Adding-on Group Research Articles

Influence of the thoracolumbar junction flexibility on the risk of adding-on after posterior vertebral arthrodesis for thoracic idiopathic adolescent scoliosis.

The objective was to analyze the role of the thoracolumbar sagittal flexibility on the outcome after posterior spinal fusion of Lenke 1 and 2 adolescent idiopathic scoliosis with last touched vertebra as the lowest instrumented vertebra. We included 105 thoracic AIS patients who had a posterior spinal fusion with a 2years minimum follow-up. Thoracolumbar junction flexibility was assessed on dynamic sagittal X-rays and compared to the standing position. Adding-on was defined according to radiographic Wang criteria. The junction was considered flexible if the variability from the static position to flexion and/or extension was greater than 10°. Mean age of the patients was 14 ± 2years. The preoperative mean Cobb angle was 61 ± 12.7° and 27.5 ± 7.7° after surgery. Mean follow-up was 3.1years. Twenty-nine patients (28%) developed an adding-on. Thoracolumbar junction range of motion was higher (p = 0.017) with higher flexibility in flexion (p < 0.001) in the no adding-on group. In no adding-on group, 53 patients (70%) had a flexible thoracolumbar junction, and 23 patients (30%) had a stiff thoracolumbar junction in flexion and flexible in extension. In adding-on group, 27 patients (93%) had a stiff thoracolumbar junction, and 2 patients (7%) had a flexible junction in flexion and stiff in extension. The flexibility of the thoracolumbar junction is a determining factor in the surgical outcome after posterior spinal fusion for AIS and should be considered in correlation with the frontal and sagittal alignment of the spine.

Distal adding-on after surgery in Lenke 5C adolescent idiopathic scoliosis: clinical and radiological outcomes

BackgroundTo evaluate the incidence and risk factors of postoperative distal adding-on in patients with Lenke 5C adolescent idiopathic scoliosis (AIS). More accurate selection criteria for the lower instrumented vertebra (LIV) should be confirmed to prevent distal adding-on.MethodsForty-six patients with Lenke 5C AIS who underwent posterior fusion were enrolled in the study. Patients were allocated into adding-on and no adding-on groups. Demographic data, clinical data, and radiographic parameters were recorded and compared.ResultsPostoperative distal adding-on occurred in eight patients (17.4%) during follow-up. Demographic data, clinical data, and baseline radiographic parameters of the two groups were not significantly different. The postoperative thoracolumbar (TL) or lumbar (L) Cobb angle, LIV translation, and LIV + 1 translation were higher in the adding-on group than those in the no adding-on group, while the postoperative coronal imbalance of the adding-on group was lower than that of the no adding-on group. The level difference of last barely touched vertebra (LBTV) and last substantial touched vertebra (LSTV) with LIV were higher in the adding-on group than in the no adding-on group.ConclusionPostoperative TL/L curve, postoperative LIV translation, postoperative LIV + 1 translation, and postoperative coronal imbalance were determined as risk factors for postoperative distal adding-on in patients with Lenke 5C AIS. Moreover, LIV selection of LBTV-1 or LSTV-1 may cause a higher risk of postoperative distal adding-on.

Distal Adding-on Phenomenon in Scoliosis Secondary to Chiari Malformation Type I: Incidence and Risk Factors.

