Cervical Disc Replacement vs. ACDF: How to Choose

If you have been told you need surgery for a cervical disc problem — a herniated disc, a pinched nerve, or spinal cord compression in the neck — you will likely be offered one of two procedures: anterior cervical discectomy and fusion (ACDF) or cervical disc replacement (also called cervical arthroplasty). Both are performed through the same small incision on the front of the neck. Both remove the damaged disc and decompress the nerve or spinal cord. Both have excellent safety records and long track records of success.

The question patients often ask is: which one is right for me? The answer depends on factors that are specific to your anatomy, your diagnosis, and your imaging — not on a general preference for one procedure over the other. Here is how to think through the decision.

The Core Difference: Motion vs. Fusion

ACDF and cervical disc replacement achieve the same decompressive goal by different means. In ACDF, the disc space is filled with a bone graft or cage and locked in place with a plate and screws. The treated level fuses permanently and no longer moves. In cervical disc replacement, the disc is replaced with an artificial implant that replicates the disc’s function and preserves motion at the treated level.

This distinction — motion versus fusion — has consequences that extend well beyond the immediate recovery period. The cervical spine is not designed to have rigid, immobile segments in the middle of a mobile chain. When a level is fused, the levels above and below it must compensate by moving more, absorbing more stress, and degenerating faster. This is called adjacent segment disease, and it is the primary long-term limitation of cervical fusion.

Cervical disc replacement was developed specifically to address this problem. By preserving motion at the treated level, it maintains more normal biomechanics and reduces the mechanical burden on adjacent discs.

What the Evidence Shows

Cervical disc replacement is one of the most thoroughly studied procedures in spine surgery, with multiple FDA investigational device exemption (IDE) trials comparing it head-to-head against ACDF, some with follow-up now extending beyond 10 years. The consistent findings across these trials:

  • Equivalent neurological outcomes — both procedures achieve similar rates of arm pain relief, neurological recovery, and patient-reported satisfaction
  • Lower adjacent segment reoperation rates with disc replacement — multiple trials have demonstrated statistically significant reductions in the rate of subsequent surgery at adjacent levels in patients treated with disc replacement at 5 to 10 years of follow-up
  • Lower overall reoperation rates with disc replacement — the cumulative reoperation rate (for any reason) is consistently lower in disc replacement groups in long-term trial data
  • Preserved motion — functional range of motion at the treated level is maintained in the majority of disc replacement patients at long-term follow-up
  • Comparable safety — complication rates are similar between the two procedures in randomized trial data

For appropriately selected patients, the long-term data increasingly favor disc replacement over fusion from a reoperation and adjacent segment standpoint. The question is whether you are an appropriate candidate.

Who Is a Candidate for Disc Replacement?

Cervical disc replacement is not appropriate for every patient with cervical disc disease. The candidacy criteria are specific, and imaging review is essential before recommending one procedure over the other. Ideal candidates for disc replacement generally have:

  • Symptomatic disc disease at one or two levels causing radiculopathy or myelopathy
  • Preserved or correctable cervical lordosis at the affected level — disc replacement is not appropriate in patients with kyphosis at the treated segment
  • No significant facet joint arthritis at the affected level — the facet joints must be functional to allow safe motion after disc replacement; arthritic facets are a contraindication
  • No instability or listhesis at the affected level
  • No significant ossification of the posterior longitudinal ligament (OPLL) — this condition typically requires more extensive decompression that is better addressed with fusion or corpectomy
  • Skeletally mature patients with good bone quality

When ACDF Is the Better Choice

ACDF remains an excellent procedure — one of the most successful operations in all of spine surgery — and is the appropriate choice in a number of situations where disc replacement is not suitable:

  • Cervical kyphosis at the affected level — a kyphotic (forward-bent) segment cannot be safely replaced with a motion-preserving implant; fusion with correction of alignment is the right approach
  • Significant facet arthritis — arthritic facet joints are a source of pain with motion; preserving motion in this setting does not help and may worsen pain
  • Three or more levels requiring treatment — disc replacement is FDA-approved for one and two levels; multilevel disease typically requires fusion
  • OPLL — ossification behind the vertebral body often requires corpectomy rather than simple discectomy; fusion is the appropriate reconstruction
  • Instability or listhesis — an unstable level needs stabilization, which fusion provides and disc replacement does not
  • Severe spondylosis with significant bony compression — when most of the compression comes from bone spurs rather than disc material, fusion may provide more reliable long-term decompression
  • Prior adjacent fusion — in some cases, extending a fusion is more appropriate than placing a disc replacement next to existing hardware, though hybrid constructs are used in selected cases

The Role of Age and Activity Level

Age and activity level are relevant but not determinative. Younger, more active patients who want to preserve as much cervical mobility as possible and minimize the risk of future adjacent segment surgery tend to have the most to gain from disc replacement — and the longest time horizon over which the adjacent segment benefit will accumulate.

Older patients with multilevel degenerative disease and significant facet arthritis may gain little from motion preservation at one level and are often better served by ACDF. But there is no absolute age cutoff. A healthy, active 60-year-old with a single-level herniation and preserved facet joints may be an excellent disc replacement candidate. A 40-year-old with significant facet arthritis and kyphosis may not be.

The imaging — specifically the MRI and CT of the cervical spine — is what determines candidacy, not age or activity level alone.

Questions to Ask Your Surgeon

If you are facing this decision, these are the right questions to bring to your consultation:

  • Am I a candidate for disc replacement based on my specific imaging?
  • If not, what specifically on my imaging rules it out?
  • If I am a candidate, what are the relative advantages of disc replacement versus fusion for my situation?
  • What implant system do you use, and is it FDA-approved?
  • What are the risks specific to each procedure for my anatomy?

A surgeon who performs both procedures regularly should be able to give you a clear, evidence-based answer to each of these questions — and should recommend the procedure that is genuinely best for your anatomy, not the one they happen to perform more often.

How Dr. Sardar Approaches This Decision

Dr. Sardar completed a dedicated fellowship in artificial disc replacement at the Texas Back Institute and is equally expert in ACDF and cervical disc replacement. Every patient with cervical disc disease is evaluated for disc replacement candidacy at their initial consultation. If you are a candidate, disc replacement is discussed as an option with a clear explanation of why it may be preferable to fusion for your specific situation. If you are not a candidate, the reasons are explained in detail — and ACDF is recommended without hesitation, because it remains an outstanding procedure for the patients it is designed to treat.

