosis in an immature animal model

BACKGROUND

The neurocentral synchondrosis plays a role in the growth of the spine. The goal of this study was to determine whether asymmetric epiphysiodesis of this synchondrosis creates a scoliotic deformity in a growing-animal model and to correlate curve magnitude with the degree of closure of the synchondrosis.

METHODS

Two-month-old pigs were assigned to three groups. In the control group, two animals received a sham operation without pedicle screw fixation; in the single-screw group, three animals were treated with a single right transpedicular screw placed across the neurocentral synchondrosis from T7 to T14; and in the double-screw group, three animals were treated in the same way as the previous group except that two screws were placed in each pedicle. The animals were killed at six months, and radiographs and axial computed tomography images of the spine were obtained. Histomorphometric analyses were performed to grade the synchondrosis at each level.

RESULTS

A scoliotic curve was seen in none of the animals in the control group, in one of the three in the single-screw group, and in all three in the double-screw group (30 degrees, 42 degrees, and 42 degrees). Vertebral rotation in the axial plane occurred toward the screw side and was significantly greater in the double-screw group (mean, 15.2 degrees) than in the single-screw (mean, 6.1 degrees) and control (0 degrees) groups (p < 0.001). There was no difference in morphology between the left and right pedicles in the control group. The left pedicle was 9% longer than the right (screw-treated) pedicle in the single-screw group, and it was 22% longer than the right pedicle in the double-screw group. Closure of the neurocentral synchondrosis was greatest in the double-screw group (>75% closure) compared with the single-screw group (<50% closure) (p < 0.0001) and the control group (no closure) (p < 0.0001), and closure correlated with the magnitude of the coronal curve (p = 0.001).

CONCLUSIONS

Unilateral transpedicular screw fixation that traverses the neurocentral synchondrosis in a growing-pig model can produce asymmetric growth of the synchondrosis to create scoliosis with the convexity on the side of the screw fixation. Double pedicle screws provided a greater epiphysiodesis effect on the neurocentral synchondrosis, which correlated with a greater degree of scoliosis.

Histologic, risser sign, and digital skeletal age evaluation for residual spine growth potential in Chinese female idiopathic scoliosis

STUDY DESIGN

A prospective study.

OBJECTIVE

To ascertain the correlation between histologic grades (HGs) of vertebral growth plates and Risser grades as well as DSA stages in the Chinese female idiopathic scoliosis (IS) patients; to identify whether digital skeletal age (DSA) is a reliable indicator for accurate evaluation of the spinal residual growth potential.

SUMMARY OF BACKGROUND DATA

DSA is considered one of the more important indicators for representing the peak height velocity (PHV) typically and predicting spinal growth potential. The correlation between HGs of growth plates and DSA stages in IS patients is unclear.

METHODS

Thirty-nine Chinese female patients were available for this study. Superior and inferior growth plates were obtained at each level when anterior approach surgeries were performed. Histologic examinations were conducted after the specimens were processed. Of these patients, 28 cases were evaluated by DSA stages in this study. Correlations between histologic grades, Risser grades, menarchal status, and chronologic age were analyzed in 39 patients. Correlations between histologic grades, DSA, menarchal status, and chronologic age were analyzed in 28 patients.

RESULTS

There was a negative correlation between the following: HGs and Risser grades in 39 patients (r = -0.645, P = 0.000-0.05), HGs and menarchal status in patients in Risser 4 (r = -0.710, P = 0.002-0.05), HGs and DSA stages in 28 cases (r = -0.541, P = 0.003-0.05), and HGs and menarchal status in patients in DSA Stage III (r = -0.591, P = 0.006-0.05). Statistical significance of growth activity of growth plates was found between patients in Risser Grades 0 to 1 and those in Risser Grades 2 to 5 (P = 0.020-0.05) and patients in DSA Stage II and those in DSA Stage III (P = 0.014-0.05).

CONCLUSION

DSA may be a reliable indicator for predicting the spinal residual growth potential in IS patients, but it should be correlated with menarchal status and chronologic ages.

