Evaluating flexibility and predicting curve correction using fulcrum-bending radiographs in Lenke type 2 adolescent idiopathic scoliosis

Association between preoperative proximal thoracic curve flexibility and postoperative spontaneous correction in Lenke type 1 adolescent idiopathic scoliosis: a retrospective study

Lenke type 1 adolescent idiopathic scoliosis (AIS) is characterized by a structural main thoracic (MT) curve and a non-structural proximal thoracic (PT) curve. Accurate prediction of postoperative PT curve correction is crucial for achieving optimal surgical outcomes, including postoperative shoulder balance. This study aimed to determine which preoperative lateral bending and traction radiographs are most appropriate for assessing spontaneous postoperative PT curve correction. Fifty-five patients with Lenke type 1 AIS who underwent PSF between January 2006 and January 2020 were included. Preoperative curve flexibility was assessed using side-bending (SB), fulcrum-bending (FB), and traction (TR) radiographs. Radiographic measurements were conducted preoperatively, immediately postoperatively, and at the 2-year follow-up. The average preoperative Cobb angles for PT, main thoracic (MT), and thoracolumbar/lumbar (TL/L) curves were 24.7°, 53.5°, and 32.4°, respectively. SB radiographs demonstrated a significant correlation with 2-year postoperative PT Cobb angles (r = 0.526, p < 0.001), with no significant difference between preoperative SB measurements and actual 2-year postoperative outcomes (mean difference - 0.03°; 95%CI - 1.57 to 1.49; p = 0.88). FB radiographs accurately reflected MT correction but overestimated PT correction (mean difference 2.29°; 95%CI - 0.51 to 5.10; p = 0.11), while TR radiographs underestimated PT correction. These results indicate that SB radiographs can be used as a reliable reference for estimating postoperative spontaneous PT curve correction in Lenke type 1 AIS.

Utility of flexibility assessment by preoperative fulcrum-side bending for distal adding-on after posterior corrective fixation in adolescent idiopathic scoliosis Lenke types 1 and 2

PURPOSE

To examine the factors associated with distal adding-on (DAO) in Lenke type 1, 2 adolescent idiopathic scoliosis (AIS), particularly concerning flexibility assessment using preoperative fulcrum side bending (FSB). In addition, a secondary aim of this study was to compare the effectiveness of Fulcrum Side Bending (FSB) and Active Side Bending (ASB) radiographs, obtained in standing and supine positions, in assessing the flexibility of the main curve.

METHODS

We analysed 32 patients who underwent posterior corrective fixation for Lenke type 1, 2 AIS. Correction was performed using the all-pedicle screw method and the fixed caudal end was the last touching vertebra (LTV). Radiographic parameters, such as the standing Cobb angle (proximal thoracic, PT; main thoracic, MT; thoracolumbar, TL), were measured before surgery, after surgery and 2 years postoperatively. The Cobb angle was also evaluated under stress conditions of ASB and FSB, and the difference from the standing Cobb angle was calculated as ΔASB and ΔFSB. Patients were grouped based on the occurrence of DAO.

RESULTS

DAO occurred in 12 patients (37.5%); comparing the DAO and non-DAO groups, ΔFSB(PT) (11.2 ± 6.0 vs. 6.9 ± 5.8, p = 0.04) and ΔFSB(MT) (43.9 ± 13.1 vs. 35.9 ± 6.7, p = 0.02) and correction rate (MT) (81.2 ± 8.4 vs. 73.6 ± 9.8, p = 0.02) were significantly greater. Logistic regression analysis showed that the risk factors for DAO were ΔFSB (MT) (odds ratio 1.23 ± 0.098, p = 0.03) and correction rate (MT) (odds ratio 1.17 ± 0.083, p = 0.04).

CONCLUSIONS

ΔFSB and correction rate in MT were a risk factor for DAO. In cases with large MT corrections, the coronal plane was overbalanced in the TL, which could cause DAO during the postoperative course. Care should be taken in the setting of the lowest instrumented vertebra (LIV) to prevent DAO in patients with significant MT correction on preoperative FSB.

