In Search of the Ever-Elusive Postoperative Shoulder Balance: Is the T2 UIV the Key?

Anterior vertebral body tethering shows clinically comparable shoulder balance outcomes to posterior spinal fusion

PURPOSE

Posterior spinal fusion (PSF) is the current gold standard in surgical treatment for adolescent idiopathic scoliosis. Vertebral body tethering (VBT) is a fusionless alternative. Shoulder balance is an important metric for outcomes and patient satisfaction. Here we compare shoulder balance outcomes between PSF and VBT.

METHODS

In this retrospective review, the pre-operative and post-operative absolute radiographic shoulder height (|RSH|) of 45 PSF patients were compared to 46 VBT patients. Mean values were compared and then collapsed into discrete groups (|RSH| GROUP) and compared. Patients were propensity score matched. Regression models based on pretest-posttest designs were used to compare procedure type on post-operative outcomes.

RESULTS

Pre-operatively there were no differences in |RSH| between PSF and VBT, however, at latest post-operative follow-up PSF maintained a larger |RSH| imbalance compared to VBT (0.91 cm vs 0.63 cm, p = 0.021). In an ANCOVA regression, PSF was associated with a larger |RSH| imbalance compared to VBT, F(1, 88) = 5.76, p = 0.019. An ordinal logistic regression found that the odds ratio of being in a worse |RSH| GROUP for PSF vs VBT is 2.788 (95% CI = 1.099 to 7.075), a statistically significant effect χ2(1) = 4.658, p = 0.031. Results were similar in subgroup analyses of Lenke 1 and Lenke 2 patients, though to less statistical significance.

CONCLUSION

While PSF was found to be associated with worse |RSH| outcomes, the actual numbers (2-3 mm) are unlikely to be clinically meaningful. Thus, in this analysis, VBT can be said to show comparable shoulder balance outcomes to PSF.

Correlation analysis and clinical significance of changes in upper thoracic vertebra tilt and clavicle angle pre- and post-operation

The imbalance of the lateral shoulder is reflected by the clavicle angle (CA) in radiology. It remains unclear how to achieve postoperative lateral shoulder balance (LSB) after spinal deformity correction surgery. A retrospective analysis was conducted on AIS patients who underwent surgery by the same spine surgeon at our hospital from 2016 to 2020. A total of 110 patients with spinal deformity were included in the study to verify the correlation between the T1-T5 tilt angle and CA before and after surgery, as well as the relation-ship between the change in T1-T5 tilt angle before and after surgery and the change in CA before and after surgery. By comparing the correlation coefficients, it was found that there may not be a direct relationship between the pre- and postoperative tilt angles of T1-5 and CA, but their changes were closely related to the changes in CA. The change in T1 tilt angle after orthopaedic surgery was significantly correlated with the change in CA, with a correlation coefficient of 0.976, indicating a close relationship between T1 and the clavicle. As the vertebrae moved down, the correlation gradually decreased. In summary, this study suggests that there is a close relationship between T1-T5 and the clavicle and that the change in T1 tilt angle after spinal scoliosis correction surgery is significantly correlated with CA, which decreases as the vertebra moves down.

Selection of Fusion Levels in Adolescent Idiopathic Scoliosis

PURPOSE OF REVIEW: Posterior spinal fusion (PSF) is the preferred treatment for adolescent idiopathic scoliosis (AIS) patients with surgical range curves. Selection of the proper upper and lower instrumented vertebrae (UIV and LIV) is essential in curve correction and achieving a successful outcome, while preventing short and long-term complications. RECENT FINDINGS: The literature lacks high-level evidence, especially on outcomes of modern surgical techniques. However, evidence seems to show that a great majority of AIS patients have excellent clinical and functional long-term outcomes after PSF. We have reviewed the evidence and provided our level selection recommendations, which should be weighed against the body of evidence on the topic when selecting fusion levels in AIS.

Patients' Perception and Satisfaction on Neck and Shoulder Imbalance in Adolescent Idiopathic Scoliosis

STUDY DESIGN

Cross-sectional.

OBJECTIVES

To evaluate the perception and satisfaction among adolescent idiopathic scoliosis (AIS) patients on Neck Tilt with Medial Shoulder Imbalance and Lateral Shoulder Imbalance.