The goal is always the procedure that gives you the best long-term outcome — not the procedure that is newer, or more profitable, or faster to perform.

About Dr. Zeeshan Sardar
Dr. Sardar is Co-Chief of Spinal Deformity Surgery at NewYork-Presbyterian / Columbia University and specializes in both ACDF and cervical disc replacement. He completed a dedicated fellowship in artificial disc replacement at the Texas Back Institute. To schedule a consultation, call 212-932-5187 or visit the contact page.

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

What Is Robotic Spine Surgery? How It Works and Why It Matters

If you have been told you need spine surgery, you may have come across the term “robotic spine surgery” and wondered what it actually means — and whether it matters for you. The word “robotic” can conjure images of a machine operating independently. The reality is more precise and, for patients, more reassuring than that. Robotic spine surgery is a tool that makes surgeons more accurate. The surgeon is always in control. The robot never operates independently.

Here is a clear explanation of what robotic spine surgery is, how it works, what the evidence shows, and what it means for your care if your surgeon uses it.

What Robotic Spine Surgery Actually Is

Robotic spine surgery is a navigation and guidance system that allows a surgeon to plan implant placement — typically pedicle screws — with precision on a three-dimensional model of the patient’s own anatomy before making a single incision, and then execute that plan with real-time robotic guidance during the procedure. The robot does not make decisions. It holds instruments along a pre-planned trajectory with a degree of precision that the human hand alone cannot consistently achieve.

The most widely used robotic platform in spine surgery in the United States is the Mazor X Stealth Edition (Medtronic), which integrates robotic guidance with O-arm intraoperative CT imaging and Stealth navigation. This is the system Dr. Sardar uses at the Och Spine Hospital at NewYork-Presbyterian. Other platforms include the ExcelsiusGPS (Globus Medical) and the ROSA Spine (Zimmer Biomet).

The Central Challenge: Pedicle Screw Placement

To understand why robotic guidance matters, it helps to understand the challenge it is designed to solve.

Pedicle screws are the anchor points of most modern spinal instrumentation. They are placed through the pedicle — a narrow bony bridge connecting the vertebral body to the posterior elements of the spine — and into the vertebral body itself. A correctly placed pedicle screw provides the strongest possible fixation for rods, plates, and other hardware.

The pedicle is narrow. In some patients, particularly those with small anatomy, deformity, or osteoporosis, it may be only a few millimeters wide. A screw placed even a few millimeters off-axis can breach the pedicle wall and injure adjacent nerves, vessels, or the spinal cord. Traditionally, pedicle screws were placed using anatomical landmarks and fluoroscopic X-ray guidance — a highly developed skill, but one that relies on two-dimensional imaging and the surgeon’s spatial judgment.

Robotic guidance transforms this from a freehand procedure guided by 2D images into a precisely planned trajectory executed on a real-time 3D model of the patient’s individual anatomy.

How It Works: Step by Step

1. Preoperative Planning

Before surgery, the patient’s CT scan is loaded into the robotic planning software. The surgeon plans every screw trajectory on a three-dimensional model of that specific patient’s anatomy — choosing the optimal entry point, angle, and depth for each screw at each level. This planning accounts for the patient’s individual pedicle dimensions, bone quality, and the surgical goals. The plan is finalized before the patient enters the operating room.

2. Intraoperative Registration

At the start of surgery, the robotic system registers the patient’s actual spinal anatomy — as it exists on the operating table — to the preoperative plan. This registration step aligns the virtual plan with the physical patient in real time, accounting for any differences in patient positioning. The accuracy of this registration step is fundamental to the accuracy of screw placement.

3. Robotic-Guided Execution

Once registered, the robotic arm positions itself along the pre-planned trajectory for each screw. The surgeon then drills and places the screw through the robotic guide. At each step, the system tracks the position of the instruments in real time relative to the patient’s anatomy. If the patient moves even slightly during the procedure, the system detects the shift and alerts the surgeon.

What the Evidence Shows

The clinical literature on robotic spine surgery has grown substantially over the past decade. Key findings include:

  • Higher pedicle screw accuracy — multiple studies have demonstrated that robotically guided pedicle screws achieve clinically acceptable accuracy rates of 95–98%, comparable to or exceeding freehand and fluoroscopy-guided techniques, particularly in anatomically challenging cases such as deformity and revision surgery
  • Reduced radiation exposure — robotic navigation significantly reduces the need for repeated intraoperative fluoroscopy, lowering radiation exposure for both the patient and the surgical team over the course of a procedure
  • Reduced revision rates for malpositioned screws — intraoperative CT confirmation at the end of the case allows any malpositioned screw to be identified and corrected before the patient leaves the operating room, avoiding the need for a return to surgery
  • Particular benefit in complex cases — the accuracy advantage of robotic guidance is most pronounced in anatomically challenging situations: severe deformity, revision surgery through scar tissue, small pedicles, osteoporotic bone, and cervicothoracic junction cases

What It Means for Patients

For patients, the practical implications of robotic spine surgery are straightforward:

  • Your surgeon has planned your specific anatomy before the first incision. Every screw trajectory is designed for your spine — not a generic template.
  • The risk of a return to surgery for a malpositioned screw is minimized. Problems that would previously only be discovered on postoperative imaging are identified and corrected intraoperatively.
  • You receive less radiation than with traditional fluoroscopy-guided techniques.
  • The benefit is greatest if your case is complex. If you have scoliosis, kyphosis, revision surgery, or other anatomically challenging features, robotic guidance provides a meaningful accuracy advantage over traditional approaches.

What Robotic Surgery Does Not Change

It is equally important to understand what robotic surgery does not do. It does not replace surgical judgment. It does not plan the operation — the surgeon does that. It does not decompress nerves, correct deformity, or achieve fusion — those steps are performed entirely by the surgeon. It does not make an inexperienced surgeon safe, or a poorly planned operation well-executed.

Robotic guidance is a precision tool that helps an experienced surgeon execute a well-planned operation more accurately. It is most valuable in the hands of a surgeon who uses it regularly, understands its limitations, and performs the full range of procedures it supports — not as a marketing differentiator, but as a genuine component of a high-standard surgical practice.

