Three-dimensional vertebral shape changes confirm growth modulation after anterior vertebral body tethering for idiopathic scoliosis.

PURPOSE: To evaluate three-dimensional (3D) vertebra and disk shape changes over 2 years following anterior vertebral body tether (AVBT) placement in patients with idiopathic scoliosis (IS). METHODS: Patients with right thoracic IS treated with AVBT were retrospectively evaluated. 3D reconstructions were created from biplanar radiographs. Vertebral body and disk height (anterior, posterior, left and right) and shape (wedging angle) were recorded over the three apical segments in the local vertebral reference planes. Changes in height and wedging were measured through 2 years postoperatively. Change in patient height was correlated with changes in the spine dimensions. RESULTS: Forty-nine patients (Risser 0-3, Sanders 2-4) were included. The mean age was 12.2 ± 1.4 years (range 8-14). The mean coronal curve was 51 ± 10° preoperatively, 31 ± 9° at first postoperative time point and 27 ± 11° at 2-year follow-up (p < 0.001). The mean patient height increased 8 cm by 2 years (p < 0.001). The left side of the spine (vertebra + disc) grew in height by 2.2 mm/level versus 0.7 mm/level on the right side (p < 0.001). This differential growth was composed of 0.5 mm/vertebral level and 1.0 mm/disk level. Evaluation of the change in disk heights showed significantly decreased height anteriorly (- 0.4 mm), posteriorly (- 0.3 mm) and on the right (- 0.5 mm) from FE to 2 years. Coronal wedging reduced 2.3°/level with 1.1°/vertebral level change and 1.2°/disk level. There was no differential growth in the sagittal plane (anterior/posterior height). Patient height change moderately correlated with 3D measures of vertebra + disk shape changes. CONCLUSIONS: Three-dimensional analysis confirms AVBT in skeletally immature patients results in asymmetric growth of the apical spine segments. The left (untethered) side length increased more than 3 × than the right (tethered) side length with differential effects observed within the vertebral bodies and disks, each correlating with overall patient height change.

The Effect of Time and Fusion Length on Motion of the Unfused Lumbar Segments in Adolescent Idiopathic Scoliosis.

OBJECTIVE: The purpose of this study was to assess L4-S1 inter-vertebral coronal motion of the unfused distal segments of the spine in patients with adolescent idiopathic scoliosis (AIS) after instrumented fusion with regards to postoperative time and fusion length, independently. METHODS: Coronal motion was assessed by standardized radiographs acquired in maximum right and left bending positions. The intervertebral angles were measured via digital radiographic measuring software and the motion from the levels of L4-S1 was summed. The entire cohort was included to evaluate the effect of follow-up time on residual motion. Patients were grouped into early (<5 years), midterm (5-10 years), and long-term (>10 years) follow-up groups. A subset of patients (n = 35) with a primary thoracic curve and a nonstructural modifier type "C" lumbar curve were grouped as either selective fusion (lowest instrumented vertebra [LIV] of L1 and above) or longer fusion (LIV of L2 and below) and effect on motion was evaluated. RESULTS: The data for 259 patients are included. The distal residual unfused motion (from L4 to S1) remained unchanged across early, midterm, to long-term follow-up. In the selective fusion subset of patients, a significant increase in motion from L4 to S1 was seen in the patients who were fused long versus the selectively fused patients, irrespective of length of follow-up time. CONCLUSION: Motion in the unfused distal lumbar segments did not vary within the >10-year follow-up period. However, in patients with a primary thoracic curve and a nonstructural lumbar curve, the choice to fuse longer versus shorter may have significant consequences. The summed motion from L4 to S1 is 50% greater in patients fused longer compared with those patients with a selective fusion, in which postoperative motion is shared by more unfused segments. The implications of this focal increased motion are unknown, and further research is warranted but can be surmised.

Computer-Generated, Three-Dimensional Spine Model From Biplanar Radiographs: A Validity Study in Idiopathic Scoliosis Curves Greater Than 50 Degrees.

