Secondary curve behavior in Lenke type 1C adolescent idiopathic scoliosis after thoracoscopic selective anterior thoracic fusion

Flexibility-tilt agreement best predicts shoulder balance following posterior spine fusion for adolescent idiopathic scoliosis

PURPOSE

We propose a novel concept, called flexibility-tilt agreement (FTA), which could be applied intra-operatively to improve shoulder balance following posterior spine fusion for Adolescent Idiopathic Scoliosis (AIS). We retrospectively applied this concept to a cohort with thoracic-only curves, seeking to: (1) evaluate the impact of FTA and other peri-operative variables on post-operative shoulder balance, and (2) evaluate deformity characteristics associated with achieving FTA.

METHODS

A single-institution registry was queried for patients undergoing PSF from 2000 to 2017 with main thoracic and double thoracic curves with at least 2-year follow-up. Flexibility was defined as the Cobb angle of the unfused proximal thoracic curve (cephalad to chosen UIV) on pre-operative bender. Tilt refers to post-operative UIV tilt angle. FTA means these values cancel (Flexibility + Tilt = 0 ± 5°). Logistic regression was performed to determine the association between peri-operative variables and shoulder balance.

RESULTS

One hundred and sixty-one patients were included, mean age 13.6 years old, and 47-month mean follow-up. FTA was achieved in 74 (46%) patients and was associated with post-operative (OR = 4.59) and final (OR = 6.98) medial shoulder balance with a threshold of 6° (AUC = 0.77, p = 0.038). FTA was the best predictor of shoulder balance of all tested variables.

CONCLUSION

Patients that showed flexibility-tilt agreement, or FTA, had vastly increased odds of medial and lateral shoulder balance at a minimum of 2-year follow-up for all thoracic curves. Future studies can evaluate whether applying FTA to determine intra-operative corrective maneuvers prospectively leads to improvements in shoulder balance.

LEVEL OF EVIDENCE

Level III-retrospective comparative study.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Evaluation of the Radiographic Risk Factors of Postoperative Shoulder Imbalance in Adult Scoliosis

Objective

This study aimed to evaluate the radiographic risk factors of postoperative shoulder imbalance (PSI) after adult scoliosis (AS) correction surgery.

Methods

Seventy-nine patients with AS undergoing correction surgery at a single institution were reviewed. The mean follow-up was 28 months. Patients were divided into two groups based on their radiographic shoulder height (RSH): (1) the balanced group (RSH <10 mm) and (2) the unbalanced group (RSH ≥10 mm). The preoperative and postoperative Cobb angles of the proximal thoracic (PT), main thoracic (MT), thoracolumbar/lumbar (TL/L) and upper instrumented vertebra (UIV) were measured.

Results

No significant difference was found between the balanced and unbalanced groups when the UIV was T1–2, T3–4, or below T4. Univariate analysis indicated that the unbalanced group had significantly higher postoperative RSH, lower percentage PT correction, and greater percentage MT correction. The classification and regression tree analysis revealed that when the correction percentage of PT curve was more than 55.3%, 84.4% of patients acquired shoulder balance. However, when the correction percentage of PT curve was less than 55.3%, and the correction percentage of MT curve was more than 56%, 65.7% of the patients developed PSI.

Conclusions

In AS correction surgery, a lower percentage correction of the PT curve and greater percentage correction of the MT curve were independent radiographic risk factors of PSI, regardless of the UIV level. Sufficient PT correction is required to achieve postoperative shoulder balance in AS correction surgery when the MT curve is overcorrected.

Clinical predictive model of lumbar curve Cobb angle below selective fusion for thoracic adolescent idiopathic scoliosis: a longitudinal multicenter descriptive study

PURPOSE

To implement a clinically applicable, predictive model for the lumbar Cobb angle below a selective thoracic fusion in adolescent idiopathic scoliosis.

