Convex-concave and anterior-posterior spinal length discrepancies in adolescent idiopathic scoliosis with major right thoracic curves versus matched controls.

PURPOSE: The apical deformation in adolescent idiopathic scoliosis (AIS) is a combination of rotation, coronal deviation and passive anterior lengthening of the spine. In AIS surgery, posterior-concave lengthening or anterior-convex shortening can be part of the corrective maneuver, as determined by the individual surgeon's technique. The magnitude of convex-concave and anterior-posterior length discrepancies, and how this needs to be modified to restore optimal spinal harmony, remains unknown. METHODS: CT-scans of 80 pre-operative AIS patients with right convex primary thoracic curves were sex- and age-matched to 80 healthy controls. The spinal length parameters of the main thoracic curves were compared to corresponding levels in controls. Vertebral body endplates and posterior elements were semi-automatically segmented to determine the length of the concave and convex side of the anterior column and along the posterior pedicle screw entry points while taking the 3D-orientation of each individual vertebra into account. RESULTS: The main thoracic curves showed anterior lengthening with a mean anterior-posterior length discrepancy of + 3 ± 6%, compared to a kyphosis of - 6 ± 3% in controls (p < 0.01). In AIS, the convex side was 20 ± 7% longer than concave (0 ± 1% in controls; p < 0.01). The anterior and posterior concavity were 7 and 22 mm shorter, respectively, while the anterior and posterior convexity were 21 and 8 mm longer compared to the controls. CONCLUSIONS: In thoracic AIS, the concave shortening is more excessive than the convex lengthening. To restore spinal harmony, the posterior concavity should be elongated while allowing for some shortening of the posterior convexity.

Cross-validation of ultrasound imaging in adolescent idiopathic scoliosis.

PURPOSE: Adolescent idiopathic scoliosis (AIS) patients are exposed to 9-10 times more radiation and a fivefold increased lifetime cancer risk. Radiation-free imaging alternatives are needed. Ultrasound imaging of spinal curvature was shown to be accurate, however, systematically underestimating the Cobb angle. The purpose of this study is to create and cross-validate an equation that calculates the expected Cobb angle using ultrasound spinal measurements of AIS patients. METHODS: Seventy AIS patients with upright radiography and spinal ultrasound were split randomly in a 4:1 ratio to the equation creation (n = 54) or validation (n = 16) group. Ultrasound angles based on the spinous processes shadows were measured automatically by the ultrasound system (Scolioscan, Telefield, Hong Kong). For thoracic and lumbar curves separately, the equation: expected Cobb angle = regression coefficient × ultrasound angle, was created and subsequently cross-validated in the validation group. RESULTS: Linear regression analysis between ultrasound angles and radiographic Cobb angles (thoracic: R2 = 0.968, lumbar: R2 = 0.923, p < 0.001) in the creation group resulted in the equations: thoracic Cobb angle = 1.43 × ultrasound angle and lumbar Cobb angle = 1.23 × ultrasound angle. With these equations, expected Cobb angles in the validation group were calculated and showed an excellent correlation with the radiographic Cobb angles (thoracic: R2 = 0.959, lumbar: R2 = 0.936, p < 0.001). The mean absolute differences were 6.5°-7.3°. Bland-Altman plots showed good accuracy and no proportional bias. CONCLUSION: The equations from ultrasound measurements to Cobb angles were valid and accurate. This supports the implementation of ultrasound imaging, possibly leading to less frequent radiography and reducing ionizing radiation in AIS patients.

A computed tomography-based spatial reference for pedicle screw placement in adolescent idiopathic scoliosis.

