Very long-term outcomes of unilateral versus bilateral pedicle screw fixation with more than 10 years of follow-up

The human spine is a remarkable structure, a flexible column of bones that supports our weight while allowing us to twist, bend, and reach. When the discs between these bones wear down or the joints become arthritic, the resulting pain can be debilitating. For many patients, the solution involves a surgery called a fusion, where two or more vertebrae are permanently joined together to stop painful movement. To hold the spine steady while the bones heal, surgeons often use metal screws and rods. For decades, the standard approach has been to place screws on both sides of the spine, creating a rigid, symmetrical frame. This method is known to be very strong, but it requires cutting through a wide area of back muscle to reach the bone, which can cause significant trauma to the body's natural support system.

In recent years, surgeons have begun testing a different approach: placing screws on only one side of the spine. The idea is that by leaving the muscles and ligaments on the other side untouched, the body suffers less surgical injury and recovers faster. However, a lingering question has remained: does this lighter touch compromise the long-term strength of the repair? If the spine is not held as tightly on one side, will the bones fail to knit together, or will the extra stress cause the neighboring joints to wear out faster? This is not just a matter of immediate recovery; it is a question of what happens a decade or more down the road, when the body has settled into its new normal and the true durability of the surgery is revealed.

A team of researchers from medical institutions in China set out to answer this question by looking back at patients who had undergone this surgery more than ten years ago. They compared two groups of people who had received treatment for a single level of spinal degeneration. One group received the traditional two-sided screw fixation, while the other received the newer, one-sided version. The researchers were particularly interested in two things: how the patients felt and functioned in the long run, and what the X-rays and scans showed about the health of the spine and the joints next to the fused area. They wanted to know if the one-sided approach was safe enough to be a standard option, or if the two-sided method remained the only reliable choice for lasting stability.

The study followed 157 patients who had been monitored for at least ten years. The researchers interviewed them to ask about their pain levels, their ability to perform daily tasks, and their overall satisfaction with the surgery. They also reviewed medical records to see if anyone had needed a second operation to fix a problem. For a smaller group of 56 patients, the team was able to gather detailed X-rays and magnetic resonance images to examine the physical state of the spine, looking for signs of bone healing, the position of the metal implants, and any wear and tear on the adjacent discs and joints. To ensure a fair comparison, the researchers used statistical methods to match patients with similar ages, body types, and surgical details, creating a balanced set of data to analyze.

The results offered a reassuring picture for the one-sided approach. After more than a decade, the patients in both groups reported nearly identical levels of back pain, leg pain, and disability. They were just as satisfied with their outcomes, and the rate at which they required a second surgery was exactly the same: about 3.8 percent in each group. When the researchers looked at the X-rays, they found that the bones had successfully fused in almost everyone, with success rates of 97.2 percent for the one-sided group and 95.0 percent for the two-sided group. The metal cages used to support the spine stayed in place equally well in both groups, showing that the one-sided screws provided enough stability to hold the spine together for the long haul.

There was, however, one distinct difference found in the images. The researchers noticed that the joints and discs just above the fused section showed signs of degeneration more often in the group that had received the two-sided screws. In the full group of patients with X-rays, 45 percent of those with two-sided screws showed this wear, compared to only 19 percent of those with one-sided screws. This pattern held true even in the smaller, carefully matched group of patients. Despite this visible difference on the scans, it did not translate into a difference in how the patients felt. The people with more visible wear on their scans did not report more pain or worse function than those with cleaner scans. This suggests that while the two-sided screws might create a stiffer environment that stresses the neighboring joints slightly more, the body is often able to adapt without the patient noticing any negative symptoms.

The study concludes that for patients needing a single-level fusion, the one-sided screw fixation is a viable and durable option. It provides the same long-term relief from pain and the same ability to function as the traditional two-sided method, without increasing the risk of needing a revision surgery. The finding that the one-sided approach is associated with less visible wear on the joints above the fusion site is an interesting observation, but it remains a radiographic finding rather than a clinical problem. The researchers emphasize that while the one-sided method appears to spare the adjacent joints from some stress, this advantage does not yet prove that it prevents future pain or the need for more surgery. The evidence suggests that surgeons can confidently offer the one-sided technique to suitable patients, knowing that it preserves the body's natural muscle attachments without sacrificing the strength or longevity of the spinal repair.