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Radiat Prot Dosimetry
Radiat Prot Dosimetry
rpd
Radiation Protection Dosimetry
0144-8420
1742-3406
Oxford University Press

39193892
10.1093/rpd/ncae175
ncae175
Paper
AcademicSubjects/SCI00180
Assessment of radiation dose values in common orthopaedic trauma examinations performed under X-ray fluoroscopy guidance
https://orcid.org/0009-0001-3156-8577
Genetay Tristan Diagnostic Department, University Hospitals of Geneva, Geneva, Switzerland

Gamulin Axel Division of Orthopaedic and Trauma Surgery, University Hospitals of Geneva, Geneva, Switzerland
Faculty of Medicine, University of Geneva, Geneva, Switzerland

Lorimier Arnaud Care Management Department, University Hospitals of Geneva, Geneva, Switzerland

Sans Merce Marta Diagnostic Department, University Hospitals of Geneva, Geneva, Switzerland

Corresponding author. Diagnostic Department, University Hospitals of Geneva, Geneva, Switzerland. E-mail: Tristan.Genetay@gmail.com
9 2024
28 8 2024
28 8 2024
200 14 13651371
03 12 2023
25 6 2024
16 7 2024
06 8 2024
© The Author(s) 2024. Published by Oxford University Press.
2024
https://creativecommons.org/licenses/by-nc/4.0/ This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (https://creativecommons.org/licenses/by-nc/4.0/), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited. For commercial re-use, please contact journals.permissions@oup.com

Abstract

This study aims to provide radiation reference levels in orthopaedic surgery. A total of 753 procedures were collected within 1 y. Categories containing several similar procedures were created based on four criteria: same anatomical area, same level of complexity, only single procedures, and at least 10 cases per category. Exposure was defined in terms of air kerma-area product, fluoroscopy time, and air kerma at the patient entrance reference point. For common procedures, median effective doses to patient were calculated using the Monte Carlo Software PCXMC. Most irradiating procedure in this study i.e. intramedullary nailing of the proximal femur was equivalent to an air kerma at the patient entrance reference point of 37.1 mGy, which is ~50 times lower than the threshold for acute deterministic effects of radiation. Optimization remains a must to reduce the dose while maintaining the image quality and reducing the likelihood of stochastic effects.
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pmcBackground

The use of X-ray fluoroscopy is a widely established practice in surgery, particularly in orthopaedics. Procedures performed under fluoroscopy guidance allow the use of minimally invasive techniques, which benefit the patient by reducing hospital stays. These procedures are also performed in less time and with less injury to patient tissues [1]. Recent technology improvements in X-ray fluoroscopy devices give more opportunities in dose optimization, but their use requires better knowledge from the operator. According to Tunçer et al. [1], 99.2% of the orthopaedic surgeons who took part in their survey did not know about the amount of radiation delivered during common orthopaedic trauma procedures. Furthermore, the number of prolonged fluoroscopic procedures has increased dramatically in the past decades [2]. In 2000, the International Commission on Radiological Protection (ICRP) gave recommendations to avoid radiation injuries from medical interventional procedures [3]. Acute deterministic effects such as skin erythema or cataract of the eye lens appear when absorbed dose delivered in a single procedure or closely performed procedures is more than 2 Gy [3]. In common radiological procedures, absorbed dose is generally well below this threshold. Ionizing radiations may also induce stochastic effects such as cancer. Stochastic effects may appear even for doses close to zero. The probability of this kind of effect increases with absorbed dose, but not its severity [3].

Assessment of diagnostic reference levels (DRLs) in this field is therefore becoming a necessity for patient doses optimization and operator education. According to the ICRP Report No. 135 [4], DRL is a supplement to professional judgement and does not provide a threshold between good and bad medical practice. They do not apply to individual patients. Setting up DRLs maintains the quality of the diagnostic information provided by the X-ray use while trying to reduce patient doses according to as low as reasonably achievable (ALARA) principle. These values also allow to compare practices between different centres and represent the state of the art of radiation use in hospitals. To establish DRLs, a commonly and easily measured or determined radiation metric that assesses the amount of ionizing radiation used to perform a medical imaging examination must be chosen. In the authors’ country, like in many other countries, there is no national DRLs in surgery yet. Providing typical values would be the first step of national DRLs assessment process.

