# Optimizing Biomechanics of Surgical Correction for Lumbar Flatback Deformity

> **NIH VA I01** · EDWARD HINES JR VA HOSPITAL · 2020 · —

## Abstract

Purpose: The long-term goal of this research is to improve the outcomes of surgical correction for lumbar
flatback deformity, which is a complex disorder that can affect a large segment of the veteran population. In
flatback deformity the torso pitches forward and affects the patient’s ability to stand upright and walk due to
muscle fatigue and worsening back pain, leading to functional loss. The goal of surgery is to correct the sagittal
malalignment to reduce muscle fatigue and allow patients to stand upright and ambulate, thus improving
function. Surgeons who treat older veterans want to know: (1) how much lordosis restoration is sufficient to
reduce the burden on muscles to maintain an upright posture; and (2) can this be achieved using a less invasive
surgical technique to minimize complications and morbidity.
Hypothesis: Our central hypothesis is that restoring lumbar lordosis using lordotic interbody fusion cages
implanted in multiple disc spaces will minimize the forces needed to maintain an upright posture in specimens
with loss of lordosis across L4 to sacrum.
Specific aims: (1) We will use human cadaveric thoracolumbar (T10-sacrum) spine specimens with a range of
PI values (35°-70°; the average adult PI is 52°) to quantify the shear force and moment required at the cephalad
and caudal boundaries of the specimen to maintain an upright standing posture under the following conditions:
(1) hypolordosis across L4-S1, creating a PI-LL mismatch (degenerative or iatrogenic), and (2) improvement of
L1-S1 lordosis using lordotic interbody fusion cages placed at one or more segments of the lumbar spine, first
without and then with posterior column (facet) osteotomies (PCO).
(2) We will analyze the data collected in aim 1 to: (1) define a relationship between the extent of PI-LL mismatch
and forces needed to maintain an upright standing posture for the reconstructed spines, and (2) quantify the
influence of the following study variables on the ability of lordotic interbody cages to improve standing lumbar
lordosis: (a) number of reconstructed disc spaces, (b) specimen’s PI value and flexibility (that is, segmental
mobility in flexion and extension), (c) influence of PCO to yield additional correction.
Methods: The experimental design consists of two arms: degenerative, and iatrogenic. In the iatrogenic arm, a
hypolordotic fusion across L4-S1 will be created by applying distraction forces across pedicle screws inserted in
L4, L5 and S1 pedicles; whereas, in the degenerative arm we will select specimens in which there is sufficient loss
of disc heights at the L5-S1 and L4-L5 disc spaces. In the iatrogenic arm, surgical restoration of L1-S1 lordosis
will be performed by implanting lordotic interbody cages at L3-L4 and L2-L3 disc spaces cephalad to the
hypolordotic L4-S1 fusion; whereas, in the degenerative arm surgical restoration of segmental lordosis will be
performed at L5-S1 and L4-L5 disc spaces. In both arms of the study, we will aim to elimina...

## Key facts

- **NIH application ID:** 10067885
- **Project number:** 1I01RX003240-01A2
- **Recipient organization:** EDWARD HINES JR VA HOSPITAL
- **Principal Investigator:** Avinash G. Patwardhan
- **Activity code:** I01 (R01, R21, SBIR, etc.)
- **Funding institute:** VA
- **Fiscal year:** 2020
- **Award amount:** —
- **Award type:** 1
- **Project period:** 2020-07-01 → 2022-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10067885

## Citation

> US National Institutes of Health, RePORTER application 10067885, Optimizing Biomechanics of Surgical Correction for Lumbar Flatback Deformity (1I01RX003240-01A2). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10067885. Licensed CC0.

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