A retrospective study. The aim of this study was to investigate the incidence and risk factors for distal adding-on (AO) phenomenon after posterior spinal fusion (PSF) in scoliosis secondary to Chiari malformation type I (CMS) patients with right major thoracic curve. Distal AO phenomenon is a common complication observed in adolescent idiopathic scoliosis (AIS), which is significantly associated with unsatisfactory outcomes. However, few studies specifically focused on the incidence and risk factors of distal AO in CMS. Seventy-eight CMS adolescents were included with a minimum of 2-year follow-up after PSF. patients with distal AO at the final follow-up were divided into AO group and those without were No-AO group. The coronal and sagittal parameters were evaluated preoperatively, immediately after surgery, and at the last follow-up. Clinical outcome was analyzed using the Chicago Chiari Outcome Scale (CCOS). Distal AO was observed in 18 of 78 patients (23.1%). Compared with No-AO group, patients with distal AO had significantly lower Risser sign (P = 0.001), more flexibility of lumbar curve (P = 0.021), higher incidence of lowest instrumented vertebra-last substantially touched vertebra (LIV-LSTV) ≤0 (P = 0.001), smaller postoperative Cobb angle of lumbar curve (P < 0.001), and greater correction rate of lumbar curve (P = 0.001). Logistic regression analysis revealed that low Risser sign (Grade 1-2, odds ratio [OR] = 5.7, P = 0.029) and LIV-LSTV ≤0 (OR = 6.4, P = 0.019) were independent risk factors for distal AO. There was no significant difference of CCOS scores between two groups at the final follow-up (P > 0.05 for all). The incidence of distal AO was 23.1% in CMS patients after PSF. Patients with low Risser sign and LIV-LSTV ≤0 were high risk factors for distal AO.Level of Evidence: 3.

The rotation of preoperative-presumed lowest instrumented vertebra: Is it a risk factor for distal adding-on in Lenke 1A/2A curve treated with selective thoracic fusion?

To investigate whether the rotation of preoperative-presumed lowest instrumented vertebra (LIV) is a risk factor for adding-on (AO) in adolescent idiopathic scoliosis (AIS) treated with selective posterior thoracic fusion (sPTF). A total of 196 AIS patients of Lenke type 1A or 2A with minimum 2-year follow-up after sPTF with all pedicle screw instrumentation were included. Radiographical parameters were measured as follows: preoperative rotation angle of presumed LIV and LIV + 1, LIV + 1/LIV rotation difference, postoperative rotation angle of LIV and LIV derotation angle on CT scans. Patients were classified into AO group and non-AO group during the follow-up. The parameters were compared between the two groups to investigate risk factors for AO. Among 196 patients, 40 (20.4%) patients developed with AO at the final follow-up. Compared with non-AO group, patients with AO had significantly larger preoperative rotation angle of presumed LIV (8.8° ± 3.4° vs. 3.4° ± 2.9°, P < 0.001) and LIV + 1 (5.9° ± 4.0° vs. 3.6° ± 2.9°, P = 0.004), LIV + 1/LIV rotation difference (- 2.6° ± 3.7° vs. 0.6° ± 3.2°, P < 0.001) and postoperative rotation angle of LIV (7.2° ± 4.3° vs. 3.0° ± 2.9°, P < 0.001). The last substantially touched vertebrae (LSTV) was selected as LIV in 148 patients, among which the above described parameters were found to be remarkably larger in AO group than non-AO group as well. Multivariate analysis presented Risser grade and preoperative rotation angle of presumed LIV as independent predictors of AO. AIS patients with low Risser grade and large preoperative rotation angle of presumed LIV are more likely to develop with AO after sPTF. Moreover, for the patients with LSTV selected as LIV, preoperative rotation of presumed LIV might be still a risk factor associated with the occurrence of AO. III These slides can be retrieved under Electronic Supplementary Material.

Selecting the LSTV as the Lower Instrumented Vertebra in the Treatment of Lenke Types 1A and 2A Adolescent Idiopathic Scoliosis: A Minimal 3-year Follow-up.

Retrospective study. The purpose of this study was to verify the last substantially touched vertebra (LSTV) as the ideal lower instrumented vertebra (LIV) and to identify predictive factors of adding-on in patients with Lenke type 1A and 2A curve patterns when LSTV was chosen as the LIV. Although several studies have indicated that the use of the LSTV as the LIV can obtain favorable outcomes in Lenke 1A and 2A curves, the factors identifying patients with Lenke 1A and 2A curve patterns who should undergo a fusion extending beyond the LSTV have not been identified. A total of 120 patients with Lenke 1 and 2 curves after posterior instrumentation and fusion to the LSTV were evaluated. All patients had a minimum 3-year follow-up. Patients were grouped based on the occurrence of the distal adding-on phenomenon: an adding-on group and a no adding-on group. We analyzed the significant independent factors associated with adding-on via univariate analysis and then via stepwise logistic regression analysis. Distal adding-on was observed in 16 patients (13.33%). Binary logistic regression analysis showed that the Risser sign (OR = 0.592, P = 0.033), preoperative distance between the LIV and the center sacral vertical line (CSVL) (LIV-CSVL) (OR = 1.286, P = 0.002), and postoperative thoracic kyphosis (T5-T12) (OR = 0.784, P = 0.002) were primary factors for distal adding-on. Selecting the LSTV as the LIV simplifies the selection of the LIV and is an effective operation strategy in patients with Lenke 1A and 2A curve types. Patients with lower Risser sign, larger preoperative LIV-CSVL, and postoperative thoracic hypokyphosis are more likely to develop distal adding-on at 3-year follow-up. 4.