Dr. Sardar’s Use of Robotic Navigation

Dr. Sardar uses the Mazor X Stealth Edition robotic navigation system as standard for instrumented spinal procedures at the Och Spine Hospital at NewYork-Presbyterian. This includes scoliosis correction, complex deformity reconstruction, revision surgery, lumbar fusion.

He adopted robotic navigation not because it is new, but because the evidence supports its use as the standard of care for accurate, safe instrumented spine surgery — particularly in the complex deformity and revision cases that define his practice.

About Dr. Zeeshan Sardar
Dr. Sardar is Co-Chief of Spinal Deformity Surgery at NewYork-Presbyterian / Columbia University and uses robotic-assisted navigation as standard in all instrumented spine procedures. He treats adolescent and adult patients with scoliosis, kyphosis, complex deformity, revision surgery, and degenerative spine conditions. To schedule a consultation, call 212-932-5187 or visit the contact page.

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

Adult vs. Teen Scoliosis: How They Differ — and Why It Matters for Treatment

If you are a parent whose teenager was just diagnosed with scoliosis, or an adult who was told you have scoliosis for the first time, you may have encountered the same word — scoliosis — being applied to two very different situations. That shared label can be misleading. Adult scoliosis and adolescent scoliosis are not the same condition. They have different causes, different symptoms, different natural histories, and different surgical goals. Understanding these differences is essential for making informed decisions about treatment.

What They Have in Common

Both adult and adolescent scoliosis are defined by an abnormal lateral (side-to-side) curvature of the spine that measures 10 degrees or more on X-ray. Both can affect quality of life when severe enough. Both are diagnosed with standing X-rays, and both may eventually require surgical treatment. And in some adults, the scoliosis they have now is a direct continuation of a curve that started in adolescence.

That is largely where the similarities end.

The Cause Is Different

Adolescent idiopathic scoliosis (AIS) — the most common form of scoliosis in teenagers — has no identified cause. The word “idiopathic” literally means “of unknown origin.” We know it tends to run in families, that it is more common in girls than boys, and that it develops during the growth spurt of puberty. But despite decades of research, the precise mechanism remains unknown. The curve develops from within an otherwise healthy spine.

Adult degenerative scoliosis, the most common form of scoliosis that develops in adulthood, has a very clear cause: the asymmetric degeneration of discs and facet joints in the lumbar spine over time. As these structures wear unevenly, the spine begins to tilt and rotate. This is not a continuation of adolescent scoliosis — it is an entirely new process, essentially the spine developing a curve as a consequence of aging and degeneration.

There is also a third group: adults with scoliosis that originated in adolescence that was never treated or treated with bracing, and which has now progressed or become symptomatic. This is different again from de novo degenerative scoliosis, and requires its own evaluation and treatment approach.

The Symptoms Are Different

This is one of the most important differences for patients and families to understand.

Teenagers with scoliosis often have no symptoms at all. The condition is frequently discovered incidentally — during a school screening, a sports physical, or when a parent notices that their child’s shoulders or hips look uneven. Even teenagers with significant curves of 40 or 50 degrees may have no pain and no functional limitations. This is one reason adolescent scoliosis can be difficult for families to take seriously at first: the child feels fine.

Adults with scoliosis almost always present with symptoms, and those symptoms are often significant. The most common are:

  • Back pain — often axial, worse with prolonged standing or walking, and frequently the primary reason the patient seeks care
  • Leg pain, numbness, or weakness — caused by nerve compression from stenosis within the degenerative and curved segments; this is far more common in adult scoliosis than in the adolescent form
  • Neurogenic claudication — leg symptoms that worsen with walking and standing and improve with sitting or bending forward
  • Difficulty standing upright — as sagittal imbalance (forward lean) develops, patients find it increasingly difficult and fatiguing to maintain an upright posture
  • Visible postural change — a shoulder or hip appearing higher, a shift of the trunk to one side, or a progressive forward stoop

The neurological symptoms in adult scoliosis — leg pain, numbness, weakness, claudication — arise because degenerative scoliosis is accompanied by disc degeneration, arthritic facet joints, and narrowing of the spinal canal. These are not present in the same way in adolescent scoliosis, which occurs in an otherwise healthy, non-degenerated spine.

The Location of the Curve Is Different

Adolescent idiopathic scoliosis most commonly involves the thoracic spine (the mid and upper back). The classic presentation is a right thoracic curve — the spine curving to the right in the chest region. There may also be a compensatory lumbar curve below it. This thoracic location is part of why teenagers with AIS often have visible rib prominence or shoulder asymmetry but little pain: the thoracic spine has more structural support from the rib cage and is less mechanically stressed during daily activities than the lumbar spine.

Adult degenerative scoliosis predominantly involves the lumbar spine (the lower back). The lumbar spine is the load-bearing region of the spine, and it is the region most subject to degenerative wear. Lumbar curves cause more mechanical pain and are more likely to compress the nerve roots that travel down into the legs.

The Risk of Progression Is Different

In adolescents, the major concern about scoliosis is progression during growth. Curves that are modest at initial diagnosis can increase significantly during the adolescent growth spurt. This is why treatment decisions in teenagers are closely tied to skeletal maturity — how much growth remains. Once growth is complete, the risk of rapid progression drops substantially, though large curves (generally above 50 degrees) may continue to progress slowly in adulthood.

In adults, the concern about progression is different. De novo degenerative scoliosis progresses slowly over years as the underlying degeneration continues — typically at a rate of one to two degrees per year on average, though with significant individual variation. Progression in adults is more concerning for its functional consequences — worsening leg symptoms, increasing forward lean, declining walking tolerance — than for the degree of curvature per se.

The Goals of Surgery Are Different

This is perhaps the most clinically significant difference.

