Uniplanar Versus Fixed Pedicle Screws in the Correction of Thoracic Kyphosis in the Treatment of Adolescent Idiopathic Scoliosis (AIS)

Comparative Analysis of Monoaxial and Polyaxial Pedicle Screws in the Surgical Correction of Adolescent Idiopathic Scoliosis

Background: Although several biomechanical studies have been reported, few clinical studies have compared the efficacy of monoaxial and polyaxial pedicle screws in the surgical treatment of adolescent idiopathic scoliosis (AIS). This study aims to compare the radiological and clinical outcomes of mono- and polyaxial pedicle screws in the surgical treatment of AIS. Methods: A total of 46 AIS patients who underwent surgery to treat scoliosis using pedicle screw instrumentation (PSI) and rod derotation (RD) were divided into two groups according to the use of pedicle screws: the monoaxial group (n = 23) and polyaxial group (n = 23). Results: The correction rate of the main Cobb's angle was higher in the monoaxial group (70.2%) than in the polyaxial group (65.3%) (p = 0.040). No differences in the rotational correction of the apical vertebra were evident between the two groups. SRS-22 scores showed no significant differences according to the type of pedicle screws used. Conclusions: The use of polyaxial pedicle screws resulted in coronal, sagittal, and rotational correction outcomes comparable to those associated with the use of monoaxial pedicle screws for surgical treatment using PSI and RD to treat moderate cases of AIS.

Does the addition of convex uniplanar screws in hybrid constructs improve 3D surgical correction in thoracic adolescent idiopathic scoliosis posterior fusion?

Purpose

Hybrid techniques using thoracic sublaminar bands have proved their efficacy in adolescent idiopathic scoliosis posterior fusion, but clinical axial correction sometimes remained disappointing. One solution found was "the frame technique" and the second alternative was the replacement of the convex sublaminar bands by periapical uniplanar screws. The goal of this study was to compare clinical and radiological outcomes of both techniques in a consecutive cohort of adolescent idiopathic scoliosis patients.

Methods

All patients undergoing primary posterior fusion for thoracic adolescent idiopathic scoliosis between January 2017 and March 2020 were included. Two groups were compared: Group 1 with thoracic sublaminar bands only and Group 2 with periapical uniplanar screws. All patients underwent standing stereoradiographs. The main frontal, sagittal, and axial (apical vertebra rotation) radiological parameters of interest were analyzed. Functional outcomes were assessed using the Scoliosis Research Society 30 score.

Results

A total of 147 adolescents were included (Group 1, n = 73 and Group 2, n = 74 patients). In the frontal plane, a greater reduction index was observed in Group 2 (68% versus 62%, p < 0.001) as well as a better apical axial correction (67.8% versus 46.6%, p = 0.03). The number of thoracoplasty performed was reduced (6.7% versus 20.5%, p = 0.02) in Group 2, with a significant decrease in the rate of mechanical complication. No significant loss of correction was observed during follow-up in any of the group.

Conclusion

The adjunction of convex uniplanar screws at the periapical levels improved the three-dimensional surgical correction of thoracic adolescent idiopathic scoliosis treated with hybrid constructs.

Level of evidence

level III, retrospective comparative study.

Can C7 Slope Substitute the T1 Slope in Idiopathic Scoliosis Patients? A Radiographic Study

BACKGROUND

The aim of this study was to investigate whether C7 slope can be used as a substitute for T1 slope in idiopathic scoliosis.

METHODS

From January 2014 to October 2019, 101 patients who received posterior spinal internal fixation and fusion in our hospital were retrospectively analyzed. After analyzing the visibility of vertebral endplates, 46 cases of C7/T1 vertebral endplates were visible, including 14 males and 32 females, aged 9 to 18 years (mean 14.6±2.0 y). The upper C7 slope, lower C7 slope, T1 slope, cervical lordosis and C2 to 7 sagittal vertebral axis were measured before and after operation and at the last follow-up. Pearson correlation coefficient was used to evaluate the correlation strength between upper C7 slope and T1 slope, and lower C7 slope and T1 slope. Through simple linear regression analysis, linear regression equations were generated from the upper and lower C7 slopes to predict T1 slope.

