Flatback Deformity Surgery New York City | Dr. Zeeshan Sardar

Dr. Zeeshan Sardar, MD, MSc, F.R.C.S.C
Co-Chief of Spinal Deformity Surgery • Director, Quality & Patient Safety • Medical Director, Spine Unit
Och Spine Hospital at NewYork-Presbyterian / Columbia University • New York, NY

Flatback deformity is one of the most debilitating late complications of spinal surgery — and one of the most commonly unrecognized. Patients describe an exhausting, relentless need to bend their knees and lean forward just to stay upright. Many have lived this way for years, told that fatigue is normal, that aging is the cause, or that nothing more can be done. In appropriate candidates, something can be done: surgical correction that restores the lumbar curve, resets the body’s center of gravity, and allows patients to stand erect with normal muscular effort for the first time in years.

WHAT IS FLATBACK DEFORMITY?

The lumbar spine normally curves inward — toward the abdomen — with approximately 40 to 60 degrees of lordosis. This inward curve is not incidental; it is essential for placing the body’s center of gravity directly over the pelvis and feet, which allows standing and walking with minimal muscular effort. When lumbar lordosis is lost and the lumbar spine becomes flat or kyphotic, the center of gravity shifts forward. The body’s response is to compensate — tilting the pelvis backward, bending the knees, extending the hips — attempting to keep the eyes level and prevent falling forward. These compensatory mechanisms work, temporarily, but they require enormous continuous muscular effort that cannot be sustained.

Over time, the compensation fails. Patients are exhausted after standing for minutes. Walking any significant distance becomes impossible. Daily activities requiring an upright posture become progressively limited. Patients who once walked normally now shuffle with bent knees, reach for walls and furniture for support, and find themselves progressively housebound. The forward lean is often visible to anyone who looks — yet many patients have gone years without understanding that this represents a treatable spinal condition rather than inevitable aging.

CAUSES

Harrington Rod Instrumentation

The most common historical cause of flatback deformity. Harrington rods, used widely for scoliosis correction from the 1960s through the 1980s, were long-segment distraction devices that corrected coronal curves but simultaneously eliminated lumbar lordosis by pulling the spine into a straight line under tension. Patients who received Harrington rod surgery as teenagers often develop progressive flatback symptoms in their 40s, 50s, and 60s as their compensatory mechanisms decline. A full discussion of this specific presentation is on the Harrington Rod Revision Surgery page.

Modern Instrumented Lumbar Fusion Without Adequate Lordosis Restoration

Any long-segment lumbar fusion — even with modern pedicle screw instrumentation — can produce flatback deformity if the required lordosis is not restored at the time of fusion. Lumbar lordosis requirements vary by individual and are determined by the patient’s pelvic incidence — an anatomical parameter that dictates how much lordosis is needed to maintain upright balance. A patient whose pelvic incidence requires 60 degrees of lumbar lordosis but whose fusion was performed with only 40 degrees will develop progressive sagittal imbalance over time as disc levels above and below the fusion degenerate further.

Adjacent Segment Collapse

When a prior fusion stops above or below a degenerated disc that was not included in the construct, that adjacent segment can collapse in kyphosis — the disc loses height, the segment tilts forward, and the sagittal alignment achieved by the original fusion is progressively undone by the adjacent collapse. Adjacent segment disease-related flatback may require extension of the fusion construct in addition to osteotomy to fully restore alignment.

Degenerative Flatback (Without Prior Surgery)

Multilevel lumbar disc degeneration can produce flatback deformity even without prior surgery. As discs lose height throughout the lumbar spine, the cumulative disc space loss progressively reduces lumbar lordosis. This is distinct from the post-surgical causes above and often develops more slowly, but the functional consequence — progressive forward lean, fatigue, and pain — is the same.

Post-Fracture Deformity

Vertebral compression fractures — particularly from osteoporosis — that are not treated or that fail to fully restore height can produce kyphotic deformity at individual levels. Multiple fractures across the lumbar spine can cumulatively eliminate lordosis and produce clinical flatback syndrome. This is an increasingly common presentation as the population ages and osteoporosis becomes more prevalent.

SYMPTOMS AND HOW PATIENTS PRESENT

Flatback deformity produces a recognizable and consistent symptom profile, though the severity varies with the degree of imbalance:

  • Progressive forward lean — the defining symptom; inability to stand erect without great effort; the lean worsens over the course of the day as muscles fatigue
  • Back and hip pain — driven by continuous muscular overuse as the paraspinal, gluteal, and hamstring muscles work constantly to maintain upright compensation
  • Leg fatigue and pain — from the need to keep knees flexed and hips extended continuously; many patients report that their legs give out before their back does
  • Rapidly declining walking tolerance — patients progress from reduced walking distance to inability to walk more than a block or two, to needing a walker or wheelchair for any meaningful distance
  • Social and psychological impact — inability to stand at social events, difficulty at restaurants, inability to keep up with grandchildren; the functional restriction is comprehensive and isolating
  • Neurological symptoms — leg pain, numbness, or weakness from nerve root compression can accompany the deformity, particularly when adjacent segment stenosis is also present