Pedicle growth asymmetry as a cause of adolescent idiopathic scoliosis: a biomechanical study

Over the last century the neurocentral junction (NCJ) has been identified as a potential cause of adolescent idiopathic scoliosis (AIS). Disparate growth at this site has been thought to lead to pedicle asymmetry, which then causes vertebral rotation and ultimately, the development of scoliotic curves. The objectives of this study are (1) to incorporate pedicle growth and growth modulation into an existing finite element model of the thoracic and lumbar spine already integrating vertebral body growth and growth modulation; (2) to use the model to investigate whether pedicle asymmetry, either alone or combined with other deformations, could be involved in scoliosis pathomechanisms. The model was personalized to the geometry of a nonpathological subject and used as the reference spinal configuration. Asymmetry of pedicle geometry (i.e. initial length) and asymmetry of the pedicle growth rate alone or in combination with other AIS potential pathogenesis (anterior, lateral, or rotational displacement of apical vertebra) were simulated over a period of 24 months. The Cobb angle and local scoliotic descriptors (wedging angle, axial rotation) were assessed at each monthly growth cycle. Simulations with asymmetrical pedicle geometry did not produce significant scoliosis, vertebral rotation, or wedging. Simulations with asymmetry of pedicle growth rate did not cause scoliosis independently and did not amplify the scoliotic deformity caused by other deformations tested in the previous model. The results of this model do not support the hypothesis that asymmetrical NCJ growth is a cause of AIS. This concurs with recent animal experiments in which NCJ growth was unilaterally restricted and no scoliosis, vertebral wedging, or rotation was noted.

Basic Science Research Related to Chiropractic Spinal Adjusting: The State of the Art and Recommendations Revisited

OBJECTIVE

The objectives of this white paper are to review and summarize the basic science literature relevant to spinal fixation (subluxation) and spinal adjusting procedures and to make specific recommendations for future research.

METHODS

PubMed, CINAHL, ICL, OSTMED, and MANTIS databases were searched by a multidisciplinary team for reports of basic science research (since 1995) related to spinal fixation (subluxation) and spinal adjusting (spinal manipulation). In addition, hand searches of the reference sections of studies judged to be important by the authors were also obtained. Each author used key words they determined to be most important to their field in designing their individual search strategy. Both animal and human studies were included in the literature searches, summaries, and recommendations for future research produced in this project.

DISCUSSION

The following topic areas were identified: anatomy, biomechanics, somatic nervous system, animal models, immune system, and human studies related to the autonomic nervous system. A relevant summary of each topic area and specific recommendations for future research in each area were the primary objectives of this project.

CONCLUSIONS

The summaries of the literature for the 6 topic sections (anatomy, biomechanics, somatic nervous system, animal models, immune system, and human studies related to the autonomic nervous system) indicated that a significant body of basic science research evaluating chiropractic spinal adjusting has been completed and published since the 1997 basic science white paper. Much more basic science research in these fields needs to be accomplished, and the recommendations at the end of each topic section should help researchers, funding agencies, and other decision makers develop specific research priorities.

Nanostructure of the neurocentral growth plate: Insight from scanning small angle X-ray scattering, atomic force microscopy and scanning electron microscopy

In this study, the experimental techniques scanning electron microscopy (SEM) including energy-dispersive X-ray analysis, atomic force microscopy (AFM) and scanning small angle X-ray scattering (SAXS) have been exploited to characterize the organization of large molecules and nanocrystallites in and around the neurocentral growth plate (NGP) of a pig vertebrae L4. The techniques offer unique complementary information on the nano- to micrometer length scale and provide new insight in the changes in the matrix structure during endochondral bone formation. AFM and SEM imaging of the NGP reveal a fibrous network likely to consist of collagen type II and proteoglycans. High-resolution AFM imaging shows that the fibers have a diameter of approximately 100 nm and periodic features along the fibers with a periodicity of 50-70 nm. This is consistent with the SAXS analysis that yields a cross-sectional diameter of the fibers in the range of 90 to 112 nm and a predominant orientation in the longitudinal direction of the NGP. Furthermore, we find inhomogeneities around 7 nm in the NGP by SAXS analysis. Moving towards the bone in the direction perpendicular to the growth plate, a systematic change in apparent thickness is observed, while the large-scale structural features remain constant. In the region of bone, the apparent thickness equals the mean mineral thickness and increases from 2 nm to approximately 3.5 nm as a function distance from the NGP. The mineral particles are organized as plates in a rather compact network structure. We have demonstrated that SEM, AFM and SAXS are valuable tools for the investigation of the organization of large molecules and nanocrystallites in the NGP and adjacent trabecular bone. Our findings will be an important basis for future work into identifying the defects on nanometer length scale responsible for idiopathic scoliosis and other growth-plate-related diseases.

