Fulcrum Bending Correction Index Research Articles

Curve Overcorrection Predicts Coronal Imbalance in Selective Thoracic Fusion in Adolescent Idiopathic Scoliosis.

Retrospective cohort Study. To identify predictive factors for coronal imbalance after selective fusion in adolescent idiopathic scoliosis (AIS) with Lenke type 1 curves. AIS patients with Lenke type 1 curve with A, B and C lumbar modifiers underwent selective thoracic fusion. The curve fulcrum flexibility and fulcrum bending correction index (FBCI) was studied. Coronal imbalance was defined as more than 2cm of truncal shift or more than 2cm list at two-year follow-up. A total of 301 patients were included in the study. Coronal imbalance at two-year follow-up was found in 38 patients (13%). At the preoperative stage, we found a significant difference in main curve flexibility with 66±15% in the balanced group and 60±15% in the imbalanced group (P = .032). At the immediate postoperative stage, mean curve correction was 71±13% vs 70±13% and mean FBCI was 112±29% vs 122±29% in the balance and unbalanced group, respectively (P = .031). Postoperative FBCI of more than 125% (third quartile) resulted in an odds ratio of 2.1 (95%CI:1.1-4.3) for coronal imbalance at two years (P=.031). No significant changes in fusion mass or LIV tilt was observed. A decreased preoperative flexibility and a higher FBCI was significantly associated with coronal imbalance. A high FBCI is an indication of a curve correction that exceeds the inherent flexibility of the spine, and our results add to a growing body of evidence that "overcorrection" of the main curve can lead to postoperative imbalance.

Reducing Uncertainty in Anterior Vertebral Body Tethering: Predicting Postoperative Curvature With Fulcrum Bending Radiographs.

Retrospective Cohort Study. Mid-term Anterior Vertebral Body Tethering (AVBT) results demonstrate an acceptable degree of clinical success, yet the revision rate remains notably higher than fusion. Fulcrum-bending radiographs have previously been shown to more reliably predict radiological outcomes in Adolescent Idiopathic Scoliosis (AIS) as compared to supine-lateral bending radiographs. This study aims to discern how Fulcrum Flexibility Rate (FFR) correlates with Correction Rate (CR) and establish whether this can reliably predict residual deformity following AVBT surgery. A review of 38 consecutive AIS patients undergoing thoracic AVBT between 2015 - 2020 was performed. Preoperative (standing and fulcrum-bending) and postoperative (first-erect) radiographs were evaluated for curve magnitude using the Cobb-method. The FFR, CR and Fulcrum Bending Correction Index (FBCI) were calculated. Patients were also percentile-ranked according to their FFR and dichotomized into flexible and rigid cohorts for comparison. Student t-test, Pearson correlation and linear stepwise regression was applied. AVBT resulted in a significant improvement in the major Cobb angle (Preoperative: 50.9±7.5° vs Postoperative: 19.9±9.4°; P < .0001) with a mean FBCI of 98.0%. Bivariate correlation revealed a moderate relationship between fulcrum-bending and first-erect Cobb angle (r = .5306, P = .0006). Linear regression demonstrated a predictive relationship between fulcrum-bending and first-erect Cobb using the equation 'Postoperative Cobb = 7.5 + .65(Fulcrum-bending Cobb).' This is the first study to demonstrate the ability of fulcrum-bending radiographs to predict early radiographic outcomes following AVBT, 'timepoint-zero' for the growth modulation process.

Dual modality of vertebral body tethering : anterior scoliosis correction versus growth modulation with mean follow-up of five years.

AimsVertebral body tethering (VBT) is a non-fusion technique to correct scoliosis. It allows correction of scoliosis through growth modulation (GM) by tethering the convex side to allow concave unrestricted growth similar to the hemiepiphysiodesis concept. The other modality is anterior scoliosis correction (ASC) where the tether is able to perform most of the correction immediately where limited growth is expected.MethodsWe conducted a retrospective analysis of clinical and radiological data of 20 patients aged between 9 and 17 years old, (with a 19 female: 1 male ratio) between January 2014 to December 2016 with a mean five-year follow-up (4 to 7).ResultsThere were ten patients in each group with a total of 23 curves operated on. VBT-GM mean age was 12.5 years (9 to 14) with a mean Risser classification of 0.63 (0 to 2) and VBT-ASC was 14.9 years (13 to 17) with a mean Risser classification of 3.66 (3 to 5). Mean preoperative VBT-GM Cobb was 47.4° (40° to 58°) with a Fulcrum unbend of 17.4 (1° to 41°), compared to VBT-ASC 56.5° (40° to 79°) with 30.6 (2° to 69°)unbend. Postoperative VBT-GM was 20.3° and VBT-ASC Cobb angle was 11.2°. The early postoperative correction rate was 54.3% versus 81% whereas Fulcrum Bending Correction Index (FBCI) was 93.1% vs 146.6%. The last Cobb angle on radiograph at mean five years’ follow-up was 19.4° (VBT-GM) and 16.5° (VBT-ASC). Patients with open triradiate cartilage (TRC) had three over-corrections. Overall, 5% of patients required fusion. This one patient alone had a over-correction, a second-stage tether release, and final conversion to fusion.ConclusionWe show a high success rate (95%) in helping children avoid fusion at five years post-surgery. VBT is a safe technique for correction of scoliosis in the skeletally immature patient. This is the first report at five years that shows two methods of VBT can be employed depending on the skeletal maturity of the patient: GM and ASC.Cite this article: Bone Jt Open 2022;3(2):123–129.