EVALUATION AND SURGICAL PLANNING

Flatback correction is one of the most carefully planned procedures in spine surgery. The planning process involves:

  • Full-length standing X-rays (36-inch cassette) measuring the key sagittal alignment parameters: sagittal vertical axis (SVA), lumbar lordosis, thoracic kyphosis, pelvic incidence, pelvic tilt, and sacral slope. The SVA — the horizontal distance between the center of C7 and the back corner of the sacrum — is the primary measure of global sagittal imbalance and the primary target of correction.
  • CT scan of the lumbar spine to assess fusion status (is the prior fusion solid?), hardware integrity, the anatomy available for osteotomy placement, and bone quality at planned instrumentation levels.
  • MRI to assess neural structures, disc levels above and below the planned fusion, and any component of nerve compression contributing to leg symptoms.
  • Bone density testing (DEXA and CT Hounsfield units) to assess osteoporosis, which significantly affects implant planning, screw fixation strategy, and the decision about preoperative bone-building therapy. See Osteoporosis & Spine Surgery for detailed discussion of this component of preoperative care.
  • Review of all prior operative reports and imaging to understand what was done before, at what levels, with what hardware, and what alignment was achieved at the time of each prior procedure.

SURGICAL CORRECTION — THE OSTEOTOMY

Flatback correction requires an osteotomy — a surgically controlled cut through bone that allows the spine to be repositioned into lordotic alignment. The concept is straightforward; the execution is among the most demanding in spine surgery. The type of osteotomy is chosen based on the degree of correction needed, the rigidity of the deformity, and the anatomy available.

Posterior Column Osteotomy (PCO) — Smith-Petersen Osteotomy

A PCO removes the posterior bony elements (lamina, spinous process, and facet joints) at one or more levels, creating a hinge through the anterior disc space. As the posterior gap is closed during rod application, the spine extends through the disc, gaining approximately 10 to 15 degrees of correction per level. Multiple PCOs can be performed at successive levels to accumulate larger degrees of total correction.

PCOs are most appropriate when the anterior disc spaces retain some flexibility — they depend on the disc hinging open posteriorly as the posterior gap closes. In patients with fully fused anterior columns (common after long-standing Harrington rod fusion), the disc spaces are solidly fused and will not flex, making PCO alone insufficient and a more powerful osteotomy necessary.

Pedicle Subtraction Osteotomy (PSO)

A PSO is a three-column osteotomy performed entirely through a posterior approach. The procedure removes the posterior elements, both pedicles, and a precisely calculated wedge of the vertebral body at a single level. When the posterior gap created by this resection is closed during rod application, the spine hings through the vertebral body itself — rather than through a disc space — providing approximately 30 to 40 degrees of correction at a single level, in a spine where all three columns (anterior, middle, and posterior) are fused.

PSO is the workhorse procedure for flatback correction, particularly in post-Harrington rod patients whose anterior disc spaces are solidly fused. A single, well-placed PSO at L2 or L3 can restore the lordosis needed to bring the SVA within acceptable range and allow erect posture. In patients with very severe imbalance, two PSOs or a PSO combined with multiple PCOs may be required to achieve the correction target.

PSO is technically demanding. The vertebral body wedge must be precisely calculated and uniformly removed, the spinal cord sits immediately posterior throughout the procedure, and the correction maneuver — closing the osteotomy gap — must be controlled and gradual. Continuous intraoperative neuromonitoring and robotic navigation are non-negotiable in PSO at this practice. Blood loss is significant; cell salvage is used as standard to minimize transfusion requirements.

Vertebral Column Resection (VCR)

Complete removal of one or more vertebrae through combined anterior and posterior approaches (or an all-posterior approach in experienced hands). VCR provides the greatest correction of any osteotomy technique but carries the highest surgical risk and complexity. It is reserved for the most severe or rigid deformities where PSO alone cannot achieve the correction necessary to restore functional alignment.

THE COMPLETE PROCEDURE

Flatback correction is not just an osteotomy. The complete procedure involves:

  • Removal of prior instrumentation — old rods, screws, and hooks from prior fusion surgery must be removed before the osteotomy can be planned and performed
  • The osteotomy (PCO, PSO, or VCR as appropriate)
  • Decompression of neural structures if stenosis is contributing to leg symptoms
  • Revision instrumentation — new pedicle screws, rods, and cross-links placed to hold the corrected alignment and support fusion; in osteoporotic patients, cement-augmented screws or other augmented fixation techniques are used to achieve adequate screw purchase in lower-density bone
  • Intraoperative CT verification confirming screw position and osteotomy correction before the wound is closed

Operating time for PSO-based flatback correction typically ranges from 4 to 8 hours depending on the number of levels being addressed and the complexity of the revision anatomy. Blood loss is significant for any three-column osteotomy; cell salvage is used as standard to minimize donor transfusion.

