Determination of the distal fusion level in the management of thoracolumbar and lumbar adolescent idiopathic scoliosis using pedicle screw instrumentation

Can Surgery Be Proposed to Adolescent Idiopathic Scoliosis Patients With Structural Lumbar Curves Associated With Nonreducible Iliolumbar Angle?

BACKGROUND

Lower instrumented vertebra (LIV) selection for adolescent idiopathic scoliosis (AIS) with structural lumbar curves (Lenke 3, 5, and 6) remains debated. The iliolumbar angle (ILA) measurement is useful for assessing the lumbosacral junction flexibility. If it is nonreducible, surgeons need to make a difficult choice between a potential "imperfect" L4, associated with a residual lumbosacral curve, or a more distal fusion performed later in life due to poorer functional outcomes. The goal of this study was, therefore, to evaluate the postoperative radiographic and functional outcomes of AIS patients with nonreducible ILA.

METHODS

All consecutive AIS patients (2017 to 2022) with a structural lumbar curve and a posterior fusion ending on L4 were retrospectively included. Radiographic and functional outcomes (SRS-30 score) were reported with a minimum 2-year follow-up. Standing low dose stereoradiographs in both erect and maximum lateral bending positions were performed in all patients, and 2 groups of subjects were compared based on preoperative ILA flexibility [reducible group (R) or nonreducible group (NR)].

RESULTS

A total of 122 patients were included (30% NR and 71% R). At a mean follow-up of 2.3±0.1 years, surgery was efficient in correcting the major curve (77% reduction rate in the R group and 76% in the NR group, P <10 -5 ), and significantly improved coronal balance (R, P <10 -5 and NR, P =0.03) as well as the ILA [mean ILA gain 14 degrees (R group), P <10 -5 and 16 degrees (NR group), P <10 -5 ]. The proportion of excellent results was higher in the R group, but 97% of outcomes were either excellent or acceptable in the NR group, and only 1 case of poor result (residual ILA >10 degrees) was reported in each group. No significant difference was found in SRS 30 scores between groups, but scores were significantly improved in the NR group for the excellent outcomes' subgroup [self-image ( P =0.04) and satisfaction ( P =0.02) domains].

CONCLUSIONS

The current study confirms that posterior fusion ending on L4 can still be proposed to young AIS patients with structural lumbar curves, even if the lumbosacral flexibility is limited.

LEVEL OF EVIDENCE

Level III-comparative study.

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.

Comparable rates of lumbar disc degeneration at long-term following adolescent idiopathic scoliosis spinal fusion extended to L3 or L4: systematic review and meta-analysis

PURPOSE

Surgical treatment of adolescent idiopathic scoliosis (AIS) requires a careful choice of fusion levels. The usual recommendation for the selection of the lowest instrumented vertebra (LIV) for double major or thoracolumbar/lumbar (TL/L) curves falls on L3 or L4. The aim of the present study is to assess if the spinal fusion with LIV selection of L3 or L4 in AIS patients has a clinical or radiological impact in terms of degenerative disc disease (DDD) in distal unfused segments at long-term follow-up.

METHODS

A systematic search of electronic databases from eligible articles was conducted. Only studies regarding long-term follow-up of AIS patients treated with spinal fusion were included. Clinical and radiographic outcomes were extracted and summarized. Meta-analysis on long-term follow-up MRI studies was performed. p value < 0.05 was considered significant.

RESULTS

Fourteen studies were included, for a total of 1264 patients. Clinical assessment of included patients showed a slight tendency to have worse clinical outcomes if spinal fusion is extended to L4 rather than L3. Despite that, meta-analysis could not be performed on clinical parameters because of heterogeneity of evaluated PROMs in included studies. Magnetic resonance imaging (MRI) evaluation at long-term follow-up showed no significant difference in terms of disc degeneration rate at overall meta-analysis (p = 0.916) between patients fused to L3 and L4.

CONCLUSION

The LIV selection of L3 rather than L4, according to current literature, does not prevent disc degeneration in distal unfused segments over the long term. Long-term studies of patients treated with contemporary spinal instrumentation are needed.

Selection of Optimal Lower Instrumented Vertebra for Adolescent Idiopathic Scoliosis Surgery

Adolescent idiopathic scoliosis (AIS) affects approximately 2% of adolescents across all ethnicities. The objectives of surgery for AIS are to halt curve progression, correct the deformity in 3 dimensions, and preserve as many mobile spinal segments as possible, avoiding junctional complications. Despite ongoing development in algorithms and classification systems for the surgical treatment of AIS, there is still considerable debate about selecting the appropriate fusion level. In this study, we review the literature on fusion selection and present current concepts regarding the lower instrumented vertebra in the selection of the fusion level for AIS surgery.

A Newer Way of Determining LIV in AIS Patients: Rotation of the Touched Vertebrae

STUDY DESIGN

A retrospective review.

OBJECTIVE

The objective of this study was to determine whether fusing to touched vertebra (TV) on prone x-rays (XRs) with minimal rotation (Gd 0/1) allow for shorter fusion with optimal correction.

SUMMARY OF BACKGROUND

Previous studies have shown risk of "adding on" when TV is not selected as lowest instrumented vertebra (LIV). Fusion proximal to TV leads to suboptimal results but fusing to TV on standing XRs can result in longer fusions. On lying down XRs, TV moves proximally, and its rotation decreases by a grade.

METHODS

TV patients with minimal rotation were selected on prone (TVP) or standing XRs (TVS). Patients fused to rotated (Gd 2+) TV on standing or prone XRs were considered touched vertebra rotated (TVR). In the non-TV (NTV) group, LIV was fused proximal to TV. Disk wedging ≥5° determined risk of "adding-on." To compare patients fused to minimally rotated TV, to those that were not, patients in group A (TVP + TVS) were compared with group B (TVR + NTV).In part II: TVP, TVS, TVR, and NTV patients were compared. Subanalysis compared levels saved as the difference between predicted and real LIV in TVP and TVS patients. Another subanalysis was carried out for Lenke 1+2 and Lenke 3, 4, 5.In part III: XRs of nonoperative adolescents idiopathic scoliosis patients with Cobb <30 and Risser 4/5 were analyzed to determine "acceptable" end vertebra tilt and disc wedging and served as controls.