STUDY DESIGN: Cross-sectional. OBJECTIVES: To determine semiautomatically the 3D position of the pedicle axis in operative adolescent idiopathic scoliosis (AIS) patients relative to the operating table and the lamina, as orientation for pedicle screw placement for better understanding and reference of spine surgeons. Pedicle morphology is well described as the angle between the convex and concave pedicle. However, the pedicle angle as relative to the neutral anterior-posterior axis or to an easy-to-use intravertebral landmark, remained unknown. METHODS: The pedicles of the apex and two adjacent vertebrae cranial and caudal to the apex of 86 right-sided primary thoracic AIS curves were evaluated using semiautomatic 3D software on high-resolution CT scans, in the same prone position as during surgery. Pedicle vectors were obtained and calculated as transverse and sagittal angles, as relative to the neutral axis (corresponding with an axis perpendicular to the operating table) and to an axis perpendicular to the lamina. RESULTS: At the apex, the mean convex and concave transverse pedicle angles were 14.3º (95% confidence interval [95% CI]: 12.0-16.6) and 30.4º (95% CI: 28.1-32.8) to the right. The angles decreased toward the adjacent levels cranial and caudal to the apex (p < 0.001) and linearly increased with a higher Cobb angle (r ≥ 0.472; p < 0.001). The mean transverse pedicle-lamina angles, sagittal pedicle angles and the sagittal pedicle-lamina angles differed along the curve as well (p < 0.001). CONCLUSIONS: Pedicle angulation differs between convex and concave and depends on the position of the vertebra relative to the apex, as well as the curve severity. The transverse and sagittal pedicle angles, as relative to the operating table and laminae, could provide useful reference for better understanding of the distorted 3D morphology, and the angles, as given in this study, could serve as an approximate guideline for the expected direction of the pedicle screw. LEVEL OF EVIDENCE: Level IV.

The role of 22q11.2 deletion syndrome in the relationship between congenital heart disease and scoliosis.

BACKGROUND CONTEXT: For over four decades, clinicians and researchers have suggested a relationship between congenital heart disease (CHD) and scoliosis, attributed to either the disease itself or to the long-term effects of cardiac surgery on the immature thoracic cage. However, no study has yet accounted for 22q11.2 deletion syndrome (22q11.2DS), the second most common cause of CHD after Down syndrome. 22q11.2DS has a scoliosis risk of 50%, but within 22q11.2DS a previous report found no significant association between scoliosis and CHD. We, therefore, hypothesized that scoliosis within a CHD cohort would be related to an underlying 22q11.2 deletion. PURPOSE: To determine the prevalence of scoliosis in CHD patients with and without 22q11.2DS. STUDY DESIGN/SETTING: Cross-sectional. PATIENT SAMPLE: A well-characterized existing database of 315 adults with CHD (primarily tetralogy of Fallot), with (n=86) and without (n=229) 22q11.2DS, matched by sex and CHD severity, and excluding other known syndromic diagnoses. We compared the scoliosis prevalence of patients with 22q11.2DS and CHD patients to the prevalence of scoliosis in a cohort of adults with 22q11.2DS without CHD based on medical records. OUTCOME MEASURES: Presence of scoliosis (Cobb angle ≥10°). METHODS: We systematically determined the presence of scoliosis in all included patients using chest radiographs, blind to genetic diagnosis. Besides 22q11.2DS, we analyzed other suspected risk factors for scoliosis using a regression model: thoracotomy before the age of 12 years, severe CHD type and sex. RESULTS: The prevalence of scoliosis in adults with CHD and 22q11.2DS (n=46, 53.5%) was significantly greater than in those without 22q11.2DS (n=18, 7.9%, p<.0001). The presence of a 22q11.2 deletion (odds ratio [OR] 25.4, 95% confidence interval [95% CI] 11.2-57.4, p<.0001), a history of thoracotomy before the age of 12 years (OR 3.5, 95% CI 1.6-8.1, p=.0027) and most complex CHD class (OR 2.3, 95% CI 1.1-4.7, p=.0196), but not sex, were significant independent predictors of scoliosis. In the 22q11.2DS group, a right-sided aortic arch was associated with a left thoracic scoliotic curve (p=.036). CONCLUSIONS: The prevalence of scoliosis in those with CHD but without a 22q11.2 deletion approximates that of the general population. However, in the CHD population with a 22q11.2 deletion, the prevalence of scoliosis approximates that of others with 22q11.2DS. The pediatric surgical approach and severity of CHD were weaker independent contributors as compared to the 22q11.2 deletion. The results support the importance of a genetic diagnosis of 22q11.2DS to the risk of developing scoliosis in individuals with CHD. The 22q11.2 deletion may represent a common etiopathogenetic pathway for both CHD and scoliosis, possibly involving early laterality mechanisms.