Radiologic evaluation of segmental translational movement in lumbar spinal stenosis patients without spondylolisthesis using flexion-extension radiographs: a descriptive study
This descriptive study of 296 patients with degenerative lumbar spinal stenosis without spondylolisthesis reveals that approximately 26% exhibit significant segmental translational movement (≥3 mm) on flexion-extension radiographs, yet this instability does not significantly influence surgical decision-making regarding which levels are decompressed.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
The lower back is a complex structure of bone, muscle, and nerve that supports the weight of the upper body while allowing us to bend and twist. When the narrow channels through which spinal nerves travel become constricted, a condition known as lumbar spinal stenosis occurs. This narrowing often causes pain that radiates down the legs, a common ailment for older adults that frequently leads to surgery. Before operating, doctors must decide whether to simply remove the tissue pressing on the nerves or to also fuse the vertebrae together to stop them from moving. This decision often hinges on whether the spine is "unstable," meaning the bones shift too much when the body moves. To check for this hidden movement, surgeons sometimes ask patients to bend forward and backward while X-rays are taken, looking for any sliding between the bones that isn't visible when the patient stands still.
A team of researchers in Norway recently investigated how often this hidden sliding occurs in patients who do not show any signs of slipping bones when standing straight up. They focused on a large group of people suffering from spinal stenosis who had no visible misalignment on their standard X-rays. The researchers examined pre-operative X-rays taken while these patients bent forward and backward, specifically looking at the space between the second and fifth vertebrae in the lower back. They defined significant movement as a slide of three millimeters or more between the bending positions. This threshold was chosen because it represents a measurable shift that could theoretically affect surgical planning, even if the bones appear perfectly aligned when the patient is stationary.
The study analyzed the records of 296 patients who had the necessary X-rays available. The results revealed that a substantial portion of these patients, roughly one in four, did indeed show this kind of sliding movement in at least one section of their lower back. Specifically, 78 patients demonstrated a shift of three millimeters or more. For many of these individuals, the movement occurred at just one level, but for others, it happened at two or even three different levels simultaneously. The average amount of sliding observed was 3.7 millimeters, with some instances reaching as high as 7.4 millimeters. Interestingly, the researchers found no difference in age, body weight, or the severity of pain and disability between the patients who had this sliding movement and those who did not. This suggests that the presence of this hidden motion is not linked to how much pain a patient feels or their general physical characteristics.
Perhaps the most significant finding concerned how this information influenced the actual surgery. The researchers wanted to know if the presence of sliding movement meant that surgeons were more likely to operate on that specific level or to add a fusion to stabilize it. The data showed that only about half of the patients with sliding movement had surgery performed at the exact level where the sliding was detected. When looking at the specific levels, the rate of surgery varied: for the lowest level of the spine, nearly 80 percent of the sliding segments were operated on, but for the higher levels, the rate dropped significantly, with less than 10 percent of the sliding segments at the top level receiving surgery. Ultimately, the study found that the presence of this sliding movement did not make a level significantly more likely to be chosen for surgery compared to levels without movement.
The researchers concluded that while hidden sliding is common in patients with spinal stenosis who appear stable on standard X-rays, it does not automatically dictate the surgical approach. The fact that surgeons operated on many levels without movement and skipped many levels with movement indicates that other factors, likely the severity of the nerve compression seen on other scans, are driving the decision-making process. This study does not prove that sliding movement is irrelevant to treatment, but it does show that its presence alone is not the deciding factor for whether a surgeon will operate on a specific spot or add a fusion. The findings suggest that the clinical relevance of this specific type of movement remains a question for further study, as the current practice does not seem to rely heavily on it for planning decompression surgery.
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