When surgery is recommended for an adolescent with scoliosis, the primary goals are:

  • Halt progression — prevent the curve from continuing to worsen over the patient’s lifetime
  • Achieve maximum curve correction — the young, flexible spine responds well to instrumentation, and significant correction is achievable
  • Preserve as many motion segments as possible — fusing the minimum number of levels necessary to control the curve
  • Cosmetic improvement — reducing the visible deformity matters significantly to adolescent patients and their families

When surgery is recommended for an adult with scoliosis, the goals shift considerably:

  • Decompress nerve roots — relieving the leg pain, numbness, and claudication caused by stenosis within the deformity is often the primary objective
  • Restore sagittal balance — correcting the forward lean that makes standing and walking exhausting; this is often more important than the degree of coronal (side-to-side) correction
  • Achieve a stable, durable fusion — in a spine with degenerative bone and compromised biology, achieving solid fusion is a greater challenge than in a healthy adolescent spine
  • Improve function and quality of life — the ability to walk farther, stand longer, and engage in daily activities is the measure of success in adult surgery

Cosmetic improvement, while welcome, is typically a secondary goal in adults. The primary driver is relief of symptoms and restoration of function.

The Surgical Complexity Is Different

Adolescent scoliosis surgery, while serious, is performed in young patients with healthy bone, excellent healing capacity, good cardiovascular reserve, and a flexible spine that responds well to instrumented correction. Recovery is typically faster and complication rates are lower than in adult surgery.

Adult scoliosis surgery is generally more complex. The reasons are multiple: degenerative bone quality (often compounded by osteoporosis) makes screw fixation more challenging; the need for decompression adds to surgical extent; sagittal imbalance correction often requires osteotomies — controlled bone cuts — that are not needed in adolescent cases; and older patients frequently have medical comorbidities that increase perioperative risk. Careful preoperative optimization — addressing bone density, nutrition, cardiovascular status, and other factors — is an essential part of adult deformity surgery that has no real equivalent in the adolescent setting.

What This Means for You

If you are the parent of a teenager with newly diagnosed scoliosis, the most important things to know are: the vast majority of adolescent scoliosis curves do not require surgery; observation and bracing are appropriate first steps for most patients; and if surgery is eventually needed, outcomes in adolescents are excellent and recovery is typically straightforward.

If you are an adult who has been told you have scoliosis — whether newly developed or a progression of a teenage curve — the picture is more nuanced. Your symptoms matter more than your curve angle. Your sagittal balance (whether you lean forward) matters as much as or more than the side-to-side curvature. Your bone quality, general health, and functional goals are central to the treatment decision. And if surgery is recommended, it should be performed by a surgeon with specific expertise in adult spinal deformity — a different skill set from adolescent scoliosis surgery.

About Dr. Zeeshan Sardar
Dr. Sardar is Co-Chief of Spinal Deformity Surgery at NewYork-Presbyterian / Columbia University and specializes in both adolescent and adult scoliosis surgery. He treats patients from age 10 through adulthood and manages the full spectrum of spinal deformity, from first-time AIS surgery to complex adult reconstruction and revision. To schedule a consultation, call 212-932-5187 or visit the contact page.

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

What Is a Harrington Rod — and Why Do Some Patients Need It Revised?

If you had scoliosis surgery between the 1960s and the early 1990s, there is a good chance you have a Harrington rod in your spine. For decades, it was the standard of care for scoliosis correction — a major advance when it was introduced, and a procedure that helped hundreds of thousands of patients. But the Harrington rod has a fundamental limitation that was not fully understood at the time, and many patients who had the surgery are now, decades later, living with complications that are directly related to how that hardware works.

If you are one of those patients — or a family member of one — this post is for you. Here is what a Harrington rod is, why complications develop, and what can be done about them.

The History: Why the Harrington Rod Was Revolutionary

Before Dr. Paul Harrington developed his rod system in the 1950s, scoliosis surgery was primitive and unreliable. The available techniques offered little correction and required months of postoperative casting. Harrington’s innovation — a single metal rod attached with hooks to the top and bottom of the curved segment, then lengthened to straighten the spine — was transformative for its time. For the first time, meaningful correction could be achieved and maintained. The Harrington rod became the dominant technique for scoliosis surgery for the next three decades.

It was, by any measure, a genuine advance in patient care. The patients who received it were well-served by the best available technology of their era. The problem emerged not from the surgery failing to do what it was designed to do — it largely succeeded — but from what it could not do.

The Core Problem: What the Harrington Rod Could Not Do

The Harrington rod corrected scoliosis by distracting (lengthening) the spine along its concave side — straightening the side-to-side curvature. This worked well for the coronal plane (the front view). What it could not do was maintain or restore the normal front-to-back curves of the spine.

The human spine is not meant to be straight from front to back. The lower back (lumbar spine) has a natural inward curve called lordosis. This curve is essential for balanced, upright posture. It positions the body’s center of gravity correctly over the pelvis and allows people to stand upright without excessive muscular effort.

The Harrington rod, by design, tended to straighten or flatten the lumbar spine as it distracted the scoliotic curve. The lordosis was lost or reduced. At the time of surgery, this was not recognized as a significant problem. Patients were young, their muscles were strong, and they could compensate. But compensation has limits — and over decades, those limits are reached.

Flatback Deformity: The Most Common Late Complication

The loss of lumbar lordosis after Harrington rod surgery leads, over time, to a condition called flatback deformity. As the name suggests, the lower back loses its normal curve and becomes flat — or in some cases, actually reverses into a kyphotic curve. Without normal lordosis, the body’s center of gravity shifts forward. To stay upright, a patient must constantly exert muscular effort to hold themselves up against gravity.

The result is exhausting. Patients with flatback deformity describe an inability to stand upright for more than a few minutes at a time. Walking becomes painful and tiring. They find themselves leaning forward progressively as the day goes on. Activities that most people take for granted — standing in line, walking through a grocery store, attending a social event — become significant challenges.

Flatback deformity typically begins to manifest in a patient’s 30s or 40s, often 20 or 30 years after the original surgery. It does not improve on its own. Without treatment, it tends to progress slowly but steadily.

Other Late Complications of Harrington Rod Surgery

Flatback deformity is the most common and most disabling late complication, but it is not the only one. Patients with Harrington rod instrumentation can also develop:

  • Hardware failure — rod fracture, hook dislodgement, or wire breakage. The hardware was designed for the shorter life expectancy assumptions of an earlier era; many patients have now had their implants for 40 or 50 years.
  • Pseudarthrosis — failure of the fusion to fully heal, creating a non-union within the fused segment. This causes pain, instability, and stress fractures of the hardware.
  • Adjacent segment degeneration — the levels immediately above and below a long spinal fusion bear increased mechanical load. Over decades, this accelerated wear causes disc degeneration, stenosis, and nerve compression at adjacent levels.
  • Neurological symptoms — new leg pain, numbness, weakness, or bladder changes arising from adjacent segment stenosis, hardware migration, or progressive deformity. These symptoms warrant prompt evaluation.
  • Crankshaft phenomenon — in patients who had surgery before skeletal maturity, continued anterior spinal growth against a posterior fusion can cause progressive rotational deformity.

