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.

COMPARISON OF IMPLANT DENSITY IN THE MANAGEMENT OF LENKE 1B AND 1C ADOLESCENT IDIOPATHIC SCOLIOSIS.

OBJECTIVE: To compare radiographic and surgical outcomes of Lenke 1B and 1C patterns. METHODS: One hundred twenty patients with Lenke 1B and 1C scoliosis were grouped according to implant density as follows: low density (LD) of ≤1.4 and high density (HD) of >1.4. Matched subgroups (30 patients each) based on age, curve magnitude, and body mass index (BMI) were analyzed. Radiographic parameters were evaluated before operation, immediately after operation (ipo), and at 2 years' follow-up. SRS-30 was administered before operation and at 2 years' follow-up. RESULTS: The major curves of the LD (n = 82) and HD groups (n=38) were respectively 59.1° and 65.6° before operation (p <.001), 26.3° and 22.9° ipo (p =.05), and 29.9° and 19.8° at 2 years' follow-up (p <.001). No significant differences in postoperative trunk shift and coronal balance were found (p =.69 and p =.74, respectively). The HD group had higher blood loss (p =.02), number of implants (p <.001), levels fused (p =.002), and surgical time (p <.001). The HD group had a higher prevalence of hypokyphosis from before operation to follow-up (p <.001). No significant differences were observed in the SRS-30 scores before operation and at 2 years' follow-up. The matched groups had similar preoperative major curves (p =.56), ages (p =.75), and BMIs (p =.61). Significantly longer surgical time (p =.009), higher density (p <.001), and better correction (p =.0001) were found in the HD group at 2 years' follow-up. No significant differences were found in the SRS-30 scores before operation and at 2 years' follow-up. CONCLUSION: LD constructs included fewer segments fused, lower intraoperative estimated surgical blood loss, and shorter operation time, and potentially decreasing complication risks due to fewer implants. Level of evidence III, Retrospective Cohort Study.

OBJETIVO: Comparar os desfechos radiográficos e cirúrgicos da escoliose Lenke 1B e 1C. MÉTODOS: Cento e vinte pacientes com escoliose Lenke 1B e 1C foram agrupados de acordo com a densidade do implante, como segue: baixa densidade (BD) de ≤ 1,4 e alta densidade (AD) de > 1,4. Foram analisados os grupos pareados (30 pacientes cada) com base na idade, magnitude da curva e índice de massa corporal (IMC). Os parâmetros radiográficos foram avaliados antes da cirurgia, no pós-operatório imediato (POI) e no acompanhamento de dois anos. O questionário SRS-30 foi administrado antes da cirurgia e no acompanhamento de dois anos. RESULTADOS: As principais curvas dos grupos BD (n = 82) e AD (n = 38) foram respectivamente 59,1° e 65,6° antes da operação (p < 0,001), 26,3° e 22,9° no POI (p = 0,05) e 29,9° e 19,8° aos 2 anos de acompanhamento (p < 0,001). Não foram encontradas diferenças significantes no desvio do tronco e no balanço coronal no pós-operatório (p = 0,69 e p = 0,74, respectivamente). O grupo AD teve mais perda sanguínea (p = 0,02), número de implantes (p < 0,001), níveis de fusão (p = 0,002) e tempo de cirurgia (p < 0,001). O grupo AD teve maior prevalência de hipocifose do período anterior à cirurgia até o acompanhamento (p < 0,001). Não houve diferenças significantes nas pontuações do SRS-30 antes da operação e aos 2 anos de acompanhamento. No pré-operatório, os grupos pareados tinham curvas principais (p = 0,56), idade (p = 0,75) e IMC (p = 0,61) semelhantes. Constatou-se tempo cirúrgico expressivamente maior (p = 0,009), maior densidade (p < 0,001) e melhor correção (p = 0,0001) no grupo AD aos 2 anos de acompanhamento. Não foram encontradas diferenças significantes nas pontuações do SRS-30 antes da cirurgia e no acompanhamento de 2 anos. CONCLUSÃO: As estruturas de BD incluíram menos segmentos fundidos, menor perda de sangue intraoperatória estimada, menor tempo de cirurgia e menos risco de complicações, com possibilidade de redução, por causa do menor número de implantes. Nível de evidência III, Estudo retrospectivo de coorte.

Comparison of implant density in the management of lenke 1b and 1c adolescent idiopathic scoliosis / Comparação da densidade do implante no tratamento da escoliose idiopática do adolescente lenke 1b e 1c

ABSTRACT Objective: To compare radiographic and surgical outcomes of Lenke 1B and 1C patterns. Methods: One hundred twenty patients with Lenke 1B and 1C scoliosis were grouped according to implant density as follows: low density (LD) of ≤1.4 and high density (HD) of >1.4. Matched subgroups (30 patients each) based on age, curve magnitude, and body mass index (BMI) were analyzed. Radiographic parameters were evaluated before operation, immediately after operation (ipo), and at 2 years' follow-up. SRS-30 was administered before operation and at 2 years' follow-up. Results: The major curves of the LD (n = 82) and HD groups (n=38) were respectively 59.1° and 65.6° before operation (p <.001), 26.3° and 22.9° ipo (p =.05), and 29.9° and 19.8° at 2 years' follow-up (p <.001). No significant differences in postoperative trunk shift and coronal balance were found (p =.69 and p =.74, respectively). The HD group had higher blood loss (p =.02), number of implants (p <.001), levels fused (p =.002), and surgical time (p <.001). The HD group had a higher prevalence of hypokyphosis from before operation to follow-up (p <.001). No significant differences were observed in the SRS-30 scores before operation and at 2 years' follow-up. The matched groups had similar preoperative major curves (p =.56), ages (p =.75), and BMIs (p =.61). Significantly longer surgical time (p =.009), higher density (p <.001), and better correction (p =.0001) were found in the HD group at 2 years' follow-up. No significant differences were found in the SRS-30 scores before operation and at 2 years' follow-up. Conclusion: LD constructs included fewer segments fused, lower intraoperative estimated surgical blood loss, and shorter operation time, and potentially decreasing complication risks due to fewer implants. Level of evidence III, Retrospective Cohort Study.

