Background: Shoulder imbalance (SI) is among the most rated manifestations of adolescent idiopathic scoliosis (AIS) pointed to by patients and spine surgeons. It serves as a criterion to assess the outcome of scoliosis surgery and is also a cause of dissatisfaction for the patients postoperatively. Despite the availability of multiple studies on this issue, a comprehensive survey of the risk factors and preventive measures has yet to be elucidated. The present study aimed to highlight the most recent approach to the evaluation and management of SI, as well as medical counseling about the expectations and limitations of the surgery. Methods: A systematic literature review using electric databases was conducted, including PubMed, Embase, the Cochrane Library, and Google Scholar, with a well-defined search strategy on SI definition, risk factors, and preventive and surgical recommendations. Results: A total of 69 articles were identified; SI > 2 cm was the most used cut-off, and its risk factors included the main thoracic Cobb angle > 80˚, preoperative level shoulder, high left shoulder, and higher Risser grade. The most stated strategies to preclude SI were the sufficient correction of the proximal thoracic curve, and moderate correction of the main thoracic and lumbar curve (LC). Conclusion: Shoulder imbalance should be prevented not only for appearance or satisfaction but also for possible complications such as distal adding-on, new LC progression, or trunk shift postoperatively in AIS patients. Level of evidence: V
Suk SI, Kim WJ, Lee CS, et al. Indications of proximal thoracic curve fusion in thoracic adolescent idiopathic scoliosis: recognition and treatment of double thoracic curve pattern in adolescent idiopathic scoliosis treated with segmental instrumentation. Spine (Phila Pa 1976). 2000;25(18):2342-2349. doi:10.1097/00007632-200009150-00012
Matamalas A, Bagó J, D’Agata E, Pellisé F. Does patient perception of shoulder balance correlate with clinical balance? Eur Spine J. 2016;25(11):3560-3567. doi:10.1007/s00586-015-3971-5
Lee SY, Ch’ng PY, Wong TS, et al. Patients’ Perception and Satisfaction on Neck and Shoulder Imbalance in Adolescent Idiopathic Scoliosis .Global Spine J. 2021; 21925682211007795. doi:10.1177/21925682211007795
Maurice B, Jean-Marie G, Jean-Michel T. Taking the shoulders and pelvis into account in the preoperative classification of idiopathic scoliosis in adolescents and young adults (a constructive critique of King’s and Lenke’s systems of classification). Eur Spine J. 2011;20(10):1780-1787. doi:10.1007/s00586-011-1899-y
Chang DG, Kim JH, Kim SS, Lim DJ, Ha KY, Suk SI. How to improve shoulder balance in the surgical correction of double thoracic adolescent idiopathic scoliosis. Spine (Phila Pa 1976). 2014;39(23):E1359-E1367. doi:10.1097/BRS.0000000000000578
Zhang S, Zhang L, Feng X, Yang H. Incidence and risk factors for postoperative shoulder imbalance in scoliosis: a systematic review and meta-analysis. Eur Spine J. 2018;27(2):358-369. doi:10.1007/s00586-017-5289-y
Yaszay B, Bastrom TP, Newton PO; Harms Study Group. Should Shoulder Balance Determine Proximal Fusion Levels in Patients With Lenke 5 Curves? Spine Deform. 2013;1(6):447-451. doi:10.1016/j.jspd.2013.08.003