Fulcrum flexibility of the main curve predicts postoperative shoulder imbalance in selective thoracic fusion of adolescent idiopathic scoliosis.

To identify preoperative predictors for postoperative shoulder imbalance (PSI) after corrective surgery of adolescent idiopathic scoliosis (AIS) and using the fulcrum-bending radiograph to assess flexibility. A consecutive surgical cohort of AIS patients undergoing selective thoracic fusion with alternate-level pedicle screw fixation was prospectively studied. Preoperative anteroposterior, lateral and fulcrum-bending radiographs were analysed. Postoperatively, a minimum of 2years clinical and imaging follow-up was performed of all patients. PSI was defined as a radiographic shoulder height difference of more than 20mm. A total of 80 patients were included, and 14 patients (18%) were confirmed with PSI at final follow-up. The flexibility of MT curve was an independent risk factor for PSI (odds ratio (OR) = 3.3 per 10% decrease, 95% confidence interval (CI) 1.6-8.2). Twenty-seven patients had a preoperative MT flexibility of < 55% (OR = 11.5, 95% CI 2.8-46.2). Postoperative T1 tilt was significantly higher in the PSI group (p < 0.001), and a T1 tilt of more than 9° resulted in 7.2 times higher odds of developing PSI (95% CI 2.0-26.0). Fulcrum-bending correction index (FBCI) was significantly higher in the PSI group at final follow-up, and 25 patients had a final postoperative MT FBCI above 120% (OR = 8.5 (95% CI 2.3-31.0). A low preoperative curve flexibility is a significant predictor for PSI. The surgical strategy should consider proximal fusion in presence of low-flexibility MT curves and consider less aggressive MT curve correction. Achieving a level T1 should be a main priority during intraoperative correction and may require fusion of the PT curve. III. These slides can be retrieved under Electronic Supplementary Material.

Characterization and Predictive Value of Segmental Curve Flexibility in Adolescent Idiopathic Scoliosis Patients.

A prospective radiographic analysis of adolescent idiopathic scoliosis (AIS) patients managed with alternate-level pedicle screw fixation was performed. The objective of this study was to characterize segmental curve flexibility and to determine its predictive value in curve correction in AIS patients. Little is known regarding the distinct segmental curve characteristics and their ability to predict curve correction in patients with AIS. The segmental Cobb angle was measured on posteroanterior standing radiographs and on fulcrum bending radiographs. Radiographs were analyzed preoperatively and at 2 years postoperatively and the curve was divided into upper, mid, and lower segments based on predefined criteria. The segmental flexibility and the segmental fulcrum bending correction index (FBCI) were calculated. Eighty patients were included with mean age of 15 years. Preoperative mean segmental Cobb angles were 18, 31, and 17 degrees in the upper, mid, and lower segments, respectively. Segmental bending Cobb angles were 6, 13, and 4 degrees, respectively, corresponding to segmental flexibilities of 50%, 47%, and 83% in the upper, mid, and lower segments, respectively (P < 0.001). At 2-year follow up, the mean segmental FBCI were 155%, 131%, and 100% in the upper, mid, and lower segments, respectively (P < 0.001), which suggested that the lower segment of the curve was more flexible than the other segments and that higher correction was noted in the upper segments. A significant, positive correlation was noted between the segmental bending Cobb angle and the segmental FBCI (P < 0.05), whereby the strength of the correlation varied based on the curve segment. This is the first study to demonstrate the segmental variations in curve flexibility using the fulcrum bending radiograph in AIS patients. Curve flexibility is not uniform throughout the curve and different segments exhibit greater flexibility/correctibility than others. Segmental flexibility should be considered in assessing AIS patients and in the clinical decision-making strategy to optimize curve correction outcomes. 03.

A randomized double-blinded clinical trial to evaluate the safety and efficacy of a novel superelastic nickel-titanium spinal rod in adolescent idiopathic scoliosis: 5-year follow-up.

To evaluate the safety and efficacy of a superelastic shape-memory alloy (SNT) rod used in the treatment of adolescent idiopathic scoliosis (AIS). AISPatients with Lenke 1 curves undergoing fusion surgery were randomized (1:1) at the time of surgery to receive either the SNT or a conventional titanium alloy (CTA) rod. Radiographs were obtained preoperatively and postoperatively up to 5years of follow-up. Parameters assessed included coronal and sagittal Cobb angles, and overall truncal and shoulder balance. Sagittal profiles were subcategorized into Types A (<20°), B (20-40°), and C (>40°). Twenty-four patients with mean age of 15years were recruited. A total of 87.0% of subjects were followed up till postoperative 5years, but all patients had minimum 2years of follow-up. The fulcrum-bending correction index for the SNT group was 113% at postoperative day 4 and 127% at half-year, while the CTA group was 112% at postoperative day 4 and only 106% at half-year. In terms of sagittal profile, the SNT group moved toward type B profile at half-year follow-up with a mean correction of 7.6°, while no significant change was observed in the CTA group (-0.7°). Nickel levels remained normal, and there were no complications. This is the first randomized clinical trial of a novel SNT rod for treating patients with AIS, noting it to be safe and has potential to gradually correct scoliosis over time. This study serves as a pilot and platform to properly power future large-scale studies to demonstrate efficacy and superiority.

Key-Vertebral Screws Strategy for Main Thoracic Curve Correction in Patients With Adolescent Idiopathic Scoliosis.

