Spontaneous Lumbar Curve Correction Research Articles

The Use of High-Density Pedicle Screw Construct with Direct Vertebral Derotation of the Lowest Instrumented Vertebra in Selective Thoracic Fusion for Adolescent Idiopathic Scoliosis: Comparison of Two Surgical Strategies.

This study was a retrospective case series. This study was designed to determine whether direct vertebral rotation (DVR) of the lowest instrumented vertebra (LIV) using a high-density (HD) construct can reduce fusion segments without increasing adverse outcomes in selective thoracic fusion (STF) for adolescent idiopathic scoliosis (AIS). LIV DVR is used to maximize spontaneous lumbar curve correction and reduce adverse outcomes during STF for AIS. However, evidence is limited on whether LIV DVR can allow a proximally located LIV and reduce fusion segments without increasing adverse outcomes. We reviewed consecutive patients with Lenke 1 AIS who underwent STF from 2000 to 2017. The patients were divided into two groups based on the surgical strategy used: low-density (LD) construct without DVR of the LIV (LD group) versus HD construct with DVR of the LIV (HD group). We collected data on the patient's demographic characteristics, skeletal maturity, operative data, and measured radiological parameters in the preoperative and final follow-up radiographs. The occurrence of adding-on (AO) and coronal decompensation was also determined. In this study, 72 patients (five males and 67 females) with a mean age of 14.1±2.3 years were included. No significant differences in the demographics, skeletal maturity, and Lenke type distribution were observed between the two groups; however, the follow-up duration was significantly longer in the LD group (64.3±25.7 months vs. 40.7±22.2 months, p <0.001). The HD group had significantly shorter fusion segments (7.1±1.3 vs. 8.5±1.2, p <0.001) and a more proximal LIV level (12.1±0.9 vs. 12.7±1.0, p =0.009). In the radiological measurements, the improvement of LIV+1 rotation (Nash-Moe scale) was significantly larger in the HD group (0.53±0.51 vs. 0.21±0.41, p =0.008). AO and decompensation occurred in 7 (9.7%) and 4 (5.6%) patients in the HD and LD groups, respectively, without any significant difference between the two groups. In this study, the HD group had a significantly shorter fusion level and a more proximal LIV than the LD group; however, the two groups had similar curve correction and adverse radiological outcome rates.

Spontaneous Lumbar Curve Correction Following Vertebral Body Tethering of Main Thoracic Curves.

Growth modulation through anterior vertebral body tethering (AVBT) has emerged as a fusionless option for the treatment of progressive scoliosis. When tethering the main thoracic curve, the compensatory thoracolumbar/lumbar curve must correct indirectly as a result. The present study evaluated the response of these lumbar curves following AVBT of the main thoracic curves. Patients who underwent thoracic AVBT and who had a minimum follow-up of 2 years were included. Magnitudes of the thoracic and lumbar curves were recorded preoperatively and at the first-erect and 2-year postoperative visits. Lumbar curves were further stratified according to their lumbar modifier (A, B, or C). Analysis of variance (ANOVA) and repeated-measures ANOVA were performed to compare correction rates, and the Pearson coefficient was utilized to determine the correlation between the tethered thoracic curve and uninstrumented lumbar curve magnitudes. A total of 218 patients were included. Thoracic curve correction was 40% at the first-erect visit and 43% at 2 years (p = 0.012). Lumbar correction was 30%, 26%, and 18% at the first-erect visit (p < 0.001 for all compared with preoperatively) and minimally changed at 31%, 26%, and 24% at 2 years for lumbar modifiers A, B, and C, respectively. A total of 118 patients (54%) showed thoracic curve improvement between the first-erect and 2-year visits. In a subgroup analysis, these patients had a correction in lumbar curve magnitude from preoperatively to the first-erect visit of 30%, 22%, and 16% for lumbar modifiers A, B, C, respectively, that increased to 42%, 34%, and 31% at 2 years, with strong correlation to thoracic correction at 2-year follow-up (r = 0.557, p < 0.001). Although there was immediate lumbar correction following AVBT of a main thoracic curve, further improvement following initial correction was only observed among patients with growth modulation of the thoracic curve. Considering all patients, the uninstrumented lumbar curve corrected 30% at 2 years and the instrumented thoracic curve corrected 40%. As indications for AVBT are refined, these data will provide insight into the response of the uninstrumented lumbar curve. Therapeutic Level III . See Instructions for Authors for a complete description of levels of evidence.