STUDY DESIGN: Reproducibility study of SterEOS 3-dimensional (3D) software in large, idiopathic scoliosis (IS) spinal curves. OBJECTIVE: To determine the accuracy and reproducibility of various 3D, software-generated radiographic measurements acquired from a 2-dimensional (2D) imaging system. SUMMARY OF BACKGROUND DATA: SterEOS software allows a user to reconstruct a 3D spinal model from an upright, biplanar, low-dose, X-ray system. The validity and internal consistency of this system have not been tested in large IS curves. METHODS: EOS images from 30 IS patients with curves greater than 50° were collected for analysis. Three observers blinded to the study protocol conducted repeated, randomized, manual 2D measurements, and 3D software generated measurements from biplanar images acquired from an EOS Imaging system. Three-dimensional measurements were repeated using both the Full 3D and Fast 3D guided processes. A total of 180 (120 3D and 60 2D) sets of measurements were obtained of coronal (Cobb angle) and sagittal (T1-T12 and T4-T12 kyphosis; L1-S1 and L1-L5; and pelvic tilt, pelvic incidence, and sacral slope) parameters. Intra-class correlation coefficients were compared, as were the calculated differences in values generated by SterEOS 3D software and manual 2D measurements. The 95% confidence intervals of the mean differences in measures were calculated as an estimate of reproducibility. RESULTS: Average intra-class correlation coefficients were excellent: 0.97, 0.97, and 0.93 for Full 3D, Fast 3D, and 2D measures, respectively (p = .11). Measurement errors for some sagittal measures were significantly lower with the 3D techniques. Both the Full 3D and Fast 3D techniques provided consistent measurements of axial plane vertebral rotation. CONCLUSIONS: SterEOS 3D reconstruction spine software creates reproducible measurements in all 3 planes of deformity in curves greater than 50°. Advancements in 3D scoliosis imaging are expected to improve our understanding and treatment of idiopathic scoliosis.

Surgical Site Infection in Adolescent Idiopathic Scoliosis Surgery.

OBJECTIVE: To define the current rate of postoperative surgical site infections (SSIs) in a large prospective series of surgical adolescent idiopathic scoliosis (AIS) cases. METHODS: A multicenter, prospective database of patients who underwent surgical correction of AIS was reviewed. Early SSIs were defined as occurring within 90 days after the index operation, as per the Center for Disease Control's definitions. Treatment and outcome information on all confirmed SSIs was compiled. Variables associated with the occurrence of an SSI were evaluated. RESULTS: Of the 1,757 patients analyzed, 28 developed an SSI within the first 90 days postoperatively (1.6%). Patient weight was associated with SSI (p < .001). There was a trend in correlation with the number of levels fused (p = .07) and blood loss as a percentage of blood volume (p = .07) and the incidence of SSI. There was no correlation with any other variables. There was variation in the rate of SSI among the 9 centers, ranging from 0.6% to 4.4% (p = .27). Of the 28 infections, 26 resolved with surgery and/or antibiotics and did not need implant removal. Only 2 patients had late pain. In addition to the 28 confirmed SSIs, there were an additional 68 other wound issues (4.2%) that did not meet the Center for Disease Control criteria for an SSI. CONCLUSIONS: Early SSIs after AIS surgery occurred at a rate of 1.6%. The federal mandate to eliminate SSI and the proposed lack of reimbursement for its treatment may change clinical practice, and these data provide average SSI rates across multiple centers for future comparison. Investigations into variations in practice between centers might yield areas for potential improvement in SSI for AIS patients. Fortunately, 92% of patients were able to retain their implants and were free of pain at final follow-up.

The association of patient characteristics and spinal curve parameters with Lenke classification types.

