Three-Month Leg Pain and Failure to Achieve the 1-Year ODI MCID After Unilateral Biportal Endoscopic Lumbar Interbody Fusion: A Landmark Comparison of Four Early Pain Measures

Back pain is a universal human experience, but for some, it is a heavy, unrelenting weight that makes simple movements a struggle. When conservative treatments fail, surgeons often turn to fusion, a procedure that joins two vertebrae together to stop painful motion. In recent years, a technique called unilateral biportal endoscopic lumbar interbody fusion has emerged as a less invasive option. It uses two small openings and a camera to remove damaged tissue and insert a spacer, aiming to relieve pressure on nerves while allowing the bones to heal into a single, stable unit. While the surgery itself can be a technical success, the journey to feeling better afterward varies wildly from person to person. Some patients bounce back quickly, while others remain stuck in pain or disability a year later. The central question for doctors is not just whether the operation was done correctly, but how to spot early on which patients are struggling to recover so they can get extra help before it is too late.

A team of researchers at Weifang People's Hospital in China set out to solve this puzzle by looking at the very first months after surgery. They wanted to know if a simple check of a patient's pain levels could predict their long-term success. Specifically, they asked whether the pain felt in the lower back or the pain radiating down the leg was a better warning sign, and whether checking this pain two weeks after surgery or waiting until three months provided a clearer picture. To find the answer, they reviewed the records of 189 patients who had undergone this specific fusion procedure. They tracked how much each patient's disability improved over the course of a year, using a standard questionnaire that measures how much back problems interfere with daily life. They defined a successful recovery as a specific, meaningful drop in disability scores, and they focused on the group of patients who failed to reach that goal.

The researchers compared four different pain checks: back pain and leg pain measured at two weeks, and the same two types of pain measured at three months. They found that the pain scores taken just two weeks after surgery were not very helpful at all; they could not reliably distinguish between those who would eventually recover and those who would not. The story changed completely when they looked at the three-month mark. At this point, the level of pain in the leg was a powerful predictor. Patients who reported higher leg pain scores at three months were far more likely to still be struggling with disability a year later. The researchers calculated that this single measure could separate the successful recoveries from the failures with a high degree of accuracy, far better than checking back pain or checking leg pain earlier in the recovery process.

However, the study also revealed a crucial limitation. While three-month leg pain was the best early warning sign among the pain checks, it was not the most powerful tool available. When the researchers looked at the patients' overall disability scores at the three-month mark, that measure was an even stronger predictor of the final outcome. In fact, adding the leg pain score to the overall disability score provided very little extra information. This suggests that while a patient complaining of significant leg pain three months after surgery is a clear signal that something is wrong, the most accurate way to judge their future is simply to ask how their overall function is at that same time. The leg pain score acts as a useful alarm bell, but it does not tell a more complete story than the broader picture of the patient's daily life.

The researchers identified a specific threshold for this alarm. They found that a leg pain score of three or higher on a scale from zero to ten was a common tipping point. Patients with scores at or above this level were much more likely to fail to achieve a meaningful recovery. Yet, the team was careful not to treat this number as a strict rule for treatment. The relationship between pain and recovery was not a straight line; the risk of a poor outcome rose sharply as pain scores increased, but the data showed that reducing the complex reality of pain to a simple "yes or no" cutoff loses valuable nuance. The study also noted that the patients in this group were mostly older adults, and the findings are specific to this type of minimally invasive fusion surgery.

Ultimately, this work offers a practical guide for the early months of recovery. It suggests that if a patient still feels moderate to severe pain in their leg three months after surgery, they should be monitored closely, as they are at higher risk for a difficult year ahead. But the study also serves as a reminder that no single number tells the whole story. The most reliable indicator of a patient's future remains their own report of how well they are functioning in their daily life. While the leg pain score is a helpful early signal, it is not a standalone crystal ball, and the researchers emphasize that these findings need to be tested in other groups of patients before they can be used to make definitive decisions for individuals.