4.9 Imaging and radiation hazards
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1 Introduction
X-rays are an essential part of the evaluation of a trauma patient and further investigations, such as ultrasound, computed tomography (CT) and magnetic resonance imaging (MRI), help with accurate diagnosis and the planning of appropriate management. Whole body (trauma) CT (WBCT) used early in the investigation of the polytrauma patient allows rapid diagnosis of life-threatening injuries. However, there must be clear indications for its use because it significantly increases the dose of radiation [1]. The use of intraoperative image intensifiers puts the patient, the surgeon, and the surgical team at risk of radiation exposure [2]. The amount of radiation used has increased dramatically over the last few years with the advent of minimally invasive surgery. Intraoperative imaging provides visualization for the treating surgeon to perform accurate approaches for fracture reduction and fixation.
The risk and effects of radiation exposure are well recognized by the orthopedic community as almost half of respondents in one study [3] perceived themselves to be at either moderate or extreme risk for cataract formation due to occupational exposure. Distal radius surgery also poses problems when the surgeon′s hands are often exposed to radiation [4]. Understanding both the benefits and hazards of radiation, it is necessary that surgical teams are able to set up image intensifiers, apply proper technique, and shield themselves to avoid unnecessary and dangerous exposure.
2 Role of imaging in operative fracture treatment
The main purpose of intraoperative imaging is to confirm fracture reduction, correct implant placement, and fixation. Extensive open reduction is now used less often, while indirect reduction, without exposure of the fracture and with biological preservation of soft tissues, is now more common. However, these techniques require more extensive radiological imaging during surgery. The image intensifier is an indispensable part of surgical equipment, but today the patient, the surgeon, and the surgical team are at greater risk of radiation exposure ( Table 4.9-1 ) [5].
New image intensifiers produce small doses of radiation compared with older models, but inappropriate, prolonged, and repetitive use will lead to greater cumulative radiation exposure for individuals.
3 Hazards of radiation exposure
Ionizing radiation is produced from the decay of radioactive materials. This radiation breaks chemical bonds between atoms, which damages living cells in the human body. The body attempts to repair the damage but sometimes the damage cannot be repaired or is too severe or widespread to be repaired.
3.1 Radiation effects
There are two types of deleterious radiation effects: nonstochastic and stochastic [6].
Nonstochastic effects are dose related and the effects will not occur below a certain threshold and the severity depends on the dose. Deterministic effects require injury to multiple cells and have a threshold dose, below which the effect is not expressed. Cataracts, leukemia, thyroid cancer, and even death are examples of the nonstochastic effects that can result from high radiation exposures [7].
Stochastic effects are not dose or threshold related; injury to any single or number of cells may result in production of the effect. Some radiation-induced cancer and genetic effects are stochastic. For example, the probability of radiation-induced leukemia is substantially higher after exposure to 1 Gy (100 rad) but this disease can occur at lower doses. Once the disease occurs, there will be no difference in the severity. Stochastic effects are believed to lack a threshold dose because injury to even a single cell could theoretically result in production of the effect. Since there is no evidence of a lower threshold for the appearance of stochastic effects, the prudent course of action is to ensure that all radiation exposures follow the principle “As Low As Reasonably Achievable” (ALARA).
3.2 Radiosensitivity
The risk of stochastic effects is higher in children compared with adults. This happens because immature cells are more radiosensitive. Studies [8, 9] have also concluded that there is a linear dose relationship between ionizing radiation exposure and the development of radiation-induced cancers. In children, the cumulative effect has a longer time span in which these late effects can develop, and also a longer time span to accumulate further exposures [8–10].
Pregnant patients also need special consideration. If exposed to radiation in the first 30 weeks of pregnancy, delayed effects may appear in the child. These include mental and behavioral retardation, with a delay period of approximately 4 years. If any procedure is required for pregnant patients, surgeons might consider some form of treatment that has less radiation exposure. For example, open reduction and internal fixation may be used rather than minimally invasive osteosynthesis (MIO) to minimize the risk to the fetus ( Table 4.9-2 ).
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