The authors also wanted to provide dose conversion factors between air kerma-area product (KAP) and effective dose (ED) for common orthopaedic trauma procedures. Indeed, ED can be used to determine the likelihood of stochastic effects and gives information about general radiation exposure levels for a dedicated procedure compared to other ionizing radiation exposures [5]. It is also more meaningful for most healthcare professionals because it allows comparison with other common X-ray imaging procedures.

Materials and methods

Data from 1642 fluoroscopic procedures performed to assist orthopaedic trauma interventions were collected between April 2022 and April 2023. Patients under 16 y old were excluded in this study. All the data used for this study were extracted from the dose archiving and communication system (DACS) of the authors’ institution and exclusively represent radiographic device data, and not patient data, as no measurements were taken directly in the operating room at the time of the surgery. Furthermore, no treatment outcome data (i.e. treatment quality assessed using X-ray images) were analysed, and all the datasets used were anonymous.

Three mobile X-ray units were used, two Siemens CIOS FUSION (Siemens Healthcare GmbH, Erlangen, Germany) and one Siemens CIOS FLOW (Siemens Healthcare GmbH, Erlangen, Germany). Each one was equipped with a 30 cm × 30 cm flat panel detector. For CIOS FLOW, inherent filtration of the X-ray tube is 2.8 mm Al and for CIOS FUSION 3.0 mm Al. For each of these devices, the focus-to-image receptor distance corresponded to 102 cm, and Interventional Reference Point (IRP) was 15 cm away from the isocenter in the direction of the X-ray tube. This point was meant to correspond to the entrance of the patient at the skin’s surface. Orthopaedic surgeons at the authors’ institution regularly use the fluoroscopy system in pulsed mode at five pulses per second but in most cases, field collimation is not used.

In X-ray fluoroscopy, the radiation metric that assesses patient irradiation, according to Table 2.4 from ICRP report No. 135 [4], are the KAP in Gy·cm2, fluoroscopy time (FT) in s, entrance air kerma at IRP (Ka,r) in mGy, and number of images in cine mode. These data were extracted at the end of each intervention by using the Radiation Dose Structured Report, which was automatically sent to the vendor neutral archiving system and further to the institutional DACS. The number of images acquired in cine mode, if any, could not be extracted with the devices, so only the three other quantities were used i.e. KAP, Ka,r, and FT. Since this study involved <10 devices, the median value of the distribution from each quantity was used in agreement with Table 2.2 from ICRP report No. 135 [4]. These values were thus considered as ‘typical values’ according to the same ICRP report [4].

The number of distinct types of procedures, which were performed using fluoroscopy systems in orthopaedics is wide, 172 in this case. Categories containing several similar procedures were created to have more statistically significant results. For this purpose, procedure categories creation was based on four main criteria:

Same anatomical area: patient irradiation is linked to several specific factors varying a lot from one anatomical area to another i.e. the amount and the densities of tissues crossed by the beam or their radiosensitivity.

Same level of complexity and equivalent implants: fluoroscopy use also depends on the complexity and type of implant used for the intervention.

Only single procedures: if multiple procedures are performed during the same intervention, identification of the specific irradiation linked to each procedure is not possible.

At least 10 cases for each category: this allows to achieve sufficient statistical density.

To ensure results accuracy, the calibration of the ionization chamber inside the system was checked using a KAP meter (DAP CHECK+, Radcal, Monrovia, CA). The measure was performed by placing the detector between the tube and the flat detector halfway to avoid backscatter effect as much as possible. Distance between KAP meter and tube does not matter, as the KAP is distance invariant. In the authors’ national Public Health Office directive on quality control of radiological facilities [6], X-ray devices are calibrated again when the difference between the measured and displayed value is superior to 35%.

To evaluate the ED for each of these categories, a dose conversion factor between KAP and ED was defined using the Monte Carlo calculations software PCXMC (STUK, Vantaa, Finland). This software is based on the simulation of stochastic interactions between photons and matter and uses mathematical hermaphrodite phantom models of Cristy [7]. It is one of the most frequently used programs as it allows the computation of ED in freely adjustable X-ray projection [8]. The PCXMC software can calculate ED with both the tissue weighting factors presented by ICRP Report no. 103 [9] and those presented by ICRP report no. 60 [10]. Its accuracy for ED calculations has already been fully demonstrated [11, 12], that is why its utilization is relevant to this purpose. To fix femoral neck fractures, orthopaedic surgeons use both posterior–anterior (PA) and Lateral Crosstable 45° (LC) projections. The average percentage of each projection use during femoral neck fracture fixations was estimated by analysing the habits of orthopaedic surgeons during the procedures. Absorbed dose due to each projection is not equivalent, because the amount of tissues crossed by the beam is higher with LC projection, and the focus-to-skin distance (FSD) is also different. In PA projection, FSD was assumed to be equal to 72 cm in common use, while in LC projection, FSD value is estimated to be 55 cm.

