Cervical Disc Replacement vs. Fusion: What 10+ Years of Data Actually Shows

When patients are told they need surgery for a cervical disc problem — a herniated disc, a pinched nerve, or early signs of spinal cord compression — two procedures are typically on the table: anterior cervical discectomy and fusion (ACDF) and cervical disc replacement (arthroplasty). Both decompress the nerve or spinal cord through the same anterior approach. The key difference is what happens afterward: ACDF permanently immobilizes the treated level, while disc replacement preserves motion.

For much of the history of cervical spine surgery, ACDF was the default. Disc replacement was introduced as an alternative in the early 2000s and, after extensive clinical trials, received FDA approval. The question patients and surgeons reasonably asked was: does preserving motion actually matter? Does it translate into better outcomes over time? More than a decade of prospective randomized clinical trial data now gives us a meaningful answer.

What the trials measured

Multiple FDA investigational device exemption (IDE) trials compared cervical disc replacement to ACDF in patients with one or two level cervical disc disease causing radiculopathy or myelopathy. These were prospective, randomized, controlled trials — the highest level of clinical evidence — with follow-up extended to 7, 10, and in some cases beyond 10 years. Primary outcome measures included neck disability index, pain scores for neck and arm, neurological success, overall success, and the need for secondary surgical procedures.

What the data shows

Neurological outcomes are equivalent. Both procedures achieve similar rates of arm pain relief, neurological recovery from radiculopathy, and neurological stabilization in myelopathy. This was expected and confirmed consistently across trials. Patients should not choose one procedure over the other based on an expectation of better nerve decompression — the decompression is identical.

Disc replacement patients have lower reoperation rates at adjacent levels. This is the most clinically significant finding of the long-term data. Multiple trials have demonstrated that patients treated with disc replacement have significantly lower rates of requiring a second surgery at adjacent levels compared to patients treated with ACDF. At 10-year follow-up in several trials, the absolute difference in adjacent level reoperation rates has ranged from roughly 5 to 10 percentage points — meaningful numbers when considering a surgical decision.

The mechanism is straightforward: ACDF eliminates motion at the fused level, transferring increased mechanical stress to the adjacent discs and facet joints. Over years to decades, this accelerated stress contributes to degeneration at adjacent levels. Disc replacement preserves motion at the treated level, distributing forces more normally.

Disc replacement patients maintain functional range of motion. Long-term imaging in disc replacement patients confirms that the treated level retains functional motion in the majority of cases.

Safety profiles are comparable. The trials have not demonstrated a higher rate of serious complications with disc replacement compared to ACDF.

What the data does not show

It would be inaccurate to conclude that disc replacement is universally superior to ACDF. The trials enrolled carefully selected patients who met specific candidacy criteria — preserved lordosis, no significant facet arthritis, no instability, 1–2 level disease. For patients with cervical kyphosis, significant facet joint disease, instability, multilevel spondylosis, or OPLL, ACDF remains the appropriate procedure and disc replacement data does not apply.

The difference in adjacent level reoperation at 10 years is meaningful but not dramatic. The absolute numbers mean that the majority of ACDF patients do not require adjacent level reoperation. The data supports offering disc replacement to candidates — it does not mean ACDF patients are destined for revision surgery.

What this means for patients

For patients who meet the candidacy criteria for cervical disc replacement — 1–2 level disc disease, preserved lordosis, no significant facet arthritis or instability — the 10-year data supports disc replacement as the preferred option when the goal is minimizing the likelihood of future surgery at adjacent levels while achieving equivalent neurological outcomes.

For patients who do not meet these criteria, ACDF remains an excellent procedure with a long track record of success. The choice between the two should be based on individual anatomy and pathology, not on general preference for one technique over another.

Dr. Sardar completed a dedicated fellowship in artificial disc replacement at the Texas Back Institute and is equally expert in both procedures. His approach is to evaluate every patient for disc replacement candidacy and recommend genuinely what is best for each patient’s anatomy, diagnosis, and goals.

References

  1. Nunley PD, Hisey M, Smith M, Stone MB. Cervical Disc Arthroplasty vs Anterior Cervical Discectomy and Fusion at 10 Years: Results From a Prospective, Randomized Clinical Trial at 3 Sites. Int J Spine Surg. 2023;17(2):230–240. PMID: 37028803
  2. The Incidence of Adjacent Segment Pathology After Cervical Disc Arthroplasty Compared With Anterior Cervical Discectomy and Fusion: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. World Neurosurg. 2022. PMID: 35085804

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 →

This post is for educational purposes only and does not constitute individualized medical advice. The clinical trial data referenced reflects the published literature on FDA IDE trials for cervical arthroplasty. Please consult a qualified spine specialist to discuss your specific situation.