STUDY DESIGN: Retrospective review. OBJECTIVE: To determine the association of patient characteristics and spinal curve parameters with Lenke curve types. SUMMARY OF BACKGROUND DATA: The Lenke curve classification may be used for surgical planning and clinical research. METHODS: We retrospectively reviewed the records of 1912 patients with adolescent idiopathic scoliosis who underwent initial surgery at 21 years of age or younger; collected data on patient's age, patient's sex, primary curve magnitude (<50°, 50°-75°, and .75°), and Scoliosis Research Society (SRS) outcomes questionnaire (SRS-22) score; and compared that data by Lenke curve type. Analysis of variance and χ tests were used as appropriate (significance level, P ≤ 0.005). RESULTS.: Lenke types vary by sex: male patients had more major thoracic (types 1-4) than major thoracolumbar/lumbar (types 5 and 6) curves, fewer lumbar C-modifiers (32% vs. 44%), and less apical lumbar translation (1.1 vs. 1.7 cm). Lenke types vary by frequency: the most common type was 1 (50%); the least common, 4 (4%). Lenke types vary by magnitude: type 4 had the greatest percentage of large curves (52% of curves .75°), most smaller curves were types 1 and 5, and type 4 had the largest mean magnitude (78° ± 17°). Lenke types vary by patient age: type 5 curves occurred in the oldest patients (average age at surgery: 15.4 ± 2.2 vs. 14.3 ± 14.6 years for all others) despite having the lowest mean magnitude (P = 0.001); curve size was negatively correlated with age at surgery (r = -0.16, P = 0.001). Lenke types vary by patient self-image: patients with type 4 curves had lower preoperative SRS outcome scores for self-image than did patients with type 1 curves (P = 0.005). CONCLUSION: Lenke types vary by sex, frequency magnitude, patient age, and patient self-image, which should be considered in designing studies.

Postoperative segmental motion of the unfused spine distal to the fusion in 100 patients with adolescent idiopathic scoliosis.

STUDY DESIGN: A cross-sectional study. OBJECTIVE: The purpose of this study was to assess intervertebral segmental and cumulative motion in the distal unfused segments of the spine in patients with adolescent idiopathic scoliosis after instrumentation as a function of the lowest instrumented level. SUMMARY OF BACKGROUND DATA: The implications of hyper- or hypomobility in the unfused segments of the spine after instrumentation are poorly understood. There is little research on changes in functional movement capabilities of the spine after thoracolumbar spinal fusion. METHODS: Patients were prospectively offered inclusion into this institutional review board-approved cross-sectional study at their routine 2-, 3-, 4-, or 5-year postoperative visits at 1 of the 5 participating centers. Motion was assessed by standardized radiographs acquired in maximum right, left and forwarding bending positions. The intervertebral angles were measured via digital radiographic measuring software at each level from T12 to S1. The relationship of the vertebral segmental motion for each interspace to the lowest instrumented vertebrae was evaluated with an analysis of variance. The relationship between the cumulative preserved motion and each domain of the Scoliosis Research Society questionnaire were evaluated using a Pearson correlation coefficient. RESULTS: The data for 100 patients are included. The lowest instrumented vertebrae ranged from T10 to L4. In lateral bending, an association was detected between the lowest fused vertebral level and the degree of motion at the distal unfused segments. With a more distal instrumented vertebrae, there was significantly greater L2-L3, L3-L4, and L4-L5 segment motion (P = 0.002, 0.009, and 0.001, respectively). A similar trend was noticed at L5-S1 level. In addition, the summed motion from L3 to S1 also increased with a more distal fusion (P = 0.001). Similar results were not found in forward bending. None of the domains of the Scoliosis Research Society questionnaire correlated with the preserved L3-S1 motion. CONCLUSION: In a group of postoperative patients with adolescent idiopathic scoliosis, evaluation of the distal unfused intervertebral motion showed that preservation of vertebral motion segments allowed greater distribution of functional motion across more levels. With each distal fusion level, motion was significantly increased at the L2-L3, L3-L4, and L4-L5 segmental levels in lateral bending. The relationship between the increased motion and subsequent disc degeneration with a more distal fusion is unknown, but suspected.

Adolescent idiopathic scoliosis patients report increased pain at five years compared with two years after surgical treatment.