RESULTS

There were a significantly greater number of patients in group B patients(TVR + NTV) with final disk wedging ≥5°, final LIV translation ≥1 and ≥2 cm ( P <0.001).Utilizing prone XRs in TVP saved average 1 level, and 1.2 levels in TVS patients. TVP patients also had similar LIV tilt, disk wedging and coronal balance( P >0.05) to controls.

CONCLUSION

Choosing minimally rotated (Gd 0/1) TV on prone XR saves levels without sacrificing radiographic outcomes.

The Role of Bending Films in the Lowest Instrumented Vertebra Selection in Adolescent Idiopathic Scoliosis Lenke Type 1A,B Based on Asymmetrical Disc Loading and Decompensation

Patients with severe adolescent idiopathic scoliosis (AIS) require instrumented spinal fusion surgery. The range of instrumented vertebra is still questioned, especially the selection of the lowest instrumented vertebra (LIV). This single institution retrospective consecutive study is to provide real-world data on outcomes. The study aims to assess whether bending films can determine the LIV. The method of determination of the lower tilted vertebra (LTV) is presented. The selection of the LTV was identified on standing PA (LTVs) and on bending X-rays (LTVb). Group A is a reference group, with less flexible curves. Groups B and C contained patients with more flexible curves. Group B covered patients with instrumentation ending at the LTVs and group C with shorter instrumentation ending at LTVb. The disc angle below the LIV was monitored for postoperative decompensation. Sixty-eight subjects with AIS Lenke 1A and 1B types underwent selective fusion. The decompensation criteria of the unfused disc below the fusion were determined as a wedging disk of >5° of the Cobb angle. The patients were monitored during the postoperative period with 5.8 years average followup (minimum of 2 years). The rate of decompensation was comparable in groups A and B (31% and 33%, respectively). In contrast, the rate of decompensation was doubled in group C (60%). Caudal fusion shortening in more flexible curves according to bending films is associated with the first free disc asymmetry, which leads to decompensation below the fusion. This method should be considered in addition to other LIV selection criteria.

Distal adding-on after surgery in Lenke 5C adolescent idiopathic scoliosis: clinical and radiological outcomes

Background

To evaluate the incidence and risk factors of postoperative distal adding-on in patients with Lenke 5C adolescent idiopathic scoliosis (AIS). More accurate selection criteria for the lower instrumented vertebra (LIV) should be confirmed to prevent distal adding-on.

Methods

Forty-six patients with Lenke 5C AIS who underwent posterior fusion were enrolled in the study. Patients were allocated into adding-on and no adding-on groups. Demographic data, clinical data, and radiographic parameters were recorded and compared.

Results

Postoperative distal adding-on occurred in eight patients (17.4%) during follow-up. Demographic data, clinical data, and baseline radiographic parameters of the two groups were not significantly different. The postoperative thoracolumbar (TL) or lumbar (L) Cobb angle, LIV translation, and LIV + 1 translation were higher in the adding-on group than those in the no adding-on group, while the postoperative coronal imbalance of the adding-on group was lower than that of the no adding-on group. The level difference of last barely touched vertebra (LBTV) and last substantial touched vertebra (LSTV) with LIV were higher in the adding-on group than in the no adding-on group.

Conclusion

Postoperative TL/L curve, postoperative LIV translation, postoperative LIV + 1 translation, and postoperative coronal imbalance were determined as risk factors for postoperative distal adding-on in patients with Lenke 5C AIS. Moreover, LIV selection of LBTV-1 or LSTV-1 may cause a higher risk of postoperative distal adding-on.

Prediction of long-term postoperative results of disc wedge and vertebral tilt with intraoperative prone radiograph in posterior correction of thoracolumbar/lumbar curve in adolescent idiopathic scoliosis: a minimum 5-year follow-up

BACKGROUND CONTEXT

Preservation of the more mobile lumbar segments is important during thoracolumbar/lumbar scoliosis surgery; however, the remaining disc wedge angle (DWA) below lowermost instrumented vertebra (LIV) and vertebral body tilt below LIV (LIV+1 tilt) can cause curve progression.

PURPOSE

This study aimed to evaluate the efficacy of intraoperative radiograph to predict the postoperative DWA below LIV and LIV+1 tilt on standing radiographs in patients with LIV of L3 or L4.

STUDY DESIGN/SETTING

Retrospective cohort study PATIENT SAMPLE: A total of 235 patients with idiopathic scoliosis who underwent posterior correction and fusion for the structural thoracolumbar curve and were followed up for >5 years were reviewed.

OUTCOME MEASURES

DWA below LIV, LIV+1 tilt, Cobb angle, trunk shift, apical vertebra translation, and pelvic parameters were measured.

METHODS

Correlation between intraoperative and postoperative measurements of DWA below LIV and LIV+1 tilt were assessed. Additional analysis was performed to identify risk factors and prognosis of LIV+1 tilt ≥10° and DWA below LIV of ≥4° RESULTS: LIV+1 tilt measured on intraoperative radiograph was significantly correlated with the postoperative 5-day and postoperative 5-year evaluation in both groups. However, the intraoperative DWA below LIV was only correlated with the postoperative 5-year value in the L3 group (p=.018). At the 5-year follow-up, patients with LIV+1 tilt ≥10° on intraoperative radiography showed significantly greater LIV+1 tilt (p<.001), apical vertebral translation (p<.001), thoracic curve (p=.008), and thoracolumbar curve (p<.001) than patients with LIV+1 tilt <10°. Intraoperative DWA below LIV of ≥4° was only associated with higher DWA below LIV at the 5-year follow-up.

CONCLUSIONS

Intraoperative measurement of LIV+1 tilt was correlated with long-term postoperative outcomes, and intraoperative LIV+1 tilt ≥10° was associated with a less favorable radiographic outcome. Intraoperative DWA below LIV demonstrated less correlation with postoperative values and was not a prognostic factor for other radiographic parameters.

Risk factors for persistent coronal imbalance or revision surgery following L3 LIV selection in adolescent idiopathic scoliosis (AIS)

STUDY DESIGN

Retrospective case-control.