Results

Table 1 shows the median values of the radiation metrics for the different orthopaedic categories. These values correspond to a total of 753 interventions and represent ~46% of the 1642 examinations exported between April 2022 and April 2023.

Table 1 Typical dose values for categories of orthopaedic surgery examinations.

Categories	KAP (Gy·cm2)	FT (s)	Ka,r (mGy)	Cases	
Total shoulder arthroplasty	0.03	4	0.1	14	
Acute acromioclavicular repair	0.05	6	0.1	25	
Clavicle osteosynthesis	0.12	11	0.3	68	
Proximal femur hemiarthroplasty	0.19	9	0.5	88	
Total hip arthroplasty	0.54	21	1.3	387	
Tibial plateau osteosynthesis	0.20	52	0.5	31	
Tibia IMN	0.40	99	0.9	14	
DHS	0.84	51	2.1	26	
FNS	0.88	60	2.3	26	
Proximal femur IMN	1.17	87	3.1	74	
IMN, intramedullary nailing; DHS, dynamic hip screw; FNS, femoral neck system.

The difference between the measured KAP, using the KAP meter, and the one indicated by the X-ray devices was on average 10%, with the measured KAP systematically lower. This factor was not applied on values presented in Table 1 because no new calibration was needed [6].

Dose conversion factors shown in Table 2 were estimated using PCXMC software for each of the hip categories and for both ICRP 60 and 103 weighting factors [9, 10]. Tibia, ankle, shoulder, and clavicle categories were not included because the software could not be used for the extremities. To obtain the dose conversion factors, a phantom with 168 cm height and 70 kg weight was used, representing the median values of height and weight from the dataset containing all the patients included in this study. Preoperative observation of femoral neck fracture fixations showed that grossly 70% of the incidences used were PA and 30% LC. Therefore, considering the dose differences for each projection, 97.5% of total KAP was due to LC projection and 2.5% to PA projection in femoral neck fracture fixations.

Table 2 Dose conversion factors for categories of orthopaedic surgery examinations.

Categories	X-ray tube voltage (kVp)	Projection	Dose conversion factor based on ICRP 60 (mSv·Gy−1·cm−2)	Dose conversion factor based on ICRP 103 (mSv·Gy−1·cm−2)	ED based on ICRP 60 (mSv)	ED based on ICRP 103 (mSv)	
Proximal femur IMN	63	PA	0.028	0.017	0.196	0.083	
68	LC	0.170	0.072	
DHS	63	PA	0.028	0.017	0.140	0.059	
68	LC	0.170	0.072	
FNS	63	PA	0.028	0.017	0.146	0.062	
68	LC	0.170	0.072	
Total hip arthroplasty	65	PA	0.030	0.018	0.016	0.009	
Proximal femur hemiarthroplasty	64	PA	0.030	0.018	0.005	0.003	
IMN, intramedullary nailing; DHS, dynamic hip screw; FNS, femoral neck system.

Table 3 shows the comparison of the typical values defined in Table 1 with the literature. Only four categories defined previously could be compared with the literature because no data were available for the remaining ones.

Table 3 Comparison of median and average KAP and FT values with literature.

	Sources	Cases	Median KAP (Gy·cm2)	Average KAP (Gy·cm2)	Median FT (s)	Average FT (s)	
DHS	Authors’ study	26	0.84	1.04	51	65	
Hardman et al. [13]	206	/	1.57	/	60	
Rashid et al. [14]	190	0.67	/	36	/	
Skrk &et al. [15]	40	0.52	0.71	43	45.6	
Proximal femur IMN	Authors’ study	74	1.17	2.19	87	103	
Rashid et al. [14]	39	1.04	/	49	/	
Skrk et al. [15]	23	0.53	0.6	45	48	
Tibia IMN	Authors’ study	14	0.40	0.43	99	120	
Rashid et al. [14]	14	0.36	/	104	/	
Pillai et al. [16]	15	0.28	/	27.5	/	
Tibial plateau osteosynthesis	Authors’ study	31	0.20	0.27	52	57	
Rashid et al. [14]	11	0.23	/	26	/	
IMN, intramedullary nailing; DHS, dynamic hip screw.