METHODS

Lenke 1 and 2 AIS patients were stratified into 6 groups of preoperative/ postoperative Balanced (B), Lateral Shoulder Imbalance (LSI) (>2 cm), and Neck Tilt with Medial Shoulder Imbalance (NT) (Grade 3). Patients were interviewed using Modified Neck and Shoulder Appearance and SRS-22r questionnaires. T1 tilt, Cervical Axis (CA), Clavicle Angle (Cla-A) and Radiographic Shoulder Height (RSH) were measured.

RESULTS

A total of 120 Lenke 1 and 2 AIS patients were recruited. NT patients were aware and unhappy with their abnormal neck with medial shoulder appearances (P < .001). Similarly, LSI patients were aware and unhappy with their abnormal lateral shoulder appearances (P < .001). NT group had larger preoperative/ postoperative T1 tilt (9.2 ± 5.0°; 9.5 ± 5.3°) and CA (4.6 ± 3.1°; 7.0 ± 2.0°) (P < .01). LSI group had larger preoperative/ postoperative Cla-A (4.8 ± 2.8°; 4.0 ± 1.3°) and RSH (20.1 ± 9.4 mm; 17.0 ± 6.6 mm) (P < .001). Postoperative B group scored higher in overall SRS-22r scores, self-image and satisfaction domains (4.2 ± 0.3; 4.0 ± 0.5; 4.4 ± 0.5) while preoperative LSI scored the lowest comparatively (3.5 ± 0.4; 2.4 ± 0.5; 3.3 ± 0.5) (P < .001).

CONCLUSION

NT and LSI were major concerns among AIS patients. Both NT and LSI groups were unhappy with their appearances. NT group had larger T1 tilt/ CA whereas LSI group had larger Cla-A/ RSH. Postoperative B group scored higher in overall SRS-22r scores, self-image and satisfaction domains.

Updated Criteria for Fusion Level Selection in Adolescent Idiopathic Scoliosis Including Use of Three-Dimensional Analysis

The development of new technologies and an enhanced understanding of the three-dimensional deformity in adolescent idiopathic scoliosis has led to advances in surgical management of adolescent idiopathic scoliosis. Posterior spinal approaches with pedicle screw constructs are now standard of care because they allow for powerful rotation maneuvers with three-column deformity correction. Selective fusion of the main curve while allowing for spontaneous correction of compensatory curves should be attempted whenever possible in the interest of limiting fusion size and preserving spinal mobility. Recent research provides updated criteria to determine optimal candidates for selective fusion. These criteria must be weighed against patient goals and patient-specific factors to limit complications and maximize chances of successful deformity correction.

Surgical Level Selection in Adolescent Idiopathic Scoliosis: An Evidence-Based Approach

The selection of fusion levels in the treatment of adolescent idiopathic scoliosis remains complex. The goals of surgery are to minimize the risk of future progression and optimize spinal balance while fusing the least number of levels necessary. Several classifications, rules, and algorithms exist to guide decision making, although these have previously not been easily referenced in a study. This review aims to provide an evidence-based approach of selecting fusion levels that balances the expert opinion of the authors with the current literature.

Usefulness of modified S-line for upper instrumented vertebra selection in adolescent idiopathic scoliosis Lenke type 2 curves

No validated systems exist for selecting the upper instrumented vertebra (UIV) for optimal postoperative shoulder balance in Lenke type 2 adolescent idiopathic scoliosis (AIS). This study evaluated a new method for shoulder balance prediction using the modified Shinshu line (MSL) for UIV selection in AIS Lenke type 2 curves. Fifty-five consecutive AIS patients receiving posterior spinal fusion (PSF) for a Lenke type 2 AIS curve were retrospectively analyzed according to several UIV determination models. Shoulder imbalance was judged as absolute radiographic shoulder height ≥ 10 mm at the 2-year observational endpoint. The MSL was the line between the center of the spinous process of C7 and that of the lowest instrumented vertebra. The vertebral body first touched proximally by the MSL was defined as the MSL vertebra (MSLV) and recommended as the UIV. The group with the UIV matching the MSLV had a significantly lower prevalence of shoulder imbalance of 23% (odds ratio 4.08, 95% CI 1.22-13.7, P = 0.02). Setting the MSLV as the UIV in PSF for AIS Lenke type 2 may reduce the prevalence of postoperative shoulder imbalance.

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.

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.

Risk Factors of Postoperative Shoulder Imbalance in Adolescent Idiopathic Scoliosis: The Role of Sagittal Spinopelvic Parameters and Upper Instrumented Vertebrae Selection

STUDY DESIGN

This is a retrospective study.

