When we have an injury or pain it is very tempting to want to know exactly what is wrong!
“Why can’t I just have an x-ray or MRI so that we are certain it is only a sprain!”
I understand this wish, but if we imaged every little pain or injury, our medical care would be even more expensive than it currently is. There are even circumstances where imaging can have negative consequences! So, the gatekeeper to imaging needs to be responsible and judicious. This blog we’ll look at the main types of imaging that are used in orthopedics and sports injuries and give you some idea of when and why they are used.
Radiograph (aka, X-Ray)
People often use the term X-Ray interchangeably with a radiograph. You are having an X-Ray in the sense the body absorbs X-Rays, but the image we see at the end is a radiograph. The different structures of the body absorb certain amounts of X-Rays which gives us the nice (or nasty!) picture. This is a simple 2-dimensional picture and can be taken in different positions to give us the view we want.
Radiographs simply show bone and space. With contrast (injected or consumed solution), they can show other things, such as blood vessels and food traveling down the esophagus (In the form of a live x-ray called a fluoroscopy).
Sometimes I hear people say that they had an X-Ray and were told they have worn cartilage – this is not really true as you cannot see cartilage on an X-Ray; instead they are making an inference that there is less space and therefore less of the soft tissue (cartilage) that should be there. While this might be true if you opened up the knee, it may not be the most helpful thing to tell the patient. They walk away from the appointment thinking they have a horrid arthritic knee when in fact, that may not be the cause of their pain! X-Ray has become a formality in medical and chiropractic care when it should not be. X-Rays are harmful, so they should be used only when necessary. In musculoskeletal care, they should be used when there is a concern of fracture or other significant pathology. If someone likely has a soft tissue injury, e.g. muscles, tendon, ligament, or disc, it likely is not appropriate. This principle has been considered with ankle sprains in the form of rules to help decide if there is a risk of a fracture and benefit of a radiograph (see our blog on this here). It has also been looked at by professional groups as part of the Choosing Wisely campaign which many countries take part in. The in 2017 as their first contribution to this campaign stated:
As you will see in these example of imaging and low back pain there is a consensus amongst the medical, chiropractic, and physical therapy organizations that certain things need to be met in order for imaging to be ordered and be useful. Some of you will read this and may realize that you have had imaging that is unnecessary. I have seen this in my patients, which is why I think it is good to publicize the result of these campaigns. I have even had patients who have had recent good quality X-Rays that were taken elsewhere, who have gone on to visit a local doctor and be told by support staff they need to have a new X-Ray using their equipment… The doctor might not be aware of this, but the X-Ray was ordered without a doctor having seen the patient! Rant finished, let’s look at the other imaging options that are out there:
Nuclear Medicine Imaging (CT, PET, SPECT scans)
In a Computed Tomography (CT) scan, many X-Ray measurements are taken to provide us with slices or a cross-sectional representation of the body. Positron Emission Tomography (PET) and Single-Photon Emission Computerized Tomography (SPECT) scans are also forms of CT scans, but use different forms of radiation than an X-Ray. Each of these technologies has their use in various types of medicine and industry. In orthopedics, CT scans are typically used for imaging fractures that are more complex and will require surgical fixation. Whereas a radiograph gives us a 2D view of the fracture, the CT scan gives us a 3D view which can be viewed in 2D or can be looked at in a 3D model. This allows us to see the route(s) that a fracture takes through the bone. In a fracture that is fragmented (comminuted) it helps visualize the fragments of bone and helps the surgeon plan how they will put it back into a normal anatomic position and what hardware they will need to use. Like X-Rays, nuclear imaging may also use contrast dyes to help identify other issues. These scans are used in other conditions in medicine from cardiology to oncology.
Magnetic Resonance Imaging (MRI)
MRI uses a magnetic field, radio waves, and computation to determine the alignment of hydrogen atoms in the various tissues of the body. NOTE, there is no radiation involved! The main risks are if someone has metal objects or implants in their body, so they should make sure they tell their provider about this as this might make this an inappropriate scan. The alignment of hydrogen atoms is detected as a signal, and the differences in the signals give us our image. Some signal differences also indicate a pathology. As with CT scans, a contrast agent can be used to help better visualize/diagnose certain issues. MRI scanners in human medicine are typically either 1.5 or 3 T (Tesla), which denotes the strength of the magnet. The stronger 3T magnets give better resolution (detail) of the scan. One of the challenges of MRI scan is that they take significantly longer than X-Ray or CT scans and are performed in a tunnel which can be claustrophobic. To help those who struggle with claustrophobia, open-sided MRI machines have been developed, but they have weaker magnets, so the images are less detailed. To reduce the time the MRI takes, slices can be thicker, but this can also lead to things being missed if they are between slices. When scans are being performed, various sequences are taken. These sequences are produced by altering parameters such as the time between radio wave pulses and the time for the pulse to be sent and the echo to be received. Two of the most common sequences are T1 and T2. T1 sequences are typically very good for looking at anatomy. T2, on the other hand, is great for looking at pathology as fluids show up as a bright signal or hotspot