METHODS

A series of 146 adolescents with Lenke 1 or 2 idiopathic scoliosis, surgically treated with posterior selective fusion, and minimum follow-up of 5 years (average 7) was analyzed. The cohort was divided in 2 groups: if lumbar Cobb angle at last follow-up was, respectively, ≥ or < 10°. A logistic regression-based prediction model (PredictMed) was implemented to identify variables associated with the group ≥ 10°. The guidelines of the TRIPOD statement were followed.

RESULTS

Mean Cobb angle of thoracic main curve was 56° preoperatively and 25° at last follow-up. Mean lumbar Cobb angle was 33° (20; 59) preoperatively and 11° (0; 35) at last follow-up. 53 patients were in group ≥ 10°. The 2 groups had similar demographics, flexibility of both main and lumbar curves, and magnitude of the preoperative main curve, p > 0.1. From univariate analysis, mean magnitude of preoperative lumbar curves (35° vs. 30°), mean correction of main curve (65% vs. 58%), mean ratio of main curve/distal curve (1.9 vs. 1.6) and distribution of lumbar modifiers were statistically different between groups (p < 0.05). PredictMed identified the following variables significantly associated with the group ≥ 10°: main curve % correction at last follow-up (p = 0.01) and distal curve angle (p = 0.04) with a prediction accuracy of 71%.

CONCLUSION

The main modifiable factor influencing uninstrumented lumbar curve was the correction of main curve. The clinical model PredictMed showed an accuracy of 71% in prediction of lumbar Cobb angle ≥ 10° at last follow-up.

LEVEL OF EVIDENCE IV

Longitudinal comparative study.

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

PURPOSE

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.

METHODS

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 2 years post-operative. Multivariate linear regression was used to identify variables most predictive of lumbar curve correction.

RESULTS

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.

CONCLUSIONS

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.

Analysis of the Change Patterns of Sagittal Alignment Values After Selective Thoracic Fusion in Lenke 1 Adolescent Idiopathic Scoliosis According to Preoperative Thoracic Kyphosis Status

STUDY DESIGN

This was a retrospective study.

OBJECTIVE

The objective of this study was to demonstrate the different change patterns in reciprocal sagittal alignment values after selective thoracic fusion (STF) in Lenke type 1 adolescent idiopathic scoliosis (AIS) according to preoperative thoracic kyphosis (TK).

SUMMARY OF BACKGROUND DATA

Several studies have found significant increase in TK after STF, while other studies have reported decrease in TK postoperatively. Similar inconclusive results on changes in lumbar lordosis (LL) have been reported, showing LL increase, decrease, or no change.

MATERIALS AND METHODS

Ninety-three patients presenting with Lenke type 1 AIS treated by posterior STF with a minimum follow-up of 2 years were included in this study. Using whole spine radiographs, sagittal parameters including TK, LL, and upper lumbar lordosis (ULL) were compared preoperatively and at the last follow-up between a hypokyphosis group (preoperative TK<20 degrees) and a normokyphosis group (preoperative TK≥20 degrees). Health-related quality of life (HRQOL) was assessed using scoliosis research society health-related quality of life-30 (SRS-30) and short from health survey-36 questionnaire at the last visit.

RESULTS

The mean follow-up duration was 74.9 months. In the hypokyphosis group (35 patients), TK, LL, and ULL statistically significantly increased after surgery by mean 7.7, 5.1, and 3.7 degrees (P<0.001, <0.001, and 0.001). In the normokyphosis group (58 patients), these parameters did not show significant changes after STF. Final TK was significantly lower in hypokyphosis group than that in the normokyphosis group (21.2 vs. 30.9 degrees, P<0.001) while final LL did not differ between 2 groups (52.4 vs. 54.6 degrees, P=0.194). HRQOL did not differ significantly between the 2 groups.

CONCLUSIONS

After STF in Lenke 1 AIS, TK, and LL statistically significantly increased through an increase in the mean ULL in the hypokyphosis group while those mean values did not change in the normokyphosis group. Despite the final mean value of the TK in the hypokyphosis group increasing by 7.7 degrees, it was statistically significantly lower than the final mean TK value in the normokyphosis group which did not increase after STF surgery by posterior approach. However, HRQOL showed no significant difference between the 2 groups.

