Defining the learning curve in CT-guided navigated thoracoscopic vertebral body tethering



Estimated blood loss (EBL), anesthesia time, operative time, and length of stay decreased over 67 navigated vertebral body tethering (VBT) surgeries performed in a 5-year period, indicating a steep learning curve.


Retrospective review of prospectively collected data.


There would be a significant improvement in the performance of VBT procedures over time at a single tertiary center in terms of perioperative and postoperative outcomes.


Learning a new procedure for surgeons takes time, and previous studies have described improved efficiency as experience grows. VBT procedures are increasingly being performed in the US, but there is limited data regarding the learning curve specifically regarding the use of CT-guided navigation. We sought to assess the learning curve of VBT with respect to estimated blood loss, anesthesia time, operative time, length of stay, percent correction of the major curve at first follow-up. We further sought to characterize change in rates of 90-day complications.


Pediatric scoliosis patients who underwent thoracic or lumbar CT-guided navigated VBT with a consistent surgical team at a single tertiary referral center between 2015 and 2020 were included. Student t-test was used to assess change in perioperative parameters over time, and also results between first and latest group of 20 patients were compared.


67 patients met inclusion criteria. Estimated blood loss (EBL), operative time, anesthesia time and length of stay significantly decreased over the 5-year study period. Specifically, on comparison of our first 20 patients with our last 20, the former had greater EBL (282 vs 116 ml, p = 0.0005; 8.5% vs 3.6%, p = 0.0024), operative time (4.8 h vs. 3.3 h, p < 0.001), anesthesia time (7.4 h vs. 5.7 h, p = 0.0001), and length of stay (3.7 days vs. 3.2 days, p = 0.019). We also found significant reduction in EBL, operative time, anesthesia time and LOS in patients who underwent VBT surgery after 2019.

There was no significant change in the percent correction of the major Cobb angle at first erect imaging or 90-day complications over the 5-year study period or between the various cohorts.


This series has demonstrated improvements in surgical efficiency for VBT including reduced EBL, operative time, anesthesia time and hospital stay over a 5-year period. This indicates improved surgical technique and outlines the significant learning curve for surgeons who wish to perform this procedure. Improved surgeon training programs and newer instrumentation may reduce this learning curve.

Take home point

67 cases in a 5-year period, VBT procedures performed at a single center had significantly decreased EBL, anesthesia time, operative time, and length of stay, indicating a steep learning curve.

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Funding for this study was obtained from Orthopedic Research and Education Foundation, Pediatric Orthopedic Society of North America, and Mayo CCaTS-CBD Pilot Award for Team Science.

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Substantial contributions to the conception or design of the work, or the acquisition, analysis, or interpretation of data: SM, TAM, DDP, ANL; Drafting the work or critically revising it for important intellectual content: SM, TAM, DDP, ANL; Final Approval of the version to be published: SM, TAM, DDP, ANL; Responsible for content and accuracy of the entire manuscript: SM, TAM, DDP, ANL; The order and inclusion should be decided by consensus among the authors and acknowledged in writing: SM, TAM, DDP, ANL.

Corresponding author

Correspondence to A. Noelle Larson.

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Conflict of interest

Outside of the study, Dr. Milbrandt reports consulting activities with Orthopediatrics, Medtronic, Zimmer and stock ownership in Viking Scientific. Dr. Larson reports consulting activities with Orthopediatrics, Medtronic, Zimmer, and Globus. Dr. Potter reports consulting activities with Medtronic.

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Mathew, S., Larson, A.N., Potter, D.D. et al. Defining the learning curve in CT-guided navigated thoracoscopic vertebral body tethering. Spine Deform (2021).

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  • Vertebral body tethering
  • Scoliosis
  • Learning curve