Signs You May Have Cervical Myelopathy — and Why Early Recognition Matters

Cervical myelopathy is one of the most commonly missed diagnoses in spine medicine. It is caused by compression of the spinal cord in the neck — not just a pinched nerve, but the cord itself — and it produces a characteristic pattern of symptoms that develop so gradually, and overlap so much with other conditions, that it often goes unrecognized for years.

The consequences of delayed diagnosis can be serious. Unlike many spinal conditions where the natural history is benign and self-limiting, cervical myelopathy tends to worsen over time. The longer the spinal cord remains compressed, the more likely it is that irreversible injury will occur — injury that surgery cannot fully reverse, even when performed correctly. Early recognition is therefore not just helpful. It is important.

What is cervical myelopathy?

The cervical spine — the neck — is the most common site of spinal cord compression in adults. As the discs degenerate and bone spurs form with age, the spinal canal can narrow to the point where the cord is compressed between degenerative structures in front and thickened ligaments behind. This is called cervical spondylotic myelopathy, the most common cause of spinal cord dysfunction in adults over 55. Unlike a pinched nerve (radiculopathy), which compresses a single nerve root and produces symptoms in a specific arm or hand distribution, myelopathy compresses the cord itself — producing a broader, more diffuse pattern of dysfunction that affects the hands, legs, balance, and sometimes the bladder.

The warning signs

Hand clumsiness. Difficulty with fine motor tasks — buttoning shirts, handling small objects, writing by hand, typing — is often one of the earliest signs of myelopathy. This is frequently attributed to carpal tunnel syndrome, arthritis, or simply getting older.

Grip weakness. Difficulty opening jars, holding objects, or maintaining grip strength. In more advanced myelopathy, patients may drop objects without warning.

Gait unsteadiness. A subtle change in walking — wider stance, shuffling steps, difficulty on uneven surfaces, a tendency to veer to one side, or a sense that the legs are not responding normally. This is frequently attributed to inner ear problems, peripheral neuropathy, or normal aging.

Arm or hand numbness. Diffuse numbness or tingling in the arms or hands, not necessarily following a single nerve root distribution. This is one reason myelopathy is confused with peripheral neuropathy or carpal tunnel syndrome.

Electric shock with neck flexion (Lhermitte’s sign). A shooting electrical sensation radiating down the spine or into the limbs when bending the neck forward. This is a relatively specific sign of cervical cord compression and should prompt immediate evaluation.

Leg stiffness or spasticity. A sense that the legs are stiff, heavy, or difficult to lift. In more advanced cases, patients notice they cannot flex their hips and knees freely when walking.

Bladder urgency or difficulty. Urinary urgency, frequency, or in advanced cases incontinence can develop as myelopathy progresses. This is a later symptom and indicates significant cord compression.

What it is often mistaken for

Patients with cervical myelopathy are frequently told their symptoms are due to carpal tunnel syndrome, peripheral neuropathy (particularly in diabetic patients), multiple sclerosis, normal aging, or Parkinson’s disease. If you have been evaluated for any of these conditions without a clear diagnosis, cervical myelopathy should be considered. An MRI of the cervical spine is the key diagnostic study.

Why early treatment matters

Cervical myelopathy does not reliably improve on its own. Without surgical decompression, most patients will plateau at best and continue to worsen at worst. The risk of sudden neurological worsening after minor trauma — a fall, a car accident, or even forceful neck movement — is significantly elevated in patients with significant cord compression.

Surgery for cervical myelopathy halts progression and in most patients produces meaningful recovery, particularly when performed before severe cord signal change (myelomalacia) is visible on MRI. The longer the cord has been compressed and the more signal change present, the less complete the recovery tends to be. This is why early recognition matters.

When to seek evaluation

If you recognize any of the following in yourself or a family member, a spine evaluation is warranted: unexplained hand clumsiness or deterioration in fine motor skills; gait unsteadiness or balance problems without a clear explanation; diffuse arm or hand numbness not clearly explained by a peripheral nerve condition; electric shock sensations with neck flexion; or leg stiffness or difficulty walking that has developed gradually.

Dr. Sardar specializes in the diagnosis and surgical treatment of cervical myelopathy at the Och Spine Hospital at NewYork-Presbyterian / Columbia University and performs the full range of decompressive procedures tailored to each patient’s anatomy and degree of compression.

References

  1. Fehlings MG, Wilson JR, Kopjar B, et al. Efficacy and safety of surgical decompression in patients with cervical spondylotic myelopathy: results of the AOSpine North America prospective multi-center study. J Bone Joint Surg Am. 2013;95(18):1651–1658. PMID: 24048552
  2. Karadimas SK, Erwin WM, Ely CG, Dettori JR, Fehlings MG. Pathophysiology and natural history of cervical spondylotic myelopathy. Spine (Phila Pa 1976). 2013;38(22 Suppl 1):S21–S36. PubMed
  3. Matz PG, Anderson PA, Holly LT, et al. The natural history of cervical spondylotic myelopathy. J Neurosurg Spine. 2009;11(2):104–111. PubMed

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 →

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

I Had a Harrington Rod in the 1970s or 80s. What Should I Know Now?