Discussion

The aim of this study was to define typical dose values for most of the common trauma orthopaedic surgical procedures and compare them with values from other institutions. The main challenge in typical values assessment was the amount of different procedure types encountered. Half of the data collected could not be used because certain types of examinations were recorded less than 10 times during the study length on the three devices.

The reader should be aware that even though 35% uncertainties could be intrinsically contained in displayed KAP values [6], in the present study, a 10% uncertainty seems more realistic. Therefore, when comparing KAP values, only larger differences should be considered meaningful. Furthermore, a lot of uncertainties could not be estimated because of lack of information in the relevant studies i.e. the beam quality (voltage and filtration) or the surgical technique used. This could explain some of the discrepancies with the literature reported in the present study.

As shown in Table 3, Hardman et al. [13] gave average KAP and FT values for dynamic hip screw (DHS) osteosynthesis. Their study was performed in four major reference hospitals in London. Unlike the present study, patients outside of the weight range from 50 kg to 90 kg were excluded. Their average FT was equivalent to the present study, while their KAP was 1.5 times superior. Higher values could most be attributed to differences in device parameters like higher pulse rate or dose per pulse involving a higher patient dose. Unfortunately, they did not give indications, which could eventually help to set a clear conclusion. Median DHS values from the present study were also compared with Rashid et al. [14] and Skrk et al. [15] studies. Skrk et al. [15] also defined a weight range from 60 kg to 90 kg, but Rashid et al. [14] did not. Both these studies were performed in a single hospital. Median KAP values from Rashid et al. [14] and Skrk et al. [15] for DHS osteosynthesis were, respectively, 25% and 62% inferior to this study. Associated FT were, respectively, 42% and 20% inferior. An explanation for these findings could be that fluoroscopy was more extensively used in the authors’ institution for DHS osteosynthesis, involving higher KAP values.

For proximal femoral intramedullary nailing (IMN), median KAP values presented by Rashid et al. [14] and Skrk et al. [15] were, respectively, 12% and 120% inferior to the authors’ values. Both of their FT values were also approximately twice inferior. In that case, KAP values presented in this study were equivalent to those presented by Rashid et al. [14] for proximal femoral IMN. Similarly to DHS osteosynthesis, fluoroscopy could be more extensively used in the authors’ institution. Moreover, the device parameters used allow a better dose reduction compared to Rashid et al. [14], as KAP values from the present study are equivalent to them with a median FT 50% higher.

Rashid et al. [14] also reported KAP and FT values for tibia IMN. Their KAP values were 11% inferior to the present study, while FT values were equivalent. Our results were in line with those presented by Rashid et al. [14] for tibia IMN. Pillai et al. [16] reported median KAP values 43% inferior to the present study with a FT three times lower. Fluoroscopy use might have been different between their hospital and the authors’ institution, unfortunately they did not give indications, which could help to set a clear conclusion.

Values presented for tibial plateau osteosynthesis could only be compared with those of Rashid et al. [14]. Their median KAP value was 15% superior to the present study, while their FT was twice inferior. Like for proximal femoral IMN, fluoroscopy could have been more widely used in the authors’ institution but lower fluoroscopy rate pulses or pulses with lower dose allowed less irradiation to patient.

The femoral neck system (FNS) is a new technique, which has been developed recently to fix femoral neck fractures. To the best of our knowledge, the present study is the first assessing typical dose values for these interventions. According to Niemann et al. [17], FNS is a valid alternative to DHS and is superior to cannulated screws for the management of Pauwels type III fractures. In the present study, fluoroscopy use was equivalent to fixation performed using DHS. Figure 1 shows the statistical dispersion of the KAP values for both FNS and DHS, which was equivalent. Using the FNS rather than a DHS has therefore no impact in terms of X-rays delivered to the patient.

Figure 1 Statistical dispersion of KAP (Gy·cm2) for femoral neck fractures fixed by DHS or FNS.

In terms of KAP and Ka,r, values observed in orthopaedic surgery are much lower than in other surgical specialities, like vascular surgery. The ICRP report No. 117 [18] showed a factor of hundred between the most common procedures in vascular surgery and the most irradiating examination presented in this review i.e. proximal femur IMN. For this procedure, the highest Ka,r value observed was 37.1 mGy, 50 times lower than the acute deterministic effects apparition threshold, which is equivalent to 2 Gy [1, 5, 9]. This value is likely lower than the 100 mGy threshold defined in ICRP report no. 103 [9] standing for any minor tissue functional impairment. The authors computed the ED using the dose conversion factors defined in Table 2. Despite its utility to define exposure levels, the reader should be aware of the limitations of the ED use in this case. ED is computed using tissue weighting factors determined for sex- and age-average value for all organs and tissues [9, 19]. ED values should therefore not be used for individual patients or patients’ cohorts under the age of 18. ED is not a convenient tool to characterize stochastic effects in the case of heterogeneous exposures because most of the sensitive organs are outside the irradiation field. ED values presented in this study are meant to give a general radiation exposure level of common procedures in orthopaedic surgery and should not be used outside of this scope.