OBJECTIVE

To determine (1) the independent risk factors of postoperative shoulder imbalance (PSI) after adolescent idiopathic scoliosis (AIS) correction surgery; and (2) whether the level of upper instrumented vertebrae (UIV) affects postoperative shoulder balance.

SUMMARY OF BACKGROUND DATA

PSI is an important outcome of AIS correction surgery as it influences a patient's appearance and satisfaction. However, risk factors for PSI remain controversial and there are currently no studies evaluating the effect of sagittal spinopelvic parameters on PSI. Previous studies on the relationship between the level of UIV and PSI have also reported conflicting results.

MATERIALS AND METHODS

Sixty-nine AIS patients undergoing correction surgery at a single institution were retrospectively reviewed. Radiographic parameters were measured on anteroposterior and lateral x-rays preoperatively, immediate postoperatively, and 12 months postoperatively. At 1 year follow-up, patients were divided into 2 groups based on their radiographic shoulder height (RSH): (1) PSI group (RSH ≥20 mm) and (2) non-PSI group (RSH <20 mm).

RESULTS

On multivariate regression analysis, a lower postoperative main thoracic curve (MTC) [odds ratio (OR): 0.702, 95% confidence interval (CI): 0.519-0.949, P=0.022], greater percentage correction of MTC (OR: 1.526, 95% CI: 1.049-2.220, P=0.027) and higher postoperative sacral slope (OR: 1.364, 95% CI: 1.014-1.834, P=0.040) were identified as independent risk factors of PSI. When preoperative, postoperative, and absolute change in shoulder parameters were compared across the level of UIV, no significant differences were found regardless of the radiographic shoulder parameter analyzed.

CONCLUSIONS

Lower postoperative MTC, greater percentage correction of MTC and higher postoperative sacral slope were independent risk factors of PSI. Shoulder balance and symmetry were not affected by the level of UIV selected. Relative curve correction is a more important consideration than UIV to avoid PSI after AIS correction surgery.

LEVEL OF EVIDENCE

III.

Machine Learning Predicts the 3D Outcomes of Adolescent Idiopathic Scoliosis Surgery Using Patient-Surgeon Specific Parameters

STUDY DESIGN

Retrospective descriptive, multicenter study.

OBJECTIVE

The aim of this study was to predict the three-dimensional (3D) radiographic outcomes of the spinal surgery in a cohort of adolescent idiopathic scoliosis (AIS) as a function preoperative spinal parameters and surgeon modifiable factors.

SUMMARY OF BACKGROUND DATA

Current guidelines for posterior spinal fusion surgery (PSF) in AIS patients are based on two-dimensional classification of the spinal curves. Despite the high success rate, the prediction of the 3D spinal alignment at the follow-ups remains inconclusive. A data-driven surgical decision-making method that determines the combination of the surgical procedures and preoperative patient specific parameters that leads to a specific 3D global spinal alignment outcomes at the follow-ups can lessen the burden of surgical planning and improve patient satisfaction by setting expectations prior to surgery.

METHODS

A dataset of 371 AIS patients who underwent a PSF with two-year follow-up were included. Demographics, 2D radiographic spinal and pelvic measurements, clinical measurements of the trunk shape, and the surgical procedures were collected prospectively. A previously developed classification of the preoperative global 3D spinal alignment was used as an additional predictor. The 3D spinal alignment (vertebral positions and rotations) at two-year follow-up was used as the predicted outcome. An ensemble learner was used to predict the 3D spinal alignment at two-year follow-up as a function of the preoperative parameters with and without considering the surgeon modifiable factors.

RESULTS

The preoperative and surgical factors predicted three clusters of 3D surgical outcomes with an accuracy of 75%. The prediction accuracy decreased to 64% when only preoperative factors, without the surgical factors, were used in the model. Predictor importance analysis determined that preoperative distal junctional kyphosis, pelvic sagittal parameters, end-instrumented vertebra (EIV) angulation and translation, and the preoperative 3D clusters are the most important patient-specific predictors of the outcomes. Three surgical factors, upper and lower instrumented vertebrae, and the operating surgeon, were important surgical predictors. The role of surgeon in achieving a certain outcome clusters for specific ranges of preoperative T10-L2 kyphosis, EIV angulation and translation, thoracic and lumbar flexibilities, and patient's height was significant.

