Preoperative anxiety and tourniquet use are associated with early postoperative pain trajectories after total knee arthroplasty: a retrospective cohort study
In a retrospective cohort study of 236 patients undergoing total knee arthroplasty, both higher preoperative anxiety scores and the use of a tourniquet were independently associated with increased early postoperative pain, though anxiety did not modify the effect of tourniquet use on pain trajectories.
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
Imagine you are about to climb a very steep, rocky mountain. You know the climb will be tough, but you also know that once you reach the top, the view is worth it. In the world of medicine, replacing a worn-out knee joint with a new one is a bit like that climb. It's a major surgery called Total Knee Arthroplasty (TKA), and while the surgery itself is often a success, the first few days afterward can feel like a grueling hike up a slippery slope. The "weather" during this hike is pain.
Two things can make this hike feel much harder than it needs to be. First, there's the "mental weather": how nervous or anxious you feel before you even start. Think of this like your brain's volume knob for pain; if the knob is turned up high because you're scared, every little ache might feel like a thunderclap. Second, there's the "physical gear": a special tool surgeons sometimes use called a tourniquet. This is like a giant rubber band wrapped tightly around your thigh to stop blood from flowing while they work. It makes the surgery cleaner, but it can leave your leg feeling like it's been squeezed by a giant hand, which might make the recovery feel more painful. Scientists have long wondered if these two factors—the nervous mind and the tight rubber band—work together to make the pain worse, or if they are just two separate troublemakers.
This study, conducted by researchers at the Zigong Fourth People's Hospital, decided to investigate exactly that. They looked back at the records of 236 people who had just had their knees replaced. They wanted to see if the amount of anxiety a patient felt before surgery (measured by a simple questionnaire called the APAIS) and whether a tourniquet was used during the operation could predict how much pain the patient would feel in the first week after waking up. They tracked the pain levels on days 1, 3, 5, and 7, like checking the temperature of a fever every few hours to see if it's going up or down.
The researchers found that both the "mental weather" and the "physical gear" were indeed troublemakers, but they acted like two separate engines driving the pain train, not a single super-engine.
First, the tourniquet made a big difference. Patients who had the tight rubber band used during their surgery reported significantly higher pain scores. On a scale where 0 is no pain and 10 is the worst pain imaginable, the group with the tourniquet had pain scores that were about 1.26 points higher on average than the group without it. It's as if the tourniquet added an extra heavy backpack to their recovery hike. This group also had slightly lower scores on a test that measures how well their knee was working (the HSS score), suggesting the squeeze might have made it harder for the leg to get moving again quickly.
Second, the anxiety level was a powerful predictor, too. For every single point a patient's anxiety score went up, their pain score went up by about 0.15 points. It wasn't a tiny effect; it was a steady climb. If you imagine the pain scale as a ladder, a patient with high anxiety was standing several rungs higher on the pain ladder than a calm patient, even if they had the exact same surgery.
Here is the most interesting part of the story: the researchers checked to see if these two troublemakers were working together. Did the rubber band make the anxious people feel even more pain than the calm people? Did the anxiety make the rubber band feel tighter? The answer was a clear no. The study found no evidence that anxiety changed how the tourniquet affected pain. They were independent forces. A calm person with a tourniquet still had more pain than a calm person without one. An anxious person without a tourniquet still had more pain than a calm person without one. They didn't team up to create a "super-pain" monster; they just each added their own weight to the backpack.
The study also looked at how well the knees functioned over the next year. The tourniquet group seemed to have a slightly harder time getting their knee function back to its best, while the anxiety level didn't seem to change the physical recovery of the joint itself. This suggests that while anxiety might make the feeling of pain louder, the tourniquet might actually be causing more physical stiffness or swelling that slows down the leg's movement.
In short, this research suggests that to make the post-surgery hike easier, doctors should pay attention to two separate things: they should try to calm the patient's nerves before the operation, and they should carefully consider whether they really need to use that tight rubber band (tourniquet) during the surgery. The study didn't find a magic cutoff number for anxiety where things suddenly get bad, nor did it find that anxiety and the tourniquet combine to make things worse than the sum of their parts. Instead, it paints a picture where managing the mind and managing the surgical tools are two different, but equally important, keys to a smoother recovery.
Drowning in papers in your field?
Get daily digests of the most novel papers matching your research keywords — with technical summaries, in your language.