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

INTRODUCTION

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°.

METHODS

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.

RESULTS

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%).

CONCLUSION

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.

Radiographic evaluation of posterior selective thoracolumbar or lumbar fusion for moderate Lenke 5C curves

INTRODUCTION

Posterior selective thoracolumbar or lumbar (TL/L) fusion with pedicle screw constructs for adolescent idiopathic scoliosis (AIS) has been studied in a few researches. However, few studies have discussed the indication for selective TL/L fusion and the behaviors of its adjacent disc angle. The present study aims to discuss the indication for posterior selective TL/L fusion and the behavior of the adjacent disc angle.

METHODS

45 consecutive cases of AIS undergoing posterior selective TL/L fusion were retrospectively evaluated, with an average follow-up of 36 months. Radiographs were reviewed to determine the coronal curve magnitude and the sagittal alignment preoperatively, postoperatively and at final follow-up. Thoracic curves in groups A had a correction loss of more than 5°, while thoracic curves in group B had a correction loss of not more than 5°.

RESULTS

The coronal curve magnitude of the TL/L curve averaged 44° preoperatively and it was corrected to 6° immediately with a correction rate of 84.8 %. At final follow-up it was 9° with a correction loss of 3°. The minor thoracic curve was 26° preoperatively, and the convex side bending curve magnitude averaged 8° with a flexibility of 72.7 %. It was corrected to 13° immediately with a spontaneous correction of 48.5 %. At final follow-up it was 14° with a correction loss of 1°. UIVA decreased from 4° to 2° after surgery, and it was 2° at final follow-up. LIVA decreased from 7° to 4° after surgery, and it was 5° at final follow-up. Maximal correction of TL/L curves in group A is significantly less than that in group B. 1 patient received revision surgery to fuse the progressive thoracic curve.

CONCLUSION

Posterior selective TL/L fusion with pedicle screw constructs allows for spontaneous thoracic correction and maintains coronal and sagittal balance during the follow-up. Maximal correction instead of undercorrection was recommended for moderate Lenke 5C curves. Disc wedging could be improved after surgery and well maintained during the follow-up.

The Spontaneous Development of Cosmetic Shoulder Balance and Shorter Segment Fusion in Adolescent Idiopathic Scoliosis With Lenke I Curve: A Consecutive Study Followed Up for 2 to 5 Years

STUDY DESIGN

A single-center, retrospective, consecutive case series.

OBJECTIVE

To evaluate the spontaneous development of cosmetic shoulder balance (SDCSB) after surgery and to investigate the feasibility of shorter segment fusion in adolescent idiopathic scoliosis (AIS) with Lenke I curve.

SUMMARY OF BACKGROUND DATA

Upper instrumented vertebrae (UIV) at a more proximal level are always chosen to keep postoperative shoulder balance in AIS. In the guidelines of Rose and Lenke proposed in 2007, for Lenke I right thoracic curves, UIV should be T4 or T5 when the right shoulder is elevated preoperatively, T4 or T3 if the shoulders are level, and T2 when the left shoulder is elevated. Cosmetic shoulder balance (CSB), however, corrects and improves itself postoperatively.

METHODS

Seventy-five consecutive AIS patients with Lenke I curves were followed up for 2 to 5 years postoperatively. Twenty patients (26.7%) selected UIV at the caudal levels in the guidelines of Rose and Lenke (T5 when patients were with right shoulder elevated preoperatively, T4 when patients were with even shoulders preoperatively). Forty-two patients (56.0%) selected UIV at more caudal levels than those suggested by the guidelines. In this study, UIV at the caudal levels in the guidelines and UIV at more caudal levels than those suggested by the guidelines were shorter segment fusion. CSB was measured from photographs. Spinal Appearance Questionnaire (SAQ) was acquired for subjective evaluation of shoulder balance.