OBJECTIVE

To identify a cohort of patients with persistent coronal imbalance (CIB) or revision surgery 5 years following fusion to an L3 lowest-instrumented-vertebra (LIV) and determine factors that make an L3 LIV high-risk. In surgical planning for AIS, L3 is chosen over L4 whenever possible to maximize motion segments below the LIV. Though fusion to an L3 LIV is common, the rate of failure and its risk factors have not been described.

METHODS

In this analysis of prospectively-collected multi-center data of AIS patients who underwent posterior spinal fusion (PSF) to an L3 LIV, we identified patients with CIB at 5 years and/or those who required revision surgery attributable to LIV selection. Patients who were balanced at 5 years and did not require revision surgery served as controls. Pre-operative patient and radiographic variables were compared between cases and controls to identify risk factors for CIB/revision surgery.

RESULTS

We identified 646 patients with 2-year follow-up and 225 patients with 5-year follow-up, of which 11 were found to have CIB and/or revision surgery attributable to selecting L3 as the LIV. There were statistically significant differences between cases and controls with respect to several pre-operative factors, including BMI (24.5 in cases vs. 20.1 in controls; p = 0.01), Lenke curve type (81.8% Lenke 5/6 vs. 44.4%; p = 0.03), lumbar curve magnitude (56 vs. 45°; p < 0.01), TL/L apical vertebral translation (AVT) (6.2 vs. 4.1 cm; p < 0.01), L3 angulation (30° vs. 22°; p < 0.01), L3 translation (4.3 vs. 2.9 cm; p < 0.01), thoracic rib hump (7° vs. 12°; p = 0.02), lumbar rib hump (16° vs. 10°; p < 0.01), and thoracolumbar (T10-L2) kyphosis (10.5° vs. 2°; p = 0.006). Multivariate logistic regression showed that pre-operative BMI, TL/L AVT, L3 angulation, L3 translation, lumbar rib hump, and thoracolumbar kyphosis were independent predictors of CIB/revision surgery.

CONCLUSIONS

An L3 LIV is frequently successful at 5 years post-operatively. Consider an L4 LIV when: pre-operative BMI ≥ 28, L3 angulation ≥ 25°, L3 translation ≥ 4 cm, TL/L AVT ≥ 6 cm, or the lumbar curve is large (≥ 55°) and rotated (≥ 10°).

LEVEL OF EVIDENCE

Level III.

Selection of Fusion Level for Adolescent Idiopathic Scoliosis Surgery : Selective Fusion versus Postoperative Decompensation

Adolescent idiopathic scoliosis (AIS), which is associated with an extensive range of clinical and radiological presentations, is the one of the most challenging spinal disorders. The goals of surgery are to correct the deformity in 3 dimensions and to preserve motion segments while avoiding complications. Despite the ongoing evolution of classification systems and algorithms for the surgical treatment of AIS, there has been considerable debate regarding the selection of an appropriate fusion level in AIS. In addition, there is no consensus regarding the exact description, relationship, and risk factors of coronal decompensation following selective fusion. In this review, we summarize the current concepts of selection of the fusion level for AIS and review the available information about postoperative coronal decompensation.

Transient fixation of L4 vertebra preserves lumbar motion and function in Lenke Type 5C and 6C scoliosis

This study investigated the efficacy of a novel surgical method that relies on the transient fixation of L4 in Lenke Type 5C and 6C adolescent idiopathic scoliosis. Thirty-six transient surgically treated L4 fixation patients were retrospectively evaluated. The first surgery involved mechanical correction of scoliosis; the lowest instrumented vertebra (LIV) was L4. After an average of 1.3 years (range, 0.3-3.4), the second surgery to remove transient L4 pedicle screws was performed. Radiographic parameters and SRS-22 scores were measured. Cobb's angle, coronal balance, LIV tilting angle, and LIV coronal disc angle clearly improved after the first surgery (p < 0.01). After the second surgery, the corrected Cobb angle (p = 0.446) and coronal balance were maintained (p = 0.271). Although L3/S1 lumbar lordosis decreased after the first surgery (p < 0.01), after removal of transient L4 pedicle screws, it recovered slightly (p = 0.03). Similarly, the preoperative L3/4 lateral disc mobility eventually recovered after transient L4 screw removal (p < 0.01). The function domain of the SRS-22 showed better scores after removal of transient L4 screws (p = 0.04). L4 transient fixation surgery is beneficial for Lenke Type 5C and 6C scolioses that do not fully satisfy LIV (L3) criteria. It preserves L3/4 disc motion, increases functional outcomes, and maintains spinal correction and coronal balance.

Perioperative outcome of severe rigid idiopathic scoliosis: Single-staged posterior spinal fusion utilizing a dual attending surgeon strategy. A report of 41 patients

PURPOSE

Various surgical strategies including combined approach and spinal osteotomies in severe rigid scoliosis had been reported with significant perioperative complication rates. The use of single-staged posterior spinal fusion (PSF) utilizing a dual attending surgeon strategy for severe rigid scoliosis has not been widely reported.

METHODS

This was a retrospective study aimed to evaluate the perioperative outcome of single-staged PSF in severe rigid idiopathic scoliosis patients (Cobb angle ≥90° and ≤30% flexibility). Forty-one patients with severe rigid idiopathic scoliosis who underwent single-staged PSF were included. The perioperative outcome parameters were operation duration, intraoperative blood loss, intraoperative hemodynamic parameters, preoperative and postoperative hemoglobin, transfusion rate, patient-controlled anesthesia morphine usage, length of postoperative hospital stay, and perioperative complications. Radiological parameters included preoperative and postoperative Cobb angle, correction rate, side-bending flexibility, and side-bending correction index.

RESULTS

The mean age was 16.9 ± 5.6 years. The mean preoperative Cobb angle was 110.8 ± 12.1° with mean flexibility of 23.1 ± 6.3%. The mean operation duration was 215.5 ± 45.2 min with mean blood loss of 1752.6 ± 830.5 mL. The allogeneic blood transfusion rate was 24.4%. The mean postoperative hospital stay was 76.9 ± 26.7 h. The mean postoperative Cobb angle and correction rate were 54.4 ± 12.8° and 50.9 ± 10.1%, respectively. The readmission rate in this cohort was 2.4%. Four perioperative complications were documented (9.8%), one somatosensory evoke potential signal loss, one superficial infection, one lung collapse, and one superior mesenteric artery syndrome.

