Low-Density Pedicle Screw Constructs for Adolescent Idiopathic Scoliosis: Evaluation of Effectiveness and Cost

Study Design: Retrospective cohort study. Objective: To determine whether a low-density (LD) screw construct can achieve curve correction similar to a high-density (HD) construct in adolescent scoliosis. Methods: Patients treated operatively for idiopathic scoliosis between 2007 and 2011 were identified through a database review. A consistent LD screw construct was used. Radiographic assessment included percent correction of major and fractional lumbar curves, T5-T12 kyphosis, and angle of lowest instrumented vertebra (LIV). Costs were compared with HD constructs. Results: Thirty-five patients were included in the analysis. Ages ranged from 12 to 19 years (mean = 14.9 years). Average screw density was 1.2 screws per level (range = 1.07-1.5 screws). Mean percent curve correction at latest follow-up: major curve, 66.9%; fractional lumbar curve, 63%. Average postoperative thoracic kyphosis: 29.5°. Mean LIV angle: 5.6°. Average construct cost was $14 871 per case compared with $23 840 per case if all levels had been instrumented with 2 screws, amounting to an average savings of $9000. Conclusions: Our LD screw construct is among the lowest density constructs reported and achieves curve correction comparable to HD constructs at substantially lower cost.

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Higher pedicle screw density does not improve curve correction in Lenke 2 adolescent idiopathic scoliosis

Journal of Orthopaedic Surgery and Research ◽

10.1186/s13018-021-02415-4 ◽

2021 ◽

Vol 16 (1) ◽

Author(s):

Timothy J. Skalak ◽

Joel Gagnier ◽

Michelle S. Caird ◽

Frances A. Farley ◽

Ying Li

Keyword(s):

Adolescent Idiopathic Scoliosis ◽

Idiopathic Scoliosis ◽

Thoracic Kyphosis ◽

Curve Correction ◽

Major Curve ◽

Curve Magnitude ◽

Screw Density ◽

Implant Density ◽

Lenke 2

Abstract Purpose Higher pedicle screw density posterior spinal fusion (PSF) constructs have not been shown to result in improved curve correction in Lenke 1 and 5 adolescent idiopathic scoliosis (AIS) but do increase cost. The purpose of this study questioned whether higher screw density constructs improved curve correction and maintenance of correction in Lenke 2 AIS. Secondary goals were to identify predictive factors for correction and postoperative magnitude of curves in Lenke 2 AIS. Methods We identified patients 11 to 17 years old who underwent primary PSF for Lenke 2 AIS between 2007 and 2017 who had minimum follow-up of 2 years. Demographic and radiographic data were collected to perform regression and elimination analysis. Results Thirty patients (21 females, 9 males) were analyzed. Average age and SD at time of surgery was 14.0 ± 1.8 years (range, 11–17 years), and median follow-up was 2.8 years (IQR 2.1–4.0 years). Implant density did not predict final postoperative curve magnitude. Predictors of final postoperative curve magnitude were sex and preoperative curve magnitude. Predictors of percentage of correction of major curve were sex and age at the time of surgery. Predictors of final postoperative thoracic kyphosis were sex and percent flexibility preop. Females had lower final postoperative major curve magnitude, a higher percent curve correction, and lower postoperative thoracic kyphosis. Conclusions Increased implant density is not predictive of postoperative curve magnitude in Lenke 2 AIS. Predictors of postoperative curve magnitude are sex and preoperative curve magnitude. Level of evidence Level III, retrospective observational

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“Higher Pedicle Screw Density Does Not Result in Improved Curve Correction in Lenke 2 Adolescent Idiopathic Scoliosis”

10.21203/rs.3.rs-262745/v1 ◽

2021 ◽

Author(s):

Timothy Skalak ◽

Joel Gagnier ◽

Michelle S. Caird ◽

Frances A. Farley ◽

Ying Li

Keyword(s):