Three-dimensional spinal and pelvic alignment in an asymptomatic population

STUDY DESIGN

A 3-dimensional (3-D) analysis of asymptomatic spinal and pelvic alignment.

OBJECTIVE

To obtain 3-D reference values of spinal and pelvic parameters, vertebral and intervertebral orientations.

SUMMARY OF BACKGROUND DATA

Referential values of spine and pelvis alignment are essential for the assessment of posture and balance. However, only 2-D referential values have been reported using standing sagittal radiographs, and, to our knowledge, no 3-D referential values have been reported to date.

METHODS

A biplanar radiographic technique was used to obtain the 3-D reconstruction of the spine and pelvis of 34 asymptomatic standing subjects. The 3-D values were calculated for most of the spinal and pelvic parameters. In addition, 3-D vertebral and intervertebral orientations were computed, and the apical and junctional zones were investigated.

RESULTS

As reported in 2-D, a large variability and particular correlations were observed for the 3-D spinal and pelvic parameters. However, significant differences were found between 3-D and 2-D values. The 3-D vertebral and intervertebral sagittal rotations showed specific features in the apical and junctional zones of the asymptomatic spine.

CONCLUSION

These data may be used as 3-D referential values of spinal and pelvic alignment.

Spinal fracture through the neurocentral synchondrosis in battered children: a report of three cases

STUDY DESIGN

Retrospective case series.

OBJECTIVE

To report 3 cases of unusual spinal fracture through the neurocentral synchondrosis.

SUMMARY OF BACKGROUND DATA

Traumatic lesions of the spine or spinal cord due to physical abuse are rare. We report 3 cases of vertebral fractures involving the neurocentral synchondrosis in battered children.

METHODS

The medical data of the 3 cases were retrospectively reviewed. We discuss the pathomechanism and treatment strategies.

RESULTS

In 2 cases, the vertebral body was displaced anteriorly and, in 1 case, posteriorly, all without neurologic compromise. The lateral radiographs showed vertebral displacement, but the diagnosis could be suspected on frontal views because of interpedicular distance widening. Treatment was nonoperative with bracing in 2 cases. In the third case, a posterior epiphysiodesis was done to avoid development of progressive kyphosis of the injured spine. One child treated nonoperatively died from other traumatic lesions associated with the physical abuse. In the 2 other cases, outcome was good with a well-balanced spine in 1 case and a moderate, well-tolerated kyphosis in the other case.

CONCLUSIONS

Such spinal lesions are rare but could be conservatively treated in case of anterior vertebral displacement without vertebral endplate impairment. A posterior displacement of vertebral body could be responsible for a neurologic compromise.

The effect of pedicle screw placement with or without application of compression across the neurocentral cartilage on the morphology of the spinal canal and pedicle in immature pigs

STUDY DESIGN

Experimental study.

OBJECTIVES

To investigate the effects of pedicle screw insertion on spinal canal and pedicle morphology in immature pigs, and, if transpedicular fixation has an effect, to document whether this occurs because of the inhabitance of the screw inside the growth plate (neurocentral cartilage [NCC]) or because of compression applied across the NCC.

SUMMARY OF BACKGROUND DATA

Transpedicular fixation has been less commonly applied to the pediatric population, especially because of the risk of damage to the NCC.

METHODS

Twelve newborn pigs (4-6 weeks of age) were operated on. Left sided pedicles from L1-L5 were studied, while right sides served as controls. Pigs were randomly assigned into 3 groups: (1) pedicles were probed only; (2) screws were inserted; and (3) after screw insertion, a washer and a nut were engaged at the pedicle entry point so that gradual compression across the NCC was achieved. After 4 months, spiral computerized tomography was used to measure the pedicle lengths and size of the halves of the spinal canal.