If you had surgery for scoliosis in the 1960s, 70s, or 80s, you almost certainly had a Harrington rod. At the time, it was a remarkable advance — the first instrumented system that could actually straighten a scoliosis curve and hold it in place while the spine fused. For many patients, it delivered real results and a meaningful improvement in their curve.

But decades later, a significant number of those same patients are experiencing problems they weren’t warned about — and many don’t know that what they’re experiencing has a name, a cause, and in many cases a surgical solution.

What the Harrington rod did — and what it didn’t

The Harrington rod worked by distraction: a metal rod was hooked to the spine at the top and bottom of the scoliosis curve, then lengthened to pull the curve straighter. It corrected the side-to-side curvature reasonably well by the standards of its time. What it didn’t do was maintain the normal front-to-back curves of the spine — particularly the inward curve of the lower back, called lumbar lordosis.

Modern spinal instrumentation uses multiple anchoring points along the entire curve and is designed to restore three-dimensional spinal alignment, including lordosis. Harrington rods were a single-rod system with no ability to do this. The result, in many patients, is that the scoliosis was corrected but the lumbar spine was left flat — or even reversed into slight kyphosis. At the time, this wasn’t fully understood. Now it is.

The most common late complication: flatback deformity

Flatback deformity is the loss of lumbar lordosis — and it is the single most common and most disabling late complication of Harrington rod surgery. When the lower spine is flat, the body’s center of gravity shifts forward. To avoid falling, patients must continuously compensate by bending their knees, thrusting their hips forward, and recruiting enormous muscular effort just to stay upright.

Early on, this compensation is manageable. Over years and decades, it becomes exhausting and then impossible. Patients describe it as follows: they can no longer stand upright without tremendous effort. Walking any distance becomes painful. Standing at a kitchen counter or a social event is agonizing. They lean forward when they walk, which people around them may notice before they do.

Flatback deformity typically begins to manifest in a patient’s 30s or 40s — well after the original surgery — and worsens slowly over time. Many patients assume this is simply aging. It is not. It is a mechanical consequence of the original instrumentation, and it is correctable.

Other late complications to know about

Hardware failure. The rod, hooks, and any supplemental wiring can fracture, dislodge, or loosen over decades. Hardware failure may cause a sudden change in symptoms — increased pain, a change in posture, or a palpable change under the skin. It is diagnosed on imaging and typically requires revision surgery.

Pseudarthrosis. Harrington rod fusions were performed with older bone grafting techniques that had lower fusion rates than modern methods. Some patients develop pseudarthrosis — a failure of the fusion to achieve solid bony union — that becomes symptomatic years later. CT scan is the most reliable way to diagnose it.

Adjacent segment degeneration. A long spinal fusion places increased mechanical stress on the discs and joints immediately above and below the fused segment. Over decades, this accelerated wear causes degeneration at adjacent levels that may produce new symptoms not present at the time of the original surgery.

Progressive curve. Some patients find that their scoliosis curve has progressed despite the fusion, either through pseudarthrosis, crankshaft phenomenon, or extension of the curve into unfused segments.

New neurological symptoms. Leg pain, numbness, weakness, or bladder changes in a patient with prior Harrington rod surgery warrant prompt evaluation. These symptoms can arise from adjacent segment stenosis, hardware migration, instability, or deformity progression causing nerve compression.

What a modern evaluation looks like

If you had Harrington rod surgery and are experiencing new or worsening symptoms — or simply want to understand the current state of your spine — a modern evaluation should include full-length standing X-rays to assess overall alignment and sagittal balance; CT scan to evaluate fusion integrity, hardware status, and bone quality; MRI to assess the discs, nerves, and cord above, below, and within the fused segment; and a detailed clinical examination by a surgeon familiar with late Harrington rod complications.

Can anything be done?

Yes — in many cases, significantly. Flatback deformity can be corrected with an osteotomy (a controlled cut through the fused bone) that restores lumbar lordosis and rebalances the spine. The most powerful single-level osteotomy — the pedicle subtraction osteotomy (PSO) — can provide 30–40 degrees of correction at one level. Adjacent segment problems can be addressed with revision decompression or extension of the fusion construct. Hardware failure can be revised with modern pedicle screw systems that provide far superior fixation.

These are not simple operations — they are among the most technically demanding procedures in spine surgery. But for appropriately selected patients, the functional gains can be dramatic. Many describe being able to stand upright without pain for the first time in years.

A note on age

Many patients with Harrington rods are now in their 60s, 70s, and even 80s. Age alone is not a contraindication to revision surgery. What matters is overall health, bone quality, functional status, and the extent of surgery required. A thorough pre-operative evaluation at a high-volume deformity center will give you the clearest picture of what is realistic for your situation.