RESUMO Objetivo: Comparar os desfechos radiográficos e cirúrgicos da escoliose Lenke 1B e 1C. Métodos: Cento e vinte pacientes com escoliose Lenke 1B e 1C foram agrupados de acordo com a densidade do implante, como segue: baixa densidade (BD) de ≤ 1,4 e alta densidade (AD) de > 1,4. Foram analisados os grupos pareados (30 pacientes cada) com base na idade, magnitude da curva e índice de massa corporal (IMC). Os parâmetros radiográficos foram avaliados antes da cirurgia, no pós-operatório imediato (POI) e no acompanhamento de dois anos. O questionário SRS-30 foi administrado antes da cirurgia e no acompanhamento de dois anos. Resultados: As principais curvas dos grupos BD (n = 82) e AD (n = 38) foram respectivamente 59,1° e 65,6° antes da operação (p < 0,001), 26,3° e 22,9° no POI (p = 0,05) e 29,9° e 19,8° aos 2 anos de acompanhamento (p < 0,001). Não foram encontradas diferenças significantes no desvio do tronco e no balanço coronal no pós-operatório (p = 0,69 e p = 0,74, respectivamente). O grupo AD teve mais perda sanguínea (p = 0,02), número de implantes (p < 0,001), níveis de fusão (p = 0,002) e tempo de cirurgia (p < 0,001). O grupo AD teve maior prevalência de hipocifose do período anterior à cirurgia até o acompanhamento (p < 0,001). Não houve diferenças significantes nas pontuações do SRS-30 antes da operação e aos 2 anos de acompanhamento. No pré-operatório, os grupos pareados tinham curvas principais (p = 0,56), idade (p = 0,75) e IMC (p = 0,61) semelhantes. Constatou-se tempo cirúrgico expressivamente maior (p = 0,009), maior densidade (p < 0,001) e melhor correção (p = 0,0001) no grupo AD aos 2 anos de acompanhamento. Não foram encontradas diferenças significantes nas pontuações do SRS-30 antes da cirurgia e no acompanhamento de 2 anos. Conclusão: As estruturas de BD incluíram menos segmentos fundidos, menor perda de sangue intraoperatória estimada, menor tempo de cirurgia e menos risco de complicações, com possibilidade de redução, por causa do menor número de implantes. Nível de evidência III, Estudo retrospectivo de coorte.

Onset and remodeling of coronal imbalance after selective posterior thoracic fusion for Lenke 1C and 2C adolescent idiopathic scoliosis (a pilot study).

BACKGROUND: Postoperative coronal imbalance is a significant problem after selective thoracic fusion for primary thoracic and compensatory lumbar curves in adolescent idiopathic scoliosis (AIS). However, longitudinal studies on postoperative behavior of coronal balance are lacking. This multicenter retrospective study was conducted to analyze factors related to onset and remodeling of postoperative coronal imbalance after posterior thoracic fusion for Lenke 1C and 2C AIS. METHODS: Twenty-one Lenke 1C or 2C AIS patients, who underwent posterior thoracic fusion ending at L3 or above, were included with a minimum 2-year follow-up. The mean patients' age was 15.1 years at the time of surgery. Radiographic measurements were performed on Cobb angles of the main thoracic (MT) and thoracolumbar/lumbar (TLL) curves and coronal balance. Factors related to the onset of immediately postoperative coronal decompensation (IPCD) and postoperative coronal balance remodeling (PCBR), defined as an improvement of coronal balance during postoperative follow-up, were investigated using comparative and correlation analyses. RESULTS: Mean Cobb angles for the MT and TLL curves were 57.3° and 42.3° preoperatively and were corrected to 22.8° and 22.5° at final follow-up, respectively. Mean preoperative coronal balance of -3.8 mm got worse to -21.2 mm postoperatively, and regained to -12.0 mm at final follow-up. Coronal decompensation was observed in two patients preoperatively, in ten patients immediately postoperatively, and in three patients at final follow-up. The preoperative coronal balance and lowest instrumented vertebra (LIV) selection relative to stable vertebra (SV) were significantly different between patients with IPCD and those without. PCBR had significantly negative correlation with immediately postoperative coronal balance. CONCLUSIONS: IPCD after posterior thoracic fusion for Lenke 1C and 2C AIS was frequent and associated with preoperative coronal balance and LIV selection. However, most patients with IPCD regained coronal balance through PCBR, which was significantly associated with immediately postoperative coronal balance. A fixation more distal to SV shifted the coronal balance further to the left postoperatively.

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.