Fluoroscopic Angles in S1 Transforaminal Epidural Steroid Injections: Effects on Procedure Time

Imagine your spine is a towering skyscraper, and the nerves are the electrical wires running through it. Sometimes, those wires get pinched or irritated, sending painful sparks down your legs—a condition doctors call radiculopathy. To fix this, specialists often use a "magic needle" trick called a Transforaminal Epidural Steroid Injection (TESI). Think of this as a precision delivery service: a doctor guides a needle through a tiny, hidden doorway (the foramen) in the lower back to drop off anti-inflammatory medicine right next to the irritated nerve. But here's the catch: these doorways are tiny, hidden behind bony walls, and they aren't always facing the same way. To see them, doctors use a special X-ray camera called a fluoroscope, which acts like a high-tech flashlight that can tilt and twist to find the perfect angle to peek through the door. If the doctor can't find the right angle, they have to keep moving the camera, which takes time and exposes the patient to more radiation. So, the big question for anyone with back pain is: Is there a "sweet spot" angle that makes this procedure faster and easier?

This study, conducted by a team at Şişli Etfal Training and Research Hospital, decided to play detective with the angles used during these injections for the very bottom level of the spine, known as S1. They looked at 51 patients who had this procedure done between July 2024 and January 2025. The researchers wanted to see if the specific tilt (cranial angle) and the side-to-side twist (oblique angle) of the X-ray camera had any relationship to how long the "needle hunt" took. They measured everything from the patients' ages and body sizes to the exact degrees the camera was tilted and the seconds the X-ray was active.

The team found some interesting patterns. On average, the doctors tilted the camera up by about 13.2 degrees and twisted it sideways by about 9.2 degrees to get a clear view. The whole active part of the procedure took an average of 28.46 seconds, but it varied wildly from person to person, ranging from a quick 16 seconds to a longer 93 seconds. When they crunched the numbers, they discovered a moderate connection between how much the camera was tilted upward (the cranial angle) and how long the procedure took. Specifically, when the doctors had to tilt the camera more than usual, the procedure tended to drag on longer. It's as if trying to look through a door from a very steep, awkward angle makes it harder to line up the needle, forcing the doctor to fiddle with the camera more.

However, the study also ruled out a few things that people might guess would matter. They found that the side-to-side twist (oblique angle) and whether the patient was male or female did not have a significant effect on how long the procedure took. Interestingly, while the side-to-side twist didn't matter, the patient's age did show a statistical link to procedure time in the initial analysis, with older patients tending to have longer procedures. However, when the researchers looked at all the factors together in a complex model, the tilt of the camera (cranial angle) was not the sole independent driver of time, though splitting patients into groups based on angle still showed that lower angles (under 13 degrees) resulted in significantly faster procedures.

The authors suggest that while there isn't a single "magic number" that works for everyone, using excessively high upward angles seems to make the job harder and slower. They propose that a relatively low tilt, around the 13-degree mark or less, is likely the most efficient way to line up the needle for S1 injections. They also noted that because the iliac crest (the top of the hip bone) can block the view at steeper angles, doctors might be forced to use awkward positions that waste time. While this study was done at just one hospital and by very experienced doctors, it offers a helpful clue: keeping the camera tilt moderate and accounting for patient age might be the key to a quicker, smoother procedure for patients suffering from lower back pain.