If you have been told that nothing can be done, or that you are too old or too high-risk, a second opinion from a surgeon who specializes in this population is entirely appropriate.

Dr. Sardar is Co-Chief of Spinal Deformity Surgery at the Och Spine Hospital at NewYork-Presbyterian / Columbia University and specializes in the evaluation and revision of late Harrington rod complications. Telemedicine consultations are available for patients in NY, NJ, CT, FL, PA, MO, CA, and TX.

References

  1. Louie PK, Iyer S, Khanna K, et al. Revision Strategies for Harrington Rod Instrumentation: Radiographic Outcomes and Complications. Global Spine J. 2022. PMID: 33000651
  2. Bridwell KH, et al. Pedicle subtraction osteotomy for the treatment of fixed sagittal imbalance. J Bone Joint Surg Am. 2003;85(3):454–463. PMID: 12637431

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 →

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

Preparing for Major Spine Surgery: What Patients Need to Know

Major spine surgery — whether a long-segment scoliosis correction, a complex revision reconstruction, a pedicle subtraction osteotomy, or a multilevel cervical procedure — is not something that happens to a passive patient. What you do in the weeks and months before your operation significantly affects your outcomes. Patients who arrive at surgery in the best possible physical and medical condition heal faster, have fewer complications, achieve better fusion rates, and are more satisfied with their results than patients who do not prepare.

This is not anecdotal. Preoperative optimization is now a well-studied component of major spinal surgery, and the evidence for its impact on outcomes is substantial. Here is what it involves and why it matters.

Bone Density: The Foundation of Fusion

For any spinal fusion procedure, the quality of the bone is fundamental. Pedicle screws and interbody implants rely on bone for their fixation. If the bone is osteoporotic — weak and porous — screws can pull out, cages can subside, and fusion rates fall. Osteoporosis is one of the most common and most underrecognized contributors to surgical failure in adult spinal surgery.

Before major elective spine surgery, bone density should be formally assessed with a DEXA scan. If osteoporosis or significant osteopenia is identified, medical treatment should be initiated before surgery whenever the surgical timeline allows. Anabolic agents such as teriparatide (Forteo), Abaloparatide (Tymlos), and Romosozumab (Evenity) have been shown in multiple studies to improve bone density over a period of weeks to months and may significantly reduce the risk of hardware failure and non-union in high-risk patients. This is an area where close collaboration with an endocrinologist or metabolic bone specialist is valuable.

Nutrition: Healing Requires Fuel

Nutritional status has a direct and well-documented impact on surgical outcomes. Protein is the raw material for wound healing, immune function, and bone formation. Patients who are malnourished before surgery have significantly higher rates of wound complications, infection, and poor healing.

Before major spine surgery, albumin and prealbumin levels are checked as markers of nutritional status. If deficits are identified, dietary correction and protein supplementation are initiated before the operation. Vitamin D deficiency — extremely common in the general population — is also addressed, as vitamin D is essential for calcium absorption and bone metabolism. Patients who are significantly underweight or who have recently lost significant weight should be evaluated by a nutritionist before elective surgery.

Smoking Cessation: Non-Negotiable for Fusion

Smoking is one of the strongest modifiable risk factors for surgical complications in spine surgery. Nicotine impairs bone healing at a biological level — it reduces blood flow to healing tissue, inhibits osteoblast (bone-forming cell) activity, and dramatically increases the rate of pseudarthrosis (non-union). Studies consistently show pseudarthrosis rates two to three times higher in smokers than non-smokers undergoing spinal fusion.

Smoking also increases the risk of wound infection, respiratory complications under anesthesia, and cardiovascular events. Cessation before surgery — ideally at least 6 to 8 weeks prior — significantly reduces these risks. For elective major spine surgery, smoking cessation is strongly encouraged and in some cases required before proceeding.

Diabetes Control

Elevated blood sugar impairs immune function and wound healing. Diabetic patients with poor glycemic control have significantly higher rates of surgical site infection, wound dehiscence, and slower recovery. Hemoglobin A1c (HbA1c) — a measure of average blood sugar over the preceding 3 months — is checked before major elective spine surgery. An HbA1c above 7.5 to 8.0 is associated with significantly increased complication risk, and surgery may be deferred until glucose control is optimized in close collaboration with the patient’s endocrinologist or primary care physician.

Cardiovascular and Pulmonary Optimization

Major spine surgery — particularly long-segment reconstruction — is physiologically demanding. Blood loss, fluid shifts, and prolonged anesthesia place significant demands on the heart and lungs. Patients with known cardiac or pulmonary conditions should be evaluated and cleared by the appropriate specialist before surgery. In some cases, previously undiagnosed conditions are identified during pre-surgical evaluation and need to be addressed before proceeding safely.