Adolescent Idiopathic Scoliosis ◽

Idiopathic Scoliosis ◽

Thoracic Kyphosis ◽

Curve Correction ◽

Major Curve ◽

Curve Magnitude ◽

Screw Density ◽

Implant Density ◽

Lenke 2

Abstract Purpose: Higher pedicle screw density posterior spinal fusion (PSF) constructs have not been shown to result in improved curve correction in Lenke 1 and 5 adolescent idiopathic scoliosis (AIS) but do increase cost. The purpose of this study questioned whether higher screw density constructs improved curve correction and maintenance of correction in Lenke 2 AIS. Secondary goals were to identify predictive factors for correction and postoperative magnitude of curves in Lenke 2 AIS. Methods: We identified patients 11 to 17 years old who underwent primary PSF for Lenke 2 AIS between 2007 and 2017 who had minimum follow up of 2 years. Demographic and radiographic data were collected to perform regression and elimination analysis. Results: Thirty patients (21 Female, 9 male) were analyzed. Average age and SD at time of surgery was 14.0 ± 1.8 years (range, 11-17 years) and median follow-up was 2.8 years (IQR 2.1-4.0 years). Implant density did not predict final postoperative curve magnitude. Predictors of final postoperative curve magnitude were sex and preoperative curve magnitude. Predictors of percentage of correction of major curve were sex and age at the time of surgery. Predictors of final postoperative thoracic kyphosis were sex and percent flexibility preop. Females had lower final postoperative major curve magnitude, a higher percent curve correction, and lower postoperative thoracic kyphosis.Conclusions: Increased implant density is not predictive of postoperative curve magnitude in Lenke 2 AIS. Predictors of postoperative curve magnitude are sex and preoperative curve magnitude.Level of Evidence: Level III Retrospective Observational

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Predictability of Coronal Curve Flexibility in Postoperative Curve Correction in Adolescent Idiopathic Scoliosis: The Effect of the Sagittal Profile

Global Spine Journal ◽

10.1177/2192568219877862 ◽

2019 ◽

Vol 10 (3) ◽

pp. 303-311 ◽

Cited By ~ 1

Author(s):

Søren Ohrt-Nissen ◽

Hideki Shigematsu ◽

Jason Pui Yin Cheung ◽

Keith D. K. Luk ◽

Dino Samartzis

Keyword(s):

Adolescent Idiopathic Scoliosis ◽

Idiopathic Scoliosis ◽

Cobb Angle ◽

Thoracic Kyphosis ◽

Clinical Decision Making ◽

Sagittal Profile ◽

Curve Correction ◽

Sagittal Vertical Axis ◽

Flexibility Index

Study Design: Retrospective cohort study. Objectives: To assess how the thoracic kyphosis affects the ability of the fulcrum bending radiograph (FBR) to predict the coronal thoracic curve correction. Methods: A retrospective study of prospectively collected data was conducted of 107 consecutive patients with thoracic adolescent idiopathic scoliosis (AIS) treated with a standard screw-fixation protocol. Radiographic variables were assessed preoperatively and at 2-year follow-up. Curve flexibility was determined based on the FBR and the Fulcrum Bending Flexibility Index (FBCI). Radiographic variables included preoperative Cobb angle, T5-T12 kyphosis, T12-S1 lordosis, sagittal vertical axis, list, T1-T12 length, truncal shift, and radiographic shoulder height. Patients were also categorized as hypo-, normo-, or hyperkyphotic. Results: Based on multivariate modeling, an increase in FBR Cobb angle and thoracic kyphosis were significantly associated with an increase in FBCI (increased mismatch between the FBR and postoperative Cobb angles) at 2-year follow-up ( P < 0.001). In patients with hyperkyphosis, a longer instrumented length existed despite similar curve size and shorter curve length than the hypo- and normokyphotic groups. Based on these findings, we developed a new predictive postoperative curve correction index, known as the Multiprofile Flexibility Index (MFI). Conclusions: Our results show that an increase in preoperative thoracic kyphosis is associated with an increased difference between the preoperative coronal curve flexibility and the postoperative coronal curve correction. Our findings broaden the understanding of curve flexibility and indicate that selection of fusion levels may need to take into consideration the sagittal profile to improve clinical decision making and optimize outcome.

