Incidence and predictive factors of shoulder imbalance after selective anterior spinal fusion surgery in Lenke type 5C adolescent idiopathic scoliosis.

Background: No study has assessed the incidence or predictors of postoperative shoulder imbalance (PSI) in patients with Lenke type 5C adolescent idiopathic scoliosis (AIS) who underwent selective anterior spinal fusion (ASF). This study evaluated the incidence and predictors of shoulder imbalance after selective ASF for Lenke type 5C AIS. Methods: In total, 62 patients with Lenke type 5C AIS (4 men and 58 women, mean age at surgery of 15.5 ± 1.5 years) were included and divided into the following two groups according to the radiographic shoulder height (RSH) at the final follow-up: PSI and non-PSI groups. All patients in this study underwent a whole-spine radiological evaluation. Various spinal coronal and sagittal profiles on radiographs were compared between the 2 groups. The clinical outcomes were assessed using the Scoliosis Research Society (SRS)-22 questionnaires. Results: The mean final follow-up duration was 8.6 ± 2.7 years. PSI was observed in 10 patients (16.1%) immediately after surgery; however, in the long-term follow-up period, PSI improved in 3 patients spontaneously, whereas the remaining 7 patients had residual PSI. The preoperative RSH and correction rates of the major curve immediately after surgery or at the final follow-up were significantly larger in the PSI group than in the non-PSI group (p=.001, p=.023, and p=.019, respectively). Receiver operating characteristic curve analysis indicated that the cutoff values for preoperative RSH and the correction rates immediately after surgery and at the final follow-up were 11.79 mm (p=.002; area under the curve [AUC], 0.948), 71.0% (p=.026; AUC, 0.822), and 65.4% (p=.021; AUC, 0.835), respectively. No statistically significant difference was observed in the preoperative and final follow-up SRS-22 scores in any domain between the PSI and non-PSI groups. Conclusions: Paying attention to the preoperative RSH and avoiding excessive correction of the major curve can prevent the occurrence of shoulder imbalance after selective ASF for Lenke type 5C AIS.

Achieving Shoulder Balance Using Medial and Lateral Radiological Measures in Adolescent Idiopathic Scoliosis.

Background: Research has shown that postoperative shoulder imbalance is a common problem after spinal fusion in adolescent idiopathic scoliosis (AIS). The best radiographic predictor has not yet been determined and results are inconsistent. This study was to investigate whether using medial and lateral shoulder parameters can effectively achieve postoperative shoulder balance. Methods: A prospective database of AIS undergoing posterior spinal fusion were reviewed. Patient demographics and radiological parameters including radiographic shoulder height (RSH), clavicle angle, T1-tilt and first-rib angle at baseline, 6 weeks and last minimal follow up of 2 years were recorded. Correlations between radiological parameters were assessed using Pearson's correlation coefficients. Multivariable linear models identified predictors associated with increased RSH. Results: 219 patients (mean age:13.7 years; 81.7% female) were included. The mean follow-up time was 2.8 years (range:2.0-7.0). The mean RSH at baseline, 6 weeks and last follow up was improved significantly at 95.8%. Preoperative (r=0.8; p<0.001) and post-operative measurements of RSH at 6-week (r=0.9; p<0.001) and last follow up (r=0.9; p<0.001) correlated strongly with clavicle angle measured at respective time-points. In a multivariable linear model, we noted marginal increase in clavicle angle (+4.3°; p<0.001) to be associated with increased RSH. On the contrary, first rib angle and T1-tilt demonstrated moderate to weak correlation with RSH. Conclusion: Clavicle angle is strongly consistent with RSH. First rib angle and T1-tilt as demonstrate medial shoulder balance are moderate to weak correlation. Leveling T1 tilt and first rib angle do not guarantee the postoperative shoulder balance. Level of Evidence: IV.

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.

Increased proximal vertebral rotation is associated with shoulder imbalance after posterior spinal fusion for severe adolescent idiopathic scoliosis.

