Saving Fusion Levels in Lenke 1/2 AR Curves: Can We Stop Short of the Last Substantially Touched Vertebra (LSTV)?

Harms Study Group

doi:10.1097/BRS.0000000000005602

Saving Fusion Levels in Lenke 1/2 AR Curves: Can We Stop Short of the Last Substantially Touched Vertebra (LSTV)?

Harms Study Group

Department of Surgery, Nemours Children's Hospital Delaware

Florida Atlantic University
Paley Orthopedic and Spine Institute at St. Mary’s Medical Center
Rady Children's Specialists of San Diego
Vanderbilt University Medical Center
Stanford Medicine Children's Health
Children's Healthcare of Atlanta
School of Medicine, University of Virginia
Shriners for Children Medical Center
Johns Hopkins University
Mount Sinai Hospital
British Columbia Children’s Hospital
Shriners Hospitals for Children

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Resumen

STUDY DESIGN: Retrospective cohort from a multicenter registry.

OBJECTIVE: Characterize the variability of the last substantially touched vertebra (LSTV) in Lenke 1- and 2-AR curves and evaluate whether clinical or radiographic factors permit fusion short of the LSTV without increased adding-on risk.

SUMMARY OF BACKGROUND DATA: Lenke 1 and 2A curves with an R modifier based on L4 tilt in adolescent idiopathic scoliosis (AIS) are associated with a higher risk of adding-on after posterior spinal fusion (PSF). Fusion to the LSTV may reduce this risk but often requires extending into the distal lumbar spine, compromising motion. The safety of terminating fusion proximal to the LSTV in select patients, without increasing adding-on risk, remains uncertain.

METHODS: Patients with Lenke 1- or 2-AR curves undergoing PSF with minimum 2-year follow-up were identified. Radiographs were reviewed to determine LSTV level and assess for adding-on. Patients were stratified based on whether the lowest instrumented vertebra (LIV) was proximal to or at the level of/distal to the LSTV. Among those fused proximal, univariate and multivariate analyses were used to identify protective factors. Subgroup analyses were performed by LSTV level.

RESULTS: Of 324 patients, 144 (44.4%) were instrumented proximal to the LSTV. Adding-on occurred in 16.0% of all patients, more frequently in short fusions (21.5% vs. 11.7%, P=0.016). Multivariate analysis identified higher Risser (OR=1.62, P=0.006) and greater main thoracic correction (OR=1.09, P<0.001) as protective. Adding-on was rare (4.0%) when the LSTV was L4, even when fused short.

CONCLUSIONS: In skeletally mature patients with adequate thoracic correction, fusion proximal to the LSTV in Lenke 1- and 2-AR curves may be performed safely. When the LSTV is L4, fusion to that level may be unnecessary, offering an opportunity for lumbar motion preservation without increased risk of adding-on.

LEVEL OF EVIDENCE: IV.

Idioma original	English
Publicación	Spine
DOI	https://doi.org/10.1097/BRS.0000000000005602
Estado	E-pub ahead of print - 15 dic 2025

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@article{59c45e84f0f7405a8505043513b1ecfa,

title = "Saving Fusion Levels in Lenke 1/2 AR Curves: Can We Stop Short of the Last Substantially Touched Vertebra (LSTV)?",

abstract = "STUDY DESIGN: Retrospective cohort from a multicenter registry.OBJECTIVE: Characterize the variability of the last substantially touched vertebra (LSTV) in Lenke 1- and 2-AR curves and evaluate whether clinical or radiographic factors permit fusion short of the LSTV without increased adding-on risk.SUMMARY OF BACKGROUND DATA: Lenke 1 and 2A curves with an R modifier based on L4 tilt in adolescent idiopathic scoliosis (AIS) are associated with a higher risk of adding-on after posterior spinal fusion (PSF). Fusion to the LSTV may reduce this risk but often requires extending into the distal lumbar spine, compromising motion. The safety of terminating fusion proximal to the LSTV in select patients, without increasing adding-on risk, remains uncertain.METHODS: Patients with Lenke 1- or 2-AR curves undergoing PSF with minimum 2-year follow-up were identified. Radiographs were reviewed to determine LSTV level and assess for adding-on. Patients were stratified based on whether the lowest instrumented vertebra (LIV) was proximal to or at the level of/distal to the LSTV. Among those fused proximal, univariate and multivariate analyses were used to identify protective factors. Subgroup analyses were performed by LSTV level.RESULTS: Of 324 patients, 144 (44.4\%) were instrumented proximal to the LSTV. Adding-on occurred in 16.0\% of all patients, more frequently in short fusions (21.5\% vs. 11.7\%, P=0.016). Multivariate analysis identified higher Risser (OR=1.62, P=0.006) and greater main thoracic correction (OR=1.09, P<0.001) as protective. Adding-on was rare (4.0\%) when the LSTV was L4, even when fused short.CONCLUSIONS: In skeletally mature patients with adequate thoracic correction, fusion proximal to the LSTV in Lenke 1- and 2-AR curves may be performed safely. When the LSTV is L4, fusion to that level may be unnecessary, offering an opportunity for lumbar motion preservation without increased risk of adding-on.LEVEL OF EVIDENCE: IV.",

author = "\{Harms Study Group\} and Brown, \{Michael W\} and Hariharan, \{Arun R\} and Tracey Bryan and Feldman, \{David S\} and Louer, \{Craig R\} and Vorhies, \{John S\} and Murphy, \{Joshua S\} and Keith Bachmann and Cho, \{Robert H\} and Gabos, \{Peter G\} and Amit Jain and Lonner, \{Baron S\} and Firoz Miyanji and Samdani, \{Amer F\} and Shah, \{Suken A\} and Kelly, \{Michael P\} and Newton, \{Peter O\}",

year = "2025",

month = dec,

day = "15",

doi = "10.1097/BRS.0000000000005602",

language = "English",

journal = "Spine",

issn = "0362-2436",

publisher = "Wolters Kluwer Health",

}

TY - JOUR

T1 - Saving Fusion Levels in Lenke 1/2 AR Curves

T2 - Can We Stop Short of the Last Substantially Touched Vertebra (LSTV)?