RESULTS

According to the 2 researchers' judgment, the visibility rate of the upper C7 endplate was 93.1% before operation, 93.1% after operation, and 91.1% at the last follow-up. The lower C7 endplate's visible rate was 72.3% before operation, 70.3% after operation and 68.3% at the last follow-up. The visible rate of T1 upper endplate was 52.5% before operation, 48.5% after operation and 50.5% at last follow-up. Linear regression analysis showed that the upper C7 slope and T1 slope in idiopathic scoliosis patients, regardless of preoperative (r=0.908, P<0.01), postoperative (r=0.0.886, P<0.01), follow-up (r=0.899, P<0.01), or overall (r=0.895, P<0.01), both have a close correlation; the lower C7 slope and the T1 slope are the same before surgery (r=0.882, P<0.01), after surgery (r=0.940, P<0.01), follow-up (r=0.952, P<0.01), or overall (r=0.929, P<0.01) all have statistical significance.

CONCLUSION

When the upper endplate of T1 is not visible on standard radiographs, the upper or lower C7 slope can be used as a reliable alternative measurement parameter for sagittal balance assessment.

Complications, Reoperations, and Mid-Term Outcomes Following Anterior Vertebral Body Tethering Versus Posterior Spinal Fusion: A Meta-Analysis

Background

Anterior vertebral body tethering (AVBT) is a growth-modulation technique theorized to correct adolescent idiopathic scoliosis (AIS) without the postoperative stiffness imposed by posterior spinal fusion. However, data are limited to small series examining short-term outcomes. To assess AVBT's potential as a viable alternative to posterior spinal fusion (PSF), a comprehensive comparison is warranted. The purpose of this meta-analysis was to compare postoperative outcomes between patients with AIS undergoing PSF and AVBT. Our primary objective was to compare complication and reoperation rates at available follow-up times. Secondary objectives included comparing mid-term Scoliosis Research Society (SRS)-22 scores, and coronal and sagittal-plane Cobb angle corrections.

Methods

We performed a systematic review of outcome studies following AVBT and/or PSF procedures. The inclusion criteria included the following: AVBT and/or PSF procedures; Lenke 1 or 2 curves; an age of 10 to 18 years for >90% of the patient population; <10% non-AIS scoliosis etiology; and follow-up of ≥1 year. A single-arm, random-effects meta-analysis was performed. Deformity corrections, complication and reoperation rates, and postoperative SRS-22 scores were recorded.

Results

Ten AVBT studies (211 patients) and 14 PSF studies (1,069 patients) were included. The mean follow-up durations were similar for both groups. Pooled complication rates were 26% for AVBT versus 2% for PSF, and reoperation rates were 14.1% for AVBT versus 0.6% for PSF with nonoverlapping confidence intervals (CIs). The pooled reoperation rate among studies with follow-up times of ≥36 months was 24.7% in AVBT versus 1.8% in PSF. Deformity correction, clinical outcomes, and mid-term SRS-22 scores were similar.

Conclusions

Our study showed greater rates of complications and reoperations with AVBT compared with PSF. Reoperation rates were significantly greater in AVBT studies with longer follow-up (≥36 months). Deformity correction, clinical outcomes, and mid-term SRS-22 scores were similar. While a potential fusionless treatment for AIS merits excitement, clinicians should consider AVBT with caution. Future long-term randomized prospective studies are needed.

Level of Evidence

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Uniplanar Cannulated Pedicle Screws in the Correction of Lenke Type 1 Adolescent Idiopathic Scoliosis

OBJECTIVE

To report the clinical use of uniplanar cannulated pedicle screws for the correction of Lenke type 1 adolescent idiopathic scoliosis (AIS), and to evalute its safety and clinical outcomes.