The following study was a prospective radiographic and retrospective clinical data assessment of adolescent idiopathic scoliosis (AIS) patients who had undergone a key-vertebral screws strategy (KVSS) at a single institution, with a minimum of 2 years' follow-up. The aim of the study was to introduce the KVSS for the operative treatment of AIS of the main thoracic curve, and to address the role of the fulcrum-bending radiograph (FBR) in predicting the outcome of surgical management by this method. The application of multilevel pedicle screws for the main thoracic curve in AIS patients is popular in an effort to provide spinal stability, enhance fusion outcome, and provide optimal curve correction. However, with the application of pedicle screw also comes a potential risk for soft tissue and neural injury and increased health care costs. It remains unknown whether limited screw placement can provide proper curve correction without compromising patient outcome. A total of 17 consecutive patients with AIS extending to the main thoracic spine, who had undergone posterior fusion and fixation by the KVSS, a procedure in which screws are placed at important strategic points in the spine (ie, bilaterally at the upper and lower end segments of the fusion block, apical vertebra on the convex side, adjacent cephalad, and caudal screw placement on the concave side), at a single institution, with a minimum of 2 year' follow-up, were included. The assessment of preoperative standing posteroanterior and sagittal, FBR, and postoperative standing posteroanterior and sagittal plain radiographs were assessed in all patients. The flexibility of the curve as well as the fulcrum-bending correction index (FBCI) were calculated for all patients. Postoperatively, radiographs were assessed at the immediate (ie, 1 wk) and last follow-up. Clinical assessment entailed evaluation of patient demographics and the presence of any intraoperative or postoperative complications. The mean age at the time of surgery was 15.6 years. The mean follow-up was 39.8 months. The average FBR flexibility was 62.2%. The mean immediate curve correction was 71.2%, which did not differ in comparison with the last follow-up assessment (P>0.05). The mean immediate and last follow-up FBCIs were 119.3% and 112.5%, respectively (P=0.079). A significant negative correlation was found between immediate FBCI to that of the FBR curve flexibility (r=-0.706; P=0.002), which remained similar on the last follow-up (r=-0.681; P=0.003). Sagittal alignment did not significantly change from the immediate to last follow-up (P=0.163) Fusion was achieved in all patients. No instrumentation-related complications were noted. Key-vertebral screws strategy is a safe and cost-effective method for the surgical treatment of the main thoracic curve in AIS patients. Moreover, in the context of this strategy, the FBR may have some predictive utility in the correction of the main thoracic curve in AIS patients.

Prediction of Curve Correction Using Alternate Level Pedicle Screw Placement in Patients With Adolescent Idiopathic Scoliosis (AIS) Lenke 1 and 2 Using Supine Side Bending (SB) and Fulcrum Bending (FB) Radiograph.

Prospective cohort study. To compare side bending (SB) and fulcrum bending (FB) radiographs in patients with adolescent idiopathic scoliosis (AIS) and effect of magnitude and AR curves on curve correctability. The prediction of correction using side bending flexibility (SBF) and fulcrum bending flexibility (FBF) in alternate level pedicle screw (PS) configuration and effect of curve magnitude and AR curves are not well understood. 100 AIS Lenke 1 and 2 were recruited. Curve magnitude was stratified to G1 (41°-60°), G2 (61°-80°), G3 (>80°). The main thoracic (MT) curves were subclassified to AR curves [Miyanji F, Pawelek JB, Van Valin SE, et al. Is the lumbar modifier useful in surgical decision making? Defining two distinct Lenke 1A curve patterns. Spine 2008;33:2545-51]. Preoperatively SBF and FBF were determined whereas postoperative parameters were correction rate (CR), fulcrum bending correction index (FBCI), and side bending correction index (SBCI). Correlation test were carried out between SBF, FBF versus CR for the cohort. There were 38 (G1), 42 (G2), and 20 (G3) patients. 34% were AR curves. SBF for G1, G2, and G3 were 61.3 ± 14.4, 59.2 ± 16.2 and 43.1 ± 13.1% (P = 0.000) whereas FBF for G1, G2, and G3 were 71.1 ± 16.5, 58.3 ± 18.1 and 52.7 ± 17.1% (P = 0.000). The CR was G1 (74.5 ± 11.5%), G2 (69.2 ± 12.7%), and G3 (70.2 ± 8.6%). FBCI was 1.11 ± 0.3 (G1), 1.28 ± 0.4 (G2) and 1.48 ± 0.6 for G3. SBCI was 1.26 ± 0.2 (G1), 1.50 ± 0.5 (G2), and 1.72 ± 0.4 for G3. There was strong correlation for SBF and FBF versus CR for G1 and G2. For G3, a very strong correlation was established between SBF (r = 0.846, r = 0.716) and FBF versus CR (r = 0.700, r = 0.540). AR curves demonstrated higher SBF and FBF. CR remains almost constant in G1, G2, and G3. SBCI and FBCI increase significantly in G1, G2, and G3. Correlation between SBF and FBF and CR was strong for G1, G2, and very strong for G3. AR curves showed better correctability with SB and FB films.

Comparison of Radiographic Postoperative Outcomes Between Males and Females With AIS.