CONCLUSIONS

Severe rigid idiopathic scoliosis treated with single-staged PSF utilizing a dual attending surgeon strategy demonstrated an average correction rate of 50.9%, operation duration of 215.5 min, and postoperative hospital stay of 76.9 h with a 9.8% perioperative complication rate.

How to select the lowest instrumented vertebra in Lenke type 5 adolescent idiopathic scoliosis patients?

BACKGROUND CONTEXT

The lowest instrumented vertebra (LIV) determination in Lenke type 5 Adolescent Idiopathic Scoliosis (AIS) requires a thorough understanding and prediction of the correction force on the LIV from coronal, sagittal, and axial plane. Although many LIV selection criteria have been reported, none of them comprehensively evaluated the multidimensional characteristics of the LIV till now.

PURPOSE

To develop and evaluate our LIV selection criteria in Lenke type 5 AIS patients using pedicle screw system via posterior approach.

STUDY DESIGN

A retrospective study.

PATIENT SAMPLE

All consecutive patients with Lenke 5 curves who were treated with one-stage selective lumbar fusion using complete pedicle screw system in our center from January 2006 to December 2017, with minimum 2-year follow-up.

OUTCOME MEASURES

Age, gender and Risser grade, fused levels, operating time, intraoperative blood loss, complications, and Scoliosis Research Society (SRS)-22 questionnaires outcome were recorded. Coronal, sagittal, and axial parameters were measured from plain radiographs.

METHODS

A total of 138 consecutive patients with Lenke 5 curves treated with selective lumbar fusion were retrospectively analyzed, with minimum 2-year follow-up. Our LIV selection criteria include: (1) the most cephalad vertebrae touched by central sacrum vertical line (CSVL); (2) Nash-Moe rotation being equal or less than grade I on the standing AP radiograph; (3) CSVL cross between the two pedicles of LIV on concave bending film; (4) not at the apex of kyphosis. Radiographic data, operative data, perioperative complications and SRS-22 outcomes were collected and analyzed.

RESULTS

The mean follow-up period was 50.9±24.7 months. The thoracolumbar/lumbar curve was corrected from 46.9°±8.9° before surgery to 5.5°±2.6° at the final follow-up. The C7-CSVL was 19.7±6.2 mm before surgery and 5.2±3.4 mm at the final follow-up. The LIV translation was corrected from 22.3 ±5.4 mm before surgery to 4.8 ± 2.6 mm at the final follow-up, with the correction rate of 78.4%. The LIV tilt was corrected from 21.6 ± 4.4° before surgery to 2.6 ± 2.3° at the final follow up, with the correction rate of 87.9%. Our LIV saved 0.3 level than SRS-last barely touching vertebra, 0.6 level than SRS-last substantially touching vertebra, 0.9 level than neutral vertebra, and 1.4 level than stable vertebra.

CONCLUSION

The present study indicates using our LIV criteria, our study achieved the correction rate of thoracolumbar/lumbar curve as 88.9%, with the rate of adding on or coronal imbalance as 8.7% (12/138). The criteria may provide important guidance for preoperative decision-making in Lenke 5 AIS patients, and more multicenter prospective studies with larger samples are needed to further validate the findings of this study.

Severe persistent coronal imbalance following instrumented posterior spinal fusion for adolescent idiopathic scoliosis

STUDY DESIGN

Retrospective case-control study.

OBJECTIVE

The aim of this study was to identify the risk factors and health-related quality of life (HRQoL) impact of severe (> 4 cm) post-operative coronal imbalance at 2 years following posterior spinal fusion (PSF) for adolescent idiopathic scoliosis (AIS). Coronal imbalance is an unfavorable outcome following PSF for AIS, though the degree of imbalance in such patients is typically mild. We hypothesize that a small number of patients become and remain severely imbalanced post-operatively, though this phenomenon has not been well studied.

METHODS

Prospectively collected data from a large multicenter registry were reviewed. Patients with severe coronal imbalance (SCIB; > 4 cm) 2 years after PSF were included. Matched controls without SCIB at 2 years were included at a 3:1 ratio. Comparisons were made between demographics, pre-operative radiographic measures, surgical factors, residual post-operative radiographic measures, and 2-year SRS-22 scores.

RESULTS

Nine of 954 (0.9%) patients (88.9% females; mean age 14.8 ± 2.3 years) were found to be severely imbalanced at 2 years. These patients had significantly greater pre-operative bending thoracic curve magnitude (45° vs. 33°; p = 0.013), curve flexibility (22.9% vs. 63.3%; p = 0.004), and kyphosis (41° vs. 26.5°; p = 0.034) compared to matched controls. Pre-operative curve flexibility of < 20% was associated with a 23.8 times greater odds of SCIB (95% CI 2.1-250; p = 0.008). With respect to HRQoL, median SRS-22 pain (4.1 vs. 4.8; p = 0.041), self-image (3.9 vs. 4.6; p = 0.013), general function (4.5 vs. 5; p = 0.022), and total (4.1 vs. 4.7; p = 0.012) scores at 2 years were significantly lower in cases compared to controls.

CONCLUSIONS

In the present study, thoracic curve stiffness was a strong risk factor for severe post-operative coronal imbalance, which was associated with poor HRQoL measures. Increased pre-operative thoracic curve stiffness (< 20% flexibility) should raise surgeon awareness for altering surgical approach to minimize the risk of severe post-operative coronal imbalance.

LEVEL OF EVIDENCE

Level III.

