Neutral Vertebra Research Articles

Scoliosis Imaging: What Radiologists Should Know

Scoliosis is defined as a lateral spinal curvature with a Cobb angle of 10° or more. This abnormal curvature may be the result of an underlying congenital or developmental osseous or neurologic abnormality, but in most cases the cause is unknown. Imaging modalities such as radiography, computed tomography (CT), and magnetic resonance (MR) imaging play pivotal roles in the diagnosis, monitoring, and management of scoliosis, with radiography having the primary role and with MR imaging or CT indicated when the presence of an underlying osseous or neurologic cause is suspected. In interpreting the imaging features of scoliosis, it is essential to identify the significance of vertebrae in or near the curved segment (apex, end vertebra, neutral vertebra, stable vertebra), the curve type (primary or secondary, structural or nonstructural), the degree of angulation (measured with the Cobb method), the degree of vertebral rotation (measured with the Nash-Moe method), and the longitudinal extent of spinal involvement (according to the Lenke system). The treatment of idiopathic scoliosis is governed by the severity of the initial curvature and the probability of progression. When planning treatment or follow-up imaging, the biomechanics of curve progression must be considered: In idiopathic scoliosis, progression is most likely during periods of rapid growth, and the optimal follow-up interval in skeletally immature patients may be as short as 4 months. After skeletal maturity is attained, only curves of more than 30° must be monitored for progression.

Thoracic adolescent idiopathic scoliosis: selection of fusion level

Selection of the appropriate fusion levels in thoracic adolescent idiopathic scoliosis has been traditionally a subject of debate among surgeons. Landmarks that have been suggested include the end vertebra, stable vertebra and neutral vertebra. Various results have been reported with multiple theories proposed to explain them. The clinical appearance of the patient, the type of the curve and its flexibility, the surgical technique and the instrumentation used all seem to play major roles in selecting the appropriate levels of fusion.

Changes of Deformity due to the Position and Anesthesia in Adolescent Idiopathic Scoliosis

Restrospective case series. To determine changes in the end vertebra and neutral vertebra, and in the magnitudes of coronal and rotational deformities according to position and anesthesia in patients with adolescent idiopathic scoliosis. Although it is known that coronal deformity of scoliosis has a tendency to decrease by position and anesthesia, there have been few reports on the effects of position and anesthesia on the rotational deformity of scoliosis. End vertebra and neutral vertebra can change after positioning and anesthesia, but little is known about it. Sixty-two structural curves in 31 patients were evaluated using standing, supine, side bending, postanesthesia, and postoperative anteroposterior plain radiographs. Cobb angles and rotation angles by Perdriolle torsionmeter were measured, and the end vertebra and neutral vertebra were identified in each radiograph. Coronal Cobb angles decreased significantly with the correction rates of 25.0%, 31.7%, 59.5%, and 74.0%, and rotational deformities decreased with the correction rates of 6.1%, 24.5%, 6.2%, and 25.7% by supine position, anesthesia, side bending, and surgery, respectively. The end vertebrae changed in 18 patients (58.1%) in both supine and postanesthesia radiographs, and the neutral vertebrae changed in 10 patients (32.3%) in supine radiographs and in 20 patients (64.5%) in postanesthesia radiographs. Coronal deformities are significantly corrected by supine position and anesthesia. Anesthesia significantly corrects axial rotation, but further correction cannot be achieved by rod derotation. The end vertebra and neutral vertebra have a tendency to vary by position and anesthesia, which gives rise to confusion in the determination of fusion levels.

Determination of lowest instrumented vertebra by the location of apical vertebra in Lenke type 1 adolescent idiopathic scoliosis

We postulated that the lowest instrumented vertebra (LIV) can be determined based on the apical vertebra. Seventy-two Lenke type 1 patients (average age: 13.6 years) receiving posterior spinal fusion were randomised into two groups. In group A, the apical vertebra was used to determine the LIV and in group B the neutral vertebra was used. All patients had Cobb angles <90° and average follow-up was over three years. Posteroanterior and lateral standing radiographs were used to assess flexibility, Cobb angle and distance from the C7 line to the central sacral vertical line. Both methods produced statistically significant changes in Cobb angle, sagittal T5-T12 and plumb line deviation, and there were no significant differences between the two methods. More cases of imbalance occurred in group B (five) than group A (two). We conclude that the apical vertebra can be used to determine the LIV in patients with Lenke type 1 adolescent idiopathic scoliosis.