For patients with limited cardiovascular reserve, a structured prehabilitation program — supervised aerobic exercise in the weeks before surgery — has been shown to improve postoperative recovery and reduce complication rates. Even modest improvement in cardiovascular fitness before a major operation translates into meaningful benefits during recovery.

Blood Management

Major spine surgery, particularly long-segment deformity correction, can involve significant blood loss. Preoperative blood management — identifying and treating anemia before surgery — reduces the likelihood that patients will require blood transfusion, which carries its own risks. Iron deficiency, the most common cause of preoperative anemia, is treated with oral or intravenous iron supplementation before surgery. Erythropoiesis-stimulating agents are used in selected cases.

Intraoperatively, cell salvage — a technology that collects, processes, and re-infuses the patient’s own blood during surgery — is used routinely for major deformity cases, significantly reducing the need for donor blood transfusion.

Medication Review

Several common medications need to be adjusted before spine surgery:

  • Blood thinners (warfarin, aspirin, clopidogrel, newer anticoagulants) — must be stopped before surgery according to a specific schedule to reduce bleeding risk; requires coordination with your cardiologist or prescribing physician to create the bridging plan
  • NSAIDs (ibuprofen, naproxen) — inhibit platelet function and bone healing; should be stopped before surgery and avoided during the fusion healing period
  • Steroids — chronic steroid use impairs wound healing and bone quality; a management plan is made in coordination with the prescribing physician
  • Biologics and immunosuppressants — used for rheumatologic conditions; may need to be held before surgery to reduce infection risk; requires coordination with the treating rheumatologist

Mental Health and Psychosocial Preparation

This is one of the most overlooked aspects of surgical preparation. Depression and anxiety are strongly associated with worse patient-reported outcomes after spine surgery — independent of the technical quality of the operation. Patients who arrive at surgery in a better psychological state, with realistic expectations and adequate social support, consistently do better than those who do not.

Before major surgery, it is worth asking yourself: Do I have adequate support at home during recovery? Do I understand what the recovery period will involve? Are my expectations realistic about what surgery can and cannot achieve? Depression and anxiety screening is part of the preoperative evaluation for major surgery, and patients identified with significant mood disorders are encouraged to address these with appropriate support before proceeding.

Practical Preparation: Your Home and Your Recovery

Before major spine surgery, practical home preparation makes recovery significantly easier:

  • Arrange for help at home during the first 2 to 4 weeks; you will not be able to drive and will need assistance with daily tasks
  • Set up a comfortable sleeping and resting area on the ground floor if you have stairs that will be difficult to manage initially
  • Prepare and freeze meals in advance; cooking will be difficult in the early recovery period
  • Fill all prescriptions before surgery so they are ready when you come home
  • Arrange transportation for post-operative appointments
  • If you have a physically demanding job, discuss your return-to-work timeline with Dr. Sardar well before surgery so you can arrange appropriate leave

The Bottom Line

Major spine surgery is a collaboration between patient and surgeon. The surgeon’s job is to perform the procedure safely and skillfully. The patient’s job is to arrive at the operating room in the best possible condition — with optimized bone density, nutrition, blood sugar, cardiovascular fitness, and medications. Patients who invest in this preparation consistently achieve better outcomes. Those who do not leave recoverable gains on the table.

Dr. Sardar and his team will walk you through every aspect of preoperative optimization specific to your procedure at your pre-surgical appointments. Nothing on this list should come as a surprise — preparation starts at the initial consultation, not the week before surgery.

References

  1. Glassman SD, et al. The effect of cigarette smoking and smoking cessation on spinal fusion. Spine (Phila Pa 1976). 2000;25(20):2608–2615. PMID: 11034645
  2. Zhang AS, Khatri S, Balmaceno-Criss M, Alsoof D, Daniels AH. Medical optimization of osteoporosis for adult spinal deformity surgery: a state-of-the-art evidence-based review of current pharmacotherapy. Spine Deform. 2023;11(3):579–596. PMID: 36454531
  3. Buerba RA, Sharma A, Ziino C, Arzeno A, Ajiboye RM. Bisphosphonate and Teriparatide Use in Thoracolumbar Spinal Fusion: A Systematic Review and Meta-analysis of Comparative Studies. Spine (Phila Pa 1976). 2018. PubMed

About Dr. Zeeshan Sardar
Dr. Sardar is Co-Chief of Spinal Deformity Surgery at NewYork-Presbyterian / Columbia University and specializes in major spinal deformity correction, revision surgery, and complex spine reconstruction. He takes a comprehensive approach to preoperative optimization for every patient undergoing major surgery. 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 and preparation plan.

What Is Spinal Stenosis — and When Is Surgery the Answer?

