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

A Novel Method for Predicting Ideal Postoperative Upper Instrumented Vertebra Tilt to Prevent Lateral Shoulder Imbalance after Scoliosis Correction Surgery

Lateral shoulder imbalance (LSI) is reflected radiologically by the clavicle angle (CA). How to achieve postoperative lateral shoulder balance (LSB) after scoliosis correction surgery remains unclear. In the current study, by using the preoperative upper instrumented vertebra (UIV) tilt, the CA, the flexibility between T1 and the UIV, and the ideal postoperative UIV tilt was predicted based on the following formula: ideal postoperative UIV tilt = preoperative UIV tilt—the flexibility between T1 and UIV—preoperative CA. The reliability of the formula was verified through a retrospective analysis, and 76 scoliosis patients were enrolled. The feasibility of this method was verified through a prospective analysis, and 13 scoliosis patients were enrolled. In the retrospective study, there was a significant correlation between the difference in the actual and ideal postoperative UIV tilt values and the postoperative CA, with correlation coefficients in the whole, LSI, and LSB groups of 0.981, 0.982, and 0.953, respectively (p < 0.001). In the prospective study, all patients achieved satisfactory LSB. Using the formula preoperatively to predict an ideal postoperative UIV tilt and controlling the intraoperative UIV tilt with the improved crossbar technique may be an effective digital method for achieving postoperative LSB and has important clinical significance.

Postoperative shoulder balance in Lenke type 1 adolescent idiopathic scoliosis patients with large thoracic curve (Cobb angle ≥ 70 degrees): a radiographic study

Background

Large amounts of thoracic curve correction had been considered as a risk factor for postoperative shoulder imbalance (PSI) in adolescent idiopathic scoliosis (AIS) patients. This study aims to evaluate postoperative shoulder balance in Lenke type 1 AIS patients with large thoracic curve (Cobb angle ≥ 70 degrees) and compared it with those with moderate thoracic curve (Cobb angle < 70 degrees).

Methods

A total of 47 Lenke type 1 AIS patients underwent posterior correction surgery between Sept. 2016 to Nov. 2018 in our institution were included. All these patient were divided into 2 groups based on the severity of main thoracic (MT) curve. Group A consisted of 25 cases with MT curve equal to or more than 70 degree while Group B consisted of 22 cases with MT curve less than 70 degree. Proximal thoracic (PT) Cobb angle, MT Cobb angle, MT apical vertebral translation (AVT), T2-T5 kyphosis, T5-T12 kyphosis, and radiographic shoulder height (RSH) were compared between these 2 groups preoperatively, immediately after surgery, and at a minimum of two-year follow-up.

Results

Although all the correction of PT Cobb angle (15.8° ± 6.0° vs 12.5° ± 3.6°, P = 0.028), that of MT Cobb angle 47.3° ± 9.1° vs 30.9° ± 6.7°, P < 0.001) and that of MT AVT (35.1 mm ± 16.0 mm vs 24.1 mm ± 8.9 mm, P = 0.007) were significantly larger in Group A when compared with Group B, RSH was comparable between these 2 groups at last follow up (7.5 mm ± 7.4 mm vs 9.2 mm ± 4.2 mm P = 0.363). Most of the patients gained satisfactory shoulder balance with only 7 cases with minimal PSI in group A (28%) and only 6 cases with minimal PSI in group B (27.3%) at last follow-up (P > 0.05).

Conclusions

Although Lenke type 1 AIS patients with large thoracic curve had more amounts of MT curve correction when compared with those with moderate thoracic curve, it did not lead to higher incidence of PSI if the correction rate is proper.

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.

What is the impact of scoliotic correction on postoperative shoulder imbalance in severe and rigid scoliosis

Background

Although recent studies have investigated the risk factors for PSI, few studies have focused on the impact of scoliotic correction on postoperative shoulder imbalance (PSI), especially in severe and rigid scoliosis (SRS). The purpose of the study was to study the effect of scoliotic correction on PSI in SRS.

Methods

The preoperative, postoperative, and minimum 2-year follow-up radiographs of 48 consecutive patients with SRS who underwent posterior spinal fusion surgery were evaluated. We regarded radiographic shoulder height (RSH) as a shoulder balance parameter and divided the patients into improved and aggravated groups of PSI from pre- to post-operation and from post-operation to last follow-up, respectively. In addition, patients were divided into nine groups based on the observed changes in PSI after surgery and at follow-up, and the correction rate ratios were calculated among the groups. Independent samples T test and Chi-squared test were performed between the improved and aggravated groups of PSI.

Results

After surgery, the proximal thoracic curve (PTC) flexibility (P = 0.040), correction rate of the main thoracic curve (MTC) (P = 0.010), and Cobb angle of the lumbar curve (LC) (P = 0.037) were significantly higher, while the ratio of the correction rate of the PTC to the MTC (P = 0.042) was smaller in the aggravated group. At follow-up, the improved group had significantly larger PTC flexibility (P = 0.006), larger ratio of the correction rate of PTC to MTC (P = 0.046), a larger ratio correction rate of PTC to LC (P = 0.027), and a smaller correction rate of LC (P = 0.030). The correction rate ratios of the groups after surgery were as follows: negative to negative (N-N) (1.08) > negative to balance (N-B) (0.96) > negative to positive (N-P) (0.67), B-N (1.26) > B-B (0.94) > B-P (0.89), and P-N (0.34) > P-P (0.83). The order of the correction rate ratio at follow-up was as follows: N-N (0.96) > N-B (0.51), B-B (0.97) > B-P (0.90), and P-B (0.87) > P-P (0.84).

Conclusion

Harmonizing the correction rate ratio of the PTC, MTC, and LC should be recommended for intraoperative correction and postoperative compensation of PSI. In addition, greater PTC flexibility plays an important role in the spontaneous correction and compensation of PSI in SRS.