Selective thoracic surgery in the Lenke type 1A: King III and King IV type curves

Pedicle screw fixation enables enhanced three-dimensional correction of spinal deformities and effectively shortens the distal fusion level. However, the choice of distal fusion level is still controversial in single thoracic idiopathic scoliosis with the lumbar compensatory curve not crossing the middle line (Lenke type 1 with modifier A or King type III and IV curves).The authors retrospectively analyzed 31 patients treated by segmental pedicular instrumentation alone, affected by a single thoracic adolescent idiopathic scoliosis with a compensatory lumbar curve not crossing the midline (Lenke 1A), with an average age of 16.3 years (range 10-22 years). The patients with regard to the King classification were also assessed. A statistical analysis was performed to determine whether the two groups (King III, King IV) presented differences concerning the level of the stable vertebra (SV), end vertebra (EV), and neutral vertebra (NV) and were also analyzed the results at follow-up regarding the relationships between the SV, EV, and lowest instrumented vertebra (LIV). The statistical analysis showed a significant difference between the two curve types. In the King III type curve the SV, EV, and NV appeared to be more proximal than those of the King IV type curve and the segments between the SV, EV, and NV appeared to be reduced in King III curves compared with King IV curves. At a follow-up of 3.2 years (range 2.2-5) the thoracic curve showed a correction of 58.4% (from 62.3 degrees to 26.6 degrees ) and compensatory lumbar curve an average spontaneous correction of 52.4% (from 38.1 degrees to 18.1 degrees ).The position of the LIV was shorter than the position of the SV in 30 patients (97%) with an average "salvage" of 2.1 (from 1 to 4) distal fusion levels. Four cases (13%), all affected by a King IV type curve, presented at follow-up an unsatisfactory results due to an "adding on" phenomenon. The statistical analysis confirmed that this phenomenon was correlated with The King IV curve (P = 0.043; Chi-square test) and that the only predictive parameter for its onset was the LIV-SV difference (odds ratio = 0.093; with a confidence interval of 0.008-1): every time that in King IV curve type the LIV was three or more levels shorter than the stable vertebra at follow-up the "adding on" phenomenon was present. The authors conclude that Lenke's type 1 with modifier A includes two kinds of curves, King III and King IV and that the Lenke's type 2 curves and King V with the lumbar curve not crossing the middle line have a similar behavior. Therefore, it is of authors' opinion that "the adding on phenomenon" could be prevented by more rigidly defining K. IV versus K. III curves. In Lenke's 1/2 A-K. IV/V type with the rotation of the first vertebra just below the thoracic lower EV in the same direction as the thoracic curve, and when SV and EV show more than two levels of difference, it is necessary to extend the lower fusion down to L2 or L3 (not more than two levels shorter than the SV). Whereas in Lenke's 1/2 A-K. III/V with the rotation of the first proximal vertebra of lumbar curve in the opposite direction to the thoracic apex and when SV and EV show not more than two level gap differences, the position of the lowest instrumented vertebra can be two or three levels shorter than the stable vertebra with satisfactory postoperative spinal balance. Therefore, the stable vertebra and the rotation of lumbar curve are considered to be a reliable guide for selecting the lower level of fusion.

Change of Deformity due to Position and Anesthesia in Adolescent Idiopathic Scoliosis