Why Modern Surgery Is Different

The limitations of the Harrington rod directly shaped the development of modern spinal instrumentation. Beginning in the 1980s and 1990s, segmental fixation systems using pedicle screws were introduced. Unlike a Harrington rod — which attached only at the top and bottom of the construct — pedicle screw systems attach to every vertebra in the fusion, providing three-dimensional control of each segment.

This three-dimensional control allows surgeons to correct not just the side-to-side curvature of scoliosis, but also to restore and maintain normal lumbar lordosis. Modern scoliosis surgery does not produce flatback deformity. The outcomes for patients treated today are fundamentally different from those treated in the Harrington era — not because surgeons are more skilled, but because the tools allow three-dimensional correction that was simply not achievable before.

What Revision Surgery Involves

Revision surgery for Harrington rod complications is among the most technically complex procedures in spine surgery. It typically involves:

  • Removal of the old Harrington rod hardware — often deeply embedded in scar tissue after decades in place
  • Osteotomy — a controlled cut through the fused bone to allow the spine to be repositioned. For flatback correction, this typically involves a pedicle subtraction osteotomy (PSO), which achieves 30–40 degrees of lordosis correction at a single level, or multiple Smith-Petersen osteotomies (SPOs) across several levels
  • Reconstruction with modern instrumentation — replacement of the old hardware with a modern pedicle screw-rod construct that maintains the corrected alignment
  • Extension of the fusion — in many cases, the fusion needs to be extended to include levels above or below the original construct, often including the pelvis, to achieve balanced alignment

This is major surgery. It requires an experienced team, a high-volume center with appropriate infrastructure, and a surgeon who performs these procedures regularly. The outcomes for appropriately selected patients, however, can be transformative. Many patients describe being able to stand upright without pain for the first time in years.

Should You Be Evaluated?

If you had Harrington rod surgery and are experiencing any of the following, a specialist evaluation is appropriate:

  • Progressive difficulty standing upright or a feeling that you are leaning forward
  • Worsening back pain, particularly with standing or walking
  • New or worsening leg pain, numbness, or weakness
  • Any changes in bladder or bowel function
  • A noticeable change in your posture or the way you walk
  • Pain at the site of the original hardware

You do not need to be in crisis to seek an evaluation. In fact, earlier evaluation generally means simpler treatment options and better outcomes. If you are managing day-to-day but noticing a slow decline in what you can do, that is the right time to be seen — not after years of further progression.

Even if you feel well, a baseline evaluation with full-length standing X-rays at a center experienced in Harrington rod complications can give you a clear picture of where your spine stands — and whether any intervention is likely to be needed in the future.

About Dr. Zeeshan Sardar
Dr. Sardar is Co-Chief of Spinal Deformity Surgery at NewYork-Presbyterian / Columbia University and specializes in complex revision spine surgery, Harrington rod revision, and adult spinal deformity reconstruction. He sees patients from across the United States and internationally. To schedule a consultation, call 212-932-5187 or visit the contact page.

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

When Does Scoliosis Need Surgery? A Parent’s Guide

If your child has just been diagnosed with scoliosis, the first question most parents ask is: Does this mean surgery?

The answer, for most children, is no. The majority of patients with adolescent idiopathic scoliosis (AIS) are treated with observation alone, or with bracing during the growing years. Surgery is recommended only in specific situations where the curve is severe enough that the long-term risks of leaving it untreated outweigh the risks of the operation itself.

That said, knowing when surgery is the right answer — and finding the right surgeon to make that call — matters enormously. This guide walks you through how spine surgeons think about the decision.

First: The Basics of Scoliosis Severity

Scoliosis severity is measured using the Cobb angle — the standard method for quantifying how much the spine curves on an X-ray. A Cobb angle is measured in degrees, and general treatment guidelines are organized around it:

  • Under 25°: Typically observed with periodic X-rays. No active treatment needed in most cases.
  • 25° to 45°: Bracing is usually recommended for skeletally immature patients (those still growing) to prevent the curve from worsening.
  • 45° to 50° or more: Surgery is typically recommended, particularly if the patient is still growing or the curve is progressing.

These are general thresholds, not rigid rules. Every patient is different, and the decision about surgery involves more than just the number.

The Key Factors That Go Into the Decision

When a surgeon evaluates a patient for potential scoliosis surgery, the Cobb angle is one data point among several. Here is what else matters:

1. Skeletal Maturity

A curve in a child who is still growing carries more risk of progression than the same curve in a fully grown teenager. Skeletal maturity is assessed using bone age and growth indicators visible on X-ray, including the Risser sign (which measures the maturity of the pelvic growth plate). A child with a 40° curve and significant growth remaining may be a stronger surgical candidate than a teenager with the same curve who is nearly done growing.

2. Rate of Progression

How fast is the curve changing? A curve that has grown by 10 degrees over the past six months tells a different story than one that has been stable for two years. Progression of 5 degrees or more per visit is generally considered significant, particularly during the adolescent growth spurt.

3. Curve Pattern and Location

Not all curves are the same. A curve in the thoracic spine (mid-back) behaves differently from one in the lumbar spine (lower back) or a double major curve that involves both regions. Thoracic curves tend to progress more than lumbar curves and are more likely to affect appearance and, in very severe cases, lung function. The pattern of the curve affects which levels need to be fused and how the surgery is planned.

4. Symptoms

Most adolescents with scoliosis do not have significant pain. When pain is present — especially if it is severe, constant, or associated with neurological symptoms like weakness or numbness — it warrants closer evaluation and may support an earlier surgical recommendation. Pain alone does not trigger surgery, but it is factored into the overall picture.

