The T4-L1-Hip Axis: Sagittal Spinal Realignment Targets in Long-Construct Adult Spinal Deformity Surgery: Early Impact.

dc.contributor.author

Hills, Jeffrey

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Mundis, Gregory M

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Klineberg, Eric O

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Smith, Justin S

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Line, Breton

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Gum, Jeffrey L

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Protopsaltis, Themistocles S

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Hamilton, D Kojo

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Soroceanu, Alex

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Eastlack, Robert

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Nunley, Pierce

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Kebaish, Khaled M

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Lenke, Lawrence G

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Hostin, Richard A

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Gupta, Munish C

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Kim, Han Jo

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Ames, Christopher P

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Burton, Douglas C

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Shaffrey, Christopher I

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Schwab, Frank J

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Lafage, Virginie

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Lafage, Renaud

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Bess, Shay

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Kelly, Michael P

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on behalf of the International Spine Study Group

dc.date.accessioned

2024-10-30T14:00:02Z

dc.date.available

2024-10-30T14:00:02Z

dc.date.issued

2024-09

dc.description.abstract

Background

Our understanding of the relationship between sagittal alignment and mechanical complications is evolving. In normal spines, the L1-pelvic angle (L1PA) accounts for the magnitude and distribution of lordosis and is strongly associated with pelvic incidence (PI), and the T4-pelvic angle (T4PA) is within 4° of the L1PA. We aimed to examine the clinical implications of realignment to a normal L1PA and T4-L1PA mismatch.

Methods

A prospective multicenter adult spinal deformity registry was queried for patients who underwent fixation from the T1-T5 region to the sacrum and had 2-year radiographic follow-up. Normal sagittal alignment was defined as previously described for normal spines: L1PA = PI × 0.5 - 21°, and T4-L1PA mismatch = 0°. Mechanical failure was defined as severe proximal junctional kyphosis (PJK), displaced rod fracture, or reoperation for junctional failure, pseudarthrosis, or rod fracture within 2 years. Multivariable nonlinear logistic regression was used to define target ranges for L1PA and T4-L1PA mismatch that minimized the risk of mechanical failure. The relationship between changes in T4PA and changes in global sagittal alignment according to the C2-pelvic angle (C2PA) was determined using linear regression. Lastly, multivariable regression was used to assess associations between initial postoperative C2PA and patient-reported outcomes at 1 year, adjusting for preoperative scores and age.

Results

The median age of the 247 included patients was 64 years (interquartile range, 57 to 69 years), and 202 (82%) were female. Deviation from a normal L1PA or T4-L1PA mismatch in either direction was associated with a significantly higher risk of mechanical failure, independent of age. Risk was minimized with an L1PA of PI × 0.5 - (19° ± 2°) and T4-L1PA mismatch between -3° and +1°. Changes in T4PA and in C2PA at the time of final follow-up were strongly associated (r2 = 0.96). Higher postoperative C2PA was independently associated with more disability, more pain, and worse self-image at 1 year.

Conclusions

We defined sagittal alignment targets using L1PA (relative to PI) and the T4-L1PA mismatch, which are both directly modifiable during surgery. In patients undergoing long fusion to the sacrum, realignment based on these targets may lead to fewer mechanical failures.

Level of evidence

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.
dc.identifier

00004623-990000000-01201

dc.identifier.issn

0021-9355

dc.identifier.issn

1535-1386

dc.identifier.uri

https://hdl.handle.net/10161/31600

dc.language

eng

dc.publisher

Ovid Technologies (Wolters Kluwer Health)

dc.relation.ispartof

The Journal of bone and joint surgery. American volume

dc.relation.isversionof

10.2106/jbjs.23.00372

dc.rights.uri

https://creativecommons.org/licenses/by-nc/4.0

dc.subject

International Spine Study Group

dc.title

The T4-L1-Hip Axis: Sagittal Spinal Realignment Targets in Long-Construct Adult Spinal Deformity Surgery: Early Impact.

dc.type

Journal article

duke.contributor.orcid

Shaffrey, Christopher I|0000-0001-9760-8386

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Duke

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School of Medicine

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Clinical Science Departments

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Orthopaedic Surgery

pubs.organisational-group

Neurosurgery

pubs.publication-status

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