The primary aim was to compare postoperative radiographic outcomes between sexes among adolescent idiopathic scoliosis (AIS) patients. A total of 162 AIS patients (42 males and 120 females) undergoing pedicle screw instrumentation and posterior fusion were included. Coronal and sagittal curves and flexibilities were measured and calculated. The postoperative correction rate (CR), fulcrum bending correction index (FBCI), and Cincinnati correction index were evaluated to compare the surgical benefits between sexes.Males were older (16.79 vs 14.79 years, respectively; P < 0.01) and had stiffer curves than females (lateral bending flexibility percentage: 47.77 vs 52.57, respectively, P = 0.21; traction flexibility percentage: 35.48 vs 36.98, respectively, P = 0.98; fulcrum bending flexibility percentage: 56.13 vs 66.57, respectively, P < 0.05). Males and females exhibited similar Lenke classification schemes (P = 0.72), but had different Risser signs (P < 0.01). Although males had greater postoperative curves (20.81° vs 16.83°, respectively; P = 0.009), no obvious differences in the CRs were noted between males and females (FBCI: 145.20% vs 108.37%, respectively; P = 0.92). Smaller preoperative lumbar lordosis was noted in males than in females (40.05° vs 45.72°, respectively; P = 0.03), yet no statistically significant differences in the preoperative and postoperative sagittal curves were observed between the sexes. In conclusion, considering the preoperative flexibilities, the 2 sexes achieved comparable surgical benefits without sacrificing the sagittal balance.

Selection of Fusion Levels Using the Fulcrum Bending Radiograph for the Management of Adolescent Idiopathic Scoliosis Patients with Alternate Level Pedicle Screw Strategy: Clinical Decision-making and Outcomes.

ObjectiveSelecting fusion levels based on the Luk et al criteria for operative management of thoracic adolescent idiopathic scoliosis (AIS) with hook and hybrid systems yields acceptable curve correction and balance parameters; however, it is unknown whether utilizing a purely pedicle screw strategy is effective. Utilizing the fulcrum bending radiographic (FBR) to assess curve flexibility to select fusion levels, the following study assessed the efficacy of pedicle screw fixation with alternate level screw strategy (ALSS) for thoracic AIS.MethodsA retrospective study with prospective radiographic data collection/analyses (preoperative, postoperative 1-week and minimum 2-year follow-up) of 28 operative thoracic AIS patients undergoing ALSS was performed. Standing coronal/sagittal and FBR Cobb angles, FBR flexibility, fulcrum bending correction index (FBCI), trunkal shift, radiographic shoulder height (RSH), and list were assessed on x-rays. Fusion level selection was based on the Luk et al criteria and compared to conventional techniques.ResultsIn the primary curve, the mean preoperative and postoperative 1 week and last follow-up standing coronal Cobb angles were 59.9, 17.2 and 20.0 degrees, respectively. Eighteen patients (64.3%) had distal levels saved (mean: 1.6 levels) in comparison to conventional techniques. Mean immediate and last follow-up FBCIs were 122.6% and 115.0%, respectively. Sagittal alignment did not statistically differ between any assessment intervals (p>0.05). A decrease in trunkal shift was noted from preoperative to last follow-up (p = 0.003). No statistically significant difference from preoperative to last follow-up was noted in RSH and list (p>0.05). No "add-on" of other vertebra or decompensation was noted and all patients achieved fusion.ConclusionsThis is the first report to note that using the FBR for decision-making in selecting fusion levels in thoracic AIS patients undergoing management with pedicle screw constructs (e.g. ALSS) is a cost-effective strategy that can achieve clinically-relevant deformity correction that is maintained and without compromising fusion levels.

The Effect of Metal Density on Coronal and Sagittal Curve Correction in Thoracic Adolescent Idiopathic Scoliosis

Introduction The literature is contradictory regarding the effect of metal density on correction of thoracic AIS. Given the rising cost of surgery for AIS, instrumentation should be used rationally. We aim to assess the impact of metal density on coronal and sagittal correction of AIS and assess if larger, less flexible curves necessitate high metal density. Material and Methods It is a retrospective multicenter case series. Inclusion criteria: Lenke 1–2 AIS, curve flexibility assessed by fulcrum-bending technique, single stage posterior only surgery, constructs using &gt; 80% screws, variable metal density, and &gt; 2-year follow-up. Outcome measures: Coronal main thoracic (MT) and lumbar curve correction, fulcrum-bending correction index (FBCI), thoracic kyphosis, lumbosacral lordosis, metal density (number of instrumented pedicles vs. total available), and fusion length. Surgical technique: Standard technique used in all centers employed extra hard titanium–aluminum–niobium alloy 6 mm diameter rods (DePuy Synthes, Raynham, Pennsylvania, United States) with reduction of the curvature via cantilever-segmental translation maneuvers. Implant location and density was according to curve stiffness and intraoperative bone density. The majority of the implants were on the thoracic curve convexity. Analysis: Bivariate analysis of outcome measures. Given the numerous correlations performed, a Bonferroni corrected p value was used, p &lt; 0.005. Two groups of pairs matched by curve type and exact fusion levels but differing MT curve magnitude were compared using student t-test. Outcomes for the quartiles of preoperative MT flexibility were compared using an ANOVA. Results A total of 106 patients, 94 were female patients. A total of 78 patients had Lenke 1 and 28 had Lenke 2. Mean age was 14 years. Bivariate analysis: No significant correlations were present between metal density and coronal curve correction rates of the MT (r = 0.13, p = 0.19) or lumbar curves (r = ␂ 0.15, p = 0.12) or FBCI; MT (r = ␂ 0.1, p = 0.31), lumbar (r = 0.00, p = 0.97). Metal density had no effect on change in thoracic kyphosis (r = 0.22, p = 0.04) or lumbosacral lordosis (r = 0.27 p = 0.01). Longer fusion length was associated with greater loss of thoracic kyphosis (r = ␂ 0.31, p = 0.003) and less postoperative thoracic kyphosis (r = ␂ 0.31, p = 0.003) but did not affect lumbosacral lordosis. Curve magnitude: Two groups of 21 matched cases from preoperative MT curve magnitude (&lt; 70 vs. ≥ 70 degrees) treated with comparable metal density (54 vs. 57%, p = 0.4) had equivalent MT and lumbar curve correction rates and FBCI. Sagittal profile changes did not differ significantly. Flexibility: No significant differences in MT, lumbar, and sagittal curve changes were present among the four MT flexibility quartiles (&lt; 32, 33–43, 43–51, 52–87%) despite all groups receiving comparable metal density (58, 58, 60, 62%, p = 0.2). Conclusion Metal density does not affect coronal and sagittal plane correction in surgery for thoracic AIS. Longer fusion length adversely affects sagittal profile. Larger and less flexible curves do not necessarily require high metal density.