Luhmann SJ, Sucato DJ, Johnston CE, Richards BS, Karol LA. Radiographic Assessment of Shoulder Position in 619 Idiopathic Scoliosis Patients: Can T1 Tilt Be Used as an Intraoperative Proxy to Determine Postoperative Shoulder Balance?. J Pediatr Orthop. 2016;36(7):691-694. doi:10.1097/BPO.0000000000000519
Amir D, Yaszay B, Bartley CE, Bastrom TP, Newton PO. Does Leveling the Upper Thoracic Spine Have Any Impact on Postoperative Clinical Shoulder Balance in Lenke 1 and 2 Patients?. Spine (Phila Pa 1976). 2016;41(14):1122-1127. doi:10.1097/BRS.0000000000001497
Matsumoto M, Watanabe K, Hosogane N, et al. Postoperative distal adding-on and related factors in Lenke type 1A curve. Spine (Phila Pa 1976). 2013;38(9):737-744. doi:10.1097/BRS.0b013e318279b666
Jiang J, Zhu ZZ, Qiu Y, Wang B, Yu Y. Postoperative Lumbar Curve Progression Deteriorates Shoulder Imbalance in Patients with Lenke Type 2B/C Adolescent Idiopathic Scoliosis Who Underwent Selective Thoracic Fusion. World Neurosurg. 2019; 125:e175-e182. doi:10.1016/j.wneu.2019.01.032
Wang Y, Bünger CE, Wu C, Zhang Y, Hansen ES. Postoperative trunk shift in Lenke 1C scoliosis: what causes it? How can it be prevented? Spine (Phila Pa 1976). 2012;37(19):1676-1682. doi:10.1097/BRS.0b013e318255a053
Kuklo TR, Lenke LG, Graham EJ, et al. Correlation of radiographic, clinical, and patient assessment of shoulder balance following fusion versus nonfusion of the proximal thoracic curve in adolescent idiopathic scoliosis. Spine (Phila Pa 1976). 2002;27(18):2013-2020. doi:10.1097/00007632-200209150-0000
Akel I, Pekmezci M, Hayran M, et al. Evaluation of shoulder balance in the normal adolescent population and its correlation with radiological parameters. Eur Spine J. 2008;17(3):348-354. doi:10.1007/s00586-007-0546-0
Clement RC, Anari J, Bartley CE, et al. What are normal radiographic spine and shoulder balance parameters among adolescent patients? Spine Deform. 2020;8(4):621-627. doi:10.1007/s43390-020-00074-9
Ohrt-Nissen S, Kamath VHD, Samartzis D, Luk KDK, Cheung JPY. Fulcrum flexibility of the main curve predicts postoperative shoulder imbalance in selective thoracic fusion of adolescent idiopathic scoliosis. Eur Spine J. 2018;27(9):2251-2261. doi:10.1007/s00586-018-5669-y
Hadgaonkar S, Shah S, Bhilare P, et al. Clinical and radiological factors associated with postoperative shoulder imbalance and correlation with patient-reported outcomes following scoliosis surgery. J Orthop. 2020;21:465-472. doi:10.1016/j.jor.2020. 08.036
Okada E, Suzuki T, Demura S, et al. Excessive correction impacts postoperative shoulder imbalance in lenke type 5C adolescent idiopathic scoliosis. J Orthop Sci. 2020;25(5):757-762. doi:10.1016/j.jos.2019.10.001
Miyanji F, Fields MW, Murphy J, et al. Shoulder balance in patients with Lenke type 1 and 2 idiopathic scoliosis appears satisfactory at 2 years following anterior vertebral body tethering of the spine. Spine Deform. 2021;9(6):1591-1599. doi:10.1007/s43390-021-00374-8
Yagi M, Takemitsu M, Machida M. Clavicle chest cage angle difference (CCAD): a novel predictor of postoperative shoulder imbalance in patients with adolescent idiopathic scoliosis. Spine (Phila Pa 1976). 2013;38(12):E705-E712. doi:10.1097/BRS.0b013e31828f0bcd