How Accurate Are Fulcrum Bending Radiographs in Estimating Postoperative Outcomes in Adolescent Idiopathic Scoliosis? A Systematic Review and Meta-analysis

BACKGROUND

Fulcrum bending radiographs can be used to assess coronal flexibility in patients with adolescent idiopathic scoliosis (AIS) to estimate postoperative correction. To obtain fulcrum bending radiographs, patients are passively bent over a radiolucent fulcrum at the apex of the curve. Available studies have disagreed about the accuracy in estimating postoperative correction, although these studies differed in terms of patients' baseline characteristics as well as other methods. Moreover, factors associated with accuracy were never explored. By pooling (meta-analyzing) results from these studies, we hoped to address these gaps in knowledge.

QUESTIONS/PURPOSES

In a meta-analysis, we asked: (1) Can fulcrum bending radiographs accurately estimate postoperative curve correction in patients with AIS? (2) What factors are associated with the accuracy of fulcrum bending estimation on postoperative coronal correction? (3) Is fulcrum flexibility associated with other surgical outcomes such as shoulder and coronal balance?

METHODS

PubMed, Embase, Medline, Journals@Ovid, Web of Science, and Scopus were searched from their inception up to August 27, 2024. Studies that (1) included patients with AIS undergoing single-stage posterior spinal fusion surgery without anterior release, (2) used fulcrum bending radiographs, (3) assessed radiographic surgical outcomes, and (4) had a minimum follow-up of 2 years were included. Studies that did not evaluate the use of fulcrum bending radiographs, those that did not report a p value, and studies with poor methodological quality were excluded. Our initial search yielded 433 articles, of which 172 remained after duplicate articles were removed. A total of 161 articles were excluded as the studies included patients who did not have AIS (n = 14), did not undergo surgery (n = 14), or did not undergo posterior spinal fusion (n = 23) or the studies did not evaluate the use of fulcrum bending radiographs (n = 59); had an insufficient follow-up duration of < 2 years (n = 15); did not evaluate the relationship between fulcrum bending radiographs and postoperative outcomes (n = 1); were reviews, commentaries, articles, conference proceedings, or non-English studies (n = 33); were animal studies (n = 1); or had poor methodological quality (n = 1). This left 11 studies for analysis. The Newcastle-Ottawa Quality Assessment Scale was used to evaluate the quality of evidence in three domains, including participant selection, comparability, and outcome measurement. Eleven included studies were of good quality except one with poor-quality evidence that was subsequently excluded from analysis. A random-effects meta-analysis was used to pool the data because of substantial statistical heterogeneity (I2 > 50%) in the included studies. The estimation of absolute correction was pooled using standardized mean differences, referred to as the mean difference; a value > 0 indicated overestimation and vice versa. Estimation of percentage correction was pooled using ratio of means between correction rate and fulcrum flexibility, referred to as fulcrum bending correction index (FBCI); a value > 1 indicated underestimation and vice versa.

RESULTS

Fulcrum bending radiographs tended to underestimate postoperative curve correction, although the difference was not clinically important (immediate postoperative mean difference -0.6° [95% confidence interval (CI) -0.9° to -0.4°], p < 0.001; immediate postoperative FBCI 1.15 [95% CI 1.09 to 1.21], p < 0.001; 2-year follow-up mean difference -0.43° [95% CI -0.6° to -0.2°], p < 0.001; 2-year follow-up FBCI 1.10 [95% CI 1.04 to 1.16], p = 0.001). To address the high between-study heterogeneity, we adjusted for potential confounders, which found that more flexible curves (regression coefficient 0.07 [95% CI 0.01 to 0.13]; p = 0.02) and proximal thoracic (immediate postoperative main thoracic versus proximal thoracic curves mean difference -0.8° [95% CI -1.4° to -0.2°], p = 0.01; 2-year follow-up main thoracic versus proximal thoracic curves mean difference -0.7° [95% CI -1.3° to -0.1°], p = 0.03) curves were associated with less underestimation. Segmental and alternate level screw placement were associated with underestimation of curve correction by fulcrum bending radiographs, although the difference was clinically unimportant. The degree of underestimation was worse with segmental screw placement at immediate postoperative (mean difference -1.0° [95% CI -1.9° to -0.1°]; p < 0.001) and 2-year follow-up (mean difference -1.0° [95% CI -1.6° to -0.4°]; p < 0.001). However, evidence surrounding more serious underestimation in segmental compared with alternate level screw placement was uncertain as only one study used a segmental screw placement strategy. Regarding the relationship between fulcrum flexibility and other radiographic outcomes, more rigid main thoracic curves were at risk of coronal imbalance, while more flexible curves were associated with postoperative shoulder imbalance. However, the evidence was inconclusive as it was reported by two or fewer studies.

