On the Long View in Minimally Invasive Spine Surgery

#The two-year horizon as an honest measure

If one had to name a single time point at which the truth of a spine operation becomes visible, two years is a reasonable choice. It is not arbitrary. Most of what matters clinically — reoperation rate, fusion status, the onset of adjacent segment disease, the recurrence of a herniated disc — declares itself within or just beyond this window. Patient-reported outcomes that have stabilized by twenty-four months tend to reflect a durable result rather than the transient relief of the early postoperative period.

Two years is also long enough to absorb the noise of the early months: the inflammation that resolves, the muscle that remodels, the expectation that adjusts. A patient who is doing well at six weeks is not yet telling us about the surgery. A patient who is doing well at two years is. This is the honest measure of what we have done.

#What we already know about UBE

Within this framework, the short-term advantages of unilateral biportal endoscopy are not in doubt, and this article is not an attempt to deny them. Multiple studies — cohort comparisons, meta-analyses, prospective observational series — have consistently shown that UBE, compared with conventional approaches, achieves reduced intraoperative blood loss, shorter length of stay, earlier ambulation, lower opioid consumption, and faster return to baseline function. These are not marketing claims; they are documented, reproducible findings. Combined with the principles of enhanced recovery after surgery, UBE has demonstrated a coherent short-term profile that justifies its adoption in well-selected cases.

Long-term outcomes are a different matter, and they should be discussed with corresponding honesty. The two-year, five-year, and ten-year data that we will eventually want — durability of decompression, fusion rates with newer cage and instrumentation systems, adjacent segment behavior, revision-surgery profiles — are still in the process of being established. Some early signals are encouraging; some questions remain open. None of this is unusual for a technique still in its first generation of widespread adoption. The point is simply that we should say so, plainly, both in our literature and in our conversations with patients.

#The marketing of "minimally invasive"

The phrase minimally invasive has, over the past decade, drifted away from its original meaning. Inside the operating room, the term still refers to a technical philosophy — preserving paraspinal muscle, sparing the posterior tension band, minimizing iatrogenic trauma to tissues not implicated in the disease. Outside the operating room, the phrase has taken on a different cast. It has become an adjective applied to brochures, to clinic signage, to the explanations patients read before they walk into our consulting rooms.

The patient who encounters the phrase encounters a promise: smaller, faster, safer, better. Some of this promise is fulfilled. Some of it is not so much fulfilled as quietly redefined. Minimally invasive describes the access; it does not, in itself, describe the result. A patient may be reasonably told that the incision will be shorter and recovery quicker. The same patient should also be told, with the same clarity, that the durability of the procedure over years and decades depends on factors not visible on the day of surgery.

The gap between what the surgeon means and what the patient hears is not, in most cases, the fault of either. It is a gap created by the language we have allowed to drift. Closing the gap is part of our responsibility.

#What fusion teaches

Few areas of spine surgery have a longer or more sobering evidence trail than lumbar fusion. Decades of accumulated data have established a clear principle: in fusion procedures, the long-term clinical outcome is tightly coupled to whether the fusion actually takes. Pseudarthrosis is not merely a radiographic finding. It is a predictor of persistent or recurrent pain, of revision surgery, of patient dissatisfaction that may extend years beyond the operative event. The arc of a fusion patient's life after surgery is shaped, more than by almost any other variable, by whether the bone bridged.

This principle does not yield to changes in surgical approach. It does not matter whether the cage was placed through a midline incision, a Wiltse interval, a tubular retractor, or a biportal endoscopic working portal — the patient's two-year outcome remains tethered to the same biological question. Did fusion occur?

This places a particular weight on newer endoscopic fusion techniques, including UBE-TLIF. Their short-term advantages — the same blood-loss, length-of-stay, and opioid reductions noted earlier — are real and reproducible. But the long-term verdict, by the nature of fusion surgery, rests on whether these techniques can achieve fusion rates comparable to those of conventional open and minimally invasive approaches. Achieving such parity is not a minor adjustment. It is a substantial undertaking, requiring refinement of endplate preparation, cage selection, graft handling, and supplemental fixation strategies. It will require time, accumulated data, and the willingness of the field to look honestly at intermediate results before settling on conclusions.

To recognize this is not to argue against endoscopic fusion. It is to recognize what fusion is.

#The role of the learning curve

If fusion rate is the decisive long-term outcome of fusion surgery, then the surgeon's individual learning curve becomes a variable that cannot be deferred to literature averages. Fusion rate, more than perhaps any other outcome in spine surgery, is sensitive to the technical maturity of the surgeon performing the operation. A surgeon's first fifty cases of a new fusion technique and their second two hundred cases are unlikely to produce identical biological outcomes.

