Should L3 be selected as the lowest instrumented vertebra in patients with Lenke type 5C adolescent idiopathic scoliosis whose lowest end vertebra is L4?

Variations of Radiographic Parameters Relevant to the Presumed Lower Instrumented Vertebrae During Intraoperative Fluoroscopic Positioning for Lenke 5/6 Adolescent Idiopathic Scoliosis

BACKGROUND

Radiographic evaluation of the presumed lower instrumented vertebrae (LIV) is crucial for determining the optimal fusion level for adolescent idiopathic scoliosis (AIS) with main thoracolumbar/lumbar curves. However, few studies have examined its variations intraoperatively. This study aims to investigate the radiographic variations of the presumed LIV during fluoroscopic positioning to aid surgeons in decision-making.

METHODS

Lenke 5/6 AIS patients who underwent correction surgery in our center were consecutively recruited from January 2021 to December 2023. The spinal radiographs, including preoperative standing X-ray, recumbent computed tomography (CT), and intraoperative positioning fluoroscopy, were collected. The parameters of the presumed LIV were measured and compared. The correlation analysis was also performed to establish the liner regression equation.

RESULTS

Ninety-seven patients, comprising 23 boys and 74 girls, were enrolled, with an average main curve of 55.1 ± 11.0°. The vertebral body tilt and disc angle of the presumed LIV were 27.2 ± 6.2° and 8.5 ± 3.8° on preoperative standing X-rays, respectively, both significantly decreasing on CT images and intraoperative fluoroscopy. The rotation of the presumed LIV also showed significant differences intraoperatively. Significant correlations were observed between vertebral body tilt and disc angle across X-rays, CT images, and fluoroscopy. A linear equation was established for predicting intraoperative variations of the presumed LIV based on baseline X-rays.

CONCLUSIONS

This study firstly reports the radiographic variations of the presumed LIV using intraoperative positioning fluoroscopy for Lenke 5/6 AIS and establishes the correlation with baseline measurements. This information may assist surgeons in selecting the optimal LIV, but long-term follow-up is needed to evaluate its outcomes.

Is It Enough to Stop Distal Fusion at L3 in Mild to Moderate Lenke 5C Adolescent Idiopathic Scoliosis Patients?

OBJECTIVE

There has been no definitive conclusion on the selection of the lowest instrumented vertebra (LIV) in Lenke 5C adolescent idiopathic scoliosis (AIS) patients. The purpose of this study was to evaluate whether it is enough to stop distal fusion at L3 in mild to moderate Lenke 5C AIS patients with posterior selective lumbar fusion, Ponte osteotomies and segmental direct vertebra rotation and to analyze the risk factors for postoperative complications in patients selecting L3 as the LIV.

METHODS

A retrospective review was conducted on 106 Lenke 5C AIS patients who underwent corrective surgery in our institution from 2010 to 2021, with a minimum 2-year follow-up. The LIV was L3 or L4. According to the LIV, patients were initially divided into Group I (the LIV was L3) and Group II (the LIV was L4). Then, Group I was further divided into a complication group and a non-complication group. Demographics, radiological parameters, postoperative complications, and clinical outcomes were recorded. Univariate analysis and multivariate logistic analysis were used to identify the risk factors for postoperative complications in patients with L3 as the LIV.

RESULTS

There were no significant differences in the demographics, radiological parameters, postoperative complications, or clinical outcomes between Group I and Group II (p > 0.05), and the outcomes were satisfactory in both groups. The main postoperative complications were distal adding-on (11 cases), coronal imbalance (16 cases), proximal junctional kyphosis (2 cases), and internal fixation failure (4 cases). Logistic regression analysis revealed that age and postoperative C7-CSVL were independent predictors of postoperative complications when selecting L3 as the LIV.

CONCLUSION

Terminating the distal fusion level at L3 was practical for mild to moderate Lenke 5C AIS patients. For patients selecting L3 as the LIV, younger patients should be cautious, and maintaining postoperative coronal balance is necessary for avoiding postoperative complications.

Lowest Instrumented Vertebra at L3 Versus L4 in Posterior Fusion for Moderate Lenke 5C Type Adolescent Idiopathic Scoliosis: A Case-Match Radiological Study

OBJECTIVE

To compare the radiological outcomes in Lenke 5C type patients whose lowest instrumented vertebra (LIV) was L3 or L4 in a case-match study.

METHODS

We conducted a retrospective case-match study and included 82 patients in the study. Radiological results before surgery, after surgery, and at last follow-up were recorded and analyzed in the L3 and L4 groups.

RESULTS

After matching the age, Risser's sign, sex, and main Cobb, 41 pairs of patients were enrolled in our study. The total fusion segments in the L3 group (median [interquartile range]: 5.0 [6.0-5.0]) were shorter than those in the L4 group (6.0 [6.5-6.0]). The main curve was significantly corrected after surgery in both groups, and was comparable at the last followup between groups. In addition, according to the results of Fisher precision probability test, there was no significant difference of coronal or sagittal imbalance between the 2 groups at the 2-year follow-up.

CONCLUSION

The correction in coronal and sagittal planes in L3 group and L4 group remains similar. On account of more motion segments, L3 could be an ideal choice as LIV in moderate Lenke 5C type AIS. Long-term follow-up is needed to evaluate the effect of larger compensatory lumbar-sacral curve when stopping at L3.

Should the upper end vertebra be selected as the upper instrumented vertebra in patients with Lenke type 5C adolescent idiopathic scoliosis?

STUDY DESIGN

Retrospective study.

PURPOSE

The upper end vertebra (UEV) is often selected as the upper instrumented vertebra (UIV) in patients with adolescent idiopathic scoliosis (AIS) with Lenke type 5C curves; however, the effect of adjusting UIV selection one level toward the cranial side (UEV + 1) is unknown. Therefore, this study aimed to assess the effect of UIV extension on scoliosis correction and global alignment in patients with the UIV as the UEV and UEV + 1.

METHODS

Data of 52 patients with AIS with Lenke type 5C curves who underwent selective thoracolumbar/lumbar (TL/L) fusion with a minimum follow-up period of 2 years were retrospectively analyzed. The patients were divided according to the UIV in relation to the UEV: the UEV and UEV + 1 groups. Radiographic parameters and clinical outcomes were compared between the two groups.

RESULTS

Among the 52 patients, 24 and 28 were included in the UEV and UEV + 1 group. Baseline data showed no intergroup differences except for the UIV level. While the UEV + 1 group showed a significantly greater TL/L curve correction (72.9% vs. 62.8%, p < 0.05) and a lower UIV tilt, it showed a significantly greater absolute value of radiographic shoulder height (RSH) (- 7.9 vs. - 0.9 mm, p < 0.05) and coronal balance (- 11.0 mm vs - 4.8 mm, p < 0.05) at 2 years postoperatively. The rate of post-operative shoulder imbalance (RSH ≥ 2 cm) was significantly higher in the UEV + 1 than in the UEV group. No intergroup differences were observed in the sagittal alignment and patient outcomes between the two groups.

CONCLUSION

When the UIV was selected as the UEV + 1, correction of the TL/L curve improved; however, it increased the risk of shoulder and coronal imbalance. There is no clinical benefit observed in terms of extending the UIV to the UEV + 1; therefore, the UIV should be selected as the UEV to maintain harmonious global alignment.

LEVEL OF EVIDENCE

Level 3.