Changhai fulcrum bending radiographic technique to assess curve flexibility in patients with adolescent idiopathic scoliosis

To evaluate the role and value of Changhai fulcrum bending radiograph(CH-FBR) in curve flexibility assessment of adolescent idiopathic scoliosis(AIS) patients. Thirty-seven AIS patients treated between June 2012 and August 2013 were enrolled, including 31 female and 6 male patients whose age ranged from 10 to 19 years, averaged of 15.0 years. The assessment of radiographs included preoperative standing posterior-anterior radiograph, supine side-bending radiograph, traditional fulcrum bending radiograph, Changhai fulcrum bending radiograph and postoperative standing posterior-anterior radiograph. Postoperatively, radiographs were assessed at one week. The CH-FBR was performed at the lowest height and the optimized height which means the weight on the fulcrum touch the maximum. All measurements of angle were made with use of the Cobb method. The flexibility of the curve as well as the correction rate and fulcrum bending correction index (FBCI) were calculated for all patients. The maximum height of CH-FBR, basic weight and maximum weight were measured for all AIS. Paired t-tests were used to assess differences between preoperative and postoperative curves within group samples. The Pearson correlation coefficients were calculated using bivariate analysis between CH-FBR flexibility rate and correction rate, the maximum height of CH-FBR and maximum weight, the height changes of CH-FBR and weight changes. A total of 46 curves were involved in this study, including 28 thoracic and 18 thoracolumbar/lumbar curves. Preoperatively, the mean Cobb angle of the 46 structural curves was 47° ± 11°. Postoperatively, the mean Cobb angle was 11° ± 5°. Cobb's angle in supine side-bending(t = 7.2, P = 0.001), traditional fulcrum bending (t = 7.1, P = 0.001) and lowest height of Changhai fulcrum bending (t = 6.5, P = 0.001) were significantly different from the postoperative Cobb angle; Cobb's angle in traditional FBR (t = 11.0, P = 0.001) and lowest height of Changhai fulcrum bending (t = 13.6, P = 0.001) were significantly different from the optimized height CH-FBR Cobb angle. There was no significant difference found between traditional FBR Cobb angle and lowest height CH-FBR Cobb angle (t = 2.0, P = 0.051), optimized height CH-FBR Cobb angle and postoperative Cobb angle (t = 0.9, P = 0.36), lowest height CH-FBR Cobb angle and traditional FBR Cobb angle(t = 2.0, P = 0.051). The maximum height of CH-FBR, basic weight and maximum weight were (29.6 ± 1.4)cm,(20 ± 6)kg, and (40 ± 6) kg. Preoperatively, the mean Cobb angle of the 28 structural curves(main thoracic curves) was 46° ± 11°. Postoperatively, the mean Cobb angle was 12° ± 6°. Preoperatively, the mean Cobb angle of the 18 structural curves(thoracolumbar/lumbar curves) was 49° ± 12°. Postoperatively, the mean Cobb angle was 10° ± 5°. The results were same in 28 structural curves, 18 structural curves as well as 46 curves. Correlation analysis of 46 curves indicated that the maximum height of CH-FBR positively correlated with maximum weight (r = 0.69, r(2) = 0.47, P = 0.001), the height changes of CH-FBR positively correlated with weight changes on CH-FBR (r = 0.62, r(2) = 0.38, P = 0.001). CH-FBR is a more reliable and effective method than traditional FBR and supine side-bending for curve flexibility evaluation in AIS patients. Moreover, compared to the traditional FBR and side-bending radiograph, the flexibility suggested by the optimized height CH-FBR more closely approximates the postoperative result made by pedicle screws fixation and fusion.

The Predictive Value of the Fulcrum Bending Radiograph in Spontaneous Apical Vertebral Derotation in Adolescent Idiopathic Scoliosis

A prospective cohort study of Cobb angles (CA) and apical vertebral rotations (AVR) in 25 patients who had adolescent idiopathic scoliosis. To assess in vivo the concomitant vertebral derotation occurring with correction of scoliosis deformity as a result of coupling effect by using the fulcrum bending radiograph and to assess whether the fulcrum bending radiograph can predict the amount of postoperative apical derotation when no additional intraoperative apical derotation maneuver is used. Adolescent idiopathic scoliosis (AIS) is a 3-dimensional coupling deformity. Various studies have reported vertebral derotational effects, using different implant constructs and surgical techniques for AIS. However, none of them have considered the spontaneous coupling effect on vertebral derotation produced by correction of the coronal deformity, in particular, using the predictive capacity of the preoperative fulcrum bending radiograph. Twenty-five patients with flexible Lenke type 1 AIS with CA greater than 45° who underwent posterior spinal fusion with instrumentation, without direct apical derotation were prospectively assessed. CA and AVR in standing, supine, and fulcrum bending positions preoperatively and in supine position postoperatively were assessed on radiographs and computed tomographic scans. RESULTS.: The study entailed 80% adolescent girls and 20% adolescent boys (mean age, 15.5 years). The mean AVR values on preoperative standing, supine, and fulcrum bending positions and postoperation were 24.2°, 17.7°, 9.8°, and 8.1° respectively. The preoperative AVR highly correlated with the preoperative CA (R = 0.75). The postoperative AVR was correlated with the postoperative CA (r = 0.82) and the change in curve magnitude (r = -0.49), correction rate (r = -0.83), and fulcrum bending correction index (r = -0.45) (P < 0.05). There was no significant difference in AVR between preoperative fulcrum bending and postoperative assessment. Correction of scoliosis deformity produces spontaneous reduction of rotational deformity through coupling. The amount of spontaneous apical vertebral derotation with fulcrum bending can be used to assess the flexibility of the rotational deformity. In flexible curves, it also predicts the amount of apical derotation achievable with surgery. These should be considered when assessing the derotational effect of different implants and surgical strategies.