CONCLUSION

Both preoperative patient-specific and surgeon modifiable parameters predicted the 3D global spinal alignment at two-year post PSF. Surgeon was determined as a predictor of the outcomes despite including 20 factors in the analysis that described the surgical moves. Methods to quantify the differences between the implemented surgeon modifiable factors are essential to improve outcome prediction in AIS spinal surgery.Level of Evidence: 3.

What happens to the unfused upper thoracic curve after posterior spinal fusion for adolescent idiopathic scoliosis?

OBJECTIVE

Spontaneous lumbar curve correction after selective thoracic fusion in surgery for adolescent idiopathic scoliosis (AIS) is well described. However, only a few articles have described the course of the uninstrumented upper thoracic (UT) curve after fusion, and the majority involve a hybrid construct. In this study, the authors sought to determine the outcomes and associated factors of uninstrumented UT curves in patients with AIS.

METHODS

The authors retrospectively reviewed a prospectively collected multicenter AIS registry for all consecutive patients with Lenke type 1-4 curves with a 2-year minimum follow-up. UT curves were considered uninstrumented if the upper instrumented vertebra (UIV) did not extend above 1 level from the lower end vertebra of the UT curve. The authors defined progression as > 5°, and divided patients into two cohorts: those with improvement in the UT curve (IMP) and those without improvement in the UT curve (NO IMP). Radiographic, demographic, and Scoliosis Research Society (SRS)-22 survey outcome measures were compared using univariate analysis, and significant factors were compared using a multivariate regression model.

RESULTS

The study included 450 patients (370 females and 80 males). The UT curve self-corrected in 86% of patients (n = 385), there was no change in 14% (n = 65), and no patients worsened. Preoperatively, patients were similar with respect to Lenke classification (p = 0.44), age (p = 0.31), sex (p = 0.85), and Risser score (p = 0.14). The UT curves in the IMP group self-corrected from 24.7° ± 6.5° to 12.6° ± 5.9°, whereas in the NO IMP group UT curves remained the same, from 20.3° ± 5.8° to 18.5° ± 5.7°. In a multivariate analysis, preoperative main thoracic (MT) curve size (p = 0.004) and MT curve correction (p = 0.001) remained significant predictors of UT curve improvement. Greater correction of the MT curve and larger initial MT curve size were associated with greater likelihood of UT curve improvement.

CONCLUSIONS

Spontaneous UT curve correction occurred in the majority (86%) of unfused UT curves after MT curve correction in Lenke 1-4 curve types. The magnitude of preoperative MT curve size and postoperative MT curve correction were independent predictors of spontaneous UT curve correction.

Sinister! The high pre-op left shoulder is less likely to be radiographically balanced at 2 years post-op

PURPOSE

AIS patients consider shoulder balance an important cosmetic outcome after surgery. We examined the impact of preoperative left shoulder elevation (LSE) and choice of upper instrumented vertebra (UIV) on postoperative shoulder imbalance (PostSI).

METHODS

This was a retrospective cohort study utilizing a prospective AIS database. Patients had Lenke type 1-4 curves and preoperative shoulder height ≥ 1.0 cm. Patients with preoperative LSE and right shoulder elevation (RSE) were compared. Shoulder height difference < 1 cm was considered 'mild', 1-2 cm was 'moderate', and ≥ 2.0 cm was 'severe'.

RESULTS

407 patients had ≥ 1.0 cm imbalance preoperatively, with 88 (21.6%) LSE. There were no differences in gender (p = 0.855) or age (p = 0.477). Patients with LSE more frequently had Lenke type 2 curves (43.2% vs 16.3%, p < 0.001), while preoperative RSE averaged 1.9 ± 0.9 cm versus 1.6 ± 0.5 cm for LSE (p < 0.001). Those with LSE more often had severe PostSI at 2 years (30.7% vs 5.0%, p < 0.001), and only 26.1% of patients with severe preoperative LSE corrected to mild. In contrast, most patients with RSE had mild PostSI regardless of initial imbalance. When examining only LSE patients, there was no difference in preoperative SH by final UIV (p = 0.101). Further, UIV choice did not impact the proportion of severely unbalanced patients postoperatively (p = 0.446). A PTC > 34.5° was predictive of PostSI ≥ 2.0 cm for patients with preoperative LSE.

CONCLUSION

AIS patients with preoperative LSE are less likely to achieve level shoulders postoperatively. Choice of higher UIV did not affect postoperative shoulder imbalance in this cohort. A PTC > 34.5° was predictive of severe PostSI in patients with preoperative LSE.

