Maree T. Izatt

Variability in Cobb angle measurements using reformatted computerized tomography scans.

Study Design. Survey of intraobserver and interobserver measurement variability. Objective. To assess the use of reformatted computerized tomography (CT) images for manual measurement of coronal Cobb angles in idiopathic scoliosis. Summary of Background Data. Cobb angle measurements in idiopathic scoliosis are traditionally made from standing radiographs, whereas CT is often used for assessment of vertebral rotation. Correlating Cobb angles from standing radiographs with vertebral rotations from supine CT is problematic because the geometry of the spine changes significantly from standing to supine positions, and 2 different imaging methods are involved. Methods. We assessed the use of reformatted thoracolumbar CT images for Cobb angle measurement. Preoperative CT of 12 patients with idiopathic scoliosis were used to generate reformatted coronal images. Five observers measured coronal Cobb angles on 3 occasions from each of the images. Intraobserver and interobserver variability associated with Cobb measurement from reformatted CT scans was assessed and compared with previous studies of measurement variability using plain radiographs. Results. For major curves, 95% confidence intervals for intraobserver and interobserver variability were ±6.6° and ±7.7°, respectively. For minor curves, the intervals were ±7.5° and ±8.2°, respectively. Intraobserver and interobserver technical error of measurement was 2.4° and 2.7°, with reliability coefficients of 88% and 84%, respectively. There was no correlation between measurement variability and curve severity. Conclusions. Reformatted CT images may be used for manual measurement of coronal Cobb angles in idiopathic scoliosis with similar variability to manual measurement of plain radiographs.

Recovery of pulmonary function following endoscopic anterior scoliosis correction: Evaluation at 3, 6, 12, and 24 months after surgery

Study Design. A series of patients with scoliosis undergoing endoscopic anterior instrumentation and fusion undertaking repeated pulmonary function assessments. Objective. To assess recovery of pulmonary function in the 2 years following endoscopic anterior scoliosis correction. Summary of Background Data. Recent studies have found that pulmonary function returns to preoperative levels 12–24 months following endoscopic anterior scoliosis correction, and a small improvement in forced expiratory volume (FEV1) has also been reported. Methods. A series of 44 patients with endoscopic anterior scoliosis correction had pulmonary function tests before surgery, and at 3, 6, 12, and 24 months after surgery. Forced vital capacity (FVC), FEV1, and total lung capacity (TLC) were measured. Nonparametric statistical analysis was used to investigate changes in pulmonary function between successive assessments. Results. Pulmonary function decreased by approximately 10% at 3 months after surgery. At 24 months after surgery, FVC and FEV1 recovered to 5% to 8% higher than preoperative levels, while TLC returned to preoperative levels. Statistically significant improvements in most pulmonary function values occurred between 3 and 6, and 6–12 months. Improvements in mean FVC, FEV1, and TLC continue between 12 and 24 months, although only the increase in absolute FVC for this time is statistically significant. Conclusions. Endoscopic anterior scoliosis surgery has no lasting negative effect on pulmonary function, and with prolonged follow-up, pulmonary capacity improves beyond preoperative levels.

Perioperative aspects of endoscopic anterior scoliosis surgery: The learning curve for a consecutive series of 100 patients

The reported benefits of endoscopic versus open scoliosis surgery include improved visualization, a muscle sparing approach, reduced pulmonary morbidity, reduced pain, and improved cosmesis. Some aspects of the surgical learning curve for this technically demanding method have been previously reported; however, improvements in other factors with increasing experience have not been quantified. This paper presents a series of 100 consecutive endoscopic anterior scoliosis corrections performed between April 2000 and February 2006. We report changes in the following perioperative factors with increasing experience; operative set-up time, operative time, x-ray irradiation time, number of instrumented levels, blood loss, intercostal catheter drainage, chest drain removal time, days in intensive care, days to mobilize, days in hospital, and early complications. Statistical comparisons were made between the first 20 (1 to 20), middle 20 (41 to 60), and last 20 (81 to 100) cases. Results showed statistically significant improvements and increased consistency in operative time, operative set-up time, x-ray irradiation time, blood loss, hospital stay, and mobilization time with experience. The complication rate was comparable to other recently published endoscopic studies. In the last 20 cases of the series, operative times had reduced to 35 minutes per level, x-ray irradiation times to 15 seconds per level, and blood loss to 38 mL per level. Most perioperative surgical factors therefore improve significantly with increasing experience in endoscopic anterior scoliosis correction.

