As Podiatrist’s we order A LOT of imaging studies for our patients. Such studies include x-rays, MRI’s, CT Scans, Bone Scans, and Ultrasound to name a few. It may sometimes seem unnecessary and annoying because treatment is occasionally postponed until the results of such studies are received, but I assure you, they have their purpose. This week, the intent is to briefly describe some of the imaging studies we order, why we order them and how they differ from each other. However, it should be understood that we do not arbitrarily order imaging studies to help us come up with a diagnoses, but rather we use them to confirm our suspicions of a diagnosis.
X-rays: This is typically the first imaging study that will be performed by your Podiatrist. X-rays primarily capture the bones of the foot and ankle and for this reason, they are typically ordered for fractures, bunions, hammertoes, and any pathology that may disrupt the bone including diffuse bone infection, bone tumors, gout and arthritis to name a few. They also allow us to take a closer look at the position of the bones during stance, providing a snapshot of how your foot functions during gait (walking). X-rays, although they can’t specifically convey information about the soft tissues (muscles, ligaments, tendons) they can show swelling, which most often correlates with a clinical picture. Finally, they can show calcified vessels: blood vessels in the lower extremity that have become hardened and thus indicate poor blood flow to the lower extremity. Limitations to x-rays, as mentioned above include soft tissues structures, which need further imaging studies for complete evaluation. In addition, x-rays have a lag time in recognizing stress fractures and acute (early) bone infection. For a plain x-ray to show either of those two pathologies, the pathology needs to have been present for about 10 days; long enough for significant bone destruction (50%) to be visualized on x-ray. For that reason, with a high clinical suspicion of either of those two pathologies, additional imaging studies are typically performed.
MRI’s (Magnetic Resonance Imaging): If we want to get a better picture of soft tissue structures including muscles, tendons, and ligaments in the lower extremity, MRI’s are a good option. MRI’s have the ability to hone in on inflammation within or surrounding a tendon and clearly show ruptures of such structures. They focus less on bone pathology when referring to fractures (CT’s are more accurate), but they are superior to CT scans in diagnosis bone infection (osteomyelitis). The reason being that they provide excellent visualization of the medullary canal of the bone (the central area where bone infection tends to migrate), and thus help Podiatrists determine how far the infection has spread and how aggressive their treatment regimen needs to be. Finally, they are the best option diagnosing pathology between bone and soft tissue, where it needs to be determined if bone pathology has spread into adjacent soft tissues and vice versus. The only downside with MRI usage is that, should a patient have any metal or stainless steel anywhere in their body, these studies cannot be performed as they interact with the magnets within the MRI machine.
CT Scans (Computerized Tomography): These scans are excellent for visualizing bone to a greater degree than standard x-rays can show us. Often CT Scans are ordered for evaluation of complex fractures such as Lisfranc fractures and calcaneal fractures. They can more accurately show fractures too small to be visualized on plain x-ray in addition to helping to determine the amount of joint surface involved in the pathology. CT scans can also be used in diagnosis of bone infection, but MRI’s are typically a better option as they can more accurately capture the medullary canal. CT scans can be used in patients with metal or stainless steel implants, thus are a good alternative for patients who can not undergo MRI evaluation.
Ultrasounds: This imaging studying is becoming more and more popular among Podiatric Physicians, whereby diagnosis of various pathologies can be made through its use. The test takes little time, making it more convenient for the patient in addition to providing quick results to you Podiatrist. Ultrasounds are very useful for tendon pathology, meaning any deformity or abnormality in a tendon, such as rupture, tear, or inflammation surrounding a tendon, which indicates aggravation of the tissue. These studies are also becoming more popular for use in diagnosing neuromas (inflammation of nerve tissue in the web-spaces) and have provided use in guiding injections of the foot for more accurate medication placement.
Although it can seem burdensome, imaging studies do help us confirm our suspected diagnoses and are often necessary for treatment to begin, so we appreciate you taking the time to have them completed per our request. The hope is that you now have a greater understanding of each of the imaging modalities discussed above, and can thus understand why we request them to be performed. Certainly, each type of imaging study discussed above encompasses a broader range of uses, but those discussed this week are the primary reasons for viewing in the foot and ankle.