RESULTS

In group 1, the operated hemi-canal area was not statistically different from the nonoperated side (P = 0.159). Pedicle screw insertion either with (P = 0.007) or without (P = 0.005) compression resulted in smaller hemi-canal area and shorter pedicles at the operated side, respectively (P = 0.008, P = 0.021). Approximately 4% to 9% shortening of the pedicle lengths and 20% to 26% narrowing of the hemi-canal areas on the instrumented side occurred with transpedicular instrumentation (groups 2, 3).

CONCLUSION

Even without compression, pedicle screws passing through the NCC in immature pigs disturb spinal canal growth significantly. Clinical relevance for young children should be studied further.

Evaluating MRI as a technique for visualizing the neurocentral junction

STUDY DESIGN

Magnetic resonance imaging (MRI) of the neurocentral junction (NCJ) was correlated with gross anatomic and histologic sections acquired at the same position.

OBJECTIVES

To determine the composition of the MRI of the NCJ and to explore the long-standing discrepancy between the ages of closure of the NCJ as determined by anatomic and imaging studies.

SUMMARY OF BACKGROUND DATA

Disparate growth at the site of the NCJ has been implicated as a potential cause of adolescent idiopathic scoliosis since the early 1900s. Although anatomic studies have refuted this theory by maintaining that the NCJ closes before the age of 10 years, recent MRI studies have suggested that the NCJ remains open until adolescence.

METHODS

One hundred fourteen porcine NCJs in various stages of development were visualized using MRI. Gross anatomic and histologic sections were acquired at the same position as MRI for correlation.

RESULTS

The presence or absence of NCJ cartilage was represented by the presence or absence of a line on MRI. However, the NCJ image overestimated the width of the NCJ cartilage in the anteroposterior direction during development. As the NCJ underwent the process of closure, the NCJ image underestimated the extent of closure in the medial-lateral direction.

CONCLUSIONS

Although MRI underestimated the extent of NCJ closure, MRI accurately showed whether cartilage was present or absent at the NCJ site. MRI determination of the age of NCJ closure appears reliable, and further exploration of the asymmetric growth hypothesis is required.

Biomechanical modelling of growth modulation following rib shortening or lengthening in adolescent idiopathic scoliosis

A biomechanical model was developed to evaluate the long-term correction resulting from rib shortening or lengthening in adolescent idiopathic scoliosis (AIS). A finite element model of the trunk, personalised to the geometry of a scoliotic patient, was used to simulate rib surgery. Stress relaxation of ligaments following surgery was integrated into the model, as well as longitudinal growth of vertebral bodies and ribs and its modulation due to mechanical stresses. Simulations were performed in an iterative fashion over 24 months. A concave side rib shortening, inducing load patterns on the vertebral end-plates that could act against the scoliosis progression, was tested. A fractional factorial experimental design of 16 runs documented the effects of six modelling parameters. Wedging of the apical vertebra in the frontal plane decreased from 5.2 degrees initially to a mean value of 3.8 degrees after 24 months. The wedging decrease in the thoracic apical region was reflected by changes in the spine curvature, with a Cobb angle decrease from 46 degrees to 44 degrees immediately after the surgery and to a mean of 41 degrees after 24 months. However, both rib hump and vertebral axial rotation increased, on average, by 4 degrees at the curve apex. The most significant parameters were the growth sensitivity to stress in ribs and vertebrae and the rate of stress relaxation of intercostal ligaments. The results confirmed the potential of long-term correction of spinal curvature resulting from the rib shortening on the concavity. This modelling approach could be used for further design of less invasive surgery, taking into account residual growth, for scoliosis correction.

Using magnetic resonance imaging to characterize pedicle asymmetry in both normal patients and patients with adolescent idiopathic scoliosis

STUDY DESIGN

Morphometric analysis of vertebrae from normal patients and patients with adolescent idiopathic scoliosis.

OBJECTIVES

To use magnetic resonance imaging to assess pedicle asymmetry in normal patients and patients with adolescent idiopathic scoliosis in the early stages of scoliosis development and to determine if patients with adolescent idiopathic scoliosis exhibited a consistent vertebral morphology.