The Importance of Lumbar Curve Flexibility and Apical Vertebral Rotation for the Prediction of Spontaneous Lumbar Curve Correction in Selective Thoracic Fusion for Lenke Type 1 and 2 C Curves: Retrospective Cohort Study with a Mean Follow-Up of More than 10 years

Study DesignRetrospective analysis of a prospectively collected data.ObjectiveLumbar flexibility(LF) is generally defined with preoperative side bending films;it is not clear what percentage of LF predicts the spontaneous lumbar curve correction (SLCC) at long term follow up. Aim of this study was to find out cut-off value of preoperative LF,apical vertebra rotation(AVR) and apical vertebral translation(AVT);which may predict more than 50%SLCC.MethodsPatients with Lenke 1C&2C curves,treated with posterior STF,with a minimum 10 years follow up were included.The patients who had more than 50% SLCC(Group A) or less than 50% (Group B) were compared in terms of LF,AVR and AVT to understand a cut-off value of those parameters.Statistically, Receiver Operating Characteristic(ROC) test was used.ResultsFifty five AIS patients (54F, 1M) with mean age 14 (11-17) were included to study.Thoracic curve correction rate was 75%;lumbar curve correction rate was 59% at the latest follow up.Group A included 45(82%) patients at the latest follow up.Three patients (5%) showed coronal decompensation at early postop and 2 of them became compensated at f/up.ROC analyses showed 69% flexibility as the cut-off value for SLCC (P < .01).The difference between groups in terms of preop mean AVRs was significant (P = .029) (Group A = 1.9; Group B = 2.4).ConclusionIn Lenke 1C&2C curves,whenever LF on the preoperative bending x-ray is greater than 70% (P < .01)and AVR is equal or less than grade 2,STF provides satisfactory clinical and radiological SLCC with more than mean 10 years f/up.This flexibility rate and apical vertebral rotation can be helpful in decision making for successful STF.

Characteristics analysis of segmental and regional lumbar spontaneous compensation post thoracic fusion in Lenke 1 and 2 adolescent idiopathic scoliosis

ObjectiveTo explore the characteristics of compensation of unfused lumbar region post thoracic fusion in Lenke 1 and 2 adolescent idiopathic scoliosis.BackgroundPreserving lumbar mobility in the compensation is significant in controlling pain and maintaining its functions. The spontaneous correction of the distal unfused lumbar curve after STF has been widely reported, but previous study has not concentrated on the characteristics of compensation of unfused lumbar region post thoracic fusion.MethodA total of 51 Lenke 1 and2 AIS patients were included, whose lowest instrumented vertebrae was L1 from January 2013 to December 2019. For further analysis, demographic data and coronal radiographic films were collected before surgery, at immediate erect postoperatively and final follow-up. The wedge angles of each unfused distal lumbar segments were measured, and the variations in each disc segment were calculated at the immediate postoperative review and final follow-up. Meanwhile, the unfused lumbar curve was divided into upper and lower parts, and we calculated their curve angles and compensations.ResultsThe current study enrolled 41 females (80.4%) and 10 males (19.6%). Thirty-six patients were Lenke type 1, while 15 patients were Lenke type 2. The average main thoracic Cobb angle and thoracolumbar/lumbar Cobb angle were 44.1 ± 7.7°and 24.1 ± 9.3°, preoperatively. At the final follow-up, the disc wedge angle variation of L1/2, L2/3, L3/4, L4/5 and L5/S1 was 3.84 ± 5.96°, 3.09 ± 4.54°, 2.30 ± 4.53°, − 0.12 ± 3.89° and − 1.36 ± 2.80°, respectively. The compensation of upper and lower coronal lumbar curves at final follow-up were 9.22 ± 10.39° and − 1.49 ± 5.14°, respectively.ConclusionWhen choosing L1 as the lowest instrumented vertebrae, the distal unfused lumbar segments’ compensation showed a decreasing trend from the proximal end to the distal end. The adjacent L1/2 and L2/3 discs significantly contributed to this compensation.

Clinical, radiological and HRQoL outcomes after selective thoracic fusion with minimum 15-year follow-up.

The purpose of the study was to provide a 15-year natural history evaluation of the radiographic appearance of uninstrumented compensatory lumbar curves in patients who had undergone selective thoracic fusion (STF) for scoliosis, measure any changes in health-related quality of life scores (HRQoL) and compare them with controls matched for age, gender and body-mass index (BMI). STF group included 43 female adolescent idiopathic scoliosis (AIS) patients who underwent STF with mean age 33(27-42) years and a mean follow-up of 18.7 (15-28) years, mean BMI 22(18-29). Preop, early postop and follow-up radiographs were reviewed for behavior of lumbar curves. Control group included a random selection of healthy volunteers with no history of back pain and with mean age 33(27-41), and mean BMI 22(17-33). HRQoL scores were compared between two groups in latest f/up. Radiographs including low dose biplanar imaging with EOS were used to measure disc heights and assess for radiographic evidence of degenerative changes. Various parameters were statistically compared. Posterior fusion was performed in all 43, with all pedicle screws used in 41 and all-hook constructs in 2. Main thoracic curve correction was improved from pre-op to early-post-op and maintained at latest f/up (55.6°-16.1°-16.9°). Spontaneous lumbar curve correction (SLCC) was also maintained beyond 15years (39.9°-16.6°-17.1°). Two patients developed coronal decompensation following surgery, but improved with time and were well compensated at final follow-up. Mean HRQoL scores, self-image and mental health scores were higher in STF group than control group (p < 0.05). SRS-22r pain and function, Oswestry Disability Index and Numeric Rating Scale, marital status, number of children were similar between the groups(p > 0.05). All disc heights except L5-S1 were significantly lower in STF group (p < 0.05). There was no significant difference between the groups for degenerative changes in the latest radiographs. In this group of patients, the uninstrumented lumbar curve spontaneously corrected and the correction was maintained after 18years following surgery using STF. Mild degenerative changes were seen radiographically and HRQoL scores suggest that the psychological-functional well-being are quite good in the long term in AIS patients who have undergone STF when compared with an age-gender-BMI-matched population.