5. The Long-Term Natural History

Research on the natural history of untreated scoliosis informs a key part of the surgical decision. Curves above 50 degrees at skeletal maturity tend to progress slowly but steadily in adulthood — at a rate of approximately 1 degree per year. Over decades, a 55° curve at age 18 may become a 75° or 80° curve by middle age, with increasing pain, deformity, and in severe cases, cardiopulmonary compromise. This long-term trajectory is part of why surgery is recommended at meaningful thresholds rather than waiting until symptoms appear.

What Scoliosis Surgery Actually Does

The goal of surgery for AIS is to correct the curve as much as safely possible, then fuse the involved vertebrae so the correction is permanent. This is typically done through a posterior approach (through the back) using pedicle screws, connecting rods, and bone graft.

Modern techniques have significantly improved both the safety and the outcomes of this surgery. Surgeons at high-volume centers now routinely use:

  • Intraoperative neuromonitoring (IONM): Continuous monitoring of spinal cord and nerve function throughout the procedure, allowing the surgical team to detect and respond to any changes in real time.
  • Robotic-assisted navigation: Computer-guided systems that allow pedicle screws to be placed with a high degree of precision, reducing the risk of misplacement.
  • Real-time 3D imaging: Intraoperative CT-based imaging that confirms screw position before the patient leaves the operating room.

The result, in the hands of an experienced surgeon, is a well-corrected spine, a straight and balanced posture, and a fusion that is built to last a lifetime.

What Happens If Surgery Is Delayed or Avoided?

For curves that do not meet surgical thresholds, avoiding surgery is absolutely the right call. For curves that do meet those thresholds, delay carries real risks. The larger a curve becomes before surgery, the more levels typically need to be fused to achieve correction and balance. More fusion levels mean a longer operation, a longer recovery, and less spinal mobility preserved. Correction of a 70° curve is technically more demanding and carries more risk than correction of a 50° curve in the same patient.

This is one reason why a timely evaluation by an experienced scoliosis surgeon matters, even for patients who may ultimately not need surgery. Knowing where you stand — and having a plan — is always better than watching and waiting without guidance.

Questions to Ask at Your Consultation

Whether you are seeking a first opinion or a second one, here are the questions worth asking any surgeon you see:

  • What is my child’s exact Cobb angle, and what is the curve pattern?
  • How skeletally mature is my child, and how does that affect the risk of progression?
  • What is the likelihood this curve will progress without surgery?
  • If surgery is recommended, how many levels would be fused?
  • What are the risks,?
  • Do you use robotic guidance and intraoperative neuromonitoring?

A good surgeon will welcome these questions and answer them directly. If you feel rushed, dismissed, or unable to get clear answers, seeking a second opinion is entirely appropriate — and most experienced scoliosis surgeons will tell you the same.

When to Seek a Second Opinion

Second opinions are not just acceptable in scoliosis care — they are often encouraged. AIS surgery is elective in the sense that it is planned rather than emergent, which means you have time to make an informed decision. If your child has been told surgery is necessary and you are unsure, a consultation at a high-volume deformity center can provide clarity and peace of mind. Conversely, if you have been told surgery is not yet needed but the curve has been rapidly progressing, a second set of eyes may be equally valuable.

About Dr. Zeeshan Sardar
Dr. Sardar is Co-Chief of Spinal Deformity Surgery at NewYork-Presbyterian / Columbia University and one of New York’s most experienced adolescent scoliosis surgeons. He completed his advanced spinal deformity fellowship at Columbia University and NewYork-Presbyterian and sees patients from across the United States and internationally. To schedule a consultation, call 212-932-5187 or visit the contact page.

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

Adult Scoliosis

Symptoms, Causes & When Surgery Is the Right Choice

Many people associate scoliosis with teenagers — the awkward school screening, the doctor with the scoliometer, the worried parent. But scoliosis doesn’t always stay in adolescence. For millions of adults, it either persists from childhood or develops for the first time after age 40. And unlike the mild curves that are often watched and managed in teens, adult scoliosis can cause real, daily suffering: back pain that never fully goes away, difficulty standing upright, and a gradual loss of the activities you love.

If you’ve been told you have adult scoliosis — or if your back pain just hasn’t added up — this guide will help you understand what you’re dealing with and when it might be time to seriously consider surgery.

What Is Adult Scoliosis?

Scoliosis is an abnormal sideways curvature of the spine, typically measuring 10 degrees or more on an X-ray. In adults, it comes in two main forms:

Adolescent idiopathic scoliosis (AIS) that has progressed into adulthood. If you were diagnosed with scoliosis as a child or teenager and weren’t treated — or were treated but still have a residual curve — that curve can continue to worsen over time, especially after age 40.

De novo (degenerative) scoliosis. This type develops in adulthood, usually after age 50, as the discs and joints of the spine wear down unevenly. It tends to affect the lower back and is one of the most common causes of new-onset back and leg pain in older adults.

Both types can significantly impact quality of life — and both deserve proper evaluation, not just reassurance that “it’s just getting older.”

Symptoms to Watch For

Adult scoliosis doesn’t always look the way people expect. You might not have a visible hump or dramatic lean. Instead, the signs are often subtler and easy to dismiss:

  • Persistent lower back pain, especially after standing or walking
  • Leg pain, numbness, or tingling (caused by nerve compression as the spine curves and shifts)
  • Difficulty standing upright — you may find yourself leaning on a shopping cart or countertop for relief
  • Uneven hips or shoulders that have gradually shifted
  • Fatigue from the effort of compensating for poor spinal alignment
  • A feeling that you’re getting shorter — a curve can cause measurable height loss over years

If any of these sound familiar, don’t wait. Adult scoliosis tends to worsen gradually, and earlier intervention — even if non-surgical — almost always leads to better outcomes.

What Causes Adult Scoliosis?

For degenerative scoliosis, the root cause is the cumulative wear and tear of aging. As the intervertebral discs lose height and the facet joints degenerate asymmetrically, the spine begins to tilt and rotate. Factors that accelerate this process include:

  • Osteoporosis — weakened bones are more vulnerable to collapse and deformity
  • Prior spinal surgeries — adjacent segment disease can cause curves to develop or worsen above or below a fusion
  • Genetics — a family history of spine problems raises your risk
  • Obesity — excess weight adds stress to an already compromised spine

Understanding the underlying cause matters enormously when planning treatment. A one-size-fits-all approach simply doesn’t work for adult spinal deformity.

When Is Surgery the Right Choice?