SUMMARY OF BACKGROUND DATA

To date, most studies of vertebral morphology in adolescent idiopathic scoliosis have produced conflicting data, especially on pedicle length, and have been conducted on patients in the late stages of scoliosis development, which may affect the patterns of vertebral morphology detected. Magnetic resonance imaging enables in vivo assessment of curves during development and permits improved acquisition of transverse images.

METHODS

Magnetic resonance images of 76 pedicles from 8 normal patients and 80 pedicles from 10 patients with adolescent idiopathic scoliosis were examined retrospectively. Recorded parameters included pedicle lengths, pedicle widths, pedicle areas, pedicle perimeters, and lamina lengths. The extent and direction of asymmetry in vertebrae from normal patients and patients with adolescent idiopathic scoliosis were determined and compared.

RESULTS

Normal patients displayed significant neural arch asymmetry, with the left sided measurements being greater. Patients with adolescent idiopathic scoliosis also displayed significant neural arch asymmetry; however, the longer pedicle was not consistently on the convexity or the concavity.

CONCLUSIONS

The baseline used to assess adolescent idiopathic scoliosis vertebral morphology must take into consideration the extent and direction of normal vertebral asymmetry. The pattern of vertebral asymmetry seen inadolescent idiopathic scoliosis may depend on the specific cause of the disorder, with no consistent pattern evident when data from different causes are pooled together.

Thoracic pedicle morphometry in vertebrae from scoliotic spines

STUDY DESIGN

A morphometric analysis of thoracic pedicles in vertebrae from scoliotic specimens.

OBJECTIVE

The objective of this study was to quantify the changes occurring in thoracic pedicles affected by a scoliotic deformity.

SUMMARY OF BACKGROUND DATA

There exists a lot of controversy in the literature concerning the shape and size of thoracic pedicles in idiopathic scoliosis. In recent years, thoracic pedicle screws are being used more frequently in corrective spine surgery, but few studies have evaluated the morphology of scoliotic thoracic pedicles.

MATERIAL AND METHOD

Thirty scoliotic specimens with curves presenting various degrees of severity were studied using a three-dimensional digitizing protocol developed to create a precise three-dimensional reconstruction of the vertebrae. Twenty-two parameters describing specifically the pedicles were then calculated for each vertebra from these reconstructions. Every scoliotic specimen was then matched with a normal specimen to provide for a representative control group and comparisons were made on pedicle width, length, height, surface, and orientation.

RESULTS

A total of 683 thoracic vertebrae were measured (325 scoliotic and 358 normal vertebrae). Pedicles located on the concavity of typical right thoracic curves were found to be significantly thinner than their normal counterparts with a maximal mean difference of 1.37 mm at T8. The pedicles on the concavity of the high thoracic compensatory curve were also found to be significantly diminished with a maximal mean difference of 1.68 mm at T4. Mean left pedicle width at T8 (concavity) and mean right pedicle width at T4 (concavity) were found to be 4.08 mm and 2.60 mm, respectively. Pedicle length was found to be slightly increased, and pedicle height was found to be slightly decreased in pedicles from scoliotic spines with no preference for concavity or convexity. Pedicle orientation and inclination were unchanged with respect to each corresponding vertebral body.

CONCLUSION

These results are of critical importance for clinicians performing spinal corrective surgery in patients with AIS. Pedicle width is significantly diminished on the concavity of scoliotic curves. Our results advocate caution in the use of pedicle screws in the thoracic spine especially on the concave side of the curve.

Biomechanical simulations of the spine deformation process in adolescent idiopathic scoliosis from different pathogenesis hypotheses