Spinal stenosis is one of the most common reasons adults over 60 seek care from a spine specialist. It is also one of the most undertreated conditions in spine medicine — patients often live with significant functional limitation for years, assuming their symptoms are simply part of aging, before being evaluated by a surgeon. Understanding what stenosis is, why it causes the symptoms it does, and what treatment options exist can help patients make better-informed decisions about their care.

What Is Spinal Stenosis?

Spinal stenosis is a narrowing of the spinal canal or the openings through which nerve roots exit the spine (neural foramina). When the canal narrows sufficiently, it compresses the spinal cord or nerve roots, causing the characteristic symptoms of the condition. Stenosis is almost always caused by degenerative changes — the cumulative effect of disc degeneration, facet joint arthritis, and thickening of the ligamentum flavum (a ligament that lines the back of the spinal canal) over decades.

Stenosis can occur anywhere in the spine but is most common and clinically significant in two locations:

  • Lumbar stenosis — narrowing in the lower back; compresses the nerve roots of the cauda equina (the bundle of nerve roots below the spinal cord); produces the classic syndrome of neurogenic claudication
  • Cervical stenosis — narrowing in the neck; can compress the spinal cord itself (producing myelopathy) or the cervical nerve roots (producing radiculopathy), or both

Symptoms: Lumbar vs. Cervical Stenosis

The symptoms of stenosis differ depending on where it occurs.

Lumbar Stenosis

The hallmark symptom of lumbar stenosis is neurogenic claudication — leg pain, heaviness, cramping, or weakness that comes on with walking or standing and is relieved by sitting, lying down, or leaning forward (such as on a shopping cart). This positional pattern is the key distinguishing feature of neurogenic claudication from vascular claudication (caused by arterial disease), which does not improve with bending forward.

Patients with lumbar stenosis often describe a progressive decline in walking tolerance — being able to walk only half a block before needing to stop and sit, when a year ago they could walk a mile. Back pain is common but is often less prominent than the leg symptoms. Bladder symptoms — urgency or frequency — can occur in severe cases.

Cervical Stenosis

Cervical stenosis causing nerve root compression (radiculopathy) produces arm pain, numbness, or weakness in a specific distribution. Cervical stenosis causing spinal cord compression (myelopathy) produces a broader pattern of dysfunction: hand clumsiness, gait unsteadiness, leg spasticity, and in severe cases bladder dysfunction. Cervical myelopathy is frequently misdiagnosed as carpal tunnel syndrome, peripheral neuropathy, or the normal effects of aging. It requires prompt surgical evaluation once identified.

Diagnosis

The diagnosis of spinal stenosis is made by combining the clinical history and examination findings with imaging. MRI is the primary diagnostic study — it shows the degree of canal and foraminal narrowing and identifies which nerve roots are compressed. CT myelography is used in patients who cannot undergo MRI or when greater bony detail is needed. Standing X-rays assess alignment and stability. Electrodiagnostic studies (EMG/nerve conduction) are occasionally used to differentiate stenosis from peripheral nerve conditions.

Importantly, stenosis on MRI is extremely common in older adults — many people have significant stenosis on imaging but no symptoms. Imaging findings alone do not indicate a need for treatment. The decision to treat — and how — is based on the patient’s symptoms and functional limitations, not the MRI report.

Non-Surgical Treatment

For most patients with lumbar stenosis and mild to moderate symptoms, non-surgical treatment is the appropriate first step:

  • Physical therapy — flexion-based exercises and core strengthening can reduce symptoms and improve walking tolerance in many patients; lumbar extension tends to worsen stenosis symptoms and is avoided
  • Epidural steroid injections — can provide meaningful but typically temporary relief of leg symptoms; most useful as a bridge or when surgery carries elevated risk
  • Activity modification — using a walking aid (cane or walker) allows forward lean and reduces leg symptoms during activity; cycling is often better tolerated than walking
  • Weight management — reducing load on the lumbar spine can improve symptoms

Non-surgical treatment does not decompress the nerve roots. It can help manage symptoms, but it does not change the underlying anatomy. For patients with cervical stenosis causing myelopathy, conservative treatment is generally not recommended as the primary approach — the spinal cord compression requires surgical decompression.

When Is Surgery Indicated?

Surgery for spinal stenosis is recommended when:

  • Conservative treatment has failed to provide adequate relief after a reasonable trial (typically 3 to 6 months for lumbar stenosis without neurological deficit)
  • Functional limitation is significant — inability to walk more than a short distance, difficulty with basic activities of daily living, or progressive decline in walking tolerance
  • Progressive neurological deficit — worsening leg weakness, foot drop, or bladder or bowel dysfunction are indications for expedited surgery
  • Cervical myelopathy — once moderate myelopathy is diagnosed, surgery is generally recommended without prolonged delay; the natural history of myelopathy is progressive deterioration, and irreversible cord injury can occur with continued compression or minor trauma

Surgical Options

The surgical approach for stenosis depends on the location, the number of levels involved, the presence of instability or deformity, and the patient’s overall anatomy.