PREOPERATIVE OPTIMIZATION

Flatback correction is elective surgery, and the window between the decision to operate and the procedure itself is used deliberately. Several factors are systematically addressed before surgery:

  • Osteoporosis treatment. Patients with significant osteoporosis are treated with bone-building medications (teriparatide or romosozumab) for 3 to 6 months before surgery to improve bone quality, screw purchase, and fusion rates. This is one of the most impactful modifiable risk factors in this population and should not be skipped for scheduling convenience.
  • Nutritional assessment. Albumin and prealbumin levels predict wound healing and infection risk. Nutritional supplementation is initiated early when deficiency is identified.
  • Cardiovascular evaluation. PSO and VCR carry significant physiological demand. Cardiac clearance and assessment of exercise tolerance are standard before major reconstructive surgery.
  • Smoking cessation. Smoking is associated with significantly higher pseudarthrosis rates. Cessation before elective surgery is discussed directly and enforced where possible through the preoperative period.

RECOVERY

  • Hospital stay: Typically 5 to 10 days
  • ICU or step-down care: Most patients spend 1 to 2 nights in a monitored setting after surgery
  • Early mobilization: Patients are up walking with physical therapy the first or second day after surgery
  • Visible posture improvement: Many patients notice they can stand more upright within days of surgery as the osteotomy correction becomes apparent — this is often one of the most emotionally significant moments of the recovery
  • Return to light activity: Typically 6 to 8 weeks
  • Fusion maturation: 12 to 18 months for complete fusion consolidation, though functional improvement is typically well underway long before that

FREQUENTLY ASKED QUESTIONS

Can flatback deformity be treated without surgery?

Not definitively. Physical therapy strengthens the compensatory muscles and may slow functional decline, and pain management can improve quality of life in patients who are not surgical candidates. But neither approach restores lost lumbar lordosis. The structural cause of flatback — absent or severely reduced lumbar lordosis — can only be corrected surgically. Non-surgical care is appropriate for patients who cannot safely undergo major surgery.

What is a pedicle subtraction osteotomy and why is it needed?

A PSO is a three-column osteotomy performed entirely through a posterior approach, removing the posterior elements, pedicles, and a wedge of vertebral body at one level to allow 30 to 40 degrees of lordosis restoration through bone. It is needed for flatback patients with fused anterior disc spaces — common after Harrington rod or modern long-segment fusion — because these patients cannot achieve adequate correction through posterior-only releases that rely on disc space mobility.

Will I be able to stand up straight again?

The specific goal of flatback correction surgery is to restore upright posture by correcting lumbar lordosis and reducing the sagittal vertical axis to within functional range. The degree of correction achievable depends on the severity and rigidity of the deformity and bone quality, but restoring the ability to stand and walk with normal muscular effort — without the bent-knee, forward-lean posture — is the primary outcome target and is achieved in the majority of appropriately selected patients.

I have osteoporosis. Can I still have flatback correction surgery?

Osteoporosis is common in this patient population, particularly post-Harrington rod patients who are now in their 50s and 60s. It does not automatically disqualify a patient from surgery, but it significantly affects how surgery is planned. Preoperative bone-building therapy, augmented fixation techniques (cement-enhanced screws), and modified construct designs are all tools used to safely operate in lower-density bone. See the Osteoporosis & Spine Surgery page for more detail.

I was told no further surgery is possible. Should I get a second opinion?

Yes. “Nothing more can be done” is among the most common things patients with flatback deformity have been told before coming to a high-volume deformity center. Dr. Sardar receives referrals specifically for patients in this situation — often patients who have had multiple prior surgeries and have been told they have reached the end of what is technically possible. A second opinion at a center that performs PSO and VCR regularly clarifies what is actually feasible for that specific patient’s anatomy and medical condition.

How long is the recovery from flatback correction?

Hospital stay is typically 5 to 10 days. Most patients notice improved upright posture within days to weeks of surgery as the osteotomy correction becomes apparent. Full functional improvement develops over 6 to 12 months as the fusion matures and strength is rebuilt. Most patients are returning to light daily activity within 6 to 8 weeks.

Does it matter where the PSO is performed?

Yes, significantly. PSO and VCR are performed at a very small number of centers nationally with the volume and infrastructure to do these procedures safely and regularly. The procedure requires an experienced deformity surgeon, a dedicated neuromonitoring team, experienced spine anesthesia, intraoperative imaging, cell salvage for blood conservation, and critical care availability post-operatively. These are not procedures that should be performed at a facility that encounters them rarely.

RELATED CONDITIONS & PROCEDURES

About Dr. Zeeshan Sardar
Dr. Sardar is Co-Chief of Spinal Deformity Surgery at NewYork-Presbyterian / Columbia University and performs PSO, PCO, and VCR for flatback correction as a core component of his adult spinal deformity practice. He receives referrals from across the United States for patients with severe sagittal imbalance, including many told no further surgery is possible. To schedule a consultation or request a second opinion, call 212-932-5187 or visit the contact page. Telemedicine available in NY, NJ, CT, FL, PA, MO, CA, and TX.

This page is for educational purposes only and does not constitute individualized medical advice. Please consult a qualified spine specialist to discuss your specific condition.

Reviewed by Dr. Zeeshan Sardar, MD, MSc, F.R.C.S.C — Last reviewed: August 2026.