Most patients with adult scoliosis don’t need surgery immediately — and many do very well with physical therapy, core strengthening, anti-inflammatory medications, or targeted injections. But there are clear signals that surgery deserves serious consideration:

  1. Your symptoms are severe and not improving. If conservative treatment has been tried for three to six months without meaningful relief, surgery may offer the reset your spine needs.
  2. Your curve is progressing. If serial X-rays show your curve is getting worse — particularly past 50 degrees — waiting tends to mean a more complex operation later.
  3. You have significant nerve compression. Leg weakness, loss of bladder or bowel function, or severe radicular pain that doesn’t respond to injections often requires surgical decompression.
  4. Your posture has collapsed. Patients who can no longer stand upright — who stoop forward or lean to one side — often experience dramatic improvements in function and quality of life after realignment surgery.
  5. Your quality of life has declined significantly. This is underappreciated but crucial. Research consistently shows that adult scoliosis patients who undergo well-planned surgery report outcomes comparable to hip and knee replacement in terms of life improvement.

Surgery for adult spinal deformity has advanced enormously. With the integration of robotics, AI-driven surgical planning, and custom implants, outcomes are more predictable and recovery more manageable than ever before.

Taking the Next Step

If you’re living with back pain, difficulty walking, or a progressive curve, you deserve a thorough evaluation — not a dismissive “come back if it gets worse.”

Dr. Zeeshan Sardar is a scoliosis and spinal deformity specialist at NewYork-Presbyterian / Columbia University Medical Center in New York City. He specializes in the full spectrum of adult spinal deformity — from observation and conservative management to complex reconstructive surgery — and takes time to understand each patient’s goals before recommending any treatment.

To schedule a consultation, visit sardarspine.com or call our office directly. You don’t have to just live with it.

About Dr. Zeeshan Sardar
Dr. Sardar, MD, MSc, F.R.C.S.C, is Co-Chief of Spinal Deformity Surgery at NewYork-Presbyterian / Columbia University, specializing in adult and adolescent scoliosis, spinal deformity, and complex revision spine surgery. To schedule a consultation or second opinion, call 212-932-5187 or visit the contact page.

Pushing the Boundaries of Spine Surgery with Advanced Technology

Here’s a glimpse of my recent talk at the Saudi Spine Conference in Riyadh, where I had the privilege to discuss how I leverage cutting-edge technology to deliver precision-driven spine surgeries.

From robotics and AI-driven surgical planning to virtual modeling and custom implants, I’ve embraced a combination of tools that allow me to create tailored surgical plans for my patients—particularly those with scoliosis and spinal deformities.

What sets my approach apart is the seamless integration of these advanced technologies to ensure unparalleled accuracy and better outcomes for each patient.

Grateful for the opportunity to share my methods and to learn from the incredible expertise present at the conference. Together, we’re shaping the future of spine surgery!

#SpineSurgery #InnovationInMedicine #RoboticsInSurgery #SaudiSpineConference #PatientCenteredCare

About the Author

Dr. Zeeshan Sardar, MD, MSc, F.R.C.S.C is Co-Chief of Spinal Deformity Surgery, Director of Quality & Patient Safety, and Medical Director of the Spine Unit at Och Spine Hospital, NewYork-Presbyterian / Columbia University. Board-certified in orthopaedic surgery, he completed three spine fellowships — combined orthopedic and neurosurgical spine (Cedars-Sinai), artificial disc replacement (Texas Back Institute), and complex spinal deformity (Columbia) — and specializes in scoliosis, kyphosis, complex revision and Harrington rod revision surgery, and motion-preserving and robotic-assisted spine surgery. He is a member of the Scoliosis Research Society. Read full bio →

Honored to Share and Learn at the Saudi Spine Society

I had the privilege of being invited by the Saudi Spine Society to deliver a keynote talk on the evolution of sagittal alignment of the spine. It was an incredible opportunity to dive deep into a topic that continues to shape the future of spine care.

In addition, I had the pleasure of presenting on optimizing patients prior to scoliosis and spinal deformity surgery, sharing strategies to improve outcomes and enhance patient care.

The highlight of the event, however, was reconnecting with old friends and meeting new colleagues who are as passionate about advancing spine surgery as I am. I was truly impressed by the complexity of cases being tackled in Saudi Arabia and the exceptional quality of care being provided.

Grateful for the opportunity to exchange ideas and be inspired by the innovative work being done globally.

#SpineSurgery #MedicalInnovation #GlobalCollaboration #SaudiSpineSociety

About the Author

Dr. Zeeshan Sardar, MD, MSc, F.R.C.S.C is Co-Chief of Spinal Deformity Surgery, Director of Quality & Patient Safety, and Medical Director of the Spine Unit at Och Spine Hospital, NewYork-Presbyterian / Columbia University. Board-certified in orthopaedic surgery, he completed three spine fellowships — combined orthopedic and neurosurgical spine (Cedars-Sinai), artificial disc replacement (Texas Back Institute), and complex spinal deformity (Columbia) — and specializes in scoliosis, kyphosis, complex revision and Harrington rod revision surgery, and motion-preserving and robotic-assisted spine surgery. He is a member of the Scoliosis Research Society. Read full bio →

Case Study: Spondylolisthesis with Failed Prior Treatment — Surgical Correction and Recovery

The following is a three-part case study illustrating the evaluation, surgical planning, and outcome for a patient with lumbar spondylolisthesis and stenosis who had not improved with prior treatment. All imaging is shared with patient consent for educational purposes.

Part 1: Presentation

A 55-year-old woman presented with progressive back pain and bilateral leg pain that significantly limited her ability to walk. Imaging confirmed lumbar stenosis and spondylolisthesis at L4-5, disc degeneration at L3-4, and severe arthritis at L5-S1. She had already undergone a course of physical therapy and multiple epidural steroid injections with only short-term relief.

On examination, she had significant difficulty with prolonged standing and walking. Her X-rays on presentation are shown below, demonstrating the degree of listhesis and degenerative change at multiple levels.