Purpose: To determine changes in the end vertebra and neutral vertebra as well as in the magnitudes of coronal and rotational deformities according to position and anesthesia in patients with adolescent idiopathic scoliosis. Materials and Methods: Sixty-two structural curves in 31 patients were evaluated using standing, supine, side bending, post-anesthesia, and postoperative anteroposterior plain radiographs. Cobb angles and rotation angles by perdriolle torsionmeter were measured, and the end vertebra and neutral vertebra were identified in each radiograph. Results: Coronal cobb angles decreased significantly with correction rates of 25.0%, 31.7%, 59.5%, and 74.0%, and rotational deformities decreased with correction ratesof 6.1%, 24.5%, 6.2%, and 25.7% by supine position, anesthesia, side bending and surgery, respectively.The end vertebrae changed in 18 patients (58.1%) in both supine and post-anesthesia radiographs, and the neutral vertebrae changed in 10 patients (32.3%) in supine radiographs and in 20 patients (64.5%) in post-anesthesia radiographs. Conclusion: Coronal deformities are significantly corrected by supine position and anesthesia. Anesthesia significantly corrects axial rotation, but more correction cannot be achieved by rod derotation. The end vertebra and neutral vertebra have a tendency to vary by position and anesthesia, which gives rise to confusion in the determination of fusion level.

Selective posterior fusion of single thoracic curve adolescent idiopathic scoliosis: experience in 72 cases

To prospectively evaluate the strategy of surgery and choice of the fusion segments in thoracic adolescent idiopathic scoliosis (AIS) treatment. Selective posterior fusion was used on 72 AIS patients, 13 male and 59 female, aged 14.3 (12 - 18), 50 being of Lenke-type IA, 8 Lenke-type IB, and 14 Lenke-type IC. In principle the upper neutral vertebrae were selected as upper instrumented vertebrae. The lower neutral vertebrae, the vertebrae 1 level proximal to the neutral vertebrae, or stable vertebrae were chosen as the lower instrumented vertebrae based on the analysis of the correlation among the lower end vertebrae, neutral vertebrae and stable vertebrae's locations. Standing anteroposterior and lateral and side-bending radiographs were taken preoperatively, postoperatively and during the follow-up. The coronal and sagittal Cobb angle, translation and rotation of apical vertebrae, and trunk translation were evaluated to observe the curve correction and trunk balance. The patients underwent spinal fusion of 7.3 segments (4 - 10 segments) on average. Follow-up was conducted for 15.9 months (12 - 39 months). The thoracic curves' coronal Cobb angle before the operation was 56.7 degrees +/- 14.5 degrees (40 degrees - 98 degrees), and was 18.5 degrees +/- 8.3 degrees (3 degrees - 40 degrees) after the operation. The lumbar curves' coronal Cobb angle before operation was 33.9 degrees +/- 10.4 degrees (25 degrees - 69 degrees), and was 11.1 degrees +/- 6.4 degrees (0 degrees - 30 degrees ) after operation. The spontaneous correction rate was 66.9% +/- 16% (44% - 100%). The trunk translation before operation was 16.1 +/- 10.2 mm (4 - 43 mm), and was 8.2 +/- 6.1 mm (0 - 25 mm) after operation. Two patients were found with slight trunk decompensation postoperatively, but with no progression during a 2-year follow-up. Determination of the fusion levels based on the analysis of the correlation among the end vertebrae, neutral vertebrae and stale vertebrae's location helps obtain the satisfying curative effect in the management of single thoracic curve AIS.

Surgical management of cervical myelopathy dealing with the cervical–thoracic junction

The treatment of compressive cervical myelopathy is, in general, a surgical endeavor. Surgery involves decompression, often with an accompanying fusion with stabilization. The length of the fusion can vary and the decision regarding length of fusion is not always clear. This study explores the fundamental principles regarding the length of fusion at the cervicothoracic junction. A review of the literature regarding the anatomy and biomechanics of the cervicothoracic region is provided. Surgical approaches and indications for cervicothoracic junction region fusions are discussed. Fundamental guidelines for the decision-making process are provided. The cervicothoracic region is a biomechanically complex region. Although there is little biomechanical data indicating the appropriate length of fusion, several fundamental guidelines may be followed to reduce the incidence of construct failure. A long fusion should not end at an apical vertebra nor at the cervicothoracic junction. Long cervical fusions should be extended to traverse the cervicothoracic junction to a neutral vertebra.