CONCLUSION

Fulcrum bending radiographs offer a reliable estimate of postoperative coronal correction; the amount of underestimation that we observed on some endpoints was too small to be clinically meaningful. Although there was substantial statistical heterogeneity, the direction of effect was similar across all studies. Fulcrum bending estimation was also reliable when using alternate pedicle screw constructs. More flexible curves and proximal thoracic curves were associated with less underestimation. In more rigid curves, results of fulcrum bending estimation should be interpreted with caution, and alternate flexibility assessment methods such as traction should be considered.

LEVEL OF EVIDENCE

Level III, diagnostic study.

Predicting Surgical and Non-surgical Curvature Correction by Radiographic Spinal Flexibility Assessments for Patients With Adolescent Idiopathic Scoliosis: A Systematic Review and Meta-Analysis

STUDY DESIGN

Systematic Review and Meta-analysis.

OBJECTIVES

This systematic review and meta-analysis aimed to: (1) synthesize the prevalent application ratios of 2 radiographic spinal flexibility assessment methods in AIS patients treated with PSF or bracing; and (2) quantitatively evaluate the accuracy of these methods in predicting post-intervention correction outcomes.

METHODS

A systematic search was conducted across 5 electronic databases: CINAHL, Embase, Ovid, PubMed, and Web of Science. Meta-analyses were performed to investigate the accuracy of the spinal flexibility rate in predicting the post-intervention correction rate in AIS patients treated with PSF surgery or bracing, using RevMan 5.4.1 software.

RESULTS

The results of 31 studies, involving 1868 AIS patients, showed that the side-bending method was utilized more frequently than the fulcrum-bending method in both treatments. Meanwhile, the spinal flexibility evaluated by the fulcrum-bending method may provide a more accurate prediction of post-surgical correction compared to the side-bending approach, particularly for main curves. For the bracing treatment, only a few studies have preliminarily reported good capability of the side-bending method in predicting the initial in-brace correction.

CONCLUSIONS

This review quantitatively assessed the clinical application ratio and effectiveness of side-bending and fulcrum-bending radiographs in predicting post-intervention curve corrections in AIS patients undergoing surgical or bracing treatments. The results of the current review supported to adopt the fulcrum-bending approach for AIS patients undergoing PSF surgery with main thoracic curves, and the side-bending approach for those with thoracolumbar/lumbar curves. For patients receiving bracing treatment, further research is still needed to confirm the clinical value of the side-bending method.

Five days of inpatient scoliosis-specific exercises improve preoperative spinal flexibility and facilitate curve correction of patients with rigid idiopathic scoliosis

Preoperative spine flexibility plays a key role in the intraoperative treatment course of severe scoliosis. In this cohort study, we examined the effects of 5 day inpatient scoliosis-specific exercise (SSE) on the spinal flexibility of patients with adolescent idiopathic scoliosis before surgery. A total of 65 patients were analyzed. These patients were divided into a prospective cohort (n = 43, age: 15 ± 1.6 years, 36 girls and 7 boys, Lenke class 1 and 2, Cobb angle: 64 ± 11°) who underwent spinal fusion in 2020, and a retrospective cohort (n = 22, age: 15 ± 1.5 years, 17 girls and 5 boys, Lenke class 1 or 2, Cobb angle: 63 ± 10°), who underwent surgery between 2018 and 2019 and did not receive preoperative SSE. Rigid scoliosis was defined as a reduction of less than 50% in Cobb angle between the preoperative fulcrum bending and initial standing curve magnitude. In the prospective cohort, 21 patients (Cobb angle: 65 ± 11°) presented with rigid thoracic scoliosis (pre-SSE fulcrum bending: 40 ± 9°, 39% reduction), and therefore received 5-day SSE to improve their preoperative spinal flexibility (SSE group), whereas 22 patients (Cobb angle: 63 ± 12°) presented with flexible thoracic scoliosis (pre-SSE fulcrum bending: 27 ± 8°, 58% reduction), and therefore underwent surgery without preoperative SSE (non-SSE group). For patients who received 5-day preoperative SSE for 4 h every day, the International Schroth Three-Dimensional Scoliosis Therapy technique was implemented with an inpatient model. After 5 days of SSE, improvements in Cobb angle with post-SSE fulcrum-bending radiography (23 ± 7°, 66% reduction) and pulmonary function (forced expiratory volume in 1 s/forced expiratory volume: 87% before SSE and 92% after SSE, p < 0.01) were observed. At the postoperative day 5, the degree of scoliosis had reduced from 44 ± 6.6° to 22 ± 6° in the SSE group, which is 1° less than the Cobb angle obtained on post-SSE fulcrum-bending radiography. In the non-SSE group, the degree of scoliosis decreased to 26 ± 5.7°. In the retrospective cohort, the degree of scoliosis decreased to 35 ± 5°, with the group also having higher postoperative pain (Visual Analog Scale score = 7, range = 5-10) and an extended hospitalization duration (11 ± 3 days). At 2-year follow-up, curve correction was found to be maintained without adding-on or proximal junctional kyphosis. Compared with the non-SSE group, the SSE group exhibited a greater curve correction (66%) with a shorter hospitalization duration (5 ± 1 days) and a lower degree of postoperative pain (Visual Analog Scale score = 4, range = 3-8). Taken together, our findings indicate that 5 day SSE improves preoperative spinal flexibility and facilitates curve correction.