Cao K, Watanabe K, Hosogane N, et al. Association of postoperative shoulder balance with adding-on in Lenke Type II adolescent idiopathic scoliosis. Spine (Phila Pa 1976). 2014;39(12):E705-E712. doi:10.1097/BRS.0000000000000325
Imrie M, Yaszay B, Bastrom TP, Wenger DR, Newton PO. Adolescent idiopathic scoliosis: should 100% correction be the goal? J Pediatr Orthop. 2011;31(1 Suppl):S9-S13. doi:10.1097/BPO.0b013e3181fd8a24
Lee CS, Hwang CJ, Lim EJ, Lee DH, Cho JH. A retrospective study to reveal factors associated with postoperative shoulder imbalance in patients with adolescent idiopathic scoliosis with double thoracic curve. J Neurosurg Pediatr. 2016;25(6):744-752. doi:10.3171/2016.6.PEDS16162
Isogai N, Yagi M, Otomo N, et al. Upper End Vertebra of Proximal Thoracic Curve At T1 is a Novel Risk Factor of Postoperative Shoulder Imbalance in Lenke Type 2 Adolescent Idiopathic Scoliosis .Global Spine J. 2021;21925682211023049. doi: 10.1177/21925682211023049
Yang Y, Yang M, Zhao J, Zhao Y, Yang C, Li M. Postoperative shoulder imbalance in adolescent idiopathic scoliosis: risk factors and predictive index. Eur Spine J. 2019;28(6):1331-1341. doi:10.1007/s00586-019-05933-2
Brooks JT, Bastrom TP, Bartley CE, et al. In Search of the Ever-Elusive Postoperative Shoulder Balance: Is the T2 UIV the Key? Spine Deform. 2018;6(6):707-711. doi:10.1016/j.jspd.2018.03.010
Chung WH, Chiu CK, Ng SJ, Goh SH, Chan CYW, Kwan MK. How Common Is Medial and Lateral Shoulder Discordance in Lenke 1 and 2 Curves? A Preoperative Analysis of Medial and Lateral Shoulder Balance Among 151 Lenke 1 and 2 Adolescent Idiopathic Scoliosis Patients. Spine (Phila Pa 1976). 2019;44(8):E480-E486. doi:10.1097/BRS.0000000000002890
Yang H, Im GH, Hu B, et al. Shoulder balance in Lenke type 2 adolescent idiopathic scoliosis: Should we fuse to the second thoracic vertebra? Clin Neurol Neurosurg. 2017;163:156-162. doi:10.1016/j.clineuro.2017.10.036
Bjerke BT, Cheung ZB, Shifflett GD, Iyer S, Derman PB, Cunningham ME. Do Current Recommendations for Upper Instrumented Vertebra Predict Shoulder Imbalance? An Attempted Validation of Level Selection for Adolescent Idiopathic Scoliosis. HSS J. 2015;11(3):216-222. doi:10.1007/s11420-015-9451-y
Hong JY, Suh SW, Yang JH, Park SY, Han JH. Reliability analysis of shoulder balance measures: comparison of the 4 available methods. Spine (Phila Pa 1976). 2013;38(26):E1684-E1690. doi:10.1097/BRS.0b013e3182a18486
Qiu XS, Ma WW, Li WG, et al. Discrepancy between radiographic shoulder balance and cosmetic shoulder balance in adolescent idiopathic scoliosis patients with double thoracic curve. Eur Spine J. 2009;18(1):45-51. doi:10.1007/s00586-008-0833-4
Yang S, Feuchtbaum E, Werner BC, Cho W, Reddi V, Arlet V. Does anterior shoulder balance in adolescent idiopathic scoliosis correlate with posterior shoulder balance clinically and radiographically? Eur Spine J. 2012;21(10):1978-1983. doi:10.1007/s00586-012-2434-5
Gotfryd A, Avanzi O. Current methods for the evaluation of shoulder balance in idiopathic adolescent scoliosis: a literature review. JSM Neurosurg Spine. 2018;6:1096.