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The correlations between the anchor density and the curve correction of adolescent idiopathic scoliosis surgery

BMC Musculoskeletal Disorders ◽

10.1186/s12891-019-2844-1 ◽

2019 ◽

Vol 20 (1) ◽

Cited By ~ 1

Author(s):

Yu-Cheng Yeh ◽

Chi-Chien Niu ◽

Lih-Huei Chen ◽

Wen-Jer Chen ◽

Po-Liang Lai

Keyword(s):

Adolescent Idiopathic Scoliosis ◽

Idiopathic Scoliosis ◽

Thoracic Kyphosis ◽

Three Dimensional ◽

High Density ◽

Scoliosis Surgery ◽

Low Density ◽

Curve Correction ◽

Kyphosis Correction ◽

Positive Correlations

Abstract Background The optimal anchor density in adolescent idiopathic scoliosis (AIS) surgery to achieve good curve correction remains unclear. The purpose of the study is to analyze the correlations between three-dimensional curve correction and anchor density in the pedicle screw-based posterior fusion of AIS. Methods One hundred and twenty-seven AIS patients receiving primary posterior fusion with pedicle screw instrumentation were retrospectively reviewed. Anchor density (AD) was defined as the screws number per fused spinal segment. The correlations between three-dimensional curve correction radiographic parameters and anchor density were analyzed with subgroup analysis based on different curve types, curve magnitudes, and curve flexibilities. The differences of curve correction parameters between the low-density (AD ≤1.4), middle-density (1.4 < AD ≤1.7) and high-density (AD > 1.7) groups were also calculated. Independent t-test, analysis of variance (ANOVA), and Pearson’s correlation coefficient were used for statistical analysis. Results There were no correlations between the anchor density and the coronal curve correction or apical vertebral rotation (AVR) correction. In the sagittal plane, mild positive correlations existed between anchor density and thoracic kyphosis correction in all patients (r = 0.27, p = 0.002). Subgroup analysis revealed similar mild positive correlations in Lenke 1 (r = 0.31, p = 0.02), Lenke 1–3 (r = 0.27, p = 0.01), small curves (40°-60°, r = 0.38, p < 0.001), and flexible curves (flexibility > 40%, r = 0.34, p = 0.01). There were no differences between low-density (mean 1.31), middle-density (mean 1.55), and high-density (mean 1.83) in terms of coronal or axial curve correction parameters. Low-density group has longer fused level (mean difference 2.14, p = 0.001) and smaller thoracic kyphosis correction (mean difference 9.25°, p = 0.004) than high-density group. Conclusion In our study, the anchor density was not related to coronal or axial curve corrections. Mild positive correlations with anchor density were found in thoracic kyphosis correction, especially in patients with smaller and flexible curves. Low anchor density with longer fusion level achieves similar curve corrections with middle or high anchor density in adolescent idiopathic scoliosis surgery.

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Upper instrumented vertebra to the right of the lowest instrumented vertebra as a predictor of an increase in the main thoracic curve after selective posterior fusion for the thoracolumbar/lumbar curve in Lenke type 5C adolescent idiopathic scoliosis: multicenter study on the relationship between fusion area and surgical outcome

Journal of Neurosurgery Spine ◽

10.3171/2019.5.spine181469 ◽

2019 ◽

Vol 31 (6) ◽

pp. 857-864 ◽

Cited By ~ 1

Author(s):

Hiroki Oba ◽

Jun Takahashi ◽

Sho Kobayashi ◽

Tetsuro Ohba ◽

Shota Ikegami ◽

...

Keyword(s):