RESULTS

At last follow-up, the main thoracic curve was 19.5° ± 10.4°, the coronal balance improved to 0.7 ± 0.6 cm, and T2-T12 kyphosis was 34.4° ± 10.8°. At preoperation, immediate postoperation, and last follow-up, the measurements of CSB were 1.1 ± 0.7 cm (range: -2.4 to 1.7 cm), 0.9 ± 0.6 cm (range: -0.8 to 3.1 cm), and 0.6 ± 0.4 cm (range: -0.6 to 1.5 cm). At the three time points, numbers of patients with -1.0 cm < CSB < 1.0 cm were 28 (37.3%), 46 (61.3%), and 70 (93.3%), respectively. There was significant difference between the measurements of CSB at immediate postoperation and at last follow-up (t = 3.6, P < 0.001). At last follow-up, 74 (98.7%) patients perceived even shoulders in SAQ.

CONCLUSION

SDCSB plays an important role in regaining shoulder balance after surgery in AIS. The shorter segment fusion is feasible in treating AIS patients with Lenke I curves.

LEVEL OF EVIDENCE

4.

Selective versus nonselective thoracic fusion in Lenke 1C curves: a meta-analysis of baseline characteristics and postoperative outcomes

OBJECT

Lenke 1C curves are challenging to manage surgically due to the structural thoracic deformity and nonstructural lumbar curve. Selective thoracic fusion (STF) is considered the standard of care because it preserves motion of the lumbar segment, yet nonselective STF (NSTF) remains prevalent. This study aims to identify baseline patient characteristics that drive treatment and to compare postoperative outcomes for both procedures.

METHODS

Studies that compared baseline and postoperative demographic data, health-related quality of life (HRQL) questionnaires, and radiographic parameters of patients with Lenke 1C curves undergoing STF or NSTF were identified for meta-analysis. The effect measure is expressed as a mean difference (MD) with 95% CI. A positive MD signifies a greater STF value, or a mean increase within the group.

RESULTS

One prospective and 6 retrospective case-control studies with sample size of 488 patients (344 STF and 144 NSTF) were identified. Baseline age, sex, and HRQLs were equivalent, except for better scores in the STF group for the Scoliosis Appearance Questionnaire (SAQ): Unrelated to Deformity item (3.47 vs 3.88, p = 0.01) and the Spine Research Society questionnaire, Item 22: Pain (4.13 vs 3.92, p = 0.04). Radiographic findings were significantly worse in NSTF, as measured by the thoracolumbar/lumbar (TL/L) Cobb angle (MD: -4.29°, p < 0.01) and TL/L apical vertebral translation (AVT) (MD: -6.08, p < 0.01). Radiographic findings significantly improved in STF, as measured in the main thoracic (MT) Cobb angle (MD: -27.78°, p < 0.01), TL/L Cobb angle (MD: -16.24°, p < 0.01), MT:TL/L Cobb ratio (MD: -0.21, p < 0.01), coronal balance (MD: 0.47, p = 0.02), and thoracic kyphosis (MD: 7.87°, p < 0.01); and in NSTF in proximal thoracic (PT) Cobb angle (24° vs 14.1°, p < 0.01), MT Cobb angle (53.5° vs 20.5°, p < 0.01), and TL/L Cobb angle (41.6° vs 16.6°, p < 0.01). Postoperative TL/L Cobb angle (23.1° vs 16.6°, p < 0.01) was significantly higher in STF; but PT Cobb angle, MT Cobb angle, and MT:TL/L Cobb ratio are equivalent.

CONCLUSIONS

Patients with larger lumbar compensatory curves displaying a larger degree of coronal translation, as measured by the TL/L AVT, are more likely to undergo an NSTF. Contrary to established guidelines, larger MT curve magnitudes and MT:TL/L Cobb angle ratios have not been found to influence the decision to pursue a selective thoracic fusion. Although overall both STF and NSTF groups are found to have effective postoperative coronal balance, the STF group has only modest improvements in the lumbar curve position as determined by a relatively unchanged TL/L AVT. Furthermore, surgeons may prefer NSTF in patients who may have a worse overall perception of their spinal deformity as measured by HRQL measures of pain and desire for appearance change.