Predictors of spontaneous lumbar curve correction in thoracic-only fusions: 3D analysis in AIS.

To evaluate how 3D parameters of the instrumented thoracic spine relate to the uninstrumented lumbar spine following thoracic-only fusion (TOF) for adolescent idiopathic scoliosis (AIS) and determine the factors predictive of lumbar correction. A multi-center retrospective review was conducted of AIS patients with Lenke 1-4 B or C curves undergoing fusion of their thoracic spine only with minimum 2-year follow-up and 3D spine reconstructions from biplanar radiography. Pre-operative to 2-year post-operative differences were evaluated. Pearson's correlations were used to identify 3D coronal, sagittal and axial relationships at 2years post-operative. Multivariate linear regression was used to identify variables most predictive of lumbar curve correction. Eighty-four AIS patients met inclusion (54 B modifiers, 30 C modifiers). Average pre-operative thoracic and lumbar curves were 54 ± 9° and 41 ± 7° and corrected to 19 ± 7° and 21 ± 7°, respectively. 3D T5-T12 thoracic kyphosis increased from 6 ± 13° to 26 ± 8°. Thoracic and lumbar apical rotation decreased from - 14 ± 6° to -5 ± 6° and 13 ± 5° to 11 ± 6°, respectively. Thoracic curve correction correlated with lumbar curve correction (r = 0.67, p = 0.001) and decreased LIV tilt correlated with smaller residual lumbar curve magnitude (r = 0.63, p < 0.001). Increasing 3D kyphosis of the instrumented segment correlated with increased percentage lumbar curve correction (r = 0.29, p = 0.009). Multivariate linear regression showed LIV tilt and thoracic curve magnitude as the most predictive variables of post-operative residual lumbar curve magnitude, and percent correction of the thoracic curve and change in 3D instrumented kyphosis as most predictive of percent correction of the lumbar curve. Analysis of 3D data highlights several considerations for AIS patients undergoing TOF. Maximizing thoracic curve correction, leveling the LIV, and to a lesser extent, restoring kyphosis in the instrumented segment are the factors most likely to result in greater correction of the instrumented lumbar curve following thoracic-only fusions in Lenke 1-4 B and C curves.

Risk Factors for Postoperative Distal Adding-on in Lenke Type 1B and 1C and its Influence on Residual Lumbar Curve.

Distal adding-on (DA) in adolescent idiopathic scoliosis is a radiographic complication that can negatively affect clinical results. However, the risk factors for DA and the influences of DA on the residual lumbar curves have not been fully elucidated in Lenke type 1B and 1C curves. The objective of this study was to investigate risk factors for postoperative DA in Lenke type 1B and 1C curves, and the influence of DA on residual lumbar curves. We retrospectively evaluated 46 adolescent idiopathic scoliosis patients with Lenke type 1B or 1C curves who underwent posterior correction and fusion surgery with selective thoracic fusion. Patients were grouped according to the presence or absence of DA on radiographs at the 2-year follow-up. We compared coronal radiographic parameters between the 2 groups, including the Cobb angle, L4 tilt angle, apical translation, and relative positions of the end vertebra (EV), stable vertebra (SV), neutral vertebra (NV), and last touching vertebra (LTV) to the lower instrumented vertebra (LIV). DA was present in 11 patients (24%) at the 2-year follow-up, and the mean LIV-EV, LIV-NV, LIV-SV, and LIV-LTV relative positions were significantly smaller in the DA than in the non-DA group. Preoperative radiographic parameters were similar between the 2 groups, including the mean L4 tilt angle (non-DA, -8±4 degrees; DA, -7±4 degrees). At the 2-year follow-up, the mean apical translation of the lumbar curve was smaller in the DA group (non-DA, -16±8 mm; DA, -7±11 mm) and the mean L4 tilt angle was significantly more horizontalized (non-DA, -8±4 degrees; DA, -1±5 degrees). Multivariate analysis showed that the number of levels between the LIV and LTV (LIV-LTV) was significantly associated with DA. A LIV at or cranial to the LTV was a significant risk factor for postoperative DA in Lenke type 1B and 1C curves. Spontaneous correction of the residual lumbar curve was superior in patients with DA. Level III.