A Prospective Assessment of SRS-24 Scores After Endoscopic Anterior Instrumentation for Scoliosis

Study Design. Prospective clinical case series. Objective. To evaluate the clinical outcome of anterior endoscopic instrumention for scoliosis using the SRS-24 questionnaire and to examine how these scores change over a 2-year follow-up period. Summary of Background Data. Anterior endoscopic instrumentation correction has several advantages compared with open procedures. However, the clinical results of this technique using a validated outcome measure have rarely been reported in the literature. Methods. A total of 83 consecutive patients underwent endoscopic anterior instrumentation performed at a single unit. Patients completed the SRS-24 questionnaire before surgery and at 3, 6, 12, and 24 months after surgery. The SRS-24 scores were compared between each of the follow-up intervals. Results. The pain, general self-image, and function from back condition domains improved after surgery (P < 0.05). Activity level significantly improved between 3 and 6 months, and both function domains improved between 6 and 12 months (P < 0.05). None of the domains increased significantly after 1 year. Conclusions. Endoscopic anterior instrumentation for scoliosis significantly improved pain, self-image, and function. The greatest improvement in function occurred between 6 and 12 months after surgery. The SRS-24 scores at 1 year from surgery may provide a good indicator of patient outcome in the long-term.

The Natural History of Scoliosis in Females with Rett Syndrome

Study Design. Population-based longitudinal observational study. Objective. To describe the prevalence of scoliosis in Rett syndrome, structural characteristics and progression, taking into account the influences of age, genotype, and ambulatory status. Summary of Background Data. Scoliosis is the most common orthopedic comorbidity in Rett syndrome yet very little is known about its natural history and influencing factors such as age, genotype, and ambulatory status. Methods. The infrastructure of the Australian Rett Syndrome Database was used to identify all cases with confirmed Rett syndrome in Australia and collect data on genotype and walking status. We identified radiological records and described the Cobb angle of each curve. Time to event analysis was used to estimate the median age of onset of scoliosis and the log-rank test to compare by mutation type. Latent class group analysis was used to identify groups for the trajectory of walking status over time and a multilevel linear model used to assess trajectories of scoliosis development by mutation type and walking status. We used a logistic regression model to estimate the probability of developing a scoliosis with a Cobb angle >60° at 16 years in relation to Cobb angle and walking status at 10 years of age. Results. The median age of scoliosis onset was 11 years with earliest onset in those with a p.Arg255* mutation or large deletion. Scoliosis was progressive for all mutation types except for those with the p.Arg306Cys mutation. Scoliosis progression was reduced when there was capacity to walk independently or with assistance. Cobb angle and walking ability at age 10 can be reliably used to identify those who will develop a very severe scoliosis by age 16. Conclusion. These data on prognosis of scoliosis inform clinical decision making about the likelihood of progression to very severe scoliosis and the need for surgical management. Level of Evidence: 4

The Use of Fulcrum Bending Radiographs in Anterior Thoracic Scoliosis Correction: A Consecutive Series of 90 Patients

Study Design. A prospective, consecutive series of 90 patients receiving fulcrum bending radiographs before endoscopic anterior scoliosis correction. Objective. To assess the effectiveness of fulcrum bending radiographs in predicting correction of the structural curve in anterior scoliosis surgery for a series of 90 consecutive patients. Summary of Background Data. The fulcrum bending radiograph is highly predictive of scoliosis curve correction for posterior instrumented fixation. However, its use has been questioned in relation to anterior scoliosis surgery due to the disc removal in anterior procedures. Methods. Fulcrum bending radiographs were performed before endoscopic anterior scoliosis correction following the protocol of Cheung and Luk. All patients received a single anterior rod and vertebral body screws using a standard compression technique. In all cases, cleared disc spaces were packed with mulched femoral head allograft. Surgical correction was assessed using 6- to 8-week postoperative standing radiographs. Paired t tests and least squares linear regression analysis were used to compare the preoperative major Cobb angle achieved on the fulcrum bending radiograph with the postoperative Cobb angles for each patient. Results. Mean (±SD) major curve correction rate was 60.1% ± 12.4%. Mean instrumented curve correction rate was 63.7% ± 11.7%. Mean fulcrum flexibility was 60.8% ± 15.5%. Mean fulcrum bending correction index was 104%. There was no statistically significant difference between the mean fulcrum bending radiograph Cobb angle (20.4 ± 9°) and the mean postoperative major Cobb angle for the structural curve (20.5 ± 7.1°). Conclusion. The results of this study show that fulcrum bending radiographs are predictive of surgical correction for anterior scoliosis surgery.

Secondary Curve Behavior in Lenke Type 1C Adolescent Idiopathic Scoliosis After Thoracoscopic Selective Anterior Thoracic Fusion