The median KAP value set for proximal femur IMN corresponds to an ED of ~0.083 mSv with the tissue weighting factors provided by ICRP 103 [9], which represent 1.3% of the mean annual dose received by people in the authors’ country [20]. Even if such comparisons are in agreement with the use of ED according to ICRP report 147 [5], attention should be made when comparing these scenarios because proximal femur IMN is a partial exposure involving a few radiosensitive organs, while annual mean contains several types of different irradiation types varying a lot from one people to another (i.e. medical exposure or radon exposure).

To the best of the authors’ knowledge, literature on dose conversion factors in femoral neck fractures fixation and hip arthroplasty is currently limited. Perisinakis et al. [21] published dose conversion factors for femoral neck surgery. In PA projection, they proposed a factor of 0.030 mSv·Gy−1·cm−2 on average, which is equivalent to 0.028 mSv·Gy−1.cm−2 found in the present study. In LC projection, these factors were 0.033 mSv·Gy−1·cm−2 and 0.029 mSv·Gy−1·cm−2 for left femur and right femur, respectively, which is approximately twice lower than the 0.072 mSv·Gy−1·cm−2 factor in the present study. These differences in values for LC projection could be explained by beam positioning. Indeed, in LC projection, the amount of tissues irradiated is strongly correlated with beam axis because patient thickness can vary a lot in this projection. If the beam is closer to the pelvis, the absorbed dose to bladder, testicles, and all radiosensitive organs will indeed be higher. In that case, finding values twice superior is acceptable given the many uncertainties i.e. beam positioning and quality or surgical technique used. With these considerations, the present study’s values seem to be in line with those proposed by Perisinakis et al. [21].

This study has several limitations. First, as mentioned before, unlike Hardman et al. [13] and Skrk et al. [15], no weight restriction was included as it would have led to insufficient statistics. This could have an influence on the results in terms of collective heterogenicity, as the amount of scattered radiations depends on the volume irradiated. Second, one of the devices commonly used by the orthopaedic surgeons at the authors’ institution is not connected to the DACS. Data used in this study might therefore not be completely representative of the whole activity in the orthopaedic surgery department at the authors’ institution. Third, as the authors’ institution is a teaching hospital, trainees are commonly involved as the first operator. According to Rashid et al. [14], when trainees are the first operator, KAP and FT can be up to four times higher. At the authors’ institution, participation of trainees as first operator can be up to 90% for some interventions, especially proximal femur fracture fixation and hemiarthroplasty. This consideration could explain the discrepancies with the literature reported before. Finally, conversion factors between KAP and ED calculated in the present study are meant to give an order of magnitude of EDs delivered to patient in common trauma surgery. These factors were defined using median height and weight and do not correspond to an individual patient. ED to patient is also strongly linked to FSD and field of view, which means that these conversion factors also depend on the distance between patient and X-ray tube and the field size.

For further research, the authors recommend doing multicentre studies to gather a larger dataset and apply weight restrictions or weight categories. Using the body mass index instead of weight could be relevant as it would be more representative of the volume of patient irradiated. Defining categories of fractures complexities to evaluate their impact on fluoroscopy use would also help to have more precise categories and improve practices. Moreover, a description of device parameters like pulse rate, dose per pulse, or collimation use would help to compare practices between different centres and allow more detailed comparisons between studies.

Conclusion

This study illustrates patient’s exposure to ionizing radiation in most common orthopaedic trauma surgical procedures using fluoroscopy in the authors’ institution. Typical values have been proposed for 11 categories of procedures on extremities. These values could be accepted as standards for future studies and could represent the starting point for setting up national DRLs in the authors’ country for this speciality. Dose levels received by patients in orthopaedic surgery are low, but optimization is always a must to maintain optimal image quality and limit stochastic effects in agreement with ALARA principle. These typical values could also help orthopaedic surgeons and medical physicists to identify situations at risk.

Conflict of interest

None declared.

Funding

None declared.
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