Accurate prediction of spontaneous lumbar curve correction following posterior selective thoracic fusion in adolescent idiopathic scoliosis using logistic regression models and clinical rationale.

Accurate prediction of spontaneous lumbar curve correction (SLCC) after selective thoracic fusion (STF) remains difficult. This study sought to improve prediction accuracy of SLCC. The hypothesis was preoperative and intraoperative variables could predict SLCC < 20°. A multicenter observational prospective analysis was conducted to determine predictors of SLCC in AIS patients that had posterior STF. Curve types included major thoracic curves (Lenke 1, 3-4).The primary outcome variable was to establish prediction models, and a postoperative lumbar curve (LC) ≤ 20° was defined as the target variable. Multivariate logistic regression models were established to study the relationship between selected variables and a LC ≤ 20° versus a LC > 20° at ≥ 2-year follow-up. Single and dual thresholds models in perspective of clinical rationales were applied to find models with the highest positive/negative predictive values (PPV/NPV). The secondary outcome measure was SRS scores at ≥ 2-year follow-up. 410 patients were included. At ≥ 2-year follow-up 282 patients had LC ≤ 20°. These patients had better SRS-22 scores than those with LC > 20° (P = 0.02). The postoperative LC and LC ≤ 20° were predicted by preoperative LC and LC-bending Cobb angle (P < 0.01, r = 0.4-0.6). Logistic regression models could be established to identify patients at risk for failing the target LC ≤ 20°.For preoperative LC and LC-bending, the prediction model achieved a NPV/PPV of 80%/72%. If the postoperative main thoracic curve is combined with the preoperative LC and a gray area for difficult decisions was allowed, model accuracy could even be improved (NPV/PPV = 96%/81%). An accurate prediction model for postoperative SLCC was established based on a large analysis of prospective STF cases. These models can support prediction and understanding of postoperative SLCC aiding in surgical decision making when contemplating a selective thoracic fusion. These slides can be retrieved under Electronic Supplementary Material.

Selective Thoracic Fusion for King-Moe Type II/Lenke 1C Curve in Adolescent Idiopathic Scoliosis: A Comprehensive Review of Major Concerns.

Introduction Controversies still exist in the surgical indications and outcomes of selective thoracic fusion (STF) for a primary thoracic curve with a compensatory large lumbar curve (King-Moe type II/Lenke 1C curve) in adolescent idiopathic scoliosis (AIS). Issues of the greatest concern regarding this curve type include curve criteria that indicate STF to prevent postoperative coronal decompensation and postoperative radiographic outcomes, including curve correction, coronal balance, and thoracolumbar kyphosis, after STF. Methods This review comprehensively documents the issues raised in the literature regarding surgical indications and radiographic outcomes of STF for King-Moe type II/Lenke 1C curve in AIS. Results Studies suggest that radiographic curve criteria indicating STF for this curve type include the preoperative dominance of the thoracic curve to the lumbar curve in the Cobb angle and the characteristics of the lumbar curve in magnitude and flexibility. Studies warn the need for a careful clinical evaluation of the thoracic and lumbar rotational prominences. Documented radiographic outcomes of importance include the postoperative behavior of the unfused lumbar curve, coronal or sagittal decompensation after STF, and factors associated with these issues. A comprehensive review of the literature suggests that the use of a segmental pedicle screw construct and better instrumented thoracic curve correction achieve better spontaneous lumbar curve correction. Although the causes of postoperative coronal decompensation remain multifactorial, preoperative coronal decompensation to the left and an inappropriate selection of the lowest instrumented vertebra are consistently reported to be the major causative factors. Conclusions STF has been validated in general for the treatment of King-Moe type II or Lenke 1C curve in AIS; however, controversies remain regarding the surgical indications and outcomes. Long-term impacts of residual lumbar curve, coronal decompensation, and mild thoracolumbar kyphosis on clinical outcomes after STF, along with optimal indications and strategy for STF, should further be assessed.

Radiological and clinical outcome of selective thoracic fusion for patients with Lenke 1C and 2C adolescent idiopathic scoliosis with a minimum follow-up of 2 years