STUDY DESIGN: A multicenter study of changes in Scoliosis Research Society (SRS) outcome measures after surgical treatment of adolescent idiopathic scoliosis (AIS). OBJECTIVE: To evaluate changes in patient determined outcome measures between 2 and 5 years after AIS surgery. SUMMARY OF BACKGROUND DATA: Current surgical procedures have been shown to improve subjective measures in patients with AIS. At 2-year follow-up, AIS patients reported significant improvement in all 4 preoperative domains of the SRS questionnaire. In addition, the major Cobb angle was shown to be negatively correlated with preoperative scores in the pain, general self-image, and general function domains. Five-year SRS scores have not been evaluated previously. METHODS: A multicenter, prospectively generated database was used to obtain perioperative, radiographic, and SRS-24 outcomes data. The inclusion criteria were: a diagnosis of AIS, surgical treatment (anterior, posterior, or combined), a comprehensive set of radiographic measures, and completed preoperative, 2-year, and 5-year SRS questionnaires. Repeated measures analysis of variance was used to compare changes in patient responses for each of the 7 outcome domains. Univariate analysis of variance was used to compare the change in pain score at 5 years to the level of the lowest instrumented vertebrae and surgical approach. A correlation analysis was used to determine the association between changes in any of the radiographic variables and changes in SRS scores. The data were checked for normality and equal variances, and the level of significance was set at P < 0.01. RESULTS: Forty-nine patients (42 women, 7 men; 14.2 +/- 2.1 year old; 5.4 +/- 0.6 years follow-up) met the inclusion criteria for this study. Thirty-seven of 49 (76%) of these patients underwent an open or thoracoscopic anterior procedure. SRS-24 scores improved significantly in 3 of the 4 preoperative domains at the 2-year visit. At 5 years postop, a statistically significant decrease in the pain score (4.2 +/- 0.6 to 3.9 +/- 0.9, P = 0.003) and a trend toward worsening scores in 4 other domains was observed; however, Patient Satisfaction scores remained unchanged. Lowest instrumented vertebrae and surgical approach could not be correlated to changes in the pain score. In addition, no correlation was found between changes in any of the 21 radiographic measures evaluated and changes in SRS scores. CONCLUSION: There was a statistically significant increase in reported pain from 2 to 5 years after surgical treatment; however, the etiology of worsening pain scores could not be elucidated. Given continued patient satisfaction, the clinical relevance of this small reduction remains unknown. Nevertheless, this observation deserves further evaluation and must be considered in relation to the natural history of this disease.

Does obesity affect surgical outcomes in adolescent idiopathic scoliosis?

STUDY DESIGN: A retrospective review of surgical outcomes in adolescents with idiopathic scoliosis. OBJECTIVE: To determine if an association exists between body mass and surgical outcomes in adolescent idiopathic scoliosis (AIS). SUMMARY OF BACKGROUND DATA: Obesity has reached epidemic proportions globally. In adults, obesity increases the likelihood of developing multiple medical comorbidities and has been associated with an increased incidence of perioperative complications. The effect of obesity on surgical outcomes in the treatment of AIS patients has not been studied previously. METHODS: Radiographic measures, perioperative data, and Scoliosis Research Society Outcomes scores were collected on surgically treated AIS patients. The body mass index (BMI) was calculated for each patient and normalized to sex and age (BMI %). Analysis of variance was used to identify differences between healthy weight (BMI % <85) and overweight patients (BMI % >or=85). The data were checked for normality and equal variances, and the level of significance was set at 0.01. RESULTS: Two hundred forty-one patients (204 women, 37 men; 14.3 +/- 2.0 years) with a minimum of 2-year follow-up met the inclusion criteria for this study. The average BMI (kg/m2) was 20.7 +/- 3.7 (BMI % average: 54.5, range: 1-99). No significant differences were found between the overweight (n = 48) and healthy weight (n = 193) patients with regards to surgical time, estimated blood loss, major Cobb percent correction, maintenance of correction, rate of implant failure, pseudarthrosis, and surgical revision. However, the preoperative thoracic kyphosis was significantly greater in the overweight group (27.0 degrees +/- 12.6 degrees) compared with the healthy weight patients (21.8 degrees +/- 12.5 degrees) (P = 0.004). CONCLUSION: Overweight adolescents (BMI % >or=85) had a greater thoracic kyphosis before surgery compared with their healthy weight peers. Body mass, however, did not affect the ability to achieve coronal or sagittal scoliotic deformity correction, and did not increase perioperative morbidity or mortality. These findings were either influenced by the small sample size of this cohort, or because the comorbidities responsible for increased perioperative complications in adults, had not yet developed in this adolescent population.