PURPOSE: Residual shoulder imbalance is associated with suboptimal outcomes following the surgical correction of adolescent idiopathic scoliosis (AIS) including poor patient satisfaction. In this retrospective study, we evaluate the radiographic parameters and the relationship between the global and local indices of spinal alignment with shoulder balance pre- and postoperatively utilizing EOS imaging and 3D reconstruction. METHODS: A retrospective radiographic analysis was performed on patients with AIS, treated with posterior spinal fusion. Postoperative radiographs were obtained immediately following surgery, at 6 months and final follow-up over 2 years postoperatively. 3D Radiographic measurements included in the coronal plane radiographic shoulder height difference (RSHD), proximal thoracic Cobb angle (PT) and main thoracic Cobb (MT), in the sagittal plane T4-T12 kyphosis, T12-L5 lordosis, in the axial plane proximal thoracic (PT AVR) and main thoracic apical vertebral rotation (MT AVR). RESULTS: Sixty-six patients were included (63 females) with an average main thoracic curvature of 76 degrees. RSHD averaged 14 mm ± 14 preoperatively, -15 mm ± 12 postoperatively, -8.5 mm ± 11 at 6 months, and -8.3 mm ± 8.7 at final follow-up, respectively. Statistical analysis revealed a significant correlation between RSHD and proximal thoracic Cobb angle, between RSHD and proximal thoracic apical vertebral rotation (PTAVR) (r > 0.20, p < 0.05). CONCLUSION: The significant correlation presented in this study suggests that PT Cobb angle and PT AVR are involved in postoperative shoulder imbalance. THE LEVEL OF EVIDENCE: Level 4.

Postoperative Lumbar Curve Progression Deteriorates Shoulder Imbalance in Patients with Lenke Type 2B/C Adolescent Idiopathic Scoliosis Who Underwent Selective Thoracic Fusion.

OBJECTIVE: To evaluate the association between postoperative lumbar curve progression and the shoulder height in patients with Lenke type 2B/C adolescent idiopathic scoliosis (AIS). METHODS: A total of 25 patients with Lenke type 2B/C AIS underwent posterior correction surgery in our institution from 2005-2014 were included. Standing x-ray films of the whole spine obtained before surgery, immediately after surgery, and at the last follow-up were analyzed with respect to the following parameters: proximal thoracic Cobb angle, main thoracic (MT) Cobb angle, lumbar Cobb angle, lumbar apical vertebral translation, distance between C7 plumb line and the central sacral vertical line, and radiographic shoulder height (RSH). Correlations between the change of RSH and the changes of other parameters were analyzed both immediately after surgery and at the last follow-up. RESULTS: The change of RSH was significantly negatively correlated with both the change of MT Cobb angle (P < 0.05) and that of lumbar Cobb angle (P < 0.05) immediately after surgery, whereas the interval-time change of RSH was significantly positively correlated with the interval-time change of lumbar Cobb angle (P < 0.05) and that of lumbar apical vertebral translation (P < 0.05) at the last follow-up. The change of MT Cobb angle was an independent predictor for the change of RSH immediately after surgery, whereas the interval-time change of lumbar Cobb angle was an independent predictor for the interval-time change of RSH at the last follow-up. CONCLUSIONS: Postoperative lumbar curve progression is a risk factor for deterioration of shoulder imbalance in patients with Lenke 2B/C AIS during the follow-up period.

Postoperative translation of the upper instrumented vertebra in thoracic adolescent idiopathic scoliosis.

OBJECTIVEThe aim of this retrospective study was to analyze the influence of upper instrumented vertebra (UIV) translation from the C7 plumb line (C7PL) on the long-term postoperative results of patients with main thoracic (MT) adolescent idiopathic scoliosis (AIS).METHODSTwenty-five patients had been treated surgically for AIS with a Lenke type 1 curve and had been followed up for a mean period of 18.2 years. Radiographic parameters, pulmonary function measurements, and clinical outcomes were compared between the patients (n = 15) with UIV translation < 20 mm and those (n = 10) with UIV translation ≥ 20 mm at the final follow-up. Correlations between UIV translation and radiographic or pulmonary function parameters were analyzed.RESULTSPatients with ≥ 20 mm UIV translation at the final follow-up had a significantly larger preoperative UIV translation than that in the patients with < 20 mm UIV translation at follow-up. The former group also had a significantly lower correction rate of the MT curve, higher chest cage ratio, and lower radiographic shoulder height (p = 0.01, 0.005, and 0.025, respectively) at the final follow-up. The Scoliosis Research Society (SRS)-30 Questionnaire scores were equivalent between the two groups. Correlation analysis showed that the following parameters were significantly associated with UIV translation: MT curve correction rate (r = -0.481, p = 0.015), chest cage ratio (r = 0.673, p < 0.001), and percent-predicted forced expiratory volume in 1 second (r = -0.455, p = 0.033).CONCLUSIONSThe UIV translation should be considered an important factor that influences postoperative results. In MT AIS patients whose preoperative upper end vertebra (UEV) is distant from the C7PL, the UIV should be selected above the UEV to prevent large UIV translation at the postoperative follow-up.