It is generally recognized that progressive adolescent idiopathic scoliosis (AIS) evolves within a self-sustaining biomechanical process involving asymmetrical growth modulation of vertebrae due to altered spinal load distribution. A biomechanical finite element model of normal thoracic and lumbar spine integrating vertebral growth was used to simulate the progression of spinal deformities over 24 months. Five pathogenesis hypotheses of AIS were represented, using an initial geometrical eccentricity (gravity line imbalance of 3 mm or 2 degrees rotation) at the thoracic apex to trigger the self-sustaining deformation process. For each simulation, regional (thoracic Cobb angle, kyphosis) and local scoliotic descriptors (axial rotation and wedging of the thoracic apical vertebra) were evaluated at each growth cycle. The simulated AIS pathogeneses resulted in the development of different scoliotic deformities. Imbalance of 3 mm in the frontal plane, combined or not with the sagittal plane, resulted in the closest representation of typical scoliotic deformities, with the thoracic Cobb angle progressing up to 39 degrees (26 degrees when a sagittal offset was added). The apical vertebral rotation increased by 7 degrees towards the convexity of the curve, while the apical wedging increased to 8.5 degrees (7.3 degrees with the sagittal eccentricity) and this deformity evolved towards the vertebral frontal plane. A sole eccentricity in the sagittal plane generated a non-significant frontal plane deformity. Simulations involving an initial rotational shift (2 degrees ) in the transverse plane globally produced relatively small and non-typical scoliotic deformations. Overall, the thoracic segment predominantly was sensitive to imbalances in the frontal plane, although unidirectional geometrical eccentricities in different planes produced three-dimensional deformities at the regional and vertebral levels, and their deformities did not cumulate when combined. These results support the hypothesis of a prime lesion involving the precarious balance in the frontal plane, which could concomitantly be associated with a hypokyphotic component. They also suggest that coupling mechanisms are involved in the deformation process.

Simulation of progressive deformities in adolescent idiopathic scoliosis using a biomechanical model integrating vertebral growth modulation

While the etiology and pathogenesis of adolescent idiopathic scoliosis are still not well understood, it is generally recognized that it progresses within a biomechanical process involving asymmetrical loading of the spine and vertebral growth modulation. This study intends to develop a finite element model incorporating vertebral growth and growth modulation in order to represent the progression of scoliotic deformities. The biomechanical model was based on experimental and clinical observations, and was formulated with variables integrating a biomechanical stimulus of growth modulation along directions perpendicular (x) and parallel (y, z) to the growth plates, a sensitivity factor beta to that stimulus and time. It was integrated into a finite element model of the thoracic and lumbar spine, which was personalized to the geometry of a female subject without spinal deformity. An imbalance of 2 mm in the right direction at the 8th thoracic vertebra was imposed and two simulations were performed: one with only growth modulation perpendicular to growth plates (Sim1), and the other one with additional components in the transverse plane (Sim2). Semi-quantitative characterization of the scoliotic deformities at each growth cycle was made using regional scoliotic descriptors (thoracic Cobb angle and kyphosis) and local scoliotic descriptors (wedging angle and axial rotation of the thoracic apical vertebra). In all simulations, spinal profiles corresponded to clinically observable configurations. The Cobb angle increased non-linearly from 0.3 degree to 34 degrees (Sim1) and 20 degrees (Sim2) from the first to last growth cycle, adequately reproducing the amplifying thoracic scoliotic curve. The sagittal thoracic profile (kyphosis) remained quite constant. Similarly to clinical and experimental observations, vertebral wedging angle of the thoracic apex progressed from 2.6 degrees to 10.7 degrees (Sim1) and 7.8 degrees (Sim2) with curve progression. Concomitantly, vertebral rotation of the thoracic apex increased of 10 degrees (Sim1) and 6 degrees (Sim2) clockwise, adequately reproducing the evolution of axial rotation reported in several studies. Similar trends but of lesser magnitude (Sim2) suggests that growth modulation parallel to growth plates tend to counteract the growth modulation effects in longitudinal direction. Overall, the developed model adequately represents the self-sustaining progression of vertebral and spinal scoliotic deformities. This study demonstrates the feasibility of the modeling approach, and compared to other biomechanical studies of scoliosis it achieves a more complete representation of the scoliotic spine.

Analysis of vertebral morphology in idiopathic scoliosis with use of magnetic resonance imaging and multiplanar reconstruction

BACKGROUND

Several studies have provided data on the vertebral morphology of normal spines, but there is a paucity of data on the vertebral morphology in patients with idiopathic scoliosis.

METHODS

The morphology of the pedicles and bodies of 307 vertebrae as well as the distance between the pedicles and the dural sac (the epidural space) in twenty-six patients with right-sided thoracic idiopathic scoliosis were analyzed with use of magnetic resonance imaging and multiplanar reconstruction.