Could structural and noncompensatory Lenke 3 and 4C lumbar curves be nonstructural and compensatory? Lenke 1, 2, 3, and 4 curve types were similar and could be considered collectively as a single indication for selective thoracic fusion

STUDY DESIGN

Retrospective radiographical review.

OBJECTIVE

To demonstrate that the structural and noncompensatory Lenke 3 and 4C lumbar curves could be nonstructural and compensatory.

SUMMARY OF BACKGROUND DATA

Historically, Lenke 3 and 4C curves were not recommended for selective thoracic fusion (STF) because the lumbar curve was considered structural and noncompensatory. However, consecutive series of Lenke 3 and 4C curves suggest successful treatment with STF.

METHODS

Between 2001 and 2004, 2005 and 2008, and 2010 and 2012, 3 consecutive series of 108, 134, and 78 surgically treated Lenke 1, 2, 3, and 4C curves were reviewed, respectively. The coronal curve criteria for the curves treated with STF during each period were lumbar side bending Cobb angle less than 25° and meeting the Lenke ratio criteria, lumbar side bending Cobb angle 35° or less, and lumbar side bending Cobb angle 45° or less, respectively. The sagittal curve criteria for STF during each period was absence of junctional thoracolumbar kyphosis 20° or more between T10 and L2. The technique used for STF was the Guan-Din method. Radiographs of all the curves treated with STF were analyzed before and after surgery.

RESULTS

Optimal instrumented thoracic and compensatory lumbar correction was obtained for all Lenke 1, 2, 3, and 4C curves treated with STF in each period. As the coronal criteria for STF were broadened, the extent of feasibility of STF was expanded and the rate of STF increased. Although Cobb angle, apical vertebral translation, and apical vertebral rotation magnitudes of Lenke 3 and 4C curves were larger and more severe than those of Lenke 1 and 2C curves, optimal compensatory correction could still be obtained for Lenke 3 and 4C curves.

CONCLUSION

The structural and noncompensatory Lenke 3 and 4C lumbar curves were proven to be nonstructural and compensatory. Lenke 1, 2, 3, and 4C curves have similar natures and similar responses to the same technique (Guan-Din method) used for STF and could be considered collectively as a single indication for STF. The extent of feasibility of STF could be expanded from Lenke 1 and 2 curves to Lenke 1, 2, 3, and 4 curves.

LEVEL OF EVIDENCE

2.

Biological performance of a polycaprolactone-based scaffold plus recombinant human morphogenetic protein-2 (rhBMP-2) in an ovine thoracic interbody fusion model

PURPOSE

We develop a sheep thoracic spine interbody fusion model to study the suitability of polycaprolactone-based scaffold and recombinant human bone morphogenetic protein-2 (rhBMP-2) as a bone graft substitute within the thoracic spine. The surgical approach is a mini-open thoracotomy with relevance to minimally invasive deformity correction surgery for adolescent idiopathic scoliosis. To date there are no studies examining the use of this biodegradable implant in combination with biologics in a sheep thoracic spine model.

METHODS

In the present study, six sheep underwent a 3-level (T6/7, T8/9 and T10/11) discectomy with randomly allocated implantation of a different graft substitute at each of the three levels: (a) calcium phosphate (CaP) coated polycaprolactone-based scaffold plus 0.54 μg rhBMP-2 (b) CaP-coated PCL-based scaffold alone or (c) autograft (mulched rib head). Fusion was assessed at 6 months post-surgery.

RESULTS

Computed Tomographic scanning demonstrated higher fusion grades in the rhBMP-2 plus PCL-based scaffold group in comparison with either PCL-based scaffold alone or autograft. These results were supported by histological evaluations of the respective groups. Biomechanical testing revealed significantly higher stiffness for the rhBMP-2 plus PCL-based scaffold group in all loading directions in comparison with the other two groups.

CONCLUSION

The results of this study demonstrate that rhBMP-2 plus PCL-based scaffold is a viable bone graft substitute, providing an optimal environment for thoracic interbody spinal fusion in a large animal model.