The “X-Factor” Index: a new parameter for the assessment of adolescent idiopathic scoliosis correction

The correction rate (CR) and fulcrum bending correction index (FBCI) based on the fulcrum bending radiograph (FBR) were parameters introduced to measure the curve correcting ability; however, such parameters do not account for contributions by various, potential extraneous "X-Factors" (e.g. surgical technique, type and power of the instrumentation, anesthetic technique, etc.) involved in curve correction. As such, the purpose of the following study was to propose the concept of the "X-Factor Index" (XFI) as a new parameter for the assessment of the correcting ability of adolescent idiopathic scoliosis (AIS). A historical cohort radiographic analysis of the FBR in the setting of hook systems in AIS patients (Luk et al. in Spine 23:2303-2307, 1998) was performed to illustrate the concept of XFI. Thirty-five patients with AIS of the thoracic spine undergoing surgical correction were involved in the analysis. Plain posteroanterior (PA) plain radiographs were utilized and Cobb angles were obtained for each patient. Pre- and postoperative PA angles on standing radiograph and preoperative fulcrum bending angles were obtained for each patient. The fulcrum flexibility, curve CR, and FBCI were determined for all patients. The difference between the preoperative fulcrum bending angle and postoperative PA angle was defined as Angle(XF), which accounted for the correction contributed by "X-Factors". The XFI, designed to measure the curve correcting ability, was calculated by dividing Angle(XF) by the fulcrum flexibility. The XFI was compared with the curve CR and FBCI by re-evaluating the original data in the original paper (Luk et al. in Spine 23:2303-2307, 1998). The mean standing PA and FBR alignments of the main thoracic curve were 58.3° and 24.5°, respectively. The mean fulcrum flexibility was 58.8%. The mean postoperative standing PA alignment was 24.7°. The mean curve CR was 58.0% and the mean FBCI was 101.1%. The mean XFI was noted as 1.03%. The CR was significantly positively correlated to curve flexibility (r=0.66; p<0.01).The FBCI (r=-0.47; p=0.005) and the XFI (r=-0.45; p=0.007) were significantly negatively correlated to curve flexibility. The CR was not correlated to Angle(XF) (r=0.29; p=0.089).The FBCI (r=0.97; p<0.01) and the XFI (r=0.961; p<0.01) were significantly positively correlated to Angle(XF). Variation in XFI was noted in some cases originally presenting with same FBCI values. The XFI attempts to quantify the curve correcting ability as contributed by "X-Factors" in the treatment of thoracic AIS. This index may be a valued added parameter to accompany the FBCI for comparing curve correction ability among different series of patients, instrumentation, and surgeons. It is recommended that the XFI should be used to document curve correction, compare between different techniques, and used to improve curve correction for the patient.

Coronal deformity correction in adolescent idiopathic scoliosis patients using the fulcrum-bending radiograph: a prospective comparative analysis of the proximal thoracic, main thoracic, and thoracolumbar/lumbar curves

The aim of the prospective, comparative radiographic analysis was to determine the role of the fulcrum-bending radiograph (FBR) for the assessment of the proximal thoracic (PT), main thoracic (MT), and the thoracolumbar/lumbar (TL/L) curves in patients undergoing posterior spinal pedicle screw fixation and fusion for adolescent idiopathic scoliosis (AIS). The FBR demonstrated statistically better correction than other preoperative methods for the assessment of frontal plane correction of the MT curves. The fulcrum-bending correction index (FBCI) has been considered a superior method than the correction rate for comparing curve correction undergoing posterior spinal fusion because it accounts for the curve flexibility. However, their applicability to assess the PT and TL/L curves in AIS patients remains speculative. The relation between FBR and correction obtained by pedicle screws fixation is still unknown. Thirty-eight consecutive AIS patients who underwent pedicle screw fixation and posterior fusion were included in this study. The assessment of preoperative radiographs included standing posterior-anterior (PA), FBR, supine side-bending, and postoperative standing PA and lateral plain radiographs. The flexibility of the curve, as well as the FBCI, was calculated for all patients. Postoperatively, radiographs were assessed at immediate (i.e. 1 week), 3-month, 6-month, 12-month, and 2-year follow-up. Cobb angles were obtained from the PT, MT, and TL/L curves. The study consisted of 9 PT, 37 MT, and 12 TL/L curves, with a mean age of 15.1 years. The mean FBR flexibility of the PT, MT, and the TL/L curves was 42.6, 61.1, and 66.2%, respectively. The mean operative correction rates in the PT, MT, and TL/L curves were 43.4, 69.3, and 73.9%, respectively, and the mean FBCI was 103.8, 117.0, and 114.8%, respectively. Fulcrum-bending flexibility was positively correlated with the operative correction rate in PT, MT, and TL/L curves. Although the correction rate in MT and TL/L curves was higher than PT curves, the FBCI in PT, MT, and TL/L curves was not significantly different (p < 0.05). The FBR can be used to assist in the assessment of PT, MT, and TL/L curve corrections in AIS patients. When curve flexibility is taken into account by FBR, the ability of pedicle screws to correct PT, MT, and TL/L curves is the same.