Gotfryd AO, Silber Caffaro MF, Meves R, Avanzi O. Predictors for Postoperative Shoulder Balance in Lenke 1 Adolescent Idiopathic Scoliosis: A Prospective Cohort Study. Spine Deform. 2017;5(1):66-71. doi:10.1016/j.jspd.2016.09.046
Menon KV, Tahasildar NS. What Constitutes Shoulder Imbalance in Adolescent Idiopathic Scoliosis? Aesthetic Threshold for Surgical Correction. World Neurosurg. 2020;138:e827-e838. doi:10.1016/j.wneu.2020.03.106
Ono T, Bastrom TP, Newton PO. Defining 2 components of shoulder imbalance: clavicle tilt and trapezial prominence. Spine (Phila Pa 1976). 2012;37(24):E1511-E1516. doi:10.1097/BRS.0b013e31826e2bbb
Bagó J, Carrera L, March B, Villanueva C. Four radiological measures to estimate shoulder balance in scoliosis. J Pediatr Orthop B. 1996;5(1):31-34. doi:10.1097/01202412-199605010-00006
Kwan MK, Wong KA, Lee CK, Chan CY. Is neck tilt and shoulder imbalance the same phenomenon? A prospective analysis of 89 adolescent idiopathic scoliosis patients (Lenke type 1 and 2). Eur Spine J. 2016;25(2):401-408. doi:10.1007/s00586-015-4016-9
Elfiky TA, Samartzis D, Cheung WY, Wong YW, Luk KD, Cheung KM. The proximal thoracic curve in adolescent idiopathic scoliosis: surgical strategy and management outcomes. Global Spine J. 2011;1(1):27-36. doi:10.1055/s-0031-1296054
Matsumoto M, Watanabe K, Kawakami N, et al. Postoperative shoulder imbalance in Lenke Type 1A adolescent idiopathic scoliosis and related factors. BMC Musculoskelet Disord. 2014;15:366. doi:10.1186/1471-2474-15-366
Sakai Y, Takenaka S, Makino T, Yoshikawa H, Kaito T. Postoperative T1 tilt is a risk factor for postoperative distal adding-on in Lenke type 1 adolescent idiopathic scoliosis: A preliminary report. Medicine (Baltimore). 2020;99(21):e19983. doi:10.1097/MD. 0000000000019983
Qiu Y, Qiu XS, Ma WW, et al. How well do radiological measurements correlate with cosmetic indices in adolescent idiopathic scoliosis with Lenke 5, 6 curve types? Spine (Phila Pa 1976). 2010;35(18):E882-E888. doi:10.1097/brs.0b013e3181d6fdd7
Chiu CK, Chan CYW, Tan PH, et al. Conformity and Changes in the Radiological Neck and Shoulder Balance Parameters Throughout 3-Year Follow-up Period: Do They Remain the Same? Spine (Phila Pa 1976). 2020;45(6):E319-E328. doi:10.1097/BRS.0000000000003275
Sharma S, Andersen T, Wu C, et al. How well do Radiologic Assessments of Truncal and Shoulder Balance Correlate With Cosmetic Assessment Indices in Lenke 1C Adolescent Idiopathic Scoliosis? Clin Spine Surg. 2016;29(8):341-351. doi:10.1097/BSD.0000000000000134
Chan CYW, Ch’ng PY, Lee SY, Chung WH, Chiu CK, Kwan MK. Preoperative “Cervical Axis” Deviation Increases the Risk of Distal Adding-On Following Surgery in Lenke 1 and 2 Adolescent Idiopathic Scoliosis Patients .Global Spine J. 2021;2192568221998642. doi:10.1177/2192568221998642
Yang Y, Yang M, Yang Z, et al. Postoperative neck tilt in Lenke 1 and 2 AIS patients after correction surgery: a novel predictive index. BMC Musculoskelet Disord. 2019;20(1):405.. doi:10.1186/s12891-019-2792-9
Arlet V, Marchesi D, Papin P, Aebi M. Decompensation following scoliosis surgery: treatment by decreasing the correction of the main thoracic curve or “letting the spine go”. Eur Spine J. 2000;9(2):156-160. doi:10.1007/s005860050227
Jiang J, Qian BP, Qiu Y, Wang B, Yu Y, Zhu ZZ. Full fusion of proximal thoracic curve helps to prevent postoperative cervical tilt in Lenke type 2 adolescent idiopathic scoliosis patients with right-elevated shoulder. BMC Musculoskelet Disord. 2017;18(1):362. doi:10.1186/s12891-017-1730-y
Terheyden JH, Wetterkamp M, Gosheger G, et al. Predictors of shoulder level after spinal fusion in adolescent idiopathic scoliosis. Eur Spine J. 2018;27(2):370-380. doi:10.1007/s00586-017-5210-8.