Importance of lowest instrumented vertebra on clinical and radiological outcomes in patients with Lenke type 3C adolescent idiopathic scoliosis: a minimum 4-year follow-up

The purpose of this retrospective study was to determine the most appropriate distal fusion level in terms of clinical results and radiological changes in Lenke 3C adolescent idiopathic scoliosis (AIS). Between June 2010 and May 2014, a total of 90 consecutive patients who underwent surgery for Lenke 3C AIS were divided into three groups as L2, L3, and L4 according to the fusion levels and compared in terms of functional and radiological outcomes. Patients were evaluated with Scoliosis Research Society 22 (SRS 22) and the Oswestry disability index (ODI) at the final follow-up. Preoperative standard posteroanterior and lateral whole-spine radiographs and lateral bending radiographs were used to evaluate the curves. All patients were also assessed with lumbar MRI at the final follow-up, and classified for each patient in terms of disc degeneration (DD) and facet joint degeneration (FJD). There was a statistically significant difference between the groups in terms of ODI category (P = 0.001). The rate of minimal disability in the L3 group, moderate disability in the L2 group, and severe disability in the L4 group were higher. Statistically significant differences were observed between the groups in terms of pain, body image, mental health, and total score distribution from the SRS-22 domains (P < 0.05). No significant difference was observed between the groups in terms of DD and FJD in MRI (P = 0.263). Although the preoperative functional scores could not be evaluated due to the retrospective nature of the study, it was observed that the only significant difference between the groups was the SRS-22 score. The best SRS-22 score was obtained in patients in whom fusion was stopped at L3.

Hyper-Selective Posterior Fusion in Lenke 5C Adolescent Idiopathic Scoliosis: When Can We Stop Below the Upper End Vertebra?

STUDY DESIGN

A prospective analysis.

OBJECTIVE

To investigate whether the hyper-selective posterior fusion (upper instrumented vertebra [UIV] as the vertebra one level below the upper end vertebra [UEV], lower instrumented vertebra [LIV] as the lower end vertebra [LEV]) was applicable in posterior fusion of Lenke 5C adolescent idiopathic scoliosis (AIS) patients and what could be the indication of hyper-selective fusion.

SUMMARY OF BACKGROUND DATA

The improper UIV selection in selective fusion could lead to progressive thoracic compensatory curve, shoulder imbalance, and even coronal imbalance. However, few studies analyzed the clinical outcome of hyper-selective fusion.

METHODS

A prospective analysis of 80 patients with Lenke 5C AIS who underwent selective fusion was performed. According to the relationship between UEV and UIV, the patients were divided into UEV group (UIV = UEV) and UEV-1 group (UIV = UEV-1). Radiographic parameters and the incidence of postoperative proximal decompensation were compared. The Scoliosis Research Society (SRS)-22 scores were used to evaluate clinical outcomes between two groups.

RESULTS

Thirteen patients (27%) in UEV group and six (18.75%) in UEV-1 group showed proximal decompensation during follow-up, and the incidence was equivalent (P = 0.280). Within the UEV-1 group, the patients with proximal decompensation showed similar Risser grade, baseline thoracic Cobb angle, and main Cobb angle (P = 0.611, 0.435, 0.708, respectively). However, the baseline L-T apical vertebral translation (AVT) ratio was significantly larger in patients with proximal decompensation (P = 0.028). Meanwhile, patients with proximal decompensation in UEV group showed significantly smaller preoperative UIV translation and lumbar AVT but similar postoperative UIV tilt.

CONCLUSION

Hyper-selective posterior fusion strategy could be performed in Lenke 5C patients with Risser more than grade 2 and with thoracic compensatory curve over 15°. The UIV in patients with small baseline thoracic curve, represented by larger baseline lumbar-thoracic AVT ratio, should be selected as UEV to prevent proximal decompensation.

LEVEL OF EVIDENCE

4.

Selection of Distal Fusion Level for Lenke 5 Curve: Does the Rotation of the Presumed Lower Instrumented Vertebra Matter?

STUDY DESIGN

A retrospective analysis.

OBJECTIVE

To evaluate whether the rotation of the presumed lower instrumented vertebra (LIV) on baseline convex side-bending (SB) radiographs leads to distal adding-on in Lenke 5C adolescent idiopathic scoliosis (AIS) patients.

SUMMARY OF BACKGROUND DATA

In Lenke 1A patients, derotation of the presumed LIV on baseline bending films is important owing to the association between LIV rotation and postoperative distal adding-on. However, the relationship between distal adding-on and derotation of the presumed LIV in Lenke 5C patients remains unknown.

METHODS

Eighty-five Lenke 5C patients with a minimum of 2-year follow-up for posterior fusion were enrolled. L3 was selected as the LIV in all patients. Patients were divided into the presumed LIV derotation (DR group) and nonderotation (NDR group) groups according to derotation of the presumed LIV on SB films. Radiographic parameters, including Cobb angle, coronal balance, lower disc angle of LIV, LIV tilt, and LIV translation, were measured pre- and postoperatively.

RESULTS

Distal adding-on occurred in 16 patients (18.8%) at the final follow-up: 2 patients (10%) in the DR group and 14 patients (21.5%) in the NDR group (P = 0.248). Distal adding-on incidence was not greatly reduced with derotation of the presumed LIV on SB films at baseline. In the NDR group, the immediately postoperative lower disc angle of the LIV, LIV tilt, and LIV translation were significantly smaller in patients without than in those with distal adding-on (all P < 0.05). Logistic regression analysis revealed that the immediately postoperative LIV tilt and LIV translation were significant predictors of distal adding-on.

CONCLUSION

Derotation of the presumed LIV on SB films may hint less risk of distal adding-on in Lenke 5C patients. Nevertheless, horizontalization of the LIV and minimizing LIV translation during correction could reduce the risk of distal adding-on despite the presence of LIV rotation at baseline.

LEVEL OF EVIDENCE

4.

Disc Wedge and Vertebral Body Tilt Angle Below Lower Instrumented Vertebra After Posterior Correction and Fusion in Patients With a Structural Thoracolumbar/Lumbar Curve: A Minimum 5-Year Follow-up

STUDY DESIGN

A retrospective cohort study.

OBJECTIVE

The purpose of this study was to evaluate the stability of remained lumbar curve by the review of serial changes in L3/L4 disc wedge and L4 body tilt angle in patients with idiopathic scoliosis who underwent posterior-only fusion to L3 lower instrumented vertebra (LIV) for the correction of structural thoracolumbar/lumbar (TL/L) curve for a minimum 5-year follow-up.