For lumbar stenosis:

  • Laminectomy — removal of the lamina and thickened ligamentum flavum to decompress the nerve roots; the most common surgery for lumbar stenosis; may be performed minimally invasively in selected patients
  • Laminectomy with fusion — when instability or spondylolisthesis is present alongside stenosis, decompression alone may worsen instability; fusion is added to stabilize the segment
  • Minimally invasive decompression — for carefully selected patients with focal stenosis without instability, minimally invasive techniques offer equivalent decompression with faster recovery

For cervical stenosis:

  • ACDF or cervical disc replacement — for anterior compression at one to three levels
  • Laminoplasty — a posterior procedure that expands the canal by hinging the laminae open; well-suited for multilevel cervical stenosis with preserved lordosis
  • Laminectomy with posterior cervical fusion — for multilevel stenosis with kyphosis or instability

What to Expect from Surgery

Surgery for spinal stenosis, in appropriately selected patients, is highly effective. The SPORT trial showed that patients treated surgically for lumbar spinal stenosis had substantially greater improvement in pain, function, and walking ability than those treated non-operatively, with the clearest advantage through the first four years of follow-up. Longer-term results at eight years were more mixed: the benefit remained durable in the observational group, while the gap between the surgical and non-surgical groups narrowed over time in the randomized comparison — in part because many patients initially assigned to non-operative care ultimately chose surgery. Leg symptoms typically improve more reliably than back pain, and neurological recovery depends on the severity and duration of compression before surgery.

The best outcomes occur when surgery is performed before irreversible nerve injury has occurred — which is why timely evaluation matters, particularly for patients with progressive neurological symptoms.

References

  1. Weinstein JN, Tosteson TD, Lurie JD, et al. Surgical versus nonsurgical therapy for lumbar spinal stenosis. N Engl J Med. 2008;358(8):794–810. PubMed
  2. Weinstein JN, Tosteson TD, Lurie JD, et al. Surgical versus nonoperative treatment for lumbar spinal stenosis: four-year results of the Spine Patient Outcomes Research Trial. Spine (Phila Pa 1976). 2010;35(14):1329–1338. PMID: 20453723
  3. Lurie JD, Tosteson TD, Tosteson A, et al. Long-term outcomes of lumbar spinal stenosis: eight-year results of the Spine Patient Outcomes Research Trial (SPORT). Spine (Phila Pa 1976). 2015;40(2):63–76. PubMed

About Dr. Zeeshan Sardar
Dr. Sardar is Co-Chief of Spinal Deformity Surgery at NewYork-Presbyterian / Columbia University and treats the full spectrum of spinal stenosis — cervical and lumbar — from minimally invasive decompression to complex multilevel reconstruction. 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.

Spondylolisthesis: When Does It Need Surgery?

Spondylolisthesis is one of the most common conditions evaluated by spine surgeons — and one of the most commonly misunderstood. Patients are often told they have a “slipped disc” when what they actually have is a slipped vertebra. The two conditions are different, their symptoms overlap in important ways, and the treatment decisions are not always straightforward. Here is what spondylolisthesis is, why it causes symptoms, and when surgery is and is not the right answer.

What Is Spondylolisthesis?

Spondylolisthesis is the forward displacement of one vertebra over the vertebra below it. The word comes from the Greek spondylos (vertebra) and olisthesis (slipping). It is graded by severity using the Meyerding classification, from Grade I (less than 25% slip) to Grade IV (greater than 75% slip), with Grade V (spondyloptosis) reserved for complete dislocation.

The most common location is the lower lumbar spine, particularly L4–L5 and L5–S1. There are several types, each with a different underlying cause:

  • Degenerative spondylolisthesis — the most common type in adults; occurs when the disc and facet joints degenerate and lose their ability to restrain normal motion, allowing one vertebra to slip forward on the one below; most common at L4–L5 and more prevalent in women and older adults
  • Isthmic spondylolisthesis — caused by a stress fracture (spondylolysis) of the pars interarticularis, a small bridge of bone in the posterior arch; common in young athletes, particularly gymnasts, football linemen, and weightlifters; the fracture allows the vertebra to slip forward; most common at L5-S1
  • Congenital spondylolisthesis — due to abnormal development of the posterior spinal elements at birth; less common
  • Iatrogenic or postoperative spondylolisthesis — can develop after laminectomy or other posterior surgery that destabilizes the spinal segment

What Symptoms Does It Cause?

Many people have spondylolisthesis and never know it — the slip is discovered incidentally on imaging obtained for another reason. Whether spondylolisthesis causes symptoms depends on the degree of slip, the presence of stenosis, the stability of the segment, and individual factors including age and activity level.