SURGICAL TREATMENT OF THORACIC IDIOPATHIC SCOLIOSIS

Objective. To analyze results of surgical treatment of patients with thoracic idiopathic scoliosis. Material and Methods. Fifty-two patients with Lenke type 1 idiopathic scoliosis were operated on. Follow-up periods ranged from 2 weeks to 8 years (mean 1.8 years). Surgical treatment included four types of operation: spine deformity correction with CD instrumentation; supramalleolar-andskull traction and CDI correction; discectomy and interbody fusion with bone autograft and CDI correction; supramalleolar- and-skull traction, discectomy and interbody fusion with bone autograft, and CDI correction. Patients were interrogated with pre- and postoperative SRS-24 questionnaires and examined with Computer Optical Topograph (COMOT). Results. Scoliosis was corrected from a mean of 67.7° to 26.6°, with a mean deformity value being 30.3° at the last follow- up. Thus, postoperative progression of the thoracic curve with a mean follow-up 1.8 years was 3.7° (9 % from the achieved correction). Anterior fusion provided a threefold decrease in postoperative progression. Sagittal shape of the thoracic and lumbar spine remained within norm limits. The location of the lowest instrumented vertebra (LIV) relative to a neutral vertebra, lower stable vertebra and neutralized disc did not reliably influence on the postoperative course. Postoperative deformity progression was associated only with increase in LIV tilt. SRS-24 data showed a high rate of patients’ satisfaction with the obtained effect of treatment, the rate growing with the extension of follow-up terms. Severe complications were not observed. Conclusion. Modern 3rd generation segmental instrumentation allows to obtain stable and high results of treatment for single curve thoracic idiopathic deformities, while all regularities of postoperative course are not fully understood yet.

Reliability of End, Neutral, and Stable Vertebrae Identification in Adolescent Idiopathic Scoliosis

Analysis of radiographic interpretation and vertebral level identification. To assess the intra- and interobserver reliability by observer training level used for selecting the end vertebra (EV), neutral vertebra (NV), and stable vertebra (SV) in adolescent idiopathic scoliosis patients. Various radiographic and clinical factors are important in surgical planning. For adolescent idiopathic scoliosis, an analysis of the end, neutral, and stable vertebrae are of paramount importance for understanding spinal deformity management and determining the distal fusion level. Additionally, the development and comparison of optimal surgical techniques requires reliable, reproducible radiographic parameters. One hundred consecutive radiographs of operative cases of adolescent idiopathic scoliosis were evaluated on three separate occasions by three surgeons (2700 data points) at various levels of training (fellowship-trained spine surgeon, fellow in-training, orthopedic surgery resident). For each iteration, the observers attempted to identify the distal structural Cobb curve EV, NV, and SV. The radiographs included preselected Lenke type 1, 3, and 5 curves in random order. The average main thoracic curve was 53 degrees (range, 30-82 degrees) with a T8-T9 average apex, whereas the average thoracolumbar curve was 33 degrees (range, 18-65 degrees). Intra- and interobserver reliability was assessed by means of Cohen's Kappa correlation coefficient, and raw percentages of agreement were recorded. Intraobserver reliability was good to excellent for determining the EV (kappaa = 0.69-0.88), good for determining the NV (kappaa = 0.65-0.73), and good to excellent for determining the SV (kappaa = 0.74-0.91) with 83.5, 72.2, and 85.6% intraobserver agreement, respectively. A trend was noted towards greater intraobserver reliability with increasing levels of observer experience. Interobserver reliability was poor (kappaa = 0.26-0.39) for each vertebral level, with interobserver agreement for only 48.7% of EV, 41.7% of NV, and 51.0% of SV. However, interobserver agreement increased significantly when concurrence within one vertebral level was assessed, with 91, 73, and 76% agreement for identifying the EV, NV, and SV, respectively. Radiographic determination of the EV, NV, and SV demonstrated good to excellent intraobserver, but poor interobserver, reliability. Interobserver agreement was fair to good when concurrence within one adjacent level was assessed. Observer experience level may be a factor. The difficulties in identifying these vertebral levels represent a potential obstacle to reproducible patient-specific fusion level determination and to the optimization and uniformity of patient care.

