What is Fusion?
Spinal fusion is a surgery designed to eliminate painful motion between two or more vertebrae by encouraging them to grow into a single, solid piece of bone. The plates, screws, rods, and cages used in these procedures are not the fusion itself — they are scaffolding that holds the spine steady while your body does the biological work of building new bone across the intended bridge. Understanding that distinction matters, because it changes how you think about the recovery, the risks, and the realistic expectations for what surgery can and cannot deliver.
THE BASICS
What Spinal Fusion Actually Does — and Why Mechanics Matter
Any surgery on the spine carries real short- and long-term consequences, and I think it is worth being direct about that. People often categorize procedures as minor or major, but any operation that alters spinal mechanics deserves serious consideration regardless of how it is labeled. By eliminating motion at one spinal level, fusion shifts mechanical stress to the segments immediately above and below. Over time, this additional workload can accelerate wear at those adjacent levels — a process called adjacent segment degeneration — and in some cases produce symptoms that require further treatment or revision surgery. Radiographic evidence of adjacent segment degeneration is commonly reported in the 20 to 40 percent range over time following lumbar fusion, with rates of revision surgery for symptomatic disease ranging from 7 to 20 percent depending on the study, the technique, and the length of follow-up. These are not reasons to avoid fusion when it is genuinely indicated. They are reasons to understand what you are agreeing to and to be appropriately selected before proceeding.
KEY DISTINCTION
The Complication Most Patients Do Not Hear Enough About
Pseudarthrosis — the failure of the intended fusion to fully consolidate — is one of the leading causes of ongoing pain after spinal fusion and a primary driver of what is commonly called failed back surgery syndrome. When the fusion does not take, persistent micro-motion remains at the intended fusion site, often producing pain that is indistinguishable from the original complaint and sometimes requiring revision surgery to address. The risk of pseudarthrosis increases meaningfully with the number of levels fused, and is compounded by smoking, older age, poorly controlled diabetes, osteoporosis, and suboptimal spinal alignment. Modern outcomes data suggest symptomatic pseudarthrosis occurs in approximately 2 to 3 percent of patients at ten years for single-level procedures, with risk rising substantially as more vertebral levels are included in the construct. This is not a rare or theoretical complication — it is a clinically important one that deserves an honest conversation before any patient proceeds to surgery.
CLINICAL EVIDENCE
What Does the Research Show?
The evidence on spinal fusion outcomes is nuanced and worth understanding in detail. Multilevel fusions carry more complications and produce less pain improvement on average than single-level procedures, a finding that has been replicated across multiple outcomes studies including Harada et al. 2021. In the cervical spine, contemporary data suggest that two-level fusions consolidate more reliably than three-level constructs, reinforcing the principle that biological and mechanical demands increase with each additional level added to a construct. Alignment matters significantly as well — malalignment following fusion is an established risk factor for both adjacent segment disease and pseudarthrosis, with one analysis estimating surgically relevant adjacent segment disease at approximately 2.4 percent per year following L4 to S1 fusion in the setting of poor alignment. Patients with poorly controlled diabetes face higher nonunion rates and worse overall outcomes, as documented by Steinmetz et al. in Spine Journal 2025. The literature on high-profile athletes, including Tiger Woods whose most recent lumbar surgery occurred in October 2025, illustrates how spinal mechanics and biology play out over years and across multiple procedures — a real-world pattern that reflects what the evidence predicts.
PATIENT SELECTION
When Fusion Is and Is Not the Right Answer
Surgery is never the first step in my practice, and fusion specifically is never a treatment for isolated axial low back pain without a clearly identified, surgically correctable structural problem. When I recommend surgical consultation, it is because conservative care has been exhausted and the pattern of pain correlates with a problem that surgery is genuinely well-suited to address, because progressive neurological deficit requires intervention to arrest nerve injury and prevent long-term disability, or because the patient is medically optimized and biologically positioned to heal. That last point is more important than most patients realize. A non-smoker with well-controlled metabolic health and adequate bone density has a fundamentally different risk profile than a patient who is actively smoking, has uncontrolled diabetes, or has significant osteoporosis. Addressing modifiable risk factors before proceeding to surgery is not a bureaucratic hurdle — it is how we improve the probability that the fusion actually works.
Patients with poorly controlled diabetes, active nicotine use, severe osteoporosis, or significant wound-healing risks carry higher complication and nonunion rates across the literature. I discuss these factors directly with every patient I evaluate for surgical referral, and I work with them to optimize whatever can be optimized before a recommendation is made.
FOR REFERRING CLINICIANS
Patients presenting for evaluation of potential spinal fusion benefit significantly from a thorough pre-surgical interventional medicine assessment — particularly to confirm the pain generator through diagnostic blocks, assess for non-surgical alternatives that may have been incompletely explored, and identify modifiable risk factors that could affect fusion outcomes. I offer comprehensive imaging review, diagnostic and therapeutic spinal injections, metabolic and musculoskeletal optimization guidance, and alignment-aware pre-surgical planning in collaboration with surgical partners. For patients who have undergone fusion and continue to experience pain, I provide post-surgical evaluation to distinguish adjacent segment pathology, pseudarthrosis, and other treatable causes from non-structural contributors to ongoing symptoms. I welcome direct physician-to-physician consultation.
PERSPECTIVE
A Note on Shared Decision-Making in Spine Care
Spinal fusion can be genuinely life-changing for the right problem, in the right patient, with meticulous planning and committed post-operative rehabilitation. It is not a cure for back pain broadly, and it is not a procedure whose consequences are limited to the operating room. The hardware is scaffolding. The fusion is biology. And biology does not always cooperate on the timeline or to the degree that either the patient or the surgeon hopes. What I can offer every patient who comes to me with this decision in front of them is a comprehensive evaluation, an honest interpretation of their imaging and clinical picture, and a clear-eyed discussion of all available options — from targeted injections and structured rehabilitation to surgical second opinions — so that whatever choice is made, it is made with full information and realistic expectations. That is the standard I hold myself to, and it is the only standard I think is acceptable when the stakes are this high.
DISCLOSURE & REFERENCES
This article is for educational purposes and reflects clinical experience and interpretation of published literature. It is not a substitute for individualized medical evaluation. Key references: Boonsirikamchai et al. 2024 (pseudarthrosis risk factors); Shahzad et al. 2023–2024 (symptomatic pseudarthrosis rates); Steinmetz et al. 2025 (diabetes and fusion outcomes, Spine J); Loggia et al. 2025 (alignment and adjacent segment disease, Spine J); Soh et al. 2025 (temporal patterns of ASD, J Clin Med); Okuda et al. 2018 (ASD after PLIF); Harada et al. 2021 (multilevel fusion outcomes); Nouh et al. 2012 (instrumentation principles).
ABOUT THE AUTHOR
Dr. Mahajer is a double board-certified physiatrist and sports medicine physician, fellowship-trained in Interventional Spine & Sports Medicine at the Icahn School of Medicine at Mount Sinai. He is an Assistant Professor of Neuroscience at FIU Herbert Wertheim College of Medicine. He is the Immediate Past President of the American Osteopathic College of Physical Medicine and Rehabilitation (AOCPMR), holds medical licenses in Florida, New York, and California, and has been recognized as a Top Physiatrist and Top Doctor in both Florida and New York.