The relationship between thoracic hyperkyphosis and the Scoliosis Research Society outcomes instrument.

STUDY DESIGN: A retrospective chart review and radiographic analysis. OBJECTIVE: To evaluate the association between thoracic hyperkyphosis and patient quality of life measures as determined by the Scoliosis Research Society (SRS) outcomes instrument. SUMMARY OF BACKGROUND DATA: Although validated outcomes questionnaires (e.g., Pediatric Outcomes Data Collection Instrument and SRS) have been used to evaluate patients with scoliosis, there has been little written about the effects of sagittal plane alignment on these functional outcome measurements. METHODS: Data from the SRS outcomes instrument were collected from patients with thoracic hyperkyphosis as well as those with normal spinal alignment. A total of 50 patients with thoracic kyphosis >or=45 degrees were compared with 50 normal patients with thoracic kyphosis <45 degrees . Correlation analysis was performed to identify significant relationships between the magnitude of the major kyphotic curve and the 4 SRS outcome questionnaire domains (Total Pain, General Self-Image, General Function, and Activity). Lower SRS scores indicate an increase in symptoms. RESULTS: The average age of the subjects was 14 +/- 4 years (range, 8-18 years). The thoracic kyphosis varied between 11 degrees and 95 degrees for all subjects. Significant negative correlations were found between kyphosis magnitude and the total pain, general self-image, general function, overall level of activity, and total SRS scores (P < 0.0001). Of the 4 domains, self-image had the highest correlation with kyphosis magnitude while activity had the lowest. CONCLUSION: These findings indicate that higher kyphosis magnitudes were associated with increased pain, lower self-image, and decreased function and activity. Patients with thoracic hyperkyphosis were significantly more symptomatic than normal subjects in all domains. The r values for this analysis of kyphosis (0.40-0.66), in fact were substantially greater than those previously reported for scoliosis magnitude versus SRS Questionnaire scores (0.16-0.26), suggesting this instrument may be even better suited for the evaluation of hyperkyphosis patients.

Outcomes of surgical treatment in male versus female adolescent idiopathic scoliosis patients.

STUDY DESIGN: This research was part of a multicenter study of the surgical treatment of adolescent idiopathic scoliosis (AIS). OBJECTIVE: To compare the radiographic and perioperative surgical treatment outcomes of male AIS patients with female AIS patients. SUMMARY OF BACKGROUND DATA: The results of treatment in male patients with idiopathic scoliosis have not been widely reported. Only 1 study has evaluated the differences in operative treatment outcomes between male and female patients with AIS. METHODS: Data were collected for patients who met the indications for surgical intervention at 8 separate institutions. Radiographic, perioperative, and pulmonary function variables for male and female AIS patients treated surgically were analyzed. A univariate analysis of variance with the alpha level adjusted to P < or = 0.01 was used. RESULTS: The data for 547 (449 females and 98 males) patients were included in this analysis. Posterior instrumentation (vs. anterior instrumentation) was performed slightly more often in males than females (51% vs. 44%, respectively). The preoperative primary curve magnitude was similar for both genders, but flexibility was less in males (44% vs. 49%; P = 0.01). Postoperative percent correction and the ratio of percent correction to preoperative flexibility were both similar in males versus females. Analysis of the perioperative variables yielded that estimated blood loss was higher in males than females (1342 vs. 898 cc, respectively; P = 0.001). Males reported greater pain on postoperative day 1 (6.1 vs. 5.4; P = 0.01), however, conversion to oral pain medication was similar for both. Preoperative and postoperative pulmonary function was similar for both genders. CONCLUSION: Male AIS patients had slightly more rigid primary curves compared to females but a similar degree of postoperative scoliosis correction. Differences in the preoperative status and perioperative course did not compromise the outcomes of surgical treatment as in all other measures; the results were comparable between the genders.