Hong JY, Suh SW, Modi HN, Yang JH, Park SY. Analysis of factors that affect shoulder balance after correction surgery in scoliosis: a global analysis of all the curvature types. Eur Spine J. 2013;22(6):1273-1285. doi:10.1007/s00586-013-2697-5
Ghandhari H, Sabbaghan S, Nikouei F, Rahbarian F, Tayebi H, Ameri E. Determinants of Pre-Operative Shoulder Imbalance in Patients with Adolescent Idiopathic Scoliosis. J. Res. Orthop. Sci. 2017;4 (1). doi: 10.17795/soj-9614
Bram JT, Mehta N, Flynn JM, et al. Sinister! The high pre-op left shoulder is less likely to be radiographically balanced at 2 years post-op. Spine Deform. 2021;9(2):451-460. doi:10.1007/s43390-020-00236-9
Kuklo TR, Lenke LG, Won DS, et al. Spontaneous proximal thoracic curve correction after isolated fusion of the main thoracic curve in adolescent idiopathic scoliosis. Spine (Phila Pa 1976). 2001;26(18):1966-1975. doi:10.1097/00007632-200109150-00006
Zang L, Fan N, Hai Y, et al. Evaluation of the predictors of postoperative aggravation of shoulder imbalance in severe and rigid thoracic or thoracolumbar scoliosis. Eur Spine J. 2016;25(10):3353-3365. doi:10.1007/s00586-015-4313-3
Lee CS, Hwang CJ, Lee DH, Cho JH. Does fusion to T2 compared with T3/T4 lead to improved shoulder balance in adolescent idiopathic scoliosis with a double thoracic curve? J Pediatr Orthop B. 2019;28(1):32-39. doi:10.1097/BPB.0000000000000520
Wei Chan CY, Chiu CK, Ng YH, et al. An analysis of preoperative shoulder and neck balance and surgical outcome in 111 adolescent idiopathic scoliosis patients with two subtypes of Lenke 1 curves. J Neurosurg Spine. 2020;34(1):37-44. doi:10.3171/2020.5.SPINE20397
Ilharreborde B, Even J, Lefevre Y, et al. How to determine the upper level of instrumentation in Lenke types 1 and 2 adolescent idiopathic scoliosis: a prospective study of 132 patients. J Pediatr Orthop. 2008;28(7):733-739. doi:10.1097/BPO.0b013e318185a36b
Menon KV, Tahasildar N, Pillay HM, Anbuselvam M, Jayachandran RK. Patterns of shoulder imbalance in adolescent idiopathic scoliosis: a retrospective observational study. J Spinal Disord Tech. 2014;27(7):401-408. doi:10.1097/BSD.0000000000000166
Sielatycki JA, Cerpa M, Beauchamp EC, et al. The Amount of Relative Curve Correction Is More Important Than Upper Instrumented Vertebra Selection for Ensuring Postoperative Shoulder Balance in Lenke Type 1 and Type 2 Adolescent Idiopathic Scoliosis. Spine (Phila Pa 1976). 2019;44(17):E1031-E1037. doi:10.1097/BRS.0000000000003088
Yagi M, Takemitsu M, Machida M. Chest cage angle difference and rotation of main thoracic curve are independent risk factors of postoperative shoulder imbalance in surgically treated patients with adolescent idiopathic scoliosis. Spine (Phila Pa 1976). 2013;38(19):E1209-E1215. doi:10.1097/BRS. 0b013e31829e0309
Akazawa T, Kuroya S, Kotani T, et al. Anchor type at upper instrumented vertebra and postoperative shoulder imbalance in patients with Lenke type 1 adolescent idiopathic scoliosis. Eur J Orthop Surg Traumatol. 2021;31(2):245-251. doi:10.1007/s00590-020-02766-4