Background ContextIn Lenke 1C and 2C curves, the choice between selective thoracic fusion (STF) versus non-selective thoracic fusion as the optimal surgical treatment is controversial. ObjectiveThis study aimed to assess the radiological and clinical outcome of patients with Lenke 1C and 2C curves treated with STF. Study DesignThis is a retrospective study. Patient SampleA total of 44 patients comprised the study sample. MethodsForty-four patients with Lenke 1C and 2C curves with adolescent idiopathic scoliosis who underwent STF were reviewed. Radiological parameters and Scoliosis Research Society (SRS)-22r scores were assessed preoperatively, postoperatively, and on final follow-up. The incidence of coronal decompensation, lumbar decompensation, and adding-on phenomenon were reported. ResultsMean follow-up duration was 45.1±12.3 months and mean age was 17.0±5.1 years. The preoperative middle thoracic and thoracolumbar/lumbar (MT:TL/L) Cobb angle ratio was 1.4±0.3 and the MT:TL/L apical vertebra translation (AVT) ratio was 1.6±0.8. Final follow-up coronal balance was −13.0±11.5 mm, main thoracic AVT was 6.9±11.8 mm, and lumbar AVT was −20.4±13.8 mm (p<.05). Lumbar Cobb angle improved from 47.5°±7.8° to 24.9°±8.2° after operation and 23.3°±9.8° at final follow-up. The spontaneous lumbar curve correction rate was 50.9%. There were 9 patients (20.5%) who had coronal decompensation, 4 patients (9.1%) who had lumbar decompensation, and 11 patients (25.0%) who had adding-on phenomenon. We did not perform any revision surgery. The SRS-22r scores improved significantly in the overall scores, self-image, and mental health domain. ConclusionsSelective thoracic fusion led to improvement in the radiological and clinical outcome for patients with Lenke 1C and 2C. Although no patients required revision surgery, the rate of coronal decompensation, lumbar decompensation, and adding-on phenomenon are significant.

Relationships Between the Axial Derotation of the Lower Instrumented Vertebra and Uninstrumented Lumbar Curve Correction: Radiographic Outcome in Lenke 1 Adolescent Idiopathic Scoliosis With a Minimum 2-Year Follow-up.

Preoperative spinal parameters are used to guide the fusion levels in adolescent idiopathic scoliosis (AIS) spinal surgery. However, the impact of the factors modifiable by the surgeon in varying levels of preoperative patient-specific variables is not fully explored. The goal of this study was to identify the association between axial rotation correction of the lower instrumented vertebra (LIV) and spontaneous correction of the uninstrumented lumbar spine as a function of preoperative 3 dimensional (3D) curve characteristics in Lenke 1 AIS. Twenty-three Lenke1 AIS with a minimum 2-year follow-up were included. All patients had biplanar spinal x-rays and 3D reconstructions at preoperative, first erect, and 2-year follow-up visits. Five patient factors were measured preoperatively: kyphosis and lumbar modifiers, and thoracic to lumbar curve rotation, translation, and frontal deformity angle ratios. One surgical factor, percentage of LIV rotation correction, was determined from the preoperative and first erect 3D models. A factorial design analysis was implemented to determine the impact of surgical and patient factors, both separately and in combination, on 2-year radiographic outcomes of spontaneous correction of the uninstrumented spine. Spontaneous lumbar Cobb and lumbar apical rotation correction were predicted significantly by patient and surgical factors, P<0.05. Lumbar modifier, percentage correction of LIV rotation, the interaction between LIV rotation correction and lumbar modifier, and the interaction between LIV rotation correction and thoracic to lumbar apical vertebrae translation ratio correlated significantly to 2-year outcomes of spontaneous lumbar Cobb correction, P<0.05. Lumbar modifier and the interaction between the Cobb ratio and the percentage of the LIV rotation correction correlated significantly to 2-year outcomes of lumbar apical rotation correction, P<0.05. The relationship between LIV rotation correction and spontaneous lumbar curve correction after selective thoracic fusion varied based on the patient's 3D preoperative curve characteristics. Patients with lumbar modifier C and apical vertebrae translation ratios >1.5 showed improved lumbar Cobb correction in 2-years when 50% or more LIV rotation correction was achieved surgically.

Outcomes of selective thoracic fusion for Lenke 1 adolescent idiopathic scoliosis: predictors of success from the sagittal plane.

To determine the link between the rate of spontaneous lumbar curve correction (SLCC) and the sagittal profile characteristics both before and after selective thoracic fusion in Lenke 1 adolescent idiopathic scoliosis (AIS). Sixty-three Lenke 1 B and C were enrolled and followed up to 2years. Twenty non-scoliotic controls were included. 3D reconstruction of the spine was generated from bi-planar X-rays at pre-operative, first erect post-operative, and the most recent follow-up. The 3D spinal models were used to determine the frontal and sagittal Cobb angles and 3D coordinate of each vertebral centroid. A K-mean cluster analysis allocated patients into two groups based on the rate of SLCC between the pre-operative and the most recent follow-up visits (SLCCHigh and SLCCLow groups). The ratio of the thoracic to lumbar curve apical translations in sagittal plane was determined. ANOVA test compared the sagittal apical translation ratio between the three visits of the AIS clusters and between the AIS groups and controls. The rate of theSLCC was significantly different between the two clusters: 31% (SLCCLow) versus 76% (SLCCHigh). No significant difference was found between the two clusters pre-operative Cobb angles, kyphosis, and lordosis. The pre-operative ratio of the thoracic to lumbar apical translation in the sagittal plane was significantly lower in SLCCHigh compared to SLCCLow group, a magnitude of 1.2 and 2.2, respectively, p < 0.05. In Lenke 1, patients with a higher pre-operative sagittal thoracic to lumbar apical translation ratio are associated with lower rate of SLCC at the most recent follow-up. These slides can be retrieved under Electronic Supplementary Material.