METHODS

A total of 68 patients with Lenke type 1 AIS were retrospective analyzed, among which 38 patients were treated with uniplanar cannulated screws at the concave side of periapical levels and multiaxial screws at the other levels (group A). The remaining 30 patients were treated with all multiaxial screws (group B). The preoperative and postoperative radiographic parameters, axial vertebral rotation, and the safety of the pedicle screws were evaluated.

RESULTS

Preoperative data were comparable between the 2 groups. The postoperative proximal thoracic curve, main thoracic curve, thoracolumbar/lumbar curve, and apical vertebral rotation were significantly improved in both groups (P < 0.05). The coronal correction rates in group A and B were 83% and 81.9% (P = 0.723). The derotation rates in group A and B were 60.8% and 43.2% (P < 0.05). The rotation classification in the group A was also better than group B. The misplacement rate in group A and B was 7.9% and 11.8% (P < 0.05), and the total misplacement rate on the concave side (11.4%) was higher than that of convex side (8.4%). On the concave side, the misplacement rate in group A and B was 9.7% and 12.3%. On the convex side, the misplacement rate in group A and B was 5.9% and 11.1% (P < 0.05).

CONCLUSIONS

Collectively, uniplanar cannulated pedicle screws could effectively increase the accuracy of pedicle screws and facilitate the derotation of the apical vertebra compared with the multiaxial pedicle screws.

Posterior Correction Techniques for Adolescent Idiopathic Scoliosis

Adolescent idiopathic scoliosis represents a complex, three-dimensional deformity of the spine. Posterior spinal fusion is commonly performed in severe cases to avoid the long-term adverse sequelae associated with progressive spinal deformity. The goals of spinal fusion include halting the progression of deformity, optimizing spinal balance, and minimizing complications. Recent advances in short-segment spinal fixation have allowed for improved three-dimensional deformity correction. Preoperative planning and assessment of spinal flexibility is essential for successful deformity correction and optimization of long-term outcomes. Judicious use of releases and/or spinal osteotomies may allow for increased mobility of the spine but are associated with increased surgical time, blood loss, and risk of complications. Appreciation of implant design and material properties is critical for safe application of correction techniques. Although multiple reduction techniques have been described, no single technique is optimal for every patient.

Three-Dimensional Computed Tomography Analysis of Spinal Canal Length Increase After Surgery for Adolescent Idiopathic Scoliosis: A Multicenter Study

BACKGROUND

The most severe complication after surgery for adolescent idiopathic scoliosis is spinal cord injury. There is a relationship between corrective surgery and subsequent elongation of the spinal canal. We sought to investigate which factors are involved in this phenomenon.

METHODS

Seventy-seven patients with adolescent idiopathic scoliosis (49 with Lenke type 1 and 28 with type 2) who underwent spinal correction surgery were included. The mean patient age at surgery was 14.2 years (range, 11 to 20 years). The spines of all patients were fused within the range of T2 to L2, and computed tomography (CT) data were retrospectively collected. We measured the preoperative and postoperative lengths of the spinal canal from T2 to L2 using 3-dimensional (3D) CT-based imaging software. We also examined the association between the change in T2-L2 spinal canal length and the radiographic parameters.

RESULTS

The length of the spinal canal from T2 to L2 was increased by a mean of 8.5 mm in the patients with Lenke type 1, 12.7 mm in those with type 2, and 10.1 mm overall. Elongation was positively associated with the preoperative main thoracic Cobb angle in both the type-1 group (R = 0.43, p < 0.005) and the type-2 group (R = 0.77, p < 0.000001). The greatest elongation was observed in the periapical vertebral levels of the main thoracic curves.

CONCLUSIONS

Corrective surgery for adolescent idiopathic scoliosis elongated the spinal canal. The preoperative proximal, main thoracic, and thoracolumbar/lumbar Cobb angles are moderate predictors of postoperative spinal canal length after scoliosis surgery.

CLINICAL RELEVANCE

It is important to understand how much the spinal canal is elongated after surgery to lessen the risk of intraoperative and postoperative neurological complications.