Trobisch PD, Ducoffe AR, Lonner BS, Errico TJ. Choosing fusion levels in adolescent idiopathic scoliosis. J Am Acad Orthop Surg. 2013;21(9):519-528. doi:10.5435/JAAOS-21-09-519
Rose PS, Lenke LG. Classification of operative adolescent idiopathic scoliosis: treatment guidelines. Orthop Clin North Am. 2007;38(4):521-vi. doi: 10.1016/j.ocl.2007.06.001
Hiett A, Tung R, Emanuelli E, Sherman A, Anderson JT, Schwend RM. 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. Spine Deform. 2020;8(6):1279-1286. doi:10.1007/s43390-020-00147-9
Tang X, Luo X, Liu C, et al. The Spontaneous Development of Cosmetic Shoulder Balance and Shorter Segment Fusion in Adolescent Idiopathic Scoliosis With Lenke I Curve: A Consecutive Study Followed Up for 2 to 5 Years. Spine (Phila Pa 1976). 2016;41(12):1028-1035. doi:10.1097/BRS.0000000000001442
Jian YM, Yang SH, Hu MH. Assessment of Change of Shoulder Balance in Patients with Adolescent Idiopathic Scoliosis after Correctional Surgery. Orthop Surg. 2018;10(3):198-204. doi:10.1111/os.12399
Suk SI, Kim WJ, Lee CS, et al. Indications of proximal thoracic curve fusion in thoracic adolescent idiopathic scoliosis: recognition and treatment of double thoracic curve pattern in adolescent idiopathic scoliosis treated with segmental instrumentation. Spine (Phila Pa 1976). 2000;25(18):2342-2349. doi:10.1097/00007632-200009150-00012
Wang Y, Hansen ES, Høy K, Wu C, Bünger CE. Distal adding-on phenomenon in Lenke 1A scoliosis: risk factor identification and treatment strategy comparison. Spine (Phila Pa 1976). 2011;36(14):1113-1122. doi:10.1097/BRS.0b013e3181f51e95
Cho RH, Yaszay B, Bartley CE, Bastrom TP, Newton PO. Which Lenke 1A curves are at the greatest risk for adding-on... and why? Spine (Phila Pa 1976). 2012;37(16):1384-1390. doi:10.1097/BRS. 0b013e31824bac7a
Nikouei, F., Ghandhari, H., Ameri, E., & Mokarami, F. (2022). Shoulder Imbalance in Adolescent Idiopathic Scoliosis: A Systematic Review of the Current State of the Art. The Archives of Bone and Joint Surgery, 10(12), 992-1003. doi: 10.22038/abjs.2022.64282.3086
MLA
Farshad Nikouei; Hasan Ghandhari; Ebrahim Ameri; Farzam Mokarami. "Shoulder Imbalance in Adolescent Idiopathic Scoliosis: A Systematic Review of the Current State of the Art", The Archives of Bone and Joint Surgery, 10, 12, 2022, 992-1003. doi: 10.22038/abjs.2022.64282.3086
HARVARD
Nikouei, F., Ghandhari, H., Ameri, E., Mokarami, F. (2022). 'Shoulder Imbalance in Adolescent Idiopathic Scoliosis: A Systematic Review of the Current State of the Art', The Archives of Bone and Joint Surgery, 10(12), pp. 992-1003. doi: 10.22038/abjs.2022.64282.3086
VANCOUVER
Nikouei, F., Ghandhari, H., Ameri, E., Mokarami, F. Shoulder Imbalance in Adolescent Idiopathic Scoliosis: A Systematic Review of the Current State of the Art. The Archives of Bone and Joint Surgery, 2022; 10(12): 992-1003. doi: 10.22038/abjs.2022.64282.3086