LEVEL OF EVIDENCE

II.

The amount of surgical correction of the main thoracic curve is the best predictor of postoperative clinical shoulder balance in patients with Adolescent Idiopathic Scoliosis

PURPOSE

This study sought to analyze factors that predict postoperative shoulder balance based on clinical photography.

METHODS

Based on inclusion criteria, 132 AIS patients were selected. Age, sex, and BMI of each patient were recorded. The following parameters were recorded from radiographs: clavicle angle, T1 tilt, the upper instrumented vertebra (UIV), lowest instrumented vertebra (LIV) thoracic kyphosis, lumbar modifier, preoperative and postoperative proximal thoracic Cobb angle, preoperative and postoperative main thoracic Cobb angle, and preoperative and postoperative thoracolumbar Cobb angle, if applicable. Two spine surgeons independently assigned the photographs shoulder balance grades based on the WRVAS (1-2 = Acceptable, 3-5 = Unacceptable). Surgeons were blinded as to whether the photographs were taken preoperatively or postoperatively. The shoulders were also graded as right high, left high, or balanced.

RESULTS

Of all variables analyzed, only main thoracic Cobb angle correction (MTCAC) showed a statistically significant relationship with postoperative shoulder balance (p = 0.01). Odds of having unacceptable shoulder balance increase by 21% for every 5° increase in MTCAC (Adjusted OR = 1.21, 95% CI 1.015-1.452). The odds of unbalanced shoulders are 4.7 times higher for patients whose MTCAC is 40° or more (p = 0.001). Inter-rater reliability was excellent (k =0 .7). Intra rater reliability was perfect for Surgeon 1 (kappa = 1.0) and showed substantial agreement for Surgeon 2 (kappa = 0.8) CONCLUSIONS: Greater correction of main thoracic Cobb angle predicts unacceptable postoperative shoulder balance with 40° of correction signifying a major dichotomy between acceptable and unacceptable.

A Positive (+ve) Postoperative Upper Instrumented Vertebra Tilt Angle (≥0°) Significantly Increases the Risk of Medial Shoulder and Neck Imbalance in Lenke 1 and 2 Adolescent Idiopathic Scoliosis Patients

STUDY DESIGN

Retrospective study.

OBJECTIVE

To investigate the relationship between a +ve postoperative Upper Instrumented Vertebra (UIV) (≥0°) tilt angle and the risk of medial shoulder/neck and lateral shoulder imbalance among Lenke 1 and 2 Adolescent Idiopathic Scoliosis (AIS) patients following Posterior Spinal Fusion.

SUMMARY OF BACKGROUND DATA

Current UIV selection strategy has poor correlation with postoperative shoulder balance. The relationship between a +ve postoperative UIV tilt angle and the risk of postoperative shoulder and neck imbalance was unknown.

METHODS

One hundred thirty-six Lenke 1 and 2 AIS patients with minimum 2 years follow-up were recruited. For medial shoulder and neck balance, patients were categorized into positive (+ve) imbalance (≥+4°), balanced, or negative (-ve) imbalance (≤-4°) groups based on T1 tilt angle/Cervical Axis measurement. For lateral shoulder balance, patients were classified into +ve imbalance (≥+3°) balanced, and -ve imbalance (≤-3°) groups based on Clavicle Angle (Cla-A) measurement. Linear regression analysis identified the predictive factors for shoulder/neck imbalance. Logistic regression analysis calculated the odds ratio of shoulder/neck imbalance for patients with +ve postoperative UIV tilt angle.

RESULTS

Postoperative UIV tilt angle and preoperative T1 tilt angle were predictive of +ve medial shoulder imbalance. Postoperative UIV tilt angle and postoperative PT correction were predictive of +ve neck imbalance. Approximately 51.6% of patients with +ve medial shoulder imbalance had +ve postoperative UIV tilt angle. Patients with +ve postoperative UIV tilt angle had 14.9 times increased odds of developing +ve medial shoulder imbalance and 3.3 times increased odds of developing +ve neck imbalance. Postoperative UIV tilt angle did not predict lateral shoulder imbalance.

CONCLUSION

Patients with +ve postoperative UIV tilt angle had 14.9 times increased odds of developing +ve medial shoulder imbalance (T1 tilt angle ≥+4°) and 3.3 times increased odds of developing +ve neck imbalance (cervical axis ≥+4°).

LEVEL OF EVIDENCE

4.