SUMMARY OF BACKGROUND DATA

There has been some debate in the selection of L3 or L4 as the LIV for the correction of structural TL/L curve. However, there is a limited information about the changes in disc wedge or vertebral body tilt angles below the L3 LIV.

METHODS

Forty-seven patients were included (mean age 16 yr 7 mo, follow-up 8 yr 2 mo). The Cobb angle of the TL/L curve, L3/L4 disc wedge angle, L4 tilt angle, trunk shift (TS), and apical vertebral translation (AVT) were compared preoperatively and at postoperative 5 days, 1 month, 6 months, 2 years, and final follow-up.

RESULTS

At postoperative 5 days, Cobb angle of the TL/L curve, L4 tilt angle, and AVT were improved, except TS and L3/L4 disc wedge angle. The L3/L4 disc wedge and L4 tilt angle were most increased at postoperative 6 months and decreased thereafter. L4 tilt angle, AVT, and TS were improved during postoperative follow-up, except L3/L4 disc wedge angle. Finally, Cobb angle of the TL/L curve (11.8° ± 5.1°, P < 0.001), L4 tilt angle (7.6° ± 4.0°, P < 0.001), AVT (19.2 ± 9.3 mm, P < 0.001), and TS (-5.0 ± 10.0 mm, P = 0.041) were improved; however, L3/L4 disc wedge angle (3.3° ± 2.3°, P = 0.442) was not improved compared to the preoperative evaluation.

CONCLUSION

When LIV was selected as the L3, the correction of TL/L curve was maintained in a minimum 5-year follow-up with the improvement of L4 tilt angle, AVT, and TS; however, L3/L4 disc wedge angle may remain.

LEVEL OF EVIDENCE

3.

How to Avoid Distal Adding-on Phenomenon for Rigid Curves in Major Thoracolumbar and Lumbar Adolescent Idiopathic Scoliosis? Identifying the Incidence of Distal Adding-on by Selection of Lowest Instrumented Vertebra

OBJECTIVE

We sought to compare the radiologic outcomes for different distal fusion levels in a rigid curve with major thoracolumbar and lumbar (TL/L) adolescent idiopathic scoliosis (AIS) using rod derotation (RD) with direct vertebral rotation (DVR) after pedicle screw instrumentation (PSI).

METHODS

This study finally enrolled 28 patients who were diagnosed with AIS in rigid curve with major TL/L curves, treated by PSI with RD and DVR and with a minimum 2-year follow-up. Patients were divided into 2 groups, L3 and L4, on the basis of the distal fusion level at the lowest instrumented vertebra (LIV) of L3 or L4.

RESULTS

There was no significant difference in TL/L curve, thoracic (minor), and compensatory (caudal) curves between the L3 and L4 groups either postoperatively (P = 0.162, 0.426, and 0.762, respectively) or at the last follow-up (P = 0.952, 0.620, and 0.562, respectively). The overall prevalence of unsatisfactory results was 42.9% (12/28 patients). The prevalence of unsatisfactory results was 61.1% (11/18) in the L3 group and 10% (1/10) in the L4 group, which was significantly different (P < 0.05).

CONCLUSIONS

Unsatisfactory results occurred more often in the L3 group than in the L4 group, and unsatisfactory results had significant influence on progression of TL/L and distal compensatory curves. Such progression was closely correlated with deteriorating LIV disk angle in the L3 group. Therefore if the curve is rigid, LIV should be extended to L4 to avoid the adding-on phenomenon in the treatment of major TL/L AIS using RD with DVR after PSI.

Where to stop distally in Lenke modifier C AIS with lumbar curve more than 60°: L3 or L4?

OBJECTIVE

Selecting lowest instrumented vertebra (LIV) in adolescent idiopathic scoliosis (AIS) with large lumbar curve can be difficult. Stopping the distal fusion at L3 could save more mobile lumbar segments but may increase the risk of decompensation. This study was designed to evaluate preoperative radiographic factors that were associated with the selection of either L3 or L4 as LIV in posteriorly treated AIS patients with large lumbar curve.

PATIENTS AND METHODS

A total of 84 AIS patients with lumbar curve >60° were analyzed with a minimum of 2-year follow-up after posterior instrumentation with lumbar curves included in fusion. Patients were grouped according to the selection of LIV, either L3 or L4 group. All radiograph parameters were measured pre- and post-operatively including Cobb angle, lumbar flexibility, L3 translation and rotation on posteroanterior (PA) and side-bending (SB) film, etc. The SRS-22 score was used to assess clinical outcomes. Radiographic and clinical parameters were compared between the two groups.

RESULTS

There were 24 patients in L3 group and 60 patients in L4 group. At last follow-up, no difference was found in the clinical and radiographic parameters between the two groups. Preoperatively, the L3 group had lower L3 translation on PA view, L3 translation on concave SB film, L3 rotation on convex SB film, more L3/4 disc opening on convex SB film and larger lumbar flexibility. Multivariate regression found L3 translation on concave SB film was the single most important predictor of LIV selection. Specifically, L3 translation on concave SB film <10 mm was a potential threshold for selecting L3 as LIV.

CONCLUSIONS

For AIS patients with large lumbar curve, instrumentation can be reliably stopped at L3 if L3 translation on preoperative concave SB film was less than 10 mm, with the same radiographic and clinical outcomes as fusing to L4.

Does fusion to T2 compared with T3/T4 lead to improved shoulder balance in adolescent idiopathic scoliosis with a double thoracic curve?

