Is the Radiation Level a Concern During Fixation of Pediatric SCH Fractures?
A recently published study suggests that in the operating room, the radiation level children are exposed to during surgery for supracondylar humerus fractures is about the same as normal daily background radiation. Dr. Rivka Ihejirika and Dr. Alice Chu review the study.
Rivka C. Ihejirika, MD, and Alice Chu, MD
Martus JE, Hilmes MA, Grice JV, et al. Radiation exposure during operative fixation of pediatric supracondylar humerus fractures: is lead shielding necessary? J Pediatr Orthop 2018 May/Jun;38(5):249-253. doi: 10.1097/BPO.0000000000000810.
In the pediatric population, supracondylar humerus (SCH) fracture is one of the most common elbow fractures requiring operative intervention. Patients with displaced SCH fractures undergo closed or open reduction and percutaneous pinning in the operating room with the use of fluoroscopy. Much attention has been focused on the amount of the radiation used intraoperatively due to concern for overexposure and an increased risk of malignancy.
The goal of a recently published study by Martus et al was to evaluate the effect of scattered radiation incurred during SCH fracture pinning on organs most sensitive to radiation-associated malignancy: the ovaries, testes, and thyroid. They described radiation terminology to set a framework for understanding:
- Air kerma: Energy released by radiation, measured per unit mass
- Absorbed dose: The amount of radiation absorbed by an object. This is based on the type of tissue and the photon energy of the radiation and is also expressed per unit mass: absorbed dose = skin entrance dose (mGy/min) x fluoroscopy duration (min).
- Equivalent dose: Measure of damage caused to a tissue from an absorbed dose of radiation. It is measured in sieverts and is equal to the absorbed dose multiplied by a weighing factor of the radiation source.
- Effective dose: The sum of the equivalent doses multiplied by a factor for sensitivity of each organ type. This is measured to assess the probability of malignancy or genetic defects occurring from exposure.
- Phantom: Device used to model and determine the absorbed dose for an irradiated object
Martus et al prospectively evaluated 18 pediatric patients who sustained displaced SCH fractures and underwent percutaneous pinning, measuring the distance between the image intensifier and the elbow, ovaries, testes, and thyroid. All patients were positioned supine with the elbow on an inverted C-arm. They were shielded with lead at the neck and pelvis and had a dosimeter placed at sensitive locations to capture the amount of scattered radiation. A forearm phantom was placed at the elbow to ascertain the absorbed skin dose at the elbow in comparison with a retrospective cohort of patients (n=163) who had undergone SCH fracture pinning.
The prospective cohort patients had a mean age of 4.9 years, weight of 21.4 kg, fluoroscopy time of 65.0 seconds, and absorbed skin dose at the elbow 0.47 mGy – all of which were not significantly different in the retrospective cohort: mean age of 5.5 years, weight of 21.6 kg, fluoroscopy time of 74.1 seconds, and absorbed skin dose of 0.53 mGy.
The ratio of type II to type III SCH fractures was 8:10 in the prospective group and 60:103 in the retrospective group. Type II fractures had significantly longer fluoroscopy times and greater absorbed skin doses at the elbow than type III fractures in the prospective and retrospective groups.
The average distance of the image intensifier to the gonads was 43.0 cm; to the thyroid, it was 28.9 cm. The effective dose measured from these sites via the dosimeter was < 0.01 millisieverts.
Although several papers have discussed the amount of radiation at the elbow, few have looked at scattered radiation to determine the need for lead shielding. Martus et al recorded less than 0.01 mSv of radiation at the gonads and thyroid during routine SCH fracture pinning, which is not much greater than the normal daily background radiation of approximately 0.007 mSv per day.
The authors include a quote from the International Commission on Radiological Protection on “shielding of the child’s body in the immediate proximity of the diagnostic field. The use of additional shielding should also be considered for certain examinations to protect against external scattered and extrafocal radiation. When the breasts, gonads, and/or thyroid lie within 5 cm of the primary beam, they should be protected whenever this is possible without impairing the necessary diagnostic information.”
These guidelines would suggest that breast, gonadal, and thyroid tissue that is not close to the beam does not need to be shielded routinely. However, state guidelines and the authors argue that shielding of these organs should be done whenever possible to reduce the amount of cumulative radiation in children.
Martus et al also highlight the importance of moving the elbow away from the radiation source by using an inverted C-arm to reduce the amount of radiation to the exposed site. A possible drawback of this method is the increased radiation needed to obtain a high-quality image at increasing distances away from the primary beam.
A future study to measure the absorbed dose at areas even further from the beam over a longer period of time is warranted to evaluate the cumulative exposure a medical professional might receive as a bystander. As not all medical centers use the inverted C-arm technique, a further evaluation of radiation exposure using standard C-arm orientation may also be valuable.
Rivka Chinyere Ihejirika, MD is an orthopaedic surgery resident at NYU Langone Orthopedic Hospital, New York, New York. Alice Chu, MD is an attending pediatric orthopaedic surgeon and associate professor in the Department of Orthopaedic Surgery at NYU Langone Orthopedic Hospital, New York, New York, where she specializes in hand and upper extremity surgery.
The authors have no disclosures relevant to this article.