Reviewer’s comment on “The ‘X-Factor’ Index: a new parameter for the assessment of the adolescent idiopathic scoliosis correction” by Yuqing Sun et al. (ESJO-D-09-00493 R1)

According to Luk et al. [1] the fulcrum bending radiograph can predict the magnitude of correction of idiopathic scoliosis. The fulcrum bending is a measure of the intrinsic properties of the scoliotic spine like fixed bony deformity of vertebrae, as well as flexibility of discs, thoracic cage, muscles, and ligaments. Correction depends on extrinsic factors: on instrumentation pattern, mobilisation technique, magnitude and sequence of applied forces and moments, as well as on positioning of the patient. Furthermore, we can expect some random variation between fulcrum bending Cobb angles and postoperative Cobb angles. According to equation 7 the authors have defined the X-Factor Index as the difference between the fulcrum bending angle and the postoperative Cobb angle, divided by a factor indicating flexibility of the curve. The dividend (fulcrum bending angle minus the postoperative Cobb angle) depends on the extrinsic factors as well as on random variation, the divisor (equation 4) is an expression of the intrinsic factors (and of the performance of the fulcrum bending radiograph). An example will demonstrate how the X-Factor Index (XFI) is responding to variation of the fulcrum angle. Let us assume the preoperative Cobb angle be 50°, and the postoperative Cobb angle be 20°. The resulting X-Factor is 0%, if the fulcrum bending is 20° (same correction obtained by fulcrum bending and postoperatively), 25% with a fulcrum bending angle of 30°, 100% with 40°, and 250% with 45°, respectively. With a 50° fulcrum bending angle, no X-factor can be obtained because of division by zero. If the preoperative angle be 50°, the postoperative 20°, and the fulcrum angle 10° (final correction worse than fulcrum bending), the X-Factor Index will get negative and would be −12.5%, and with a fulcrum angle of 0° −20%. Therefore, in a typical range of pre- and postoperative angles as well as fulcrum angles, the X-Factor Index provides reasonable results, but not in a linear correlation. If no correction can be obtained, the X-Factor Index will be infinite. If rigid and flexible curves are mixed in a sample of patients, the average may tend to extreme values. The X-Factor Index is a quotient of extrinsic factors divided by intrinsic factors, with the intention to create a parameter to measure extrinsic factors. The original construct of Luk et al. to measure extrinsic factors, the Fulcrum Bending Correction Index (FBCI, equation 6), is comparable to the XFI, with a different dividend and the same divisor, the dividend being fulcrum bending angle minus the postoperative Cobb angle in the XFI, and the correction rate (preop − postop)/preop in the FBCI. In Luk et al. [2] the FBCI was almost the same for four different instrumentations. We do not know, whether the XFI reacts more than the FBCI to particular surgical techniques such as mobilisation of ribs, or the use of pedicle screws in every pedicle versus in “strategic” pedicles. The authors recommend the X-Factor Index in order to compare between different surgical techniques. These extrinsic factors may be associated with the X-Factor Index in different and varying proportions. An analysis of variance can demonstrate the varying degree of impact of different techniques, but will need a much higher number of patients, bearing in mind the considerable variation in curve magnitude, curve extension and rigidity of idiopathic scoliotic curves. Such an analysis could not be addressed in the current study due to an entire sample of only 30 patients. The X-Factor Index is presumably not a good indicator for surgical skill, but may be valuable as a construct to measure the impact of different surgical techniques. As the techniques vary often in a way, which is not communicated, because surgeons consider their personal technique as a matter of course, differences in reported X-Factor Index values may induce a search for the reasons explaining differences. Furthermore, the proportion of the effect of a surgical measure can be expressed as a proportion of the X-Factor.

Predictability of the Fulcrum Bending Radiograph in Scoliosis Correction with Alternate-Level Pedicle Screw Fixation

The fulcrum bending radiograph accurately predicts scoliosis curve correction in patients with thoracic adolescent idiopathic scoliosis who are managed with hooks. We assessed the predictive value of the fulcrum bending radiograph in the context of alternate-level pedicle screw fixation of the scoliotic spine. A prospective radiographic analysis of patients with thoracic adolescent idiopathic scoliosis who were managed operatively with alternate-level pedicle screw fixation at a single institution was performed. The Cobb angle was measured on posteroanterior standing coronal radiographs that were made preoperatively and one week postoperatively. The fulcrum flexibility percentage and the fulcrum bending correction index percentage were calculated. Forty-two patients were assessed. The mean age at the time of surgery was 14.6 years, and the mean number of fused levels was 9.4. On the preoperative radiographs, the mean values for the standing Cobb angle, the fulcrum bending radiograph Cobb angle, and fulcrum flexibility were 57.9 degrees, 21.8 degrees, and 62.7%, respectively. On the one-week postoperative radiographs, the mean Cobb angle was 15.4 degrees, the mean curve correction was 73.4%, and the mean fulcrum bending correction index was 122.1%. A significant, positive correlation was noted between the fulcrum bending radiograph angle and the fulcrum bending correction index, indicating that the fulcrum bending radiograph could predict the correction of flexible curves; however, for stiff curves, pedicle screws could provide more correction than the fulcrum bending radiograph predicted. To our knowledge, this is the first study to demonstrate the predictive value of the fulcrum bending radiograph in the context of alternate-level pedicle screw fixation in patients with adolescent idiopathic scoliosis. Curve flexibility may dictate the degree of the fulcrum bending correction index, whereby a curve that is less flexible may achieve a greater fulcrum bending correction index. The fulcrum bending radiograph has potential predictive utility. In addition, pedicle screw constructs appear to have a better ability to correct scoliosis in comparison with hooks and hybrid constructs.