Selective Thoracic Fusion With Segmental Pedicle Screw Fixation in the Treatment of Thoracic Idiopathic Scoliosis

Retrospective study. To evaluate outcomes of selective thoracic fusion with segmental pedicle screw fixation in thoracic idiopathic scoliosis with a minimum 5-year follow-up. Segmental pedicle screw fixation has been proven to enable true segmental control and greater correction both in coronal and sagittal planes of scoliosis. However, there is no long-term study of selective thoracic fusion with segmental pedicle screw fixation in thoracic idiopathic scoliosis. Two hundred and three thoracic idiopathic scoliosis patients with 236 thoracic curves subject to selective thoracic fusion with segmental pedicle screw fixation were analyzed. Mean patient age at the time of operation was 13.8 years (range: 8.9-18). The preoperative thoracic curve of 51 +/- 12 degrees was corrected to 16 +/- 7 degrees (69% correction, 3% loss of correction) at the most recent follow-up. The noninstrumented lumbar curve of 30 +/- 10 degrees was corrected to 10 +/- 8 degrees (66% correction, 5% loss of correction) at the most recent follow-up. The preoperative thoracic kyphosis of 18 +/- 11 degrees and the lumbar lordosis of 43 +/- 10 degrees were improved to 23 +/- 8 degrees and 46 +/- 9 degrees , respectively, at the most recent follow-up. There was no junctional kyphosis at the most recent follow-up. Coronal decompensation at the most recent follow-up occurred in 10 patients. Postoperative adding-on occurred in 17 patients, who were fused two levels short of the neutral vertebra. Of the 2,867 thoracic pedicle screws inserted in the thoracic level, 43 screws were found to be malpositioned (1.5%), but they did not cause neurologic complications or adversely affect the long-term results. Selective thoracic fusion with segmental pedicle screw fixation in thoracic idiopathic scoliosis had satisfactory radiographic and clinical outcomes after surgery and has been well-maintained for minimum 5-year follow-up. It is a safe and effective method for preservation of lumbar motion segments as well as for restoration and maintenance of both coronal and sagittal alignment.

Selective Thoracic Fusion with Segmental Pedicle Screw Fixation for the Treatment of Thoracic Idiopathic Scoliosis: More than Five Year's Follow-Up

‐ Abstract ‐ Study Design: This is a retrospective study. Objectives: We wanted to evaluate the outcomes of selective thoracic fusion with segmental pedicle screw fixation for treating thoracic idiopathic scoliosis with a minimum 5-year follow-up. Summary of the Literature Review: Segmental pedicle screw fixation has been proven to achieve true segmental control and greater correction of scoliosis in both the coronal and sagittal planes. However, there is no long-term study of selective thoracic fusion with segmental pedicle screw fixation for treating thoracic idiopathic scoliosis. Materials and Methods: We analyzed 203 thoracic idiopathic scoliosis patients (236 thoracic curves) who underwent selective thoracic fusion with segmental pedicle screw fixation. The mean patient age at the time of operation was 13.8 years (range: 8.9~18 years). Results: The preoperative thoracic curve of 51±12°was corrected to 16±7°(69% correction with 3% loss of correction) at the most recent follow-up. The non-instrumented lumbar curve of 30±10°was corrected to 10±8°(66% correction with 5% loss of correction) at the most recent follow-up. The preoperative thoracic kyphosis of 18±11°and the lumbar lordosis of 43±10° were improved to 23±8°and 46±9° , respectively, at the most recent follow-up. There was no junctional kyphosis at the most recent follow-up. Coronal decompensation at the most recent follow-up occurred in 10 patients. Postoperative adding-on occurred in 17 patients who were fused two levels short of the neutral vertebra. Of the 2867 thoracic pedicle screws inserted at the thoracic level, 43 screws were found to be malpositioned (1.5%), but they did not cause neurologic complications or adversely affect the long-term results. Conclusions: Selective thoracic fusion with segmental pedicle screw fixation for treating thoracic idiopathic scoliosis had satisfactory radiographic and clinical outcomes after surgery, and the outcomes were well-maintained for a minimum of 5 years follow-up. It is a safe and effective method for preserving segments of lumbar motion as well as for the restoration and maintenance of both the coronal and sagittal alignments.