Proximal fusion level selection in adolescent idiopathic scoliosis (AIS) with a double thoracic curve (Lenke-2) remains debatable. The aim of this study was to compare the radiological outcomes of corrective surgery for Lenke-2 AIS according to the upper instrumented vertebra (UIV). This study included 74 patients who underwent corrective surgery for Lenke-2 AIS with the right main thoracic and left proximal thoracic (PT) curve at a single center. Various radiological parameters were measured using whole-spine standing radiographs preoperatively and postoperatively. Patients were grouped by proximal fusion level: T2 (group F; fusion, N=15) or T3/T4 (group NF; nonfusion, N=59). Preoperative and postoperative radiological parameters were compared between the two groups. Group NF was divided on the basis of the existence of a postoperative shoulder imbalance (PSI; >15 mm) and a subgroup analysis was carried out. PT curve correction rate (58.5 vs. 46.3%, P=0.005), right shoulder depression (4.3 vs. 10.3 mm, P=0.020), and proximal adjacent wedging (1.1 vs. 3.5°, P<0.001) were different between groups F and NF postoperatively. In the subgroup analysis, the Risser grade (3.9 vs. 2.8, P=0.009) and the main thoracic curve flexibility (53.5 vs. 42.6%, P=0.038) were different between the PSI positive and the PSI negative group when T3 or T4 was chosen as the UIV in Lenke-2 AIS. If T2 is selected as the UIV in patients with Lenke-2 AIS, more PT curve correction, less right shoulder depression, and less adjacent disc wedging can be anticipated. If T3 or T4 is chosen as the UIV, then right shoulder depression can be a problem postoperatively. Greater skeletal maturity and higher flexibility of the main thoracic curve might be preoperative risk factors for PSI. Thus, extension of the proximal fusion to T2 can be considered if the patient shows greater skeletal maturation and more flexible main thoracic curve to prevent PSI in Lenke-2 AIS with the right main thoracic and left PT curve.

Criteria for Ending the Distal Fusion at the L3 Vertebra vs. L4 in Surgical Treatment of Adolescent Idiopathic Scoliosis Patients with Lenke Type 3C, 5C, and 6C Curves: Results After Ten Years of Follow-up

Introduction

The selection of the most distal caudal vertebra in spinal fusion surgeries in adolescent idiopathic scoliosis patients with structural lumbar curvatures is still a matter of debate. The aim of this study was to determine the preoperative radiological criteria on the traction X-rays under general anesthesia (TrUGA) for selection between the L3 and L4 vertebrae and to assess the efficacy of these criteria via the long-term results of patients with Lenke Type 3C, 5C, and 6C curves.

Methods

Radiological data of 93 patients (84 females, 9 males) who met the inclusion criteria were retrospectively evaluated. The relationship between the L3 vertebra and the central sacral vertebral line, the portion of the L3 vertebra in the stable zone of Harrington, the parallelism of the L3 with the sacrum, and the tilt and rotation of the L3 on TrUGA radiographs were evaluated for the selection of the lowest instrumented vertebrae (LIV). Clinical results were analyzed using the Scoliosis Research Society-22 (SRS-22) questionnaire.

Results

The mean follow-up period of the study group was 149.3 months. According to the Lenke classification, 29 patients had Type 3C, 33 had Type 5C, and 31 had Type 6C curves. The preoperative analysis was based on standing anteroposterior (AP), supine traction, and bending X-rays, and the L3 vertebra was selected as the LIV in 37 patients (40%). These X-rays suggested L4 as the LIV in 56 patients (60%); however, based on our study criteria, the L3 vertebra was selected. No significant loss of correction was observed nor additional surgery due to decompensation was required in the follow-up period.

Conclusion 

The use of TrUGA radiographs with the identified criteria is an efficient alternative method in the selection of the LIV in patients with Lenke Type 3C, 5C, and 6C curves.

Current concepts in the surgical management of adolescent idiopathic scoliosis

Adolescent idiopathic scoliosis (AIS) is a complex 3D deformity of the spine. Its prevalence is between 2% and 3% in the general population, with almost 10% of patients requiring some form of treatment and up to 0.1% undergoing surgery. The cosmetic aspect of the deformity is the biggest concern to the patient and is often accompanied by psychosocial distress. In addition, severe curves can cause cardiopulmonary distress. With proven benefits from surgery, the aims of treatment are to improve the cosmetic and functional outcomes. Obtaining correction in the coronal plane is not the only important endpoint anymore. With better understanding of spinal biomechanics and the long-term effects of multiplanar imbalance, we now know that sagittal balance is equally, if not more, important. Better correction of deformities has also been facilitated by an improvement in the design of implants and a better understanding of metallurgy. Understanding the unique character of each deformity is important. In addition, using the most appropriate implant and applying all the principles of correction in a bespoke manner is important to achieve optimum correction.

In this article, we review the current concepts in AIS surgery.

Cite this article: Bone Joint J 2018;100-B:415–24.

Importance of Distal Fusion Level in Major Thoracolumbar and Lumbar Adolescent Idiopathic Scoliosis Treated by Rod Derotation and Direct Vertebral Rotation Following Pedicle Screw Instrumentation

STUDY DESIGN

A retrospective comparative study.

OBJECTIVE

The aim of this study was to analyze the exact distal fusion level in the treatment of major thoracolumbar and lumbar (TL/L) adolescent idiopathic scoliosis (AIS) using rod derotation (RD) and direct vertebral rotation (DVR) following pedicle screw instrumentation (PSI).

SUMMARY OF BACKGROUND DATA

Proper determination of distal fusion level is a very important factor in deformity correction and preservation of motion segments in the treatment of major TL/L AIS.

METHODS

AIS patients with major TL/L curves (n = 64) treated by PSI with RD and DVR methods with a minimum 2-year follow-up were divided into AL3 (flexible) and BL3 (rigid) according to the flexibility and rotation by preoperative bending radiographs.

RESULTS

There was no significant difference in TL/L (major) curve between the AL3 and BL3 groups postoperatively (P = 0.933) and at the last follow-up (P = 0.144). In addition, there was no significant difference in thoracic (minor) and compensatory (caudal) curve postoperatively (thoracic curve: P = 0.828, compensatory curve: P = 0.976); however, there was a significant difference in compensatory (caudal) curve at the last follow-up (P = 0.041). The overall prevalence of unsatisfactory results was 28.1% (18/64 patients), and the prevalence was 15.2% (7/46) in the AL3 group and 61.1% (11/18) in the BL3 group, which was significantly different (P < 0.05).

CONCLUSION

Lowest instrumented vertebra (LIV) would be selected at L3 (EV) when the curve is flexible; L3 crosses CSVL with a rotation of less than grade II in preoperative bending radiographs. However, if the curve is rigid, LIV should be extended to L4 (EV + 1) in order to prevent the adding-on phenomenon in the treatment of major TL/L AIS using RD and DVR following PSI.