Timing of Changes in Three-Dimensional Spinal Parameters After Selective Thoracic Fusion in Lenke 1 Adolescent Idiopathic Scoliosis: Two-Year Follow-up

Study DesignRetrospective analysis of the prospectively collected data. ObjectiveTo investigate the relationship between the axial rotation of the unfused lumbar spine and the parameters of the instrumented thoracic spine at varying time points after selective thoracic fusion (STF) in Lenke 1B and 1C adolescent idiopathic scoliosis (AIS). Summary of Background DataThe impact of STF on the spontaneous lumbar curve correction in AIS has been studied mainly in the frontal planes. The relationship between the spontaneous transverse plane correction of the lumbar spine and the parameters of the fused thoracic spine is not well documented. MethodsTwenty-one Lenke 1B and 1C patients who had received STF with minimum two years' follow-up were selected. Thoracic and lumbar Cobb angles, kyphosis, lordosis, and thoracic and lumbar apical vertebrae rotations were measured at preoperative, first-erect, six-month, one-year, and two-year follow-ups. The association between the lumbar apical vertebral rotation and other thoracic and lumbar variables at different time points were determined using regression analysis. The variables significantly predicting the lumbar axial rotation correction at two years were determined from the preceding follow-up visits. ResultsKyphosis, thoracic Cobb, thoracic apical vertebral rotation, and lumbar Cobb were significantly different between the preoperative and all the postoperative follow-ups (p < .05). At the two-year follow-up, a decrease in thoracic rotation and lumbar Cobb and a higher residual thoracic Cobb were associated with an improved spontaneous lumbar rotation (R2 = 0.41, p < .05). Lumbar rotation at two years was predicted from thoracic derotation and lumbar Cobb at first erect (R2 = 0.30, p < .05). ConclusionSpontaneous lumbar curve rotation correction correlated to the fused and unfused spinal parameters in the three anatomic planes. The relationship between thoracic and lumbar rotation persist up to two years after STF. Thoracic derotation is an important factor determining the lumbar rotation correction at two years after STF.

Maintenance of spontaneous lumbar curve correction following thoracic fusion of main thoracic curves in adolescent idiopathic scoliosis.

The aims of our study were to provide long-term information on the behaviour of the thoracolumbar/lumbar (TL/L) curve after thoracic anterior correction and fusion (ASF) and to determine the impact of ASF on pulmonary function. A total of 41 patients (four males, 37 females) with main thoracic (MT) adolescent idiopathic scoliosis (AIS) treated with ASF were included. Mean age at surgery was 15.2 years (11 to 27). Mean follow-up period was 13.5 years (10 to 18). For the TL/L curve, the mean curve flexibility evaluated with supine pre-operative bending radiographs was 78.6% (standard deviation 16.5%), with no significant loss of correction observed. On comparing patients with an increase of the TL/L curve increase (> 4º, n = 9, 22%) to those without, significant differences were observed in the correction rate of the MT curve at the final follow-up (p = 0.011), correction loss of the MT curve (p = 0.003) and the proportion of patients who had semi-rigid instrumentation (p = 0.003). Pre-operative percentage predicted forced vital capacity (%FVC) was 80%, dropping to 72% at final follow-up (p < 0.001). The Scoliosis Research Society questionnaire score was not significantly different between patients with and without a TL/L curve increase (p = 0.606). Spontaneous lumbar curve correction (SLCC) was maintained up to 18 years following selective ASF in most patients and demonstrated significant correlation with maintenance of MT curve correction. Maintenance of MT curve correction using rigid instrumentation provided stable SLCC over time. An observed 8% decrease in %FVC indicates that ASF should be reserved for patients with no or only mild pulmonary impairment. Cite this article: Bone Joint J 2016;98-B:997-1002.

Assessment of spontaneous correction of lumbar curve after fusion of the main thoracic in Lenke 1 adolescent idiopathic scoliosis

ObjectiveTo evaluate the clinical and radiographic response of the lumbar curve after fusion of the main thoracic, in patients with adolescent idiopathic scoliosis of Lenke type 1. MethodsForty-two patients with Lenke 1 adolescent idiopathic scoliosis who underwent operations via the posterior route with pedicle screws were prospectively evaluated. Clinical measurements (size of the hump and translation of the trunk in the coronal plane, by means of a plumb line) and radiographic measurements (Cobb angle, distal level of arthrodesis, translation of the lumbar apical vertebral and Risser) were made. The evaluations were performed preoperatively, immediately postoperatively and two years after surgery. ResultsThe mean Cobb angle of the main thoracic curve was found to have been corrected by 68.9% and the lumbar curve by 57.1%. Eighty percent of the patients presented improved coronal trunk balance two years after surgery. In four patients, worsening of the plumb line measurements was observed, but there was no need for surgical intervention. Less satisfactory results were observed in patients with lumbar modifier B. ConclusionsIn Lenke 1 patients, fusion of the thoracic curve alone provided spontaneous correction of the lumbar curve and led to trunk balance. Less satisfactory results were observed in curves with lumbar modifier B, and this may be related to overcorrection of the main thoracic curve.