Changes in Alignment of the Scoliotic Spine in Response to Lateral Bending

A retrospective cross-sectional review studied the posteroanterior and lateral bending radiographs of 26 preoperative patients with thoracic major adolescent idiopathic scoliosis. To characterize the relation of vertebral axial rotation, apparent vertebral wedging, and disc wedging with lateral bending in patients with severe adolescent idiopathic scoliosis. Lateral bending radiographs are used commonly in surgical planning to assess the flexibility of the spine and to establish the placement of instrumentation. However, their use in the assessment of motion in the axial plane has not been clearly established. Data were collected retrospectively from 26 subjects immediately before spinal surgery. All the subjects had adolescent idiopathic scoliosis with right thoracic major curves. Axial rotation, vertebral wedging, and disc wedging were measured from T4 to L4 on left and right supine bending and standing posteroanterior radiographs. The apexes of the major and minor curves, the neutral vertebrae, and the Cobb angles were recorded. No significant differences in axial rotation were found at the thoracic apex, neutral vertebrae, or lumbar apex in response to lateral bending. Most of the wedging occurs in the disc, and is maximal at the apex of the curve. The total amount of wedging was higher in more severe curves. Lateral bending does not improve axial rotation in severe scoliosis (scoliosis for which surgical correction is advised). Structural changes including disc and vertebral wedging may be responsible for the lack of rotational correction of the scoliotic spine. Lack of axial flexibility in the thoracic region may hamper surgical attempts to correct the deformities of the trunk.

Possibilities of computed tomography in the complex assessment of scoliotic spinal deformity

Complex evaluation of scoliotic deformity was performed using CT. Fifty patients with displastic scoliosis of IIIIV degree were examined before and after surgical intervention dorsal correction and spine fixation with Cotrel-Dubousset instrumentation. No marked derotation of spine at the deformity apex was noted postoperatively. Changes of thorax in the plane of apical vertebra were studied and quantitatively evaluated: postoperatively thorax became of more correct oval shape in all cases. Density of trabecular bone of apical and neutral vertebrae coincided with the understanding about asymmetry of deformed vertebrae bone density. No marked immediate postoperative changes were noted. Combination of CT and myelography showed the dislocation of dural sac to the side opposite to the deformity convexity; either partial (up to 6070% in patients with deformity of III and early IV degree) or complete (in patients with severe deformity) disturbance of contrast distribution in subarachnoidal space from concave side and compensatory widening of subarachnoidal space from the opposite side with maximum changes at the apex of scoliotic deformity.

A King Type II Curve Pattern Treated with Selective Thoracic Fusion

The optimal surgical treatment of the King-Moe type II thoracic curve pattern is controversial. The issue of postoperative "decompensation" has arisen in conjunction with the use of third-generation instrumentation systems. This report presents the 44-year clinical and radiographic follow-up of a patient with a type II scoliosis treated with uninstrumented selective thoracic fusion using the criteria of King and Moe. The caudal extent of the fusion was defined by proper identification of the neutral and stable vertebra. At final follow-up, the patient remained well balanced and essentially pain free. Her level of function was "above average" for her age, as per SF-36 evaluation.

JUVENILE IDIOPATHIC SCOLIOSIS. CURVE PATTERNS AND PROGNOSIS IN ONE HUNDRED AND NINE PATIENTS

We reviewed the medical records and radiographs of 109 consecutive patients who had juvenile idiopathic scoliosis. The sixty-seven girls and forty-two boys were a mean of six years and ten months old (range, three years and four months to nine years and eleven months old) when the curve was recognized. One hundred and four patients had a progressive curve: twenty-eight had a single mid-thoracic curve with the apex usually at the eighth thoracic vertebra (Group 1A), twenty-nine had a major mid-thoracic curve with the apex usually at the eighth thoracic vertebra and a secondary minor lumbar curve (Group 1B), twenty-seven had a single thoracic curve with the apex usually at the ninth or tenth thoracic level (Group 2), eight had a single thoracolumbar curve with the apex at the twelfth thoracic level (Group 3), and twelve had a major lumbar curve with the apex at the second or third lumbar level and a secondary minor thoracic curve (Group 4). Five patients (5 per cent) had a resolving curve. Eighty-nine of the patients who had a progressive curve were followed to skeletal maturity. Eighty-eight patients were managed with a brace. The curve progressed at a rate of 1 to 3 degrees per year before the age of ten years and 4.5 to 11 degrees per year after the age of ten years. In sixty-seven of the eighty-four patients in Groups 1 and 2, a spinal arthrodesis was performed before the age of fifteen years (mean age, eleven years and ten months; range, nine years and three months to fourteen years and eight months), at which time the mean curve was 47 degrees (range, 24 to 90 degrees). Eight patients were not seen by us until they were fifteen years old or more, at which time the thoracic curve was 74 to 120 degrees; a spinal arthrodesis was done in seven. The curves in Groups 3 and 4 had a more benign prognosis, and only three patients in these two groups had an arthrodesis. The pattern of the final curve was not always apparent at an early stage, and there was extension of the primary curve or development of secondary structural curves with progression. The chief prognostic feature at an early stage was the level of the most rotated vertebra at the apex of the primary curve, and the final pattern of deformity was defined by the level of the caudad neutral vertebra in the primary thoracic curve.