Additional Risk Factors for Adding-On After Selective Thoracic Fusion in Adolescent Idiopathic Scoliosis: Implication of Lowest Instrumented Vertebra Angle and Lumbosacral Takeoff

Study DesignRetrospective chart and radiographic review. ObjectiveThe purpose of this study was to identify any additional risk factors adding-on after selective thoracic fusion in adolescent idiopathic scoliosis (AIS). Summary of Background DataPrevious studies have shown that the proper selection of lowest instrumented vertebra (LIV) is critical in preventing adding-on (AD) phenomenon after selective thoracic fusion (STF). However, even after selecting the correct LIV, AD can still occur. MethodsThis is a retrospective review of 380 consecutive AIS patients who underwent corrective surgery by a single surgeon. LIV was chosen as stable vertebra (SV) or SV–1 if intersected by the center sacral vertical line (CSVL). One hundred thirty-five patients were identified who had complete radiographic images stored in PACS. After Lenke 5, anterior or combined surgeries, TL fusion, and hybrid construct were excluded, two groups were identified out of 78 patients who received STF with all pedicle screw construct: Adding-on (AD) and Control. AD was defined as >5° angle of the superior endplate of LIV–1 to the inferior endplate of LIV+1 between postoperation and the final follow-up. We analyzed the values for the AD group and compared them with those for the control group to identify risk factors not previously defined. ResultsPatients with other complication and follow-up less than 2 years were excluded, and there remained 11 patients in AD (14%), and 8 in the control group. There was no significant difference between the 2 groups in terms of demographic data, LIV selection, and curve types. In AD, there was significant curve progression within fused segments. Even though lumbosacral takeoff (LSTO) was not significantly different, (LIV-H)+LSTO and LIV-H (LIV horizontal) showed significant difference. ConclusionAfter excluding the effect of known risk factors for AD, LIV-H angle, and LIV-H mismatch with LSTO were found to be the additional risk factors for AD. In addition to consideration of other risk factors such as LIV selection or Risser stage, these risk factors should be considered.

Distal adding-on phenomenon in adolescent idiopathic scoliosis patients with thoracolumbar vertebra fusion: A case-control study.

The adding-on phenomenon is a common complication in adolescent idiopathic scoliosis (AIS) patients after correction surgery. However, the risk factors of previous studies and the optimal treatment strategies remain controversial. The aim of this study was to identify new risk factors for the adding-on phenomenon after posterior correction surgery in AIS patients and compare different treatment strategies to guide the selection of the lowest instrumented vertebra (LIV).All types of Lenke AIS patients who received correction surgery at our center from January 2009 to July 2014 were analyzed. The anteroposterior and lateral films were evaluated before surgery, at the 2-week follow-up, and at the 2-year or later follow-up. The patients were divided into 2 groups according to whether adding-on was observed at the last follow-up. The factors predictive of the adding-on phenomenon were identified in a multivariate binary logistic regression model. Different methods for LIV selection were compared in both the adding-on group and the control group (no adding-on).Out of the 346 patients reviewed, 92 met the inclusion criteria; 22 of these met the definition for distal adding-on, and were included in adding-on group. The remaining 70 patients were included in the no adding-on group. The average follow-up was 3.6 years. Touch classification (P < .000), Dnfs (P = .005), and vertebra number between LIV and angle velocity (AV) (P = .001) were significantly different between the 2 groups. Age, gender, Risser sign, and screw density were not found to be affiliated with the presence of adding-on. The results of the Scoliosis Research Society (SRS)-22 were not significantly different between the adding-on group and the control group for any section or overall (P > .05). Binary logistic regression results indicated that postoperative LAV deviation from the CSVL and Touch classification were independent predictive factors. Among the 4 methods, only choosing touch type A as LIV shows satisfactory outcome.The Touch classification is an important risk factor that is highly correlated with the incidence of the adding-on phenomenon. The best LIV choice to preserve the lumbar activity segment as much as possible is Touch type C, and no significant difference was observed in the SRS-22 scores between the Touch type C group and the control group in the short-term follow-up.