Study Design. Analysis of a case series of 24 patients with Lenke 1C adolescent idiopathic scoliosis (AIS) receiving selective thoracoscopic anterior scoliosis correction. Objective. To report the behavior of the compensatory lumbar curve in a group of patients with Lenke IC AIS after thoracoscopic anterior scoliosis correction and to compare the results of this study with previously published data. Summary of Background Data. Several prior studies have reported spontaneous lumbar curve correction for both anterior and posterior selective fusions in patients with Lenke 1C/King-Moe 2; however, to our knowledge no previous studies have reported outcomes of thoracoscopic anterior correction for this curve type. Methods. All patients with AIS with a curve classification of Lenke 1C and a minimum of 24-month follow-up were obtained from a consecutive series of 190 patients with AIS who underwent thoracoscopic anterior instrumented fusion. Cobb angles of the major curve, instrumented levels, compensatory lumbar curve, and T5–T12 kyphosis were recorded, as well as coronal spinal balance, T1 tilt angle, and shoulder balance. All radiographical parameters were measured before surgery and at 2, 6, 12, and 24 months after surgery. Results. Twenty-four female patients with right thoracic curves had a mean thoracic Cobb angle of 53.0° before surgery, decreasing to 24.9° 2 years after surgery. The mean lumbar compensatory Cobb angle was 43.5° before surgery, spontaneously correcting to 25.4° 2 years after surgery, indicating balance between the thoracic and lumbar scoliotic curves. The lumbar correction achieved (41.8%) compares favorably to previous studies. Conclusion. Selective thoracoscopic anterior fusion allows spontaneous lumbar curve correction and achieves coronal balance of main thoracic and compensatory lumbar curves, good cosmesis, and patient satisfaction. Correction and balance are maintained 24 months after surgery.

CT and radiographic analysis of sagittal profile changes following thoracoscopic anterior scoliosis surgery

BackgroundPrevious studies report an increase in thoracic kyphosis after anterior approaches and a flattening of sagittal contours following posterior approaches. Difficulties with measuring sagittal parameters on radiographs are avoided with reformatted sagittal CT reconstructions due to the superior endplate clarity afforded by this imaging modality.MethodsA prospective study of 30 Lenke 1 adolescent idiopathic scoliosis (AIS) patients receiving selective thoracoscopic anterior spinal fusion (TASF) was performed. Participants had ethically approved low dose CT scans at minimum 24 months after surgery in addition to their standard care following surgery. The change in sagittal contours on supine CT was compared to standing radiographic measurements of the same patients and with previous studies. Inter-observer variability was assessed as well as whether hypokyphotic and normokyphotic patient groups responded differently to the thoracoscopic anterior approach.ResultsMean T5-12 kyphosis Cobb angle increased by 11.8 degrees and lumbar lordosis increased by 5.9 degrees on standing radiographs two years after surgery. By comparison, CT measurements of kyphosis and lordosis increased by 12.3 degrees and 7.0 degrees respectively. 95% confidence intervals for inter-observer variability of sagittal contour measurements on supine CT ranged between 5-8 degrees. TASF had a slightly greater corrective effect on patients who were hypokyphotic before surgery compared with those who were normokyphotic.ConclusionsRestoration of sagittal profile is an important goal of scoliosis surgery, but reliable measurement with radiographs suffers from poor endplate clarity. TASF significantly improves thoracic kyphosis and lumbar lordosis while preserving proximal and distal junctional alignment in thoracic AIS patients. Supine CT allows greater endplate clarity for sagittal Cobb measurements and linear relationships were found between supine CT and standing radiographic measurements. In this study, improvements in sagittal kyphosis and lordosis following surgery were in agreement with prior anterior surgery studies, and add to the current evidence suggesting that anterior correction is more capable than posterior approaches of addressing the sagittal component of both the instrumented and adjacent non instrumented segments following surgical correction of progressive Lenke 1 idiopathic scoliosis.

Radiographic outcomes over time after endoscopic anterior scoliosis correction: a prospective series of 106 patients.

Study Design. A prospective, consecutive series of 106 patients receiving endoscopic anterior scoliosis correction. Objective. To analyze changes in radiographic parameters and rib hump in the 2 years after surgery. Summary of Background Data. Endoscopic anterior scoliosis correction is a level sparing approach and therefore, it is important to assess the amount of decompensation which occurs after surgery. Methods. All patients received a single anterior rod and vertebral body screws using a standard compression technique. Cleared disc spaces were packed with either mulched femoral head allograft or rib head/iliac crest autograft. Radiographic parameters (major, instrumented, minor Cobb, T5-T12 kyphosis) and rib hump were measured at 2, 6, 12, and 24 months after surgery. Paired t tests and Wilcoxon signed ranks tests were used to assess the statistical significant of changes between adjacent time intervals. Results. Mean loss of major curve correction from 2 to 24 months after surgery was 4°. Mean loss of rib hump correction was 1.4°. Mean sagittal kyphosis increased from 27° at 2 months to 30.6° at 24 months. Rod fractures and screw-related complications resulted in several degrees less correction than patients without complications, but overall there was no clinically significant decompensation after complications. Conclusion. There are small changes in deformity measures after endoscopic anterior scoliosis surgery, which are statistically significant but not clinically significant.

Surgical fusion of early onset severe scoliosis increases survival in Rett syndrome: a cohort study.

Scoliosis is a common comorbidity in Rett syndrome and spinal fusion may be recommended if severe. We investigated the impact of spinal fusion on survival and risk of severe lower respiratory tract infection in Rett syndrome.