When it does cause symptoms, the most common presentations include:

  • Lower back pain — often worse with activity, prolonged standing, or extension (bending backward); typically relieved by sitting or flexion
  • Leg pain, numbness, or weakness — caused by nerve root compression from the slipped vertebra narrowing the neural foramen or from associated stenosis of the spinal canal; may mimic sciatica
  • Neurogenic claudication — leg symptoms that worsen with walking or standing and improve with sitting or leaning forward; a hallmark of lumbar stenosis that accompanies many degenerative spondylolisthesis cases
  • Hamstring tightness — particularly in younger patients with isthmic spondylolisthesis; a classic but often overlooked finding
  • Visible postural change — in high-grade slips, patients may develop a characteristic crouched posture or altered gait

When Is Non-Surgical Treatment Appropriate?

The majority of patients with spondylolisthesis — including those with significant symptoms — can be managed successfully without surgery. Non-surgical treatment is the appropriate first step for most patients and may include:

  • Physical therapy — core strengthening, postural training, and flexion-based exercises can significantly reduce symptoms and improve function in many patients; this is the most important non-surgical intervention
  • Activity modification — avoiding activities that aggravate symptoms while maintaining general fitness
  • Anti-inflammatory medications — NSAIDs can help manage pain flares
  • Epidural steroid injections — can provide meaningful, though typically temporary, relief of leg pain from nerve compression; most useful as a bridge to physical therapy or while awaiting surgical planning
  • Bracing — particularly in adolescents with isthmic spondylolysis or low-grade spondylolisthesis; bracing during the acute phase can allow the stress fracture to heal

An important point: the degree of slip on imaging does not directly predict the severity of symptoms or the need for surgery. A Grade II slip in one patient may cause debilitating symptoms; the same grade in another patient may cause none. Treatment decisions are driven by symptoms and function, not imaging findings alone.

When Is Surgery Indicated?

Surgery for spondylolisthesis is recommended when:

  • Conservative treatment has failed — typically after 3 to 6 months of appropriate non-surgical management without adequate improvement in symptoms and function
  • Progressive neurological deficit — worsening leg weakness, foot drop, or loss of bladder or bowel control warrant urgent or expedited surgical evaluation regardless of how long conservative treatment has been tried
  • Severe or intractable pain — pain that significantly impairs quality of life and does not respond to non-surgical measures
  • High-grade slip — Grade III or IV slips are generally unstable and carry a higher risk of neurological compromise; surgery is more frequently recommended even in the absence of severe symptoms
  • Progressive slip — documented worsening of the degree of displacement on serial imaging, particularly in adolescents with isthmic spondylolisthesis

What Does Surgery Involve?

Surgery for spondylolisthesis typically involves two goals: decompression of the compressed nerve roots and stabilization (fusion) of the unstable segment. The specific procedure depends on the type and grade of spondylolisthesis, the degree of stenosis, the patient’s anatomy, and other factors.

Common surgical approaches include:

  • Posterior lumbar interbody fusion (PLIF) or transforaminal lumbar interbody fusion (TLIF) — the most common approaches; decompression is performed from the back, an interbody cage is placed in the disc space for stability and fusion, and pedicle screws and rods complete the construct
  • Minimally invasive TLIF (MIS-TLIF) — for selected patients, the same procedure can be performed through smaller incisions with less muscle disruption
  • Anterior lumbar interbody fusion (ALIF) — an anterior approach may be used alone or in combination with posterior fixation for selected cases, particularly when greater disc height restoration or lordosis correction is needed
  • Reduction of the slip — in high-grade spondylolisthesis, partial reduction of the vertebral displacement before fusion may be performed to improve alignment and neural decompression; this is technically demanding surgery that requires specific expertise

Dr. Sardar uses robotic-assisted navigation and intraoperative neuromonitoring as standard for all spondylolisthesis fusions, providing enhanced screw accuracy and real-time feedback on nerve function throughout the procedure.

What to Expect from Surgery

Surgery for spondylolisthesis, when performed in appropriately selected patients, reliably improves leg pain and neurological symptoms. Back pain improvement is meaningful in most patients, though complete elimination of all back pain is not guaranteed. The landmark SPORT trial — one of the largest surgical trials in spine surgery — demonstrated significant and durable advantages of surgery over non-operative care for symptomatic degenerative spondylolisthesis at 4-year follow-up.

Recovery from a single-level lumbar fusion for spondylolisthesis typically involves a hospital stay of 1 to 3 days, return to light activity within 4 to 6 weeks, and return to most normal activities within 3 to 4 months. Full fusion maturation takes 12 months.

About Dr. Zeeshan Sardar
Dr. Sardar is Co-Chief of Spinal Deformity Surgery at NewYork-Presbyterian / Columbia University and treats the full spectrum of lumbar spine conditions including spondylolisthesis, stenosis, disc herniation, and complex deformity. 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.

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.