“Starker than expected” radiation from fluoroscopy in TLIF surgery

Aaron J Buckland

A study of radiation exposure among patients undergoing transforaminal lateral interbody fusion (TLIF) surgery presents a “starker than expected” difference in dosage between patients having intraoperative fluoroscopy-guided procedures than those aided by image-guided navigation (IGN) or robotic assistance.

The findings should raise concerns about the proportion of total radiation dose applied to surgeons and operating staff, the researchers at New York Langone Medical Center (New York, USA) say. Published in the Global Spine Journal, the retrospective study carried out by Erik Wang, Aaron J Buckland, and colleagues sought to assess patient radiation exposure and perioperative outcomes from the use of IGN and robotic assistance in one- or two-level TLIF surgeries. According to the research team, the study is the first to assess this relationship across IGN, robotic assistance, fluoroscopically-guided minimally invasive surgery (fluoro-MIS), and open TLIF.

Discussing the findings with Spinal News International, Buckland says: “We were a little surprised at just how much radiation dosage there was just from fluoroscopy. That is only to the patient, let alone what we are seeing as staff. It was a little alarming from that standpoint, especially when a lot of the surgeons doing minimally invasive surgery using fluoroscopy are younger surgeons with their whole career ahead of them, it really does start to raise some serious questions about the way you are going to practice in the next 30 years.”

Writing in the study, Wang and Buckland noted that dosimetry readings during fluoroscopically-guided spinal surgery have been shown to be 10 to 12 times greater than those in non-spine orthopaedic procedures, based on measured fluoroscopy times.

Several studies have raised concerns over radiation exposure with both robotic assistance and IGN, particularly in weighing the reduction of intraoperative radiation exposure to operative staff against potentially increased exposure to the patient. The study suggests that radiation exposure for spine surgeons using conventional fluoroscopy may approach or exceed the annual cumulative exposure acceptable for established lifetime dose equivalent limits.

In the study paper, Wang and Buckland write that as rates of lumbar spinal instrumentation and minimally invasive surgery (MIS) continue to increase, methods to improve accuracy and reduce radiation burden have also adapted.

Two-dimensional fluoroscopic navigation has been a mainstay of multiple medical disciplines since gaining popularity in the 1980s, the study team write, adding that technologies such as robotic navigational guidance and intraoperative computed tomography (CT) IGN have increasingly been used to improve the accuracy of pedicle screw positioning and patient safety. However, concern has been raised regarding the potential increased radiation dose to the patient as a result of requiring a CT scan.

Wang, Buckland and colleagues assessed the relative radiation exposure in each of the selected techniques, undertaking a retrospective review of all adult patients (≥18 years) undergoing one- or two-level TLIF at their institution between January– December 2018. Patients were grouped by type of
guidance used for pedicle screw insertion, which were: intraoperative CT IGN, robotic assistance, fluoro-MIS, and open surgery. Procedures carried out by 19 surgeons were involved in the study.

The robotic guidance system used was the ExcelsiusGPS system (Globus Medical), which was used for open and mini-open cases, as well as MIS cases in lieu of conventional fluoroscopic guidance. The IGN system was an Airo mobile intraoperative CT scanner (BrainLab) which was used for open instrumented cases.

A total of 165 patients underwent one- or two-level TLIF during the study period (51.83% female). The mean age was 59.13±13.18 years, BMI was 29.43±6.72 kg/m2, and CCI 1.20±1.56. Twelve cases utilised intraoperative CT IGN for pedicle screw placement and 62 used robotic assistance.

In all, 56 cases were open and 35 were fluoroscopically-guided MIS. The open (38.18% female) and fluoro-MIS (45.71% female) patient groups had a lower proportion of females compared with the IGN (66.67% female) and robotic (64.52% female) patient groups (p=0.021).

In terms of perioperative outcomes, fluoro-MIS group had the lowest mean posterior levels fused (1.06 levels in MIS vs. 1.42 in IGN, 1.27 in robotic, and 1.32 in open; p=0.015), although estimated blood loss was significantly lower in the MIS group compared with all others (162.14 vs. 441.67mL in IGN, 380.24mL in robotic, and 355.36mL in open, p=0.002). Operative time was found to be highest for IGN patients (303.5 minutes IGN vs. 264.85 minutes robotic, 229.91 minutes open, and 213.43 minutes MIS, p<0.001). There were found to be no significant differences in postoperative complications among any of the groups (p=0.644).

Looking at the total procedure radiation exposure among the different methods, the study team found that this was highest in the fluoro-MIS group (82.02±56.24mGy), followed by the robotics (59.84±32.48mGy), IGN (50.21±22.84mGy) and open (22.56±22.62) groups (p<0.001). Total-procedure radiation per level fused was also highest in the MIS group.

In discussing the findings, Wang and Buckland describe the contrast in radiation dosage exposure between the MIS group and the IGN and robotic groups as “starker than one may expect”. They noted: “Mean total-procedure radiation for the MIS cohort
was 82.02mGy compared with 50.21mGy and 59.84mGy in the IGN and robotic groups, respectively (p<0.001). The MIS patients also had the fewest number of levels fused on average, so the difference was more apparent when calculating total-procedure radiation per level (79.41mGy for MIS vs. 41.88mGy for IGN and 51.18mGy for robotic; P>0.001). Despite the MIS patients having by far the lowest rate of preoperative CT, which adds approximately 20mGy of radiation to the total-procedure sum, they were still exposed to substantially more radiation overall.”
The study team write that while the aforementioned radiation measurements are for the patient, as this radiation dose total stemmed primarily from intraoperative fluoroscopy in MIS cases, “it raises concerns about the proportion of total radiation dose applied to the surgeon and operating staff, who are performing these surgeries on a regular basis”.

Buckland added, however, that he does not believe the findings suggest robotics and navigation are “definitively the answer” when compared against fluoroscopy in all cases. He said: “It is not just about radiation dose, but trying to work out the safety and efficacy of robotics and navigation because that still remains somewhat controversial. There are other trade-offs with these modern modalities, they take increased time in the operating room, there is extra capital cost associated with it, so it is a difficult formula here to work out where the value lies. What sort of increased cost are we using to reduce radiation dose and what does that mean to patient and OR staff safety? It is still unanswered, certainly the radiation piece seems to be in favour of robotics and navigation for minimally invasive procedures at least, the efficacy and safety of these modalities we are yet to definitively prove.”

The study team acknowledged that the sample size, as well as that the fact that procedures in different groups were not all performed by the same surgical team proved to be limitations of the research, and added that a multicentre study would potentially address these issues.


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