The Use of Fulcrum Bending Radiographs in Anterior Thoracic Scoliosis Correction

A prospective, consecutive series of 90 patients receiving fulcrum bending radiographs before endoscopic anterior scoliosis correction. To assess the effectiveness of fulcrum bending radiographs in predicting correction of the structural curve in anterior scoliosis surgery for a series of 90 consecutive patients. The fulcrum bending radiograph is highly predictive of scoliosis curve correction for posterior instrumented fixation. However, its use has been questioned in relation to anterior scoliosis surgery due to the disc removal in anterior procedures. Fulcrum bending radiographs were performed before endoscopic anterior scoliosis correction following the protocol of Cheung and Luk. All patients received a single anterior rod and vertebral body screws using a standard compression technique. In all cases, cleared disc spaces were packed with mulched femoral head allograft. Surgical correction was assessed using 6- to 8-week postoperative standing radiographs. Paired t tests and least squares linear regression analysis were used to compare the preoperative major Cobb angle achieved on the fulcrum bending radiograph with the postoperative Cobb angles for each patient. Mean (+/-SD) major curve correction rate was 60.1% +/- 12.4%. Mean instrumented curve correction rate was 63.7% +/- 11.7%. Mean fulcrum flexibility was 60.8% +/- 15.5%. Mean fulcrum bending correction index was 104%. There was no statistically significant difference between the mean fulcrum bending radiograph Cobb angle (20.4 +/- 9 degrees) and the mean postoperative major Cobb angle for the structural curve (20.5 +/- 7.1 degrees). The results of this study show that fulcrum bending radiographs are predictive of surgical correction for anterior scoliosis surgery.

Surgical treatment for scoliosis extending to main thoracic spine by keyvertebral-screws technique (KVST)

Objective To introduce a key-vertebral-screws technique (KVST) in the surgical treatment of scoliosis extending to main thoracic levels, and to find the role of fulcrum bending in predicting the result of surgical treatment for scoliosis by this technique. Methods Seventeen consecutive patients with scoliosis extending to main thoracic spine, who underwent pure posterior fusion without anterior or posterior release by KVST between January 2004 and July 2005 were evaluated for fulcrum bending flexibility, surgical correction rate, fulcrum bending correction index (FBCI) in main thoracic curves. Universal Spine System (USS) instrumentation was used in 15 cases, Monarch in another 2 cases. The severity of the curves was measured by Cobb's method using RadWork 6.0 software. Preoperative standing AP radiographs, preoperative fulcrum bending anterioposterior (AP) radiographs, postoperative standing AP radiographs, and most recent follow-up standing AP radiographs for spine were measured and recorded. All the data were analyzed with two-sample paired t-test by Origin 7.0 software. Results Infection and neurological complications were not noted. No major complications were found. Just one case had some axial back pain, which got a full recovery from physiotherapy for 2 weeks. In the X-ray, there was an average correction of 71.5% of the fused main thoracic curves, which had no significant lose of correction in final follow-up. For the whole fused main thoracic curves, the fulcrum bending flexibility were lower to operation correction rate ( P = 0.013). The average FBCI was 123%. From the data, the more rigid curves (especially fulcrum bending flexibility <50%), the more correction rate operation could get, compared with fulcrum bending flexibility. Conclusion (1) KVST is a good method in the surgical treatment of thoracic scoliosis, which can get satisfying result with lower medical cost. (2) Fulcrum bending flexibility is lower than operative correction rate by KVST in main thoracic curves ( P<0.05). In the more rigid curves assessed by fulcrum-bending radiograph, the operative corrective could be gained, especially in the curves which FBCI is lower than 50%.

Assessment of scoliosis correction in relation to flexibility using the fulcrum bending correction index.

A prospective study on adolescent idiopathic scoliosis to assess a new method of describing frontal plane correction. To assess the difference between using the correction rate and using the new fulcrum bending correction index when describing scoliosis correction. A description of the outcome of scoliosis surgery based on the correction rate does not take into account the curve's flexibility. The fulcrum bending correction index is calculated by dividing the correction rate by the fulcrum flexibility (based on the fulcrum bending radiograph) and is expressed as a percentage. The fulcrum bending correction index was compared with the correction rate in 35 patients with adolescent idiopathic scoliosis undergoing surgical correction. These patients were divided into a stiff and a flexible group based on a fulcrum flexibility of 50% to show the advantage of the fulcrum bending correction index over the correction rate. The difference in correction rate between the flexible (66%) and the stiff group (45%) was significant (P < 0.05). The difference in the fulcrum bending correction index between the flexible (96%) and the stiff group (107%) was not significant (P = 0.2). The fulcrum bending correction index takes into account the curve flexibility and is therefore better than the correction rate for comparing curve correction and use of instrumentation systems between different series of patients. A fulcrum bending correction index of close to 100% suggests that the instrumentation has taken up all the flexibility revealed by the fulcrum bending radiograph. It is recommended that the fulcrum bending correction index be used in the future as part of the postoperative assessment of frontal plane correction in cases of thoracic scoliosis.