RESULTS

A distinct vertebral asymmetry was found at the apical region of the thoracic curves, with significantly thinner pedicles on the concave side than on the convex side (p < 0.05). The degree of intravertebral deformity diminished farther away from the apex, with vertebral symmetry restored at the neutral level. In the thoracic spine, the transverse endosteal width of the apical pedicles measured between 2.3 mm and 3.2 mm on the concave side and between 3.9 mm and 4.4 mm on the convex side (p < 0.05). In the lumbar spine, the pedicle width measured between 4.6 mm at the cephalad part of the curve and 7.9 mm at the caudad part of the curve. The chord length and the pedicle length gradually increased from 34 mm and 18 mm, respectively, at the fourth thoracic vertebra to 51 mm and 25 mm, respectively, at the third lumbar vertebra. The transverse pedicle angle measured 15 in the cephalad aspect of the thoracic spine, decreased to 7 at the twelfth thoracic vertebra, and increased again to 16 at the fourth lumbar vertebra. The width of the epidural space was <1 mm at the thoracic apical vertebral levels and averaged 1 mm at the lumbar apical vertebral levels on the concave side, whereas it was between 3 mm and 5 mm on the convex side (p < 0.05).

CONCLUSION

Idiopathic scoliosis is associated with distinctive intravertebral deformity, with smaller pedicles on the concave side and a shift of the dural sac toward the concavity.

The effect of continued posterior spinal growth on sagittal contour in patients treated by anterior instrumentation for idiopathic scoliosis

STUDY DESIGN

Retrospective analysis of radiographs on a prospective cohort of patients undergoing anterior instrumentation for thoracic idiopathic scoliosis.

OBJECTIVES

To analyze the change in sagittal profile after growth.

SUMMARY OF BACKGROUND DATA

The authors previously reported some advantages of anterior instrumentation for treatment of thoracic idiopathic scoliosis. However, postsurgery hyperkyphosis has resulted in some patients, especially those who were skeletally immature at the time of surgery.

METHODS

Inclusion criteria required that participants have thoracic idiopathic scoliosis treated with anterior instrumentation and a confirmed solid fusion, no rod breakage, and a minimum follow-up period of 2 years. The 47 patients meeting the criteria were divided into a study group of 10 patients who were Risser 0 at the time of surgery and a control group of 37 patients who were Risser 1 to 5. Progressive sagittal kyphosis was defined as an increase of 10 degrees or more (T5-T12) after surgery.

RESULTS

Sagittal progression greater than 10 degrees (average, 15 degrees ) occurred in 6 of 10 patients (60%) in the study group (Risser 0). Five patients progressed from 10 degrees to 19 degrees, and one patient from 20 degrees to 30 degrees. In contrast, sagittal progression occurred in only 10 of 37 patients (27%) in the control group (Risser 1 to 5).

CONCLUSIONS

Some patients with thoracic adolescent idiopathic scoliosis treated with anterior instrumentation may be at risk for progressive sagittal kyphosis secondary to growth. Skeletal immaturity (Risser 0) appears to be a risk factor. In these immature patients, preserving the sagittal profile with intervertebral spacers, rigid rods, and bone graft (allowing for an average 15 degrees increase of kyphosis with growth) may be appropriate.

Spinal growth and a histologic evaluation of the Risser grade in idiopathic scoliosis

STUDY DESIGN

Thirty-four patients with idiopathic scoliosis who underwent anterior spinal surgery as part of the correction of spinal deformity were studied prospectively. Superior and inferior endplates were harvested and examined histologically for evidence of residual growth activity. This was then correlated with Risser grades, chronologic age, and pubertal status.

OBJECTIVES

To clarify the correlation between Risser grade and vertebral endplate growth potential in patients with idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

The importance of longitudinal spinal growth in patients with idiopathic scoliosis and its correlation with curve progression and the crankshaft phenomenon after posterior fusion are well recognized. The Risser grade, which shows the extent of excursion of the iliac apophysis on serial plain radiographs, is commonly used to estimate residual spinal growth. However, the correlation between the Risser grade and vertebral endplate growth potential in patients with idiopathic scoliosis remains unclear.

METHODS

Superior and inferior endplates were harvested from these patients and examined histologically for evidence of residual growth. This was correlated with Risser grade, chronologic age, and pubertal status.

