Abstract
Hypothesis
Fusing shorter than the last touched vertebra (LTV) is a safe approach in flexible main thoracic (MT) adolescent idiopathic scoliosis (AIS) curves.
Methods
This was a prospective study on consecutive AIS patients surgically treated with selective fusion of the MT curve. Fusion-level selection was based on the fulcrum-bending radiograph method. Patients were grouped based on the position of the lowest instrumented vertebra as proximal to the LTV (proxLTV, n = 43), at the LTV (atLTV, n = 45), and distal to the LTV (distLTV, n = 21).
Results
A total of 109 patients were included in the study. Preoperatively, the distLTV group had greater lumbar Cobb angle, lumbar apical translation, and less flexibility in the MT curve. At 2-year follow-up, the groups did not differ in MT curve correction, but the distLTV had larger lumbar Cobb angle, more apical translation, and worse coronal balance. Distal adding-on was observed in 11 patients (26%) in the proxLTV group, four patients (9%) in the atLTV group, and one patient (5%) in the distLTV group (p = 0.031). Adding-on was associated with younger patients and lower Risser grade at the time of surgery but not with any other radiographic parameter. No differences in SRS-22r scores were observed between the groups.
Conclusions
Proximal fusion carries the risk of adding-on, but leaving unfused segments in the lower spine increases the potential for compensatory mechanisms to improve spinal and truncal balance. In mature patients with a flexible MT curve, surgeons may consider fusion at or cranial to the LTV.
Similar content being viewed by others
References
Fischer CR, Kim Y (2011) Selective fusion for adolescent idiopathic scoliosis: a review of current operative strategy. Eur Spine J 20:1048–1057
Rose PS, Lenke LG (2007) Classification of operative adolescent idiopathic scoliosis: treatment guidelines. Orthop Clin North Am 38:521–529
Lee MC, Õunpuu S, Solomito M et al (2013) Loss in spinal motion from inclusion of a single midlumbar level in posterior spinal fusion for adolescent idiopathic scoliosis. Spine (Phila Pa 1976) 38:1405–1410
Marks M, Newton PO, Petcharaporn M et al (2012) Postoperative segmental motion of the unfused spine distal to the fusion in 100 patients with adolescent idiopathic scoliosis. Spine (Phila Pa 1976) 37:826–832
Sanchez-Raya J, Bago J (2012) The effect of the lower instrumented vertebra (LIV) on pain and quality of life in patients surgically treated for an idiopathic scoliosis. Scoliosis 7:437–442
Larson AN, Polly DW, Ackerman SJ et al (2016) What would be the annual cost savings if fewer screws were used in adolescent idiopathic scoliosis treatment in the US? J Neurosurg Spine 24:116–123
Erickson MA, Baulesh DM (2011) Lowest instrumented vertebra selection in AIS. J Pediatr Orthop 31:S69–S76
Lenke L, Newton P, Lehman R et al (2017) Radiographic Results of Selecting the Touched Vertebra as the Lowest Instrumented Vertebra in Lenke Type 1 (Main Thoracic) & Type 2 (Double Thoracic) Curves at a Minimum 5-year Follow-up. Glob Spine J 7:2S–189S
Cao K, Watanabe K, Kawakami N et al (2014) Selection of lower instrumented vertebra in treating Lenke type 2A adolescent idiopathic scoliosis. Spine (Phila Pa 1976) 39:E253–E261
Lee CS, Hwang CJ, Lee DH, Cho JH (2016) Five major controversial issues about fusion level selection in corrective surgery for adolescent idiopathic scoliosis: a narrative review. Spine J 17:1033–1044
Cheung KMC, Natarajan D, Samartzis D et al (2010) Predictability of the fulcrum bending radiograph in scoliosis correction with alternate-level pedicle screw fixation. J Bone Jt Surg Am 92:169–176
Luk KDK, Don AS, Chong CS et al (2008) Selection of fusion levels in adolescent idiopathic scoliosis using fulcrum bending prediction: a prospective study. Spine (Phila Pa 1976) 33:2192–2198
Samartzis D, Leung Y, Shigematsu H et al (2015) Selection of fusion levels using the fulcrum bending radiograph for the management of adolescent idiopathic scoliosis patients with alternate level pedicle screw strategy: Clinical decision-making and outcomes. PLoS ONE 10:e0120302
Nissen SO, Kamath VHD, Samartzis D et al (2018) Fulcrum flexibility of the main curve predicts postoperative shoulder imbalance in selective thoracic fusion of adolescent idiopathic scoliosis. Eur Spine J 27:2251–2261
Shigematsu H, Cheung JPY, Bruzzone M et al (2017) Preventing fusion mass shift avoids postoperative distal curve adding-on in adolescent idiopathic scoliosis. Clin Orthop Relat Res 475:1448–1460
Cao K, Watanabe K, Hosogane N et al (2014) Association of postoperative shoulder balance with adding-on in Lenke Type II adolescent idiopathic scoliosis. Spine (Phila Pa 1976) 39:705–712
Landis JR, Koch GG (1977) The measurement of observer agreement for categorical data. Biometrics 33:159–174
Aubin C-E, Labelle H, Ciolofan OC (2007) Variability of spinal instrumentation configurations in adolescent idiopathic scoliosis. Eur Spine J 16:57–64
Robitaille M, Aubin CE, Labelle H (2007) Intra and interobserver variability of preoperative planning for surgical instrumentation in adolescent idiopathic scoliosis. Eur Spine J 16:1604–1614
Newton PO, Faro FD, Lenke LG et al (2003) Factors involved in the decision to perform a selective versus nonselective fusion of Lenke 1B and 1C (King-Moe II) curves in adolescent idiopathic scoliosis. Spine (Phila Pa 1976) 28:S217–S223
DeFrancesco CJ, Pasha S, Miller DJ et al (2018) Agreement between manual and computerized designation of neutral vertebra in idiopathic scoliosis. Spine Deform 6:644–650
Shigematsu H, Cheung JPY, Bruzzone M et al (2017) Preventing fusion mass shift avoids postoperative distal curve adding-on in adolescent idiopathic scoliosis. Clin Orthop Relat Res 1–13(475):1448–1460
Cho RH, Yaszay B, Bartley CE et al (2012) Which Lenke 1A curves are at the greatest risk for adding-on.. and why? Spine (Phila Pa 1976) 37:1384–1390
Funding
No relevant funding to report.
Author information
Authors and Affiliations
Corresponding authors
Ethics declarations
Conflict of interest
The authors have no financial or competing interests related to this work.
Ethical approval
This study was approved by the Institutional Review Board at The University of Hong Kong.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Ohrt-Nissen, S., Luk, K.D.K., Samartzis, D. et al. Selection of the lowest instrumented vertebra in main thoracic adolescent idiopathic scoliosis: Is it safe to fuse shorter than the last touched vertebra?. Eur Spine J 29, 2018–2024 (2020). https://doi.org/10.1007/s00586-020-06398-4
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00586-020-06398-4