In addition to the gross truncal imbalance caused by scoliosis, the significant local body imbalance is also the primary reason for the patient to seek treatment. The treatment of scoliosis has improved considerably over the past several years due to advancements in spinal instrumentation and surgical procedures. And the main concern about treatment is still how to achieve the gross truncal balance currently, however, the local body imbalances such as shoulder imbalance also need to be drawn attention for spine surgeon. Moreover, even if the surgeon achieves the excellent gross body balance in terms of radiological assessment, shoulder imbalance can still remain. Asymmetrical shoulder is more likely to be found in cosmetic appearance than the razor back when patient is dressed, which can significantly worsen the overall patient satisfaction. We believed the spinal deformity correction surgery should not only focus on simple spinal fusion, but should also seek to reconstruct the aesthetic appearance of scoliosis patient. In our experience, there are 3 aesthetic appearance balances should be achieved after correction surgery: shoulder balance, back balance and pelvis balance. The concept of three aesthetic appearance balances proposed by our department means that there would be no visible elevated shoulder, razor back and tilt pelvis after deformity surgery, achieving the best aesthetic appearance of scoliosis patients. Therefore, it is of great significance for patients with imbalanced shoulders after spinal deformity surgery to achieve the shoulder balance. However, there is limited research focusing on the residual shoulder imbalance worldwide right now. The correction of elevated shoulders is still mainly concentrated in patients with congenital Sprengel’s deformity. The cosmetic malformation and impairment of shoulder abduction are the 2 main problems in Sprengel’s deformity patients which caused by hypoplastic scapula. Currently, conservative treatment has been proven to be ineffective for this deformity . Therefore, several surgical procedures have been developed to address these problems, including the Woodward procedure and Green surgical procedures, which are the two classic surgical technique for the treatment of Sprengel’s deformity [10,11]. The disadvantages of Green's surgical procedure include the large trauma, the brachial plexus injury caused by excessive stretching during the operation and the limited range of the shoulder motion which might result from the detachment of the muscles. Although the clinical efficacy of Woodward is better than that of Green's procedure, there are still some disadvantages such as requirement of extra external fixation postoperatively and correction loss over time [12-14]. Therefore, it is necessary to seek a new procedure with less trauma, simple operation, reliable correction effect, and without impairment of the shoulder motion function, in order to solve the residual shoulder imbalance after correction surgery.
In the scapuloplasty procedure proposed by our department, the elevated scapula is mobilized distally to approximately the same level of the contralateral scapular spine and fixed on the same side of the titanium rod with normal tendon suture. The advantages of this surgery include short operation time, less bleeding, no need of special equipment, and limit impairment of the muscles around the scapula. We sutured the inferior medial angle of muscle sheath of the scapula, which is mainly composed of the subscapular muscle and infraspinatus muscle, to the titanium rod so as to firmly maintain the new position of the scapula. Subscapular muscle underlying the scapula is innervated by the subscapular nerves, mainly contributes to the adduction, internal rotation and posterior extension of the shoulder joint. Infraspinatus muscle which occupies the chief part of the infraspinous fossa is innervated by the suprascapular nerve mainly acts on the abduction and external rotation of the shoulder joint. However, the adduction, internal rotation, extension, and external rotation of the shoulder joint are also affected by the teres major and teres minor. Therefore, fixing the muscle sheath of partial subscapular muscle and infraspinatus muscle distally to the titanium rod has little effect on the motion function of the shoulder joint. Falla and Kibler et al. [14, 15] reported that the trapezius, rhomboids, and levator scapulae play a major role in the scapular motility and maintain its stability. Our procedure also did not impair the trapezius, rhomboids, or levator scapulae. Therefore, there is no negative effect on the flexion, extension, adduction and abduction of the scapula. Our results also showed there is no significant deterioration in the range of shoulder motion in terms of flexion, extension, abduction, and adduction over 2 years follow-up.
There is still controversy about the criteria of shoulder balance. The shoulder height difference greater than 1cm is mostly defined as shoulder imbalance, while the shoulder height difference >2 cm is thought to be obviously unbalanced [5, 16, 17]. Akel et al. found that the shoulder height difference≤1.5 cm could exist in normal adolescents . In addition, some researchers proposed that the asymmetrical shoulder heights could be noticed visually when the height difference is greater than 0.5 cm. Therefore, they believed that the shoulder height difference should be within 0.5 cm for the ideal shoulder balance. In the present study, we demonstrated that the scapuloplasty used in our department can significantly decrease the SVD and improve the cosmetic appearance of all patients. The SVD was controlled within 1cm postoperatively and at the last follow-up. Moreover, 66.7% (14/21) of the patients had an SVD of less than 0.5 cm at the last follow-up, achieving the best aesthetic cosmetic appearance.
The concept of proximal thoracic curve was first proposed by Ponseti et al in 1950. Yet, the indications of proximal thoracic curve fusion and the selection of the upper instrumented vertebra are still controversial while correction of the main curvature. Currently, it is believed that the shoulder imbalance is closely related to proximal thoracic curve, and the selection of the upper fusion vertebra in this region has a direct impact on the shoulder balance and cosmetic appearance of the patients underwent deformity corrective surgery. Suk et al  reported that idiopathic thoracic scoliosis with a proximal thoracic curve of more than 25° and a level or elevated left shoulder should be treated with fusion of upper thoracic curve, otherwise it may lead to postoperative shoulder imbalances. However, some studies have shown that even though the surgeon can achieve the successful correction of the proximal thoracic curvature, shoulder imbalance can still remain regardless of the amount of the Cobb angle correction, which can significantly worsen the outcome of the surgery . Qiu et al.  also pointed out that there was a high risk of postoperative shoulder imbalance when the patient with elevated left shoulder, low flexibility of upper thoracic curve, and large Cobb angle of main curvature before surgery. According to our study, scapuloplasty surgery can finally achieve shoulder balance in patients who still have shoulder imbalance after the fusion of the upper thoracic curve, which would improve the cosmetic appearance and patient satisfaction.
The most serious complication of scapuloplasty is the brachial plexus injury resulting from inferior displacement of the scapula. Some researchers found that children who are 8 years of age and older is more likely to suffer brachial plexus injury due to the very limited anatomy elasticity. However, all 21 patients (＞8 years old)in our study had no brachial plexus injury, which mainly due to the fact that we gradually mobilized the scapula distally with a gentle force and used intraoperative somatosensory evoked potential monitoring during the traction process .