AP standing X-ray showing lumbar spondylolisthesis at L4-5
AP standing X-ray demonstrating lumbar spondylolisthesis and multilevel degenerative changes.
Lateral extension X-ray showing lumbar spondylolisthesis
Lateral extension X-ray.
Lateral flexion X-ray showing dynamic instability at L4-5
Lateral flexion X-ray demonstrating dynamic instability.
Lumbar spine MRI sagittal view showing stenosis and disc degeneration
MRI sagittal view showing multilevel stenosis and disc degeneration.
MRI axial view at L4-5 showing severe stenosis
Axial MRI at L4-5 demonstrating severe central stenosis.
MRI axial view at L3-4 showing disc degeneration and stenosis
Axial MRI at L3-4.
MRI axial view at L5-S1 showing severe arthritis
Axial MRI at L5-S1 showing severe facet arthropathy.
MRI axial overview of lumbar spine
Axial MRI overview of the lumbar spine.

Part 2: Failed Prior Treatment and Worsening

Before presenting to Dr. Sardar, the patient had undergone a Vertiflex interspinous spacer procedure at another institution. Rather than improving her symptoms, the procedure was followed by progressive worsening. By the time of her follow-up evaluation, she was unable to stand upright and required a walker for mobility.

Repeat imaging confirmed that her underlying spondylolisthesis and sagittal malalignment had progressed. The interspinous spacer had not addressed the structural instability at the involved levels, and the added device had not stabilized the segment. Her clinical picture now represented a case of progressive lumbar deformity with neurogenic claudication and functional decline — a pattern that is not amenable to further conservative or minimally invasive intervention.

X-ray showing Vertiflex interspinous spacer in situ with worsened spondylolisthesis
X-ray showing the Vertiflex interspinous spacer in situ with worsened spondylolisthesis and alignment compared to prior imaging.
Post-Vertiflex AP X-ray showing lumbar alignment
AP X-ray at time of re-presentation.
Post-Vertiflex lateral X-ray showing sagittal malalignment
Lateral X-ray demonstrating sagittal malalignment at time of re-presentation.

Part 3: Surgical Treatment and Outcome

After a comprehensive evaluation — including full-length standing X-rays, CT, MRI, and medical optimization — the patient underwent posterior spinal reconstruction from L3 to S1/ilium with transforaminal lumbar interbody fusion (TLIF) at L4-S1. The Vertiflex device was removed as part of the procedure.

The surgical goals were to decompress the neural elements, restore lumbar lordosis, achieve solid segmental fixation, and correct the overall sagittal alignment. Robotic-assisted navigation was used for pedicle screw placement, and intraoperative neuromonitoring was maintained throughout the case.

At follow-up, the patient was able to stand upright without a walker — a functional milestone she had not achieved in years. Her leg pain resolved and her back pain improved significantly. Post-operative X-rays confirmed solid instrumentation, restored lordosis, and well-balanced sagittal alignment.

Post-operative AP X-ray showing L3-S1 posterior spinal fusion with pedicle screw instrumentation
Post-operative AP X-ray: L3-S1/ilium posterior spinal fusion with pedicle screw instrumentation and TLIF at L4-S1.
Post-operative lateral X-ray showing restored lumbar lordosis after L3-S1 fusion
Post-operative lateral X-ray demonstrating restoration of lumbar lordosis and sagittal balance.
Follow-up AP X-ray showing solid fusion and maintained alignment
Follow-up AP X-ray confirming solid instrumentation and maintained alignment.
Follow-up lateral X-ray showing maintained sagittal balance after lumbar reconstruction
Follow-up lateral X-ray showing maintained sagittal balance.

Case presented for educational purposes with patient consent. This post does not constitute individualized medical advice. Treatment decisions should be made in consultation with a qualified spine specialist based on individual clinical findings.

About Dr. Zeeshan Sardar
Dr. Sardar is Co-Chief of Spinal Deformity Surgery at NewYork-Presbyterian / Columbia University and specializes in complex spinal reconstruction, revision surgery, and adult spinal deformity. To schedule a consultation, call 212-932-5187 or visit the contact page.

New Research: Preoperative Optimization for Adult Spinal Deformity Surgery

Preoperative optimization for adult spinal deformity surgery - publication cover

Preoperative optimization of adult patients undergoing surgery for scoliosis, kyphosis, or spinal deformity is one of the most important — and often underappreciated — factors in achieving good surgical outcomes. Patients who present for major spinal deformity surgery with suboptimal bone density, nutritional deficiencies, poorly controlled diabetes, or other modifiable risk factors have measurably higher rates of complications, hardware failure, and prolonged recovery than those who have been appropriately optimized before surgery.

Our recent systematic review, published in Spine (March 2024), provides a practical, evidence-based framework for physicians managing patients in the preoperative period ahead of adult spinal deformity surgery.

Key Modifiable Risk Factors

The review identifies and synthesizes the evidence on the following modifiable risk domains:

  • Osteoporosis — bone quality directly affects pedicle screw purchase and fusion rates; medical treatment before elective deformity surgery is strongly supported by the evidence
  • Malnutrition — albumin and prealbumin levels predict wound healing and infection risk; nutritional supplementation should be initiated early in the preoperative period
  • Diabetes and glycemic control — HbA1c levels above 7.5–8% are associated with significantly higher surgical site infection rates and impaired fusion
  • Frailty — validated frailty indices predict major complication risk and should inform patient selection and timing for major deformity surgery
  • Tobacco use — smoking is associated with pseudarthrosis; smoking cessation before surgery meaningfully improves fusion rates

The central finding of the review is that systematic, proactive optimization across these domains — ideally coordinated through a multidisciplinary preoperative clinic — can meaningfully reduce complications and improve long-term outcomes in adult spinal deformity surgery.

Summary table of preoperative optimization factors for adult spinal deformity
Evidence summary for preoperative optimization in spinal deformity

Full citation: Katiyar P, Reyes J, Coury J, Lombardi J, Sardar Z. Preoperative Optimization for Adult Spinal Deformity Surgery: A Systematic Review. Spine. 49(5):304-312, 2024.

About Dr. Zeeshan Sardar
Dr. Sardar, MD, MSc, F.R.C.S.C, is Co-Chief of Spinal Deformity Surgery at NewYork-Presbyterian / Columbia University. He co-authored this systematic review and leads a multidisciplinary preoperative optimization program for complex spinal deformity patients. To schedule a consultation, call 212-932-5187 or visit the contact page.

This post is for educational purposes only and does not constitute individualized medical advice.