AU - Harms Study Group

AU - Brown, Michael W

AU - Hariharan, Arun R

AU - Bryan, Tracey

AU - Feldman, David S

AU - Louer, Craig R

AU - Vorhies, John S

AU - Murphy, Joshua S

AU - Bachmann, Keith

AU - Cho, Robert H

AU - Gabos, Peter G

AU - Jain, Amit

AU - Lonner, Baron S

AU - Miyanji, Firoz

AU - Samdani, Amer F

AU - Shah, Suken A

AU - Kelly, Michael P

AU - Newton, Peter O

PY - 2025/12/15

Y1 - 2025/12/15

N2 - STUDY DESIGN: Retrospective cohort from a multicenter registry.OBJECTIVE: Characterize the variability of the last substantially touched vertebra (LSTV) in Lenke 1- and 2-AR curves and evaluate whether clinical or radiographic factors permit fusion short of the LSTV without increased adding-on risk.SUMMARY OF BACKGROUND DATA: Lenke 1 and 2A curves with an R modifier based on L4 tilt in adolescent idiopathic scoliosis (AIS) are associated with a higher risk of adding-on after posterior spinal fusion (PSF). Fusion to the LSTV may reduce this risk but often requires extending into the distal lumbar spine, compromising motion. The safety of terminating fusion proximal to the LSTV in select patients, without increasing adding-on risk, remains uncertain.METHODS: Patients with Lenke 1- or 2-AR curves undergoing PSF with minimum 2-year follow-up were identified. Radiographs were reviewed to determine LSTV level and assess for adding-on. Patients were stratified based on whether the lowest instrumented vertebra (LIV) was proximal to or at the level of/distal to the LSTV. Among those fused proximal, univariate and multivariate analyses were used to identify protective factors. Subgroup analyses were performed by LSTV level.RESULTS: Of 324 patients, 144 (44.4%) were instrumented proximal to the LSTV. Adding-on occurred in 16.0% of all patients, more frequently in short fusions (21.5% vs. 11.7%, P=0.016). Multivariate analysis identified higher Risser (OR=1.62, P=0.006) and greater main thoracic correction (OR=1.09, P<0.001) as protective. Adding-on was rare (4.0%) when the LSTV was L4, even when fused short.CONCLUSIONS: In skeletally mature patients with adequate thoracic correction, fusion proximal to the LSTV in Lenke 1- and 2-AR curves may be performed safely. When the LSTV is L4, fusion to that level may be unnecessary, offering an opportunity for lumbar motion preservation without increased risk of adding-on.LEVEL OF EVIDENCE: IV.

AB - STUDY DESIGN: Retrospective cohort from a multicenter registry.OBJECTIVE: Characterize the variability of the last substantially touched vertebra (LSTV) in Lenke 1- and 2-AR curves and evaluate whether clinical or radiographic factors permit fusion short of the LSTV without increased adding-on risk.SUMMARY OF BACKGROUND DATA: Lenke 1 and 2A curves with an R modifier based on L4 tilt in adolescent idiopathic scoliosis (AIS) are associated with a higher risk of adding-on after posterior spinal fusion (PSF). Fusion to the LSTV may reduce this risk but often requires extending into the distal lumbar spine, compromising motion. The safety of terminating fusion proximal to the LSTV in select patients, without increasing adding-on risk, remains uncertain.METHODS: Patients with Lenke 1- or 2-AR curves undergoing PSF with minimum 2-year follow-up were identified. Radiographs were reviewed to determine LSTV level and assess for adding-on. Patients were stratified based on whether the lowest instrumented vertebra (LIV) was proximal to or at the level of/distal to the LSTV. Among those fused proximal, univariate and multivariate analyses were used to identify protective factors. Subgroup analyses were performed by LSTV level.RESULTS: Of 324 patients, 144 (44.4%) were instrumented proximal to the LSTV. Adding-on occurred in 16.0% of all patients, more frequently in short fusions (21.5% vs. 11.7%, P=0.016). Multivariate analysis identified higher Risser (OR=1.62, P=0.006) and greater main thoracic correction (OR=1.09, P<0.001) as protective. Adding-on was rare (4.0%) when the LSTV was L4, even when fused short.CONCLUSIONS: In skeletally mature patients with adequate thoracic correction, fusion proximal to the LSTV in Lenke 1- and 2-AR curves may be performed safely. When the LSTV is L4, fusion to that level may be unnecessary, offering an opportunity for lumbar motion preservation without increased risk of adding-on.LEVEL OF EVIDENCE: IV.

U2 - 10.1097/BRS.0000000000005602

DO - 10.1097/BRS.0000000000005602

M3 - Article

C2 - 41400008

SN - 0362-2436

JO - Spine

JF - Spine

ER -

Saving Fusion Levels in Lenke 1/2 AR Curves: Can We Stop Short of the Last Substantially Touched Vertebra (LSTV)?

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