2.7 Diagnostic methods

10.1055/b-0034-85584

2.7 Diagnostic methods

Introduction
X-rays
CT scans
MRIs
Other diagnostic methods
Conclusion
Further reading

Author Roshdy Guirguis

2.7 Diagnostic methods

2.7.1 Introduction

X-rays (or radiographs) are the oldest and most frequently used form of imaging in medicine. X-rays were discovered over a century ago by Wilhelm Roentgen and are sometimes called roentgenogram. X-rays produce diagnostic images of the human body on photographic film or, frequently these days, digitally on a computer screen. Diagnosis of a suspected bone fracture with x-ray is now common in the emergency department of hospitals, where the clinician’s management of the patient is often guided by x-ray appearance.

Most bone fractures are diagnosed and dealt with using only plain x-ray images. Some injuries, however, may require further, more advanced forms of imaging to either show the anatomy in more detail or diagnose an occult injury which may not be apparent on initial x-rays.

2.7.2 X-rays

Taking an x-ray (radiograph) involves exposing a part of the body to a small dose of invisible, electromagnetic radiation to produce an image of the internal organs and it is especially good for imaging bone. Conventional x-rays use film similar to photographic film that must be developed but modern imaging is shifting toward computerized and digital radiography, resulting in a digital image which can be processed faster and made available for viewing on a computer screen. Digital images can be stored or transmitted electronically. This technique is now fairly widespread; consequently, many hospitals and x-ray departments have become “filmless.”

Advantages of x-rays

X-rays are widely available, inexpensive (compared with other imaging modalities), fast, and easy to perform. They are particularly useful in emergency diagnosis and treatment. In fractures and dislocations, the images obtained are rather easy to interpret and are often sufficient to plan patient treatment without the need of additional investigations.

Disadvantages and limitations of x-rays

X-ray images give clear and detailed views of bone fractures, but provide little information about the adjacent soft tissues. All x-rays emit a radiation dose to the body. Although this dose can be small, the cumulative effect of numerous x-rays in a patient can eventually be harmful. Radiation exposure must therefore be kept to the minimum necessary, especially in children and women of childbearing age.

All health care professionals who use x-ray are also potentially exposed to ionizing radiation. Staff in the operating room are at particular risk because of the high number of fracture cases in which image intensification is used during surgery. Not infrequently staff operating these machines are not as highly trained as radiographers working in x-ray departments. All staff working in the operating room must be aware of these risks and take appropriate precautions to reduce the dose of ionizing radiation to which they are exposed. This risk mandates the wearing of appropriate x-ray dose-measuring devices by everyone working in the operating room.

Standard images

Many fractures and some dislocations are not detectable on a single view. Hence, it is standard practice to obtain a minimum of two views of any suspect bone or joint, usually at right angles to each other: “One view only is one view too few.” Radiography of a fracture requires that there is either some separation or impaction of the fragments (Fig 2.7-1). This prerequisite is not always met, so it is inevitable that some fractures do not show up on either view. Occasionally, at sites where fractures are known to be exceptionally difficult to detect (eg, the scaphoid), it is routine to obtain more than two views.

With any long-bone fracture, it is imperative to image the whole bone which has been fractured to include the joints above and below the fracture. For example, if the fracture involves the shaft of the femur, then the knee and hip joint should also be x-rayed to exclude a fracture or dislocation elsewhere. This applies especially in children who sometimes find it difficult to localize exactly where an injury has occurred. Fractures commonly missed, if inadequate x-rays are taken, include distal tibial fractures around the ankle joint where there may be a concurrent proximal fibula fracture, and a fracture of the radius with dislocation of the distal ulna (Galeazzi fracture).