A retrospective study to reveal factors associated with postoperative shoulder imbalance in patients with adolescent idiopathic scoliosis with double thoracic curve.

OBJECTIVE Postoperative shoulder imbalance (PSI) is a critical consideration after corrective surgery for a double thoracic curve (Lenke Type 2); however, the radiographic factors related to PSI remain unclear. The purpose of this study was to identify the radiographic factors related to PSI after corrective surgery for adolescent idiopathic scoliosis (AIS) in patients with a double thoracic curve. METHODS This study included 80 patients with Lenke Type 2 AIS who underwent corrective surgery. Patients were grouped according to the presence [PSI(+)] or absence [PSI(-)] of shoulder imbalance at the final follow-up examination (differences of 20, 15, and 10 mm were used). Various radiographic parameters, including the Cobb angle of the proximal and middle thoracic curves (PTC and MTC), radiographic shoulder height (RSH), clavicle angle, T-1 tilt, trunk shift, and proximal and distal wedge angles (PWA and DWA), were assessed before and after surgery and compared between groups. RESULTS Overall, postoperative RSH decreased with time in the PSI(-) group but not in the PSI(+) group. Statistical analyses revealed that the preoperative Risser grade (p = 0.048), postoperative PWA (p = 0.028), and postoperative PTC/MTC ratio (p = 0.011) correlated with PSI. Presence of the adding-on phenomenon was also correlated with PSI, although this result was not statistically significant (p = 0.089). CONCLUSIONS Postoperative shoulder imbalance is common after corrective surgery for Lenke Type 2 AIS and correlates with a higher Risser grade, a larger postoperative PWA, and a higher postoperative PTC/MTC ratio. Presence of the distal adding-on phenomenon is associated with an increased PSI trend, although this result was not statistically significant. However, preoperative factors other than the Risser grade that affect the development of PSI were not identified by the study. Additional studies are required to reveal the risk factors for the development of PSI.

Do Current Recommendations for Upper Instrumented Vertebra Predict Shoulder Imbalance? An Attempted Validation of Level Selection for Adolescent Idiopathic Scoliosis.

BACKGROUND: Shoulder balance for adolescent idiopathic scoliosis (AIS) patients is associated with patient satisfaction and self-image. However, few validated systems exist for selecting the upper instrumented vertebra (UIV) post-surgical shoulder balance. QUESTIONS/PURPOSES: The purpose is to examine the existing UIV selection criteria and correlate with post-surgical shoulder balance in AIS patients. METHODS: Patients who underwent spinal fusion at age 10-18 years for AIS over a 6-year period were reviewed. All patients with a minimum of 1-year radiographic follow-up were included. Imbalance was determined to be radiographic shoulder height |RSH| ≥ 15 mm at latest follow-up. Three UIV selection methods were considered: Lenke, Ilharreborde, and Trobisch. A recommended UIV was determined using each method from pre-surgical radiographs. The recommended UIV for each method was compared to the actual UIV instrumented for all three methods; concordance between these levels was defined as "Correct" UIV selection, and discordance was defined as "Incorrect" selection. RESULTS: One hundred seventy-one patients were included with 2.3 ± 1.1 year follow-up. For all methods, "Correct" UIV selection resulted in more shoulder imbalance than "Incorrect" UIV selection. Overall shoulder imbalance incidence was improved from 31.0% (53/171) to 15.2% (26/171). New shoulder imbalance incidence for patients with previously level shoulders was 8.8%. CONCLUSIONS: We could not identify a set of UIV selection criteria that accurately predicted post-surgical shoulder balance. Further validated measures are needed in this area. The complexity of proximal thoracic curve correction is underscored in a case example, where shoulder imbalance occurred despite "Correct" UIV selection by all methods.