Do radiographic parameters correlate with clinical outcomes in adolescent idiopathic scoliosis?

STUDY DESIGN: A radiographic assessment has been developed to include coronal, sagittal, and axial parameters. OBJECTIVE: To determine the correlation of postoperative radiographic results and percentage postoperative radiographic improvement with patient clinical self-assessment. SUMMARY OF BACKGROUND DATA: With the increasing interest in outcome studies, the authors wanted to determine whether Scoliosis Research Society clinical questionnaire results would correlate with objective radiographic improvement. METHODS: Inclusion criteria: adolescent idiopathic scoliosis treated with anterior or posterior instrumentation, a solid fusion, minimum 2-year follow-up, and a completed postoperative Scoliosis Research Society questionnaire. Seventy-eight patients met the criteria. Measurements included in the radiographic score: Cobb angles of the coronal curve, C7 to the center sacral vertical line, apical translation, apical vertebral rotation, T1 rib angle, end-instrumented vertebrae angulation, angulation of the disc below the end-instrumented vertebra, and curve type. Sagittal measurements included T2-T12, T5-T12, T2-T5, T12-L2, and L1-S1. RESULTS: The preoperative radiographic score of these 78 patients was mean 60.1 +/- 9.7 (range 41-88, maximum radiographic score, 100). The 2-year postoperative radiographic score was mean 83.8 +/- 8.8 (range, 65-100). The median Scoliosis Research Society questionnaire score was 98 +/- 12.3 (range, 58-116, maximum score, 125, showing that the patient is highly satisfied and asymptomatic). The postoperative radiographic score versus the questionnaire score showed a Spearman rank correlation of 0.04 (P = 0.68, little or no correlation throughout). Percentage improvement of the radiographic score versus the questionnaire score showed a Spearman rank correlation of 0.1 (P = 0.38, little or no correlation throughout). CONCLUSION: In this initial group of patients, the radiographic assessment shows a significant improvement between preoperative and 2-year postoperative scores. However, little correlation between the radiographic assessment and the questionnaire scores was found in this adolescent population, suggesting that separate analyses of radiographic and clinical outcome data are required when evaluating results of postoperative scoliosis surgery.     

Rib length asymmetry in thoracic adolescent idiopathic scoliosis: is it primary or secondary?

The development of scoliosis in animal models after inducing asymmetric rib growth suggests the possible role of asymmetric rib growth in the etiopathogenesis of adolescent idiopathic scoliosis (AIS). Asymmetric rib length is well recognized in idiopathic scoliosis; however, whether this rib asymmetry is primary or secondary has not been clearly documented. The objectives of this study were to investigate any rib length asymmetry in patients with AIS and compare those with scoliosis with syringomyelia (SS) with the intention of elucidating any relationship between rib growth and pathogenesis of AIS. Forty-eight AIS and 29 SS with apical vertebrae located between T7 and T9 were recruited. The average age was 13.5 ± 2.3 versus 12.5 ± 3.4 years, and the average Cobb angle of thoracic curve was 43.3° ± 16.4° versus 45.6° ± 22.6° in patients with AIS or SS, respectively. The length of all ribs was measured from the tip of costal head to the end of the same rib by built-in software on spiral computed tomography. At the levels of the apical vertebrae, the vertebrae above and below the apex, the mean discrepancy in rib length (concave minus convex rib) was 7, 4 and 7 mm, respectively, in AIS group (p < 0.01), and 6, 5 and 7 mm in SS group, respectively (p < 0.01). The rib length discrepancy between concave and convex sides was significantly correlated with the magnitude of the Cobb angle of thoracic curve in both AIS and SS groups (p < 0.01). Similar findings of the asymmetry of rib length in both AIS and SS patients pointed strongly to the fact that the rib length asymmetry in apical region is most likely secondary to the scoliosis deformity rather than playing a primary role in the etiopathogenesis.     

Pedicle morphology in thoracic adolescent idiopathic scoliosis: is pedicle fixation an anatomically viable technique?