Juvenile idiopathic scoliosis. Curve patterns and prognosis in one hundred and nine patients.

We reviewed the medical records and radiographs of 109 consecutive patients who had juvenile idiopathic scoliosis. The sixty-seven girls and forty-two boys were a mean of six years and ten months old (range, three years and four months to nine years and eleven months old) when the curve was recognized. One hundred and four patients had a progressive curve: twenty-eight had a single mid-thoracic curve with the apex usually at the eighth thoracic vertebra (Group 1A), twenty-nine had a major mid-thoracic curve with the apex usually at the eighth thoracic vertebra and a secondary minor lumbar curve (Group 1B), twenty-seven had a single thoracic curve with the apex usually at the ninth or tenth thoracic level (Group 2), eight had a single thoracolumbar curve with the apex at the twelfth thoracic level (Group 3), and twelve had a major lumbar curve with the apex at the second or third lumbar level and a secondary minor thoracic curve (Group 4). Five patients (5 per cent) had a resolving curve. Eighty-nine of the patients who had a progressive curve were followed to skeletal maturity. Eighty-eight patients were managed with a brace. The curve progressed at a rate of 1 to 3 degrees per year before the age of ten years and 4.5 to 11 degrees per year after the age of ten years. In sixty-seven of the eighty-four patients in Groups 1 and 2, a spinal arthrodesis was performed before the age of fifteen years (mean age, eleven years and ten months; range, nine years and three months to fourteen years and eight months), at which time the mean curve was 47 degrees (range, 24 to 90 degrees). Eight patients were not seen by us until they were fifteen years old or more, at which time the thoracic curve was 74 to 120 degrees; a spinal arthrodesis was done in seven. The curves in Groups 3 and 4 had a more benign prognosis, and only three patients in these two groups had an arthrodesis. The pattern of the final curve was not always apparent at an early stage, and there was extension of the primary curve or development of secondary structural curves with progression. The chief prognostic feature at an early stage was the level of the most rotated vertebra at the apex of the primary curve, and the final pattern of deformity was defined by the level of the caudad neutral vertebra in the primary thoracic curve.

Analysis of Factors Related to Truncal Decompensation Following Cotrel-Dubousset Instrumentation

Spinal imbalance following Cotrel-Dubousset (CD) instrumentation for adolescent idiopathic scoliosis is a problem that is recognized with increasing frequency. We reviewed the clinical records and radiographs of 41 consecutive patients treated with CD instrumentation and attempted to identify factors related to postoperative worsening of spinal balance. Spinal balance was determined by the perpendicular distance of C7 to the center sacral line. Twenty-five were decompensated postoperatively. Sixteen patients had balance that was worse relative to the preoperative films. Eleven of 16 patients with worsened balance postoperative were King type III curves. Of 16 patients with worsened balance postoperatively, 13 had been fused to or below the lower neutral vertebra. Overcorrection of either the primary curve or the composite curve (sum of the measurable curves) relative to the preoperative bending films was not related to postoperative worsening of spinal balance. Fusion to the neutral or stable vertebra with CD instrumentation runs a high risk for postoperative worsening of spinal balance when the derotation maneuver is used. Consideration should be given to avoiding the derotation maneuver in larger type II curves in order to preserve spinal balance and avoid extension of instrumentation into the middle or lower lumbar spine.