The published literature that we cite as the evidence base for a procedure is, in the end, an aggregate of every surgeon's learning curve compounded together. This is true of every surgical innovation; it is particularly true of techniques in which the working corridor is narrow, the visualization is unfamiliar, and the margin for error in endplate preparation or cage trajectory is small.

This implies a responsibility that the field has not always articulated clearly. The decision to adopt a new technique is not made once at the level of the specialty; it is made repeatedly at the level of the individual surgeon, on each operating day. The published evidence may be encouraging, but the surgeon standing at the table is the one whose technical maturity will determine, for the patient on the table, whether the long-term result will resemble that evidence. A frank acknowledgment of the learning curve, in writing and in conversation, is not a confession of weakness. It is a precondition for honest practice.

#The moving target paradox

There is, finally, a deeper paradox at the heart of evaluating spine innovation, and it is one that the usual call for more long-term data does not fully address.

Suppose we agreed, as a field, to wait for ten-year outcome data on a new technique before adopting it widely. Suppose we waited patiently. What would happen?

What would happen is this. The ten-year data, when it finally arrived, would describe a technique that no longer exists in the form that was studied. The instruments would have evolved two or three generations. The cage geometry would have been redesigned. The working portal triangulation, the fluid management, the hemostatic strategies would all have been refined by accumulated practice. The procedure performed today in operating rooms around the world would, in many of its essentials, be a different operation from the one whose ten-year results we had so patiently awaited.

This is the moving target paradox. The long-term evidence base for a surgical innovation can only catch up with the technique that existed at the moment the study cohort was enrolled. By the time the evidence arrives, the technique has moved on. This is not a flaw of any individual study; it is a structural property of how surgical innovation and clinical evidence relate to each other.

The paradox does not have a clean solution. But it does shape how we should read the literature. Long-term data tell us something important — but they tell us something about an earlier version of the procedure, not necessarily about the one currently being performed. This is a humbling thought, and an essential one.

#Speed and direction

Given all of this, the question facing the field is not whether to adopt new techniques. To refuse adoption is to refuse the entire history of surgical progress. Every long-term dataset we now cite was, at one point, accumulated by surgeons who began without it. The question is rather one of speed and direction.

Speed: how quickly does an individual surgeon, an institution, or a specialty incorporate a new technique into routine practice? Too fast, and the learning curve is borne disproportionately by patients who did not consent to that role. Too slow, and the field stagnates, and patients who might have benefited from refined techniques do not have access to them. The right pace varies by context — by the maturity of the technique, by the available training, by the audit infrastructure of the institution, by the individual surgeon's prior experience.

Direction: toward what is the technique evolving, and is that direction defensible? A technique that is changing in response to documented complications and outcome data is evolving in a healthy direction. A technique that is changing primarily in response to commercial incentives or to fashion is evolving in a less defensible one. The distinction is not always easy to make from inside the moment. But it deserves to be made.

These two questions — speed and direction — are the substance of what it means to practice with judgment in an era of rapid technical change. They cannot be answered by the literature alone, and they cannot be deferred to specialty societies alone. They have to be answered, repeatedly and locally, by surgeons who are paying attention.

#The long view

To take the long view in minimally invasive spine surgery is not to reject minimal invasiveness. It is also not to embrace it uncritically. It is, instead, to hold both the short and the long scales in mind at the same time, and to allow the longer scale the weight it deserves.

The length of the skin incision is a measure. It is not the measure. The patient leaves the hospital in three days, but lives with the result for thirty years. Our literature, our conversations with patients, and our own habits of thought should reflect that proportion.

None of this is a counsel of caution against progress. The surgeons who shaped minimally invasive spine surgery did so by taking on the risk of trying something whose long-term outcomes were not yet known. The same risk is being taken by surgeons who are now refining endoscopic fusion, percutaneous approaches, and integrated ERAS protocols. This work is necessary, and it will be the foundation of the next generation's standard practice.

What is required of us, as a generation of spine surgeons who happen to be present at a moment of accelerating innovation, is something quieter than enthusiasm and quieter than skepticism. It is the discipline of asking, at each step, whether the speed at which we are moving and the direction in which we are moving will be defensible two years from now. And five years from now. And, eventually, to the patient who is still living with our decisions long after the day of surgery has faded from our own memory.

That is the long view. It is harder than the short view. It is also the one our patients need us to take.

This essay reflects the author's perspective on the state of minimally invasive spine surgery and is intended as field commentary rather than as a clinical recommendation. Specific surgical decisions should always be individualized based on patient factors, available evidence, institutional context, and the surgeon's own assessment of technical maturity. The arguments in this essay are informed in part by the author's own work on uniportal and biportal endoscopic transforaminal lumbar interbody fusion (Kim JY, Ha JS, Lee CK, Lee DC, Hong HJ, Choi SY, Park CK. Journal of Minimally Invasive Spine Surgery and Technique. 2024;9(Suppl 1):S14–23).