Guan-Din method: a novel surgical technique for selective thoracic fusion to maximize the rate of selective thoracic fusion and compensatory correction

STUDY DESIGN

Retrospective radiographical review.

OBJECTIVE

To evaluate the outcome of selective thoracic fusion (STF) by using the Guan-Din method for the treatment of major thoracic compensatory lumbar (MTCL) curves.

SUMMARY OF BACKGROUND DATA

Performing STF for MTCL curves is to minimize the loss of lumbar motion and the risk of lumbar degeneration or pain. Surgical treatment of MTCL curves aims to maximize the rate of STF for MTCL curves while optimizing instrumental thoracic and compensatory lumbar correction. The Guan-Din method has been demonstrated to be able to enhance the lumbar curve's capacity for spontaneous correction and broaden the current curve criteria of MTCL curves for STF.

METHODS

Between 2004 and 2010, 510 consecutive surgically treated MTCL curves were reviewed. Of these MTCL curves, who met the criteria of lumbar side bending Cobb 35° or less and without global thoracic hyperkyphosis and/or thoracolumbar kyphosis (T10-L2 ≤20°), were treated with STF using the Guan-Din method. Radiographs were analyzed before surgery, immediately after surgery, and at the most recent follow-up (range, 2-8 yr).

RESULTS

Curve types of 510 MTCL curves according to Lenke system were as follows: 1A (n = 91), 2A (n = 74), 3A (n = 6), 4A (n = 2), 1B (n = 93), 2B (n = 34), 3B (n = 8), 4B (n = 5), 1C (n = 84), 2C (n = 26), 3C (n = 72), and 4C (n = 15). Of the 510 MTCL curves, 458 (90%) curves were treated with STF. A mean 73% thoracic correction and 63% lumbar correction was obtained at the most recent follow-up. Of the 197 surgically treated MTCL curves with a lumbar C modifier, 148 (75%) curves that contained 57 Lenke 1C and 2C curves and 40 Lenke 3C and 4C curves that did not meet Lenke curve criteria for STF, were successfully treated with STF. A mean 67% thoracic correction and 57% lumbar correction was obtained at the most recent follow-up. The rate of STF and the magnitude of correction of MTCL curves in this study were significantly greater than those in all other reports. No significant change in global coronal and sagittal imbalance was observed.

CONCLUSION

The rate of STF and the compensatory correction of MTCL curves could be maximized by using the Guan-Din method as the method for STF.

LEVEL OF EVIDENCE

4.

[Current status of thoracoscopic surgery for thoracic and lumbar spine. Part 2: treatment of the thoracic disc hernia, spinal deformities, spinal tumors, infections and miscellaneous]

INTRODUCTION

Thoracoscopic surgery or video-assisted thoracic surgery (VATS) of the thoracic and lumbar spine has evolved greatly since it appeared less than 20 years ago. It is currently used in a large number of processes and injuries. The aim of this article, in its two parts, is to review the current status of VATS of the thoracic and lumbar spine in its entire spectrum.

DEVELOPMENT

After reviewing the current literature, we developed each of the large groups of indications where VATS takes place, one by one. This second part reviews and discusses the management, treatment and specific thoracoscopic technique in thoracic disc herniation, spinal deformities, tumour pathology, infections of the spine and other possible indications for VATS.

CONCLUSIONS

Thoracoscopic surgery is in many cases an alternative to conventional open surgery. The transdiaphragmatic approach has made endoscopic treatment of many thoracolumbar junction processes possible, thus widening the spectrum of therapeutic indications. These include the treatment of spinal deformities, spinal tumours, infections and other pathological processes, as well as the reconstruction of injured spinal segments and decompression of the spinal canal if lesion placement is favourable to antero-lateral approach. Good clinical results of thoracoscopic surgery are supported by growing experience reflected in a large number of articles. The degree of complications in thoracoscopic surgery is comparable to open surgery, with benefits in regard to morbidity of the approach and subsequent patient recovery.