Selective versus hyperselective posterior fusions in Lenke 5 adolescent idiopathic scoliosis: comparison of radiological and clinical outcomes.

Recent literature has reported that the ]progression risk of Lenke 5 adolescent idiopathic scoliosis (AIS) during adulthood had been underestimated. Surgery is, therefore, proposed more to young patients with progressive curves. However, choice of the approach and fusion levels remains controversial. The aim of this study was to analyze the influence of the length of posterior fusion on clinical and radiological outcomes in Lenke 5 AIS. All Lenke 5 AIS operated between 2008 and 2012 were included with a minimum 2-year follow-up. Patients were divided into two groups according to the length of fusion. In the first group (selective), the upper instrumented level (UIV) was the upper end vertebra of the main structural curve and distally the fusion was extended to the stable and neutral vertebra, according to Lenke's classification. In the second group (hyperselective), shorter fusions were performed and the number of levels fused depended on the location of the apex of the curve (at maximum, 2 levels above and below, according to Hall's criteria). Apart from the fusion level selection, the surgical procedure was similar in both groups. Radiological outcomes and SRS-22 scores were reported. 78 patients were included (35 selective and 43 hyperselective). The number of levels fused was significantly higher in the first group (7.8±3 vs 4.3±0.6). None of the patients was fused to L4 in selective group. No correlation was found between length of fusion and complication rate. Eight patients had adding-on phenomenon among which 6 (75%) had initially undergone hyperselective fusions and had significantly higher postoperative lower instrumented vertebra (LIV) tilt. In the adding-on group, LIV was located above the last touching vertebra (LTV) in 62.5% of the cases and above the stable vertebra (SV) in 87.5%. Patients in the selective group reported a significantly lower score in the SRS function domain. Coronal alignment was restored in both groups. Hyperselective posterior fusions can be considered in Lenke 5 AIS, preserving one or two mobile segments, with similar clinical and radiological outcomes. However, selection of the LIV according to SV and LTV need to be accurately analyzed in order to avoid adding-on during follow-up.

RELATED FACTORS ANALYSIS OF DISTAL ADDING-ON PHENOMENON IN MAJOR THORACIC CURVE AFTER POSTERIOR SELECTIVE FUSION

To identify the prevalence of distal adding-on phenomenon after posterior selective fusion in type Lenke 1A idiopathic scoliosis, to analyze its risk factors so as to find the reasonable choice for lowest instrumented vertebra (LIV). A retrospective study was made on the clinical data of 43 patients with type Lenke 1A idiopathic scoliosis undergoing posterior selection fusion with pedicle screw instrumentation between July 2011 and December 2015. There were 15 males and 28 females, aged 12-18 years (mean, 16 years). The preoperative Cobb angle was (50.1±11.3)°. The anteroposterior and lateral radiographs were taken at preoperation, immediate after operation, and last follow-up to measure the radiographic parameters. Forty-three patients were divided into adding-on group and control group according to whether or not the occurrence of distal adding-on phenomenon on anteroposterior radiographs of the spine at last follow-up. All the factors that maybe cause distsal adding-on were evaluated by statistical analysis. The patients were followed up 12-50 months (mean, 26.5 months). At last follow-up, distal adding-on was observed in 10 of 43 patients (23.3%), including 2 males (13.3%) and 8 females (28.6%). Univariate analyses showed following several factors associated with adding-on:preoperative lumbar flexibility, preoperative pelvic tilt in coronal plane, preoperative LIV+1 deviation from center sacral vertical line, L4 subtype, the difference between LIV and last touching vertebra (LTV) (LIV-LTV), the difference between LIV and lower end vertebra (LEV) (LIV-LEV), and the difference between LIV and stable vertebra (SV) (LIV-SV). The risk factors above were brought into Logistic regression model, the results showed that preoperative LIV+1 deviation (deviation>10 mm, odds ratio=10.812, P=0.026), LIV-LTV (LIV-LTV<1, odds ratio=9.017, P=0.04), and L4 subtype (1A-R, odds ratio=9.744, P=0.047) were significantly associated with adding-on. Preoperative LIV+1 deviation of >10 mm, L4 subtype (1A-R) and LIV-LTV of <1 are independent predictive factors of adding-on after surgery. As high risk of adding-on was closely related with the incorrect fusion level, it plays an important role for surgeons to decide the level of the fusion before surgery thoroughly. The LIV should be extended at least to LTV+1 to avoid adding-on phenomenon.