RESULTS

Risser Grade 5 was found to be the only indicator of cessation of vertebral growth in idiopathic scoliosis. Of the 14 patients with Risser Grade 4, 10 showed significant growth activity in the vertebral endplates. The reliability of Risser Grade 4 increases when combined with chronologic age and time since menarche in female patients.

CONCLUSIONS

The crankshaft phenomenon is reported to occur only in patients with Risser Grade 2 or less, particularly those with open triradiate cartilages. Our findings of significant endplate growth activity, even in patients with Risser Grade 4, make it unlikely that the crankshaft phenomenon is caused purely by longitudinal spinal growth.

Vertebral deformities and scoliosis

Scoliosis, especially idiopathic scoliosis, is a complex three-dimensional deformity of the spine in which the vertebral deformities are known, cuneal deformation being the most commonly known deformity but not the only one. We report here data concerning these specific vertebral deformities in chickens. A pinealectomy was performed in a controlled series of animal experiments. This technique induces progressive scoliosis in more than 80% of chickens, with the advantage of being non-aggressive to the spine. Vertebrae included in major thoracolumbar curves were observed in 17 chickens (11 male, 6 female) and classified into three types of vertebral deformities. Vertebral deformity type 1 is characterized by three-dimensional corporeal torsion, which defines the horizontal disorientation of the curve. Vertebral deformities type 2 and 3 define lateral imbalance in the election plane of the curve. Radiological and anatomical data collected throughout the progression of the scoliosis indicate that there is a correlation between structural vertebral deformities and growth/maturation patterns. We compare our results with those reported in literature concerning human idiopathic scoliosis and experimental animal scoliosis.

Vertebral rotation and pedicle length asymmetry in the normal adult spine

Rotation in the horizontal plane of vertebra T8, T9 or T10 was determined on CT scans of 25 male and 25 female patients with normal spines. The pedicle length was measured using a new method, and the right/left pedicle length index was calculated. In 38 (76%) of the patients there was vertebral rotation to the right with a mean Cobb angle of 3.0 degrees, and in 4 (8%) rotation to the left, mean Cobb angle 2.2 degrees (P < 0.01). In 8 (16%) there was no measurable rotation. The pedicle length index was greater than 1.05 in 9 subjects, between 0.95 and 1.05 in 16 and less than 0.95 in 25, indicating a predominance of longer pedicles on the left side. In 21 out of the 38 patients with vertebral rotation to the right, the left pedicle was longer than the right one (P < 0.01). The results indicate that the normal spine is afflicted with a vertebral rotation to the right in association with a longer pedicle on the left. The significance of these observations for the pathogenesis of idiopathic scoliosis remain uncertain.

Posterior arthrodesis and instrumentation in the immature (Risser-grade-0) spine in idiopathic scoliosis

We performed a retrospective study of the long-term results of posterior instrumentation and arthrodesis of the spine in forty-three patients who had idiopathic scoliosis and a Risser grade of 0 at the time of the operation. The average age of the patients was 12.4 years (range, 6.7 to 15.5 years) at the time of the operation. The triradiate cartilages were open in twenty-three patients and closed in twenty. At the time of the latest follow-up evaluation (average duration of follow-up, four years; range, two to eleven years), seventeen patients had a Risser grade of 5; twenty-two, 4; two, 3; one, 2; and one, 0. The crankshaft phenomenon, a progressive deformity resulting from continued growth of the anterior aspect of the spine after posterior arthrodesis, was seen in only one patient who had closed triradiate cartilages and in ten patients who had open triradiate cartilages (p = 0.004). The most common radiographic finding was a progressive rib-vertebra angle difference, which increased more than 10 degrees in seven of the eleven patients who had the crankshaft phenomenon. The mean increase in these eleven patients was 22 degrees, compared with no increase in the thirty-two other patients (p < 0.0001). Open triradiate cartilages (r = 0.58, p = 0.0001) and a younger age at the time of the operation (p < 0.0001) were predictive of the amount of progression as a result of the crankshaft phenomenon. In patients who had open triradiate cartilages, less skeletal maturity was also predictive of progression as a result of the crankshaft phenomenon (r = -0.72, p = 0.0002).