STUDY DESIGN: A radiographic study of thoracic pedicle anatomy in a group of adolescent idiopathic scoliosis (AIS) patients. OBJECTIVE: To investigate the anatomic constraints of the thoracic pedicles and determine whether the local anatomy would routinely allow pedicle screw insertion at every level. SUMMARY OF BACKGROUND DATA: In spite of the clinical successes reported with limited thoracic pedicle screw-rod constructs for thoracic AIS, controversy exists as to the safety of this technique. MATERIAL AND METHODS: Twenty-nine patients with right thoracic AIS underwent preoperative thoracic CT scans and plain radiographs. Anatomic parameters were measured from T1 to T12. RESULTS: Information on 512 pedicles was obtained. The transverse width of the pedicles from T1 through T12 ranged from 4.6-8.25 mm. The medial pedicle to lateral rib wall transverse width from T1 through T2 ranged from 12.6 to 17.9 mm. Measured dimensions from the CT scans showed the actual pedicle width to be 1-2 mm larger than would have been predicted from the plain radiographs. Age, Risser grade, curve magnitude, and the amount of segmental axial rotation did not correlate with the morphology or size of the thoracic pedicles investigated. In no case would pedicle morphology have precluded the passage of a pedicle screw. CONCLUSION: Based on the data identified in this group of adolescent patients, it is reasonable to consider pedicle screw insertion at most levels and pedicle-rib fixation at all levels of the thoracic spine during the treatment of thoracic AIS.     

Segmental vs non-segmental thoracic pedicle screws constructs in adolescent idiopathic scoliosis: is there any implant alloy effect?

Purpose

The aim of this study is to understand how many anchor sites are necessary to obtain maximum posterior correction of idiopathic scoliotic curve and if the alloy of instrumentation, stainless steel or titanium, may have a role in the percent of scoliosis correction.

Methods

We reviewed 143 consecutive patients, affected by AIS (Lenke 1–2), who underwent a posterior spinal fusion with pedicle screw-only instrumentation between 2002 and 2005. According to the implant density and alloy used we divided the cohort in four groups.

Results

All 143 patients were reviewed at an average follow-up of 7, 2 years, the overall final main thoracic curve correction averaged 61.4%, whereas the implant density within the major curve averaged 71%. A significant correlation was observed between final% MT correction and preoperative MT flexibility and implant density.

Conclusions

When stainless steel instrumentation is used non-segmental pedicle screw constructs seem to be equally effective as segmental instrumentations in obtaining satisfactory results in patients with main thoracic AIS. When the implant alloy used is titanium one, an implant density of ≥60% should be guaranteed to achieve similar results.

     

Does anterior shoulder balance in adolescent idiopathic scoliosis correlate with posterior shoulder balance clinically and radiographically?

Purpose

Patients with adolescent idiopathic scoliosis (AIS) often present with a disfiguring shoulder imbalance. Shoulder balance (Sh.B) is of significant importance to the patient’s self-perception. Previous studies have correlated Sh.B with respect to only the clinical posterior view correlated with radiographs. It is important, however, to address Sh.B with respect to anterior view of the patients’ shoulders as if patients were viewing in a mirror. In this study, we evaluated the anterior Sh.B and correlated it with posterior Sh.B clinically and radiographically in Lenke type 1 and 2 curves.

Method

An online scoliosis database was queried to identify 74 AIS patients with Lenke 1 (n = 55, age 15.28 ± 3.35) and 2 (n = 19, age 15.66 ± 3.72) curves with a complete set of PA radiographs and anterior and posterior photos. Radiographic measures for Sh.B included Cobb angles, T1 tilt, first rib angle, and clavicle-rib intersection angle. Clinical measures for Sh.B included inner shoulder angle, outer shoulder angle, and axillary fold angle. Regression analysis with Pearson’s correlation and ANOVA for statistical significance was used for analysis.

Results

For Lenke 1 curves, there was moderate statistically significant correlation between anterior and posterior clinical Sh.B (R = 0.35–0.41). There was only weak to moderate correlation between radiographic and clinical measures. For Lenke 2 curves, there was a weak to moderate correlation between anterior and posterior clinical Sh.B (R = 0.25–0.45), though not statistically significant. There was no statistically significant correlation between any radiographic measures and posterior Sh.B. There was, however, moderate and significant correlation between radiographic measures and anterior Sh.B.

Conclusion

There is no strong correlation between anterior and posterior clinical Sh.B, and surgeons should evaluate both sides in planning deformity correction, especially in Lenke 2 curves. None of the radiographic measures showed strong correlation (R > 0.8) with anterior or posterior clinical Sh.B. A stronger correlation existed between radiographic measures and anterior Sh.B measurements compared with posterior clinical Sh.B measurements in Lenke 2 curves further necessitating anterior evaluation in this group.     

Changes in surface and radiographic deformity after Universal Spine System for right thoracic adolescent idiopathic scoliosis: is rib-hump reassertion a mechanical problem of the thoracic cage rather than an effect of relative anterior spinal overgrowth?