The effectiveness of selective thoracic fusion for treating adolescent idiopathic scoliosis: a systematic review protocol.

REVIEW QUESTION / OBJECTIVE The objective of this review is to assess the effectiveness of selective thoracic fusion as a form of treatment in adolescent idiopathic scoliosis. This will be compared with all other forms of operative management for major structural thoracic curves. INCLUSION CRITERIA Types of participants A comprehensive and exhaustive literature search will be conducted for studies that include children aged 10-18 years with adolescent idiopathic scoliosis who have a scoliosis curve with a thoracic component that is described as structural (as described by the Lenke classification). In addition those with congenital, neuromuscular or syndromic causes for their scoliosis or any previous spinal fusion will be excluded. Types of intervention This review will consider studies that evaluate fusion of the thoracic curve with distal fusion no lower than L1. Both anterior and posterior approaches will be included; however any patient who receives both will be excluded. All forms of instrumentation for fusion such as pedicle screws, hooks and rods will be included. This will be compared where possible to any other surgical fusion for a structural thoracic curve. This will include studies that compare selective and non-selective spinal fusion in the same article, or selective spinal fusion only, but not non-selective spinal fusion only. Types of outcomes Primary outcomes include: Functional/Quality of life survey (SRS- 22, SRS-24, SRS-30 or similar). Complication rate – including, but not limited to, adding on, coronal imbalance, junctional kyphosis and re-operation. Respiratory function. Secondary outcomes include: Postoperative main thoracic Cobb angle, and average change in angle. Postoperative compensatory lumbar Cobb angle, and average change in angle. Coronal balance. Sagittal balance. Apical vertebral rotation and change.

Determinants of Lumbar Curve Behavior in Lenke Type IA and B Thoracic Adolescent Idiopathic Scoliosis Treated by Posterior Spinal Fusion

Introduction Study design: prospective. Objectives To assess lumbar curve behavior in Lenke IA and B curves treated by selective thoracic posterior fusion. Test hypotheses were that spontaneous lumbar curve correction (SLCC) would be better with smaller initial deformities, in more flexible curves, and of greater magnitude with higher metal density. Summary of Background Data There are different and often conflicting recommendations regarding selection of lowest instrumented vertebra and best approach which provides the greatest SLCC. All-pedicle-screw constructs and increasing metal density are recent trends. However, few reported the fate of the residual unfused lumbar curve. Material and Methods Thirty-three patients with AIS Lenke 1A/B (single surgeon) were included with a minimum follow-up of 2 years. Mean age was 14.2 years (9–19 years). All had all-pedicle-screw constructs with mean metal density of 58% (36–75%). The mean fused level was 10.3. Results The mean thoracic Cobb angle for preoperative, immediate postoperative, at 1-year, and final follow-ups were 60.6, 15.5, 15.9, and 17.2 degrees, respectively (mean flexibility 49.4% [10–96%]). Lumbar curve preoperative mean Cobb angle was 29.6 degrees (14–53 degrees) (mean curve flexibility 79% [40–96%]). Cobb angle at immediate postoperative, 1-year, and 2-year follow-ups were 9.2, 8.9, and 9.4 degrees, respectively. The mean lumbar lordosis angle preoperatively and at final follow-up was 57.3 and 55.9 degrees. Maximum SLCC was achieved within 6 weeks and maintained throughout. No lumbar decompensation was noted. There was significant correlation between the percentage correction of the thoracic curve and SLCC percentage ( p = 0.027). There was no significant correlation between SLCC and the preoperative thoracic curve magnitude ( p = 0.16). Similarly, there was no correlation between metal density and SLCC ( p = 0.62). The patients were divided into two groups according to the flexibility (&lt; 40 and ≥ 40%). There was no correlation between the SLCC and curve flexibility. Conclusion Our results demonstrate that in Lenke IA and B curves treated with selective pedicle-only posterior fusion, there were no decompensation, lumbar curve was corrected significantly, and SLCC was completed within 6 weeks and maintained. Lumbar lordosis remained normal. The percentage of lumbar curve correction was neither associated with its initial Cobb angle magnitude nor flexibility. Finally, magnitude of preoperative thoracic curve, latter curve percentage correction, and metal density did not affect SLCC.