Adolescent Idiopathic Scoliosis ◽

Idiopathic Scoliosis ◽

Cobb Angle ◽

Posterior Fusion ◽

Main Thoracic ◽

Lowest Instrumented Vertebra ◽

Line Tilt ◽

The Right ◽

Upper Instrumented Vertebra

OBJECTIVEUnfused main thoracic (MT) curvatures occasionally increase after selective thoracolumbar/lumbar (TL/L) fusion. This study sought to identify the predictors of an unacceptable increase in MT curve (UIMT) after selective posterior fusion (SPF) of the TL/L curve in patients with Lenke type 5C adolescent idiopathic scoliosis (AIS).METHODSForty-eight consecutive patients (44 females and 4 males, mean age 15.7 ± 2.5 years, range 13–24 years) with Lenke type 5C AIS who underwent SPF of the TL/L curve were analyzed. The novel “Shinshu line” (S-line) was defined as a line connecting the centers of the concave-side pedicles of the upper instrumented vertebra (UIV) and lowest instrumented vertebra (LIV) on preoperative radiographs. The authors established an S-line tilt to the right as S-line positive (S-line+, i.e., the UIV being to the right of the LIV) and compared S-line+ and S-line− groups for thoracic apical vertebral translation (T-AVT) and MT Cobb angle preoperatively, early postoperatively, and at final follow-up. The predictors for T-AVT > 20 mm at final follow-up were evaluated as well. T-AVT > 20 mm was defined as a UIMT.RESULTSAmong the 48 consecutively treated patients, 26 were S-line+ and 22 were S-line−. At preoperative, early postoperative, and final follow-up a minimum of 2 years later, the mean T-AVT was 12.8 mm (range −9.3 to 32.8 mm), 19.6 mm (range −13.0 to 41.0 mm), and 22.8 mm (range −1.9 to 68.7 mm) in the S-line+ group, and 10.8 mm (range −5.1 to 27.3 mm), 16.2 mm (range −11.7 to 42.1 mm), and 11.0 mm (range −6.3 to 26.9 mm) in the S-line− group, respectively. T-AVT in S-line+ patients was significantly larger than that in S-line− patients at the final follow-up. Multivariate analysis revealed S-line+ (odds ratio [OR] 23.8, p = 0.003) and preoperative MT Cobb angle (OR 7.9, p = 0.001) to be predictors of a UIMT.CONCLUSIONSS-line+ was defined as the UIV being to the right of the LIV. T-AVT in the S-line+ group was significantly larger than in the S-line− group at the final follow-up. S-line+ status and larger preoperative MT Cobb angle were independent predictors of a UIMT after SPF for the TL/L curve in patients with Lenke type 5C AIS. Surgeons should consider changing the UIV and/or LIV in patients exhibiting S-line+ during preoperative planning to avoid a possible increase in MT curve and revision surgery.

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

Journal of Neurosurgery Spine ◽

10.3171/2020.11.spine201807 ◽

2021 ◽

pp. 1-10

Author(s):

Tomohiro Banno ◽

Yu Yamato ◽

Hiroki Oba ◽

Tetsuro Ohba ◽

Tomohiko Hasegawa ◽

...

Keyword(s):

Adolescent Idiopathic Scoliosis ◽

Idiopathic Scoliosis ◽

Curve Progression ◽

Global Alignment ◽

Fusion Surgery ◽

Radiographic Outcomes ◽

Lowest Instrumented Vertebra ◽

Upper Instrumented Vertebra ◽

Coronal Decompensation

OBJECTIVE L3 is most often selected as the lowest instrumented vertebra (LIV) to conserve mobile segments in fusion surgery; however, in cases with the lowest end vertebra (LEV) at L4, LIV selection as L3 could have a potential risk of correction loss and coronal decompensation. This study aimed to compare the clinical and radiographic outcomes depending on the LEV in adolescent idiopathic scoliosis (AIS) patients with Lenke type 5C curves. METHODS Data from 49 AIS patients with Lenke type 5C curves who underwent selective thoracolumbar/lumbar (TL/L) fusion to L3 as the LIV were retrospectively analyzed. The patients were classified according to their LEVs into L3 and L4 groups. In the L4 group, subanalysis was performed according to the upper instrumented vertebra (UIV) level toward the upper end vertebra (UEV and 1 level above the UEV [UEV+1] subgroups). Radiographic parameters and clinical outcomes were compared between these groups. RESULTS Among 49 patients, 32 and 17 were in the L3 and L4 groups, respectively. The L4 group showed a lower TL/L curve correction rate and a higher subjacent disc angle postoperatively than the L3 group. Although no intergroup difference was observed in coronal balance (CB), the L4 group showed a significantly higher main thoracic (MT) and TL/L curve progression during the postoperative follow-up period than the L3 group. In the L4 group, the UEV+1 subgroup showed a higher absolute value of CB at 2 years than the UEV subgroup. CONCLUSIONS In Lenke type 5C AIS patients with posterior selective TL/L fusion to L3 as the LIV, patients with their LEVs at L4 showed postoperative MT and TL/L curve progression; however, no significant differences were observed in global alignment and clinical outcome.