STUDY DESIGN: Analysis of preoperative, 8-week, 1-year, and 2-year data from patients with right thoracic adolescent idiopathic scoliosis treated by posterior Universal Spine System (Stratec Medical, Oberdorf, Switzerland). OBJECTIVE: Report 2-year results and the association between back surface and radiographic assessments. SUMMARY OF BACKGROUND DATA: Few longitudinal studies have related surface and radiographic data in the follow-up of surgical patients. METHODS: Of 34 patients with right thoracic adolescent idiopathic scoliosis having posterior Universal Spine System instrumentation, 27 had complete prospective back surface and radiographic appraisal. RESULTS: Cobb angle corrected from 58 degrees to 34 degrees (41%), apical vertebral rotation from 26 degrees to 20 degrees (23%), apical vertebral translation from 4.5 to 2.4 cm (47%), and maximum angle of trunk inclination from 17 degrees to 13 degrees (22%) (preoperative to 2 years). Rib-hump reassertion occurred between 8 weeks and 1 year, regardless of age, and correlated with changes in vertebral translation (for 10 vertebral levels corresponding to 10 back surface levels between C7 and S1, P = 0.001 MANOVA). Preoperative frontal tilt of L1 with concave fifth rib-spinal angle predicted the percentage correction of maximum angle of trunk inclination, and the concave ninth rib-spinal angle predicted reassertion of maximum angle of trunk inclination. CONCLUSIONS: Almost half of initial back surface correction is lost by 2 years. Segmental vertebral translation measurements most strongly correlate with segmental angle of trunk inclination measurements during follow-up. Rib-hump reassertion is best explained by unwinding of the thoracic cage tensioned by surgery rather than through relative anterior spinal overgrowth. Spine and thoracic cage factors determine rib-hump correction, so surgical disruption of the latter by costoplasty may prevent rib-hump reassertion. Results of scoliosis surgery should include surface data.     

How is the trachea at risk of injury from pedicle screw insertion in proximal thoracic curve of adolescent idiopathic scoliosis patients?

Purpose

The rotation or translation of vertebrae in adolescent idiopathic scoliosis (AIS) patients could cause the relative migrations of surrounding vital structures and lead to smaller safe zones for pedicle screw insertion. This study aimed to determine the changed relative position of trachea to spine in the proximal thoracic curve (T1–T4) and to analyze the potential risks of tracheal injuries from pedicle screw insertions in AIS patients.

Methods

Twenty-three patients with complete proximal thoracic curve (CPT group), 25 patients with fractional proximal thoracic curve (FPT group) and 19 normal subjects with a straight spine (normal group) were included. Axial computed tomography images from T1 to T4 level were obtained to evaluate trachea–vertebral distance (TVD, the closest distance between trachea and vertebral body) and trachea–vertebral angle (TVA, defined as 0° when the trachea was located directly laterally to the left and 180° when directly laterally to the right). The extension line of pedicle axis could cross the anterior wall of vertebra and the posterior wall of the trachea at two points when the trachea was located in the trajectory of the screw passage. If the distance between the two points was less than 5 mm, the trachea was considered to be at a potential risk of injury. The percentages of vulnerable trachea were calculated at each level.

Results

The TVA in the CPT group was significantly larger than that in the FPT group and in the normal group, while the TVA in the FPT group was significantly larger than that in the normal group at the T2–T4 level. The TVD in the FPT group was significantly smaller than that in the CPT group and in the normal group at each level, while the TVD in the CPT group was significantly smaller than that in the normal group at the T2 and T3 levels. No trachea was found to be at risk from screw insertion on both sides in both the CPT group and the normal group. However, it was at a high risk of injury from anterior cortex penetration during right screw insertion in the FPT group. The percentage of trachea at risk from right screw insertion was 40 % at T1 level, 92 % at T2 level, 100 % at both T3 and T4 levels.

Conclusions

This CT-based study demonstrates that the FPT curve has a smaller safe zone with respect to tracheal injury during screw insertion. Spine surgeons should choose the appropriate screw length to avoid anterior wall perforation.     

Restoration of thoracic kyphosis in adolescent idiopathic scoliosis with patient-specific rods: did the preoperative plan match postoperative sagittal alignment?

European Spine Journal - To determine if the planned sagittal profile for thoracic kyphosis (TK) restoration was achieved after adolescent idiopathic scoliosis (AIS) surgery using a novel hybrid...     

How accurate is visual estimation of perioperative blood loss in adolescent idiopathic scoliosis surgery?

Objective

The aim of this study was to assess whether the visual estimation method for perioperative blood loss is accurate in adolescent idiopathic scoliosis surgery.