Disc and Vertebral Responses in the Unfused Lumbar Curve to Selective Thoracic Fusion in Lenke 1B/1C Scoliosis

Introduction Several previous studies have reported spontaneous lumbar curve correction for both anterior and posterior selective fusion in patients with Lenke 1B or 1C; however, the mechanism for this phenomenon remains unclear. The objective of this study is to analyze the detailed response of compensatory lumbar curve to selective thoracic fusion in patients with adolescent idiopathic scoliosis (AIS) with Lenke 1B/1C curve. Patients and Methods This study included patients with AIS with Lenke type 1B or 1C curves treated with posterior selective thoracic fusion (LIV at L1) from 2006 to 2008 in our institution. They had a major right thoracic curve and a compensatory lumbar curve. They were followed for at least 24 months. Radiographic measurements including disc angle and vertebra tilt in the lumbar region were compared before surgery, after surgery, and at latest follow-up. Results A total of 20 patients (7 boys and 13 girls) with a mean age of 15 years were included in this study. The thoracic curve was corrected from 46 ± 7.2 degrees preoperatively to 8 ± 4.7 degrees postoperatively, and to 9 ± 5.1 degrees at the latest follow-up. The mean lumbar compensatory Cobb angle was 36 ± 6.9 degrees before surgery, spontaneously correcting to 12 ± 5.3 degrees at latest follow-up. The most significant change of vertebral tilt occurred at LIV and the L4 vertebra in the coronal plane. Change in disc angle was 6.4 ± 3.1 degrees at L1/L2, 3.2 ± 2.3 degrees at L2/L3, 1.0 ± 1.3degrees at L3/L4, −2.3 ± 1.9 degrees at L4/L5, and −0.7 ± 0.5degrees at L5/S1. L1/L2 disc ranks highest among all the discs in the contribution to correction of the lumbar curve. Conclusion LIV and the L4 vertebra have a trend to be horizontal after selective thoracic fusion. Spontaneous correction of the unfused lumbar curve relies on the compensatory changes of lumbar disc angle, which are mainly at the junctional disc right below LIV. This study suggests that the disc right below LIV assumes the greatest portion of correction force transmitting therefore is prone to degenerate earlier than normal.

Postoperative behavior of thoracolumbar/lumbar curve and coronal balance after posterior thoracic fusion for Lenke 1C and 2C adolescent idiopathic scoliosis

Background Controversy still exists around surgical strategies for Lenke type 1C and 2C curves with primary thoracic and compensatory lumbar curves in adolescent idiopathic scoliosis (AIS). The benefit of selective thoracic fusion (STF) for these curve types is spontaneous lumbar curve correction while saving more mobile lumbar segments. However, a risk of postoperative coronal decompensation after STF has also been reported. This multicenter retrospective study was conducted to evaluate postoperative behavior of thoracolumbar/lumbar (TLL) curve and coronal balance after posterior thoracic fusion for Lenke 1C and 2C AIS.

Postoperative behavior of thoracolumbar/lumbar curve and coronal balance after posterior thoracic fusion for Lenke 1C and 2C adolescent idiopathic scoliosis.

Controversy still exists around surgical strategies for Lenke type 1C and 2C curves with primary thoracic and compensatory lumbar curves in adolescent idiopathic scoliosis (AIS). The benefit of selective thoracic fusion (STF) for these curve types is spontaneous lumbar curve correction while saving more mobile lumbar segments. However, a risk of postoperative coronal decompensation after STF has also been reported. This multicenter retrospective study was conducted to evaluate postoperative behavior of thoracolumbar/lumbar (TLL) curve and coronal balance after posterior thoracic fusion for Lenke 1C and 2C AIS. Twenty-four Lenke 1C and 2C AIS patients who underwent posterior thoracic fusion were included. The mean age of patients was 15.7 years old at time of surgery. Constructs used for surgery in all cases were pedicle screw constructs ending at L3 or above. Radiographic measurements were performed on Cobb angles of the main thoracic and TLL curves and coronal balance. Factors related to final Cobb angle of TLL curve and postoperative change of coronal balance were investigated. Mean Cobb angles for main thoracic and TLL curves were 59.0° and 43.9° preoperatively, and were corrected to 21.5° and 22.0° at final follow-up, respectively. Mean coronal balance was -5.6 mm preoperatively and was corrected to -14.6 mm at final follow-up. Final Cobb angle of TLL curve was significantly correlated with immediate postoperative Cobb angle of main thoracic curve and tilt of lowest instrumented vertebra (LIV). Postoperative change of coronal balance was significantly correlated with selection of LIV relative to stable vertebra. Spontaneous correction of TLL curve occurred consistently by correcting the main thoracic curve and making the LIV more horizontal after posterior thoracic fusion for Lenke 1C and 2C AIS. The more distal fixation to stable vertebra resulted in coronal balance shifting more to the left postoperatively.