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Preoperative pelvic obliquity: possible relation to postoperative coronal decompensation in thoracolumbar/lumbar adolescent idiopathic scoliosis

Journal of Neurosurgery Spine ◽

10.3171/2021.4.spine21265 ◽

2021 ◽

pp. 1-10

Author(s):

Tomohiro Banno ◽

Yu Yamato ◽

Hiroki Oba ◽

Tetsuro Ohba ◽

Tomohiko Hasegawa ◽

...

Keyword(s):

Adolescent Idiopathic Scoliosis ◽

Idiopathic Scoliosis ◽

Clinical Outcomes ◽

Pelvic Obliquity ◽

Posterior Fusion ◽

Lumbar Curve ◽

Fusion Surgery ◽

The Right ◽

Coronal Decompensation

OBJECTIVE Pelvic obliquity is frequently observed in patients with adolescent idiopathic scoliosis with thoracolumbar/lumbar (TL/L) curve. This study aimed to assess pelvic obliquity changes and their effects on clinical outcomes of posterior fusion surgery. METHODS Data in 80 patients (69 with type 5C and 11 with type 6C adolescent idiopathic scoliosis) who underwent posterior fusion surgery were retrospectively analyzed. Pelvic obliquity was defined as an absolute pelvic obliquity angle (POA) value of ≥ 3°. The patients were divided into groups according to preoperative pelvic obliquity. Moreover, patients with preoperative pelvic obliquity were divided based on POA change from preoperative values versus 2 years postoperatively. Patients were divided based on the presence of selective or nonselective TL/L fusion. Radiographic parameters and clinical outcomes were compared between these groups. RESULTS Among 80 patients, 41 (51%) showed preoperative pelvic obliquity, and its direction was upward to the right for all cases. Coronal decompensation 2 years postoperatively was significantly elevated in patients with preoperative pelvic obliquity (p < 0.05). Thirty-two patients (40%) displayed pelvic obliquity 2 years postoperatively. Among 41 patients with preoperative pelvic obliquity, 22 patients (54%) were in the group with a decrease in POA, and 19 were in the group with no decrease. The group with no decrease in POA showed significant TL/L curve progression throughout the postoperative follow-up period. The patients with nonselective fusion showed a significantly lower incidence of pelvic obliquity at 2 years postoperatively. CONCLUSIONS Postoperative coronal decompensation more frequently occurred in patients with preoperative pelvic obliquity than in those without pelvic obliquity preoperatively. In addition, postoperative pelvic obliquity changes may be related to residual lumbar curve behavior.

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Adolescent idiopathic scoliosis: sagital plane and low density pedicle screws

Coluna/Columna ◽

10.1590/s1808-18512014130100210 ◽

2014 ◽

Vol 13 (1) ◽

pp. 13-15

Author(s):

Rodrigo Augusto do Amaral ◽

Robert Meves ◽

Maria Fernanda Silber Caffaro ◽

Ricardo Shigueaki Galhego Umeta ◽

Luciano Antônio Nassar Pelegrino ◽

...

Keyword(s):

Medical Records ◽

Lumbar Lordosis ◽

Thoracic Kyphosis ◽

Sagittal Plane ◽

Pedicle Screws ◽

Low Density ◽

Kyphosis Correction ◽

Pearson Coefficient ◽

Analysis Of Dispersion

OBJECTIVE: To examine the sagittal curves of patients treated with CD instrumentation using exclusively pedicle screws. METHODS: Image analysis of medical records of 27 patients (26 M and 1 F) with a minimum follow-up of 6 months, who underwent surgical treatment in our service between January 2005 and December 2010. The curves were evaluated on coronal and sagittal planes, taking into account the potential correction of the technique. RESULTS: In the coronal plan the following curves were evaluated: proximal thoracic (TPx), main thoracic (TPp), and thoracolumbar; lumbar (TL, L), and the average flexibility was 52%, 52%, and 92% and the capacity of correction was 51%, 72%, and 64%, respectively. In the sagittal plane there was a mean increase in thoracic kyphosis (CT) of 41% and an average reduction of lumbar lordosis (LL) of 17%. Correlation analysis between variables showed Pearson coefficient of correlation of 0.053 and analysis of dispersion of R2 = <0.001. CONCLUSION: The method has shown satisfactory results with maintenance of kyphosis correction in patients with normal and hyper kyphotic deformities.

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