Distal Adding-On Phenomenon in Lenke 1A Scoliosis

Retrospective study. To identify risk factors for the presence of distal adding-on in Lenke 1A scoliosis and compare different treatment strategies. Distal adding-on is often accompanied by unsatisfactory clinical outcome and high risk of reoperation. However, very few studies have focused on distal adding-on and its attendant risk factors and optimal treatment strategies remain controversial. All surgically treated patients with adolescent idiopathic scoliosis were retrieved from a single institutional database. Inclusion criteria included: (1) Lenke 1A scoliosis patients treated with posterior pedicle screw-only constructs, (2) minimum 1-year radiographic follow-up. Distal adding-on was defined as a progressive increase in the number of vertebrae included distally within the primary curve combined with either an increase of more than 5 mm in deviation of the first vertebra below instrumentation from the center sacral vertical line (CSVL), or an increase of more than 5° in the angulation of the first disc below the instrumentation at 1 year follow-up. Wilcoxon rank sum test, Fisher exact test, and Spearman correlation test were used to identify the risk factors for adding-on. A multiple logistic regression model was built to identify independent predictive factor(s). Risk factors included: (1) age at surgery; (2) preoperative Cobb angle; (3) correction rate; (4) the gap difference of stable vertebra-lowest instrumented vertebra (SV-LIV), neutral vertebra-lowest instrumented vertebra (NV-LIV), and end vertebra-lowest instrumented vertebra (EV-LIV). Gap difference means, for example, if SV is at L2 and LIV is at Th12, then the difference of SV-LIV is 2; (5) the preoperative deviation of LIV+1 (the first vertebra below the instrumentation) from the CSVL (the vertical line that bisects proximal sacrum). Five methods for determining LIV were compared in both the adding-on group and no adding-on group. Out of the 278 patients reviewed, 45 met the inclusion criteria; 23 of these met the definition for distal adding-on, and were included in the adding-on group. The remaining 22 patients were included in the no adding-on group. The average follow-up was 3.6 years. Age, SV-LIV difference, EV-LIV difference, and LIV+1 deviation from CSVL were significantly different (P<0.05) between the two groups, and were also found to be significantly correlated with the presence of adding-on (P<0.05). Preoperative Cobb angle, correction rate, and NV-LIV difference were not found to be affiliated with the presence of adding-on. Multiple logistic regression results indicated that preoperative LIV+1 deviation from CSVL was an independent predictive factor. Among the five methods, choosing EV as LIV was nearly unable to prevent distal adding-on; choosing EV+1 as LIV resulted in fusing many more segments than necessary; only choosing DV as LIV showed satisfactory outcome from both perspectives. In Lenke 1A type scoliosis, the selection of LIV is highly correlated with the presence of adding-on; incidence increases dramatically when the preoperative LIV+1 deviation from CSVL is more than 10 mm. Choosing DV (the first vertebra in cephalad direction from sacrum with deviation from CSVL of more than 10 mm) as LIV may provide the best outcome as it not only prevents adding-on but also conserves more lumbar motion.