Usefulness of the spectral shaping dual-source computed tomography imaging technique in posterior corrective fusion for adolescent idiopathic scoliosis

PURPOSE

Since childhood exposure to radiation has been demonstrated to increase cancer risk with increase in radiation dose, reduced radiation exposure during computed tomography (CT) evaluation is desired for adolescent idiopathic scoliosis (AIS). Therefore, this retrospective study aimed to investigate the radiation dose of dual-source CT using a spectral shaping technique and the accuracy of the thoracic pedicle screw (TPS) placement for posterior spinal fusion (PSF) in patients with AIS.

METHODS

Fifty-nine female patients with thoracic AIS who underwent PSF using CT-guided TPSs were included and divided into two groups comprised of 23 patients who underwent dual-source CT (DSCT) with a tin filter (DSCT group) and 36 who underwent conventional multislice CT (MSCT group). We assessed the CT radiation dose using the CT dose index (CTDIvol), effective dose (ED), and accuracy of TPS insertion according to the established Neo's classification.

RESULTS

The DSCT and MSCT groups differed significantly (p < 0.001) in the mean CTDIvol (0.76 vs. 3.31 mGy, respectively) and ED (0.77 vs. 3.47 mSv, respectively). Although the correction rate of the main thoracic curve in the DSCT group was lower (65.7% vs. 71.2%) (p = 0.0126), the TPS accuracy (Grades 0-1) was similar in both groups (381 screws [88.8%] vs. 600 screws [88.4%], respectively) (p = 0.8133). No patient required replacement of malpositioned screws.

CONCLUSION

Spectral shaping DSCT with a tube-based tin filter allowed a 75% radiation dose reduction while achieving TPS insertion accuracy similar to procedures based on conventional CT without spectral shaping.

Defining "successful" treatment outcomes in adolescent idiopathic scoliosis: a scoping review

PURPOSE

Adolescent idiopathic scoliosis (AIS) is the most common type of scoliosis that affects children aged 10-18 years old, manifesting in a three-dimensional spinal deformity. This study aimed to explore outcome measures used in defining AIS treatment success. Particularly, analyzing the extent of qualitative and quantitative (radiographic and quality of life domains) measures to evaluate AIS and whether AIS treatment approaches (surgical, bracing and physiotherapy) influences outcomes used as proxies of treatment success.

METHODS

EMBASE and MEDLINE databases were used to conduct a systematic scoping review with 654 search queries. 158 papers met the inclusion criteria and were screened for data extraction. Extractable variables included: study characteristics, study participant characteristics, type of study, type of intervention approach and outcome measures.

RESULTS

All 158 studies measured quantitative outcomes. 61.38% of papers used radiographic outcomes whilst 38.62% of papers used quantitative quality of life outcomes to evaluate treatment success. Irrespective of treatment intervention utilized, the type of quantitative outcome measure recorded were similar in proportion. Moreover, of the radiographic outcome measures, the subcategory Cobb angle was predominantly used across all intervention approaches. For quantitative quality of life measures, questionnaires investigating multiple domains such as SRS were primarily used as proxies of AIS treatment success across all intervention approaches.

CONCLUSION

This study identified that no articles employed qualitative measures of describing the psychosocial implications of AIS in defining treatment success. Although quantitative measures have merit in clinical diagnoses and management, there is increasing value in using qualitative methods such as thematic analysis in guiding clinicians to develop a biopsychosocial approach for patient care.