LEVEL OF EVIDENCE

4.

Five major controversial issues about fusion level selection in corrective surgery for adolescent idiopathic scoliosis: a narrative review

BACKGROUND CONTEXT

Shoulder imbalance, coronal decompensation, and adding-on phenomenon following corrective surgery in patients with adolescent idiopathic scoliosis are known to be related to the fusion level selected. Although many studies have assessed the appropriate selection of the proximal and distal fusion level, no definite conclusions have been drawn thus far.

PURPOSE

We aimed to assess the problems with fusion level selection for corrective surgery in patients with adolescent idiopathic scoliosis, and to enhance understanding about these problems.

STUDY DESIGN

This study is a narrative review.

METHODS

We conducted a literature search of fusion level selection in corrective surgery for adolescent idiopathic scoliosis. Accordingly, we selected and reviewed five debatable topics related to fusion level selection: (1) selective thoracic fusion; (2) selective thoracolumbar-lumbar (TL-L) fusion; (3) adding-on phenomenon; (4) distal fusion level selection for major TL-L curves; and (5) proximal fusion level selection and shoulder imbalance.

RESULTS

Selective fusion can be chosen in specific curve types, although there is a risk of coronal decompensation or adding-on phenomenon. Generally, wider indications for selective fusions are usually associated with more frequent complications. Despite the determination of several indications for selective fusion to avoid such complications, no clear guidelines have been established. Although authors have suggested various criteria to prevent the adding-on phenomenon, no consensus has been reached on the appropriate selection of lower instrumented vertebra. The fusion level selection for major TL-L curves primarily focuses on whether distal fusion can terminate at L3, a topic that remains unclear. Furthermore, because of the presence of several related factors and complications, proximal level selection and shoulder imbalance has been constantly debated and remains controversial from its etiology to its prevention.

CONCLUSIONS

Although several difficult problems in the diagnosis and treatment of adolescent idiopathic scoliosis have been resolved by understanding its mechanism and via technical advancement, no definite guideline for fusion level selection has been established. A review of five major controversial issues about fusion level selection could provide better understanding of adolescent idiopathic scoliosis. We believe that a thorough validation study of the abovementioned controversial issues can help address them.

Selective versus hyperselective posterior fusions in Lenke 5 adolescent idiopathic scoliosis: comparison of radiological and clinical outcomes

PURPOSE

Recent literature has reported that the ]progression risk of Lenke 5 adolescent idiopathic scoliosis (AIS) during adulthood had been underestimated. Surgery is, therefore, proposed more to young patients with progressive curves. However, choice of the approach and fusion levels remains controversial. The aim of this study was to analyze the influence of the length of posterior fusion on clinical and radiological outcomes in Lenke 5 AIS.

METHODS

All Lenke 5 AIS operated between 2008 and 2012 were included with a minimum 2-year follow-up. Patients were divided into two groups according to the length of fusion. In the first group (selective), the upper instrumented level (UIV) was the upper end vertebra of the main structural curve and distally the fusion was extended to the stable and neutral vertebra, according to Lenke's classification. In the second group (hyperselective), shorter fusions were performed and the number of levels fused depended on the location of the apex of the curve (at maximum, 2 levels above and below, according to Hall's criteria). Apart from the fusion level selection, the surgical procedure was similar in both groups. Radiological outcomes and SRS-22 scores were reported.

RESULTS

78 patients were included (35 selective and 43 hyperselective). The number of levels fused was significantly higher in the first group (7.8 ± 3 vs 4.3 ± 0.6). None of the patients was fused to L4 in selective group. No correlation was found between length of fusion and complication rate. Eight patients had adding-on phenomenon among which 6 (75%) had initially undergone hyperselective fusions and had significantly higher postoperative lower instrumented vertebra (LIV) tilt. In the adding-on group, LIV was located above the last touching vertebra (LTV) in 62.5% of the cases and above the stable vertebra (SV) in 87.5%. Patients in the selective group reported a significantly lower score in the SRS function domain.

CONCLUSION

Coronal alignment was restored in both groups. Hyperselective posterior fusions can be considered in Lenke 5 AIS, preserving one or two mobile segments, with similar clinical and radiological outcomes. However, selection of the LIV according to SV and LTV need to be accurately analyzed in order to avoid adding-on during follow-up.

Short fusion strategy for thoracolumbar and lumbar adolescent idiopathic scoliosis using anterior dual-rod instrumentation

Aims

A total of 30 patients with thoracolumbar/lumbar adolescent idiopathic scoliosis (AIS) treated between 1989 and 2000 with anterior correction and fusion surgery using dual-rod instrumentation were reviewed.

Patients and Methods

Radiographic parameters and clinical outcomes were compared among patients with lowest instrumented vertebra (LIV) at the lower end vertebra (LEV; EV group) (n = 13) and those treated by short fusion (S group), with LIV one level proximal to EV (n = 17 patients).

Results

The allocation of the surgical technique was determined by the flexibility of the TL/L curves and/or neutral vertebrae located one level above LEV as determined on preoperative radiographs. If these requirements were met a short fusion was performed. The mean follow-up period was 21.4 years (16 to 27). The mean correction rate at final follow-up was significantly lower in the S group (74 sd 11%) than in the EV group (88 sd 13%) (p = 0.004).Coronal and sagittal balance, thoracic kyphosis, lumbar lordosis, and clinical outcomes evaluated by the Scoliosis Research Society-22 questionnaire scores were equivalent between the two groups.

Conclusion

Short fusion strategy, which uses LIV one level proximal to LEV can be considered as an alternative to the conventional strategy, which includes LEV in the fusion, when highly flexible TL/L curves are confirmed and/or neutral vertebrae are located one level above LEV in patients with thoracolumbar/lumbar AIS curves. Take home message: Short fusion strategy can be considered as an alternative to the conventional strategy in patients with thoracolumbar/lumbar AIS curves undergoing anterior spinal fusion with dual-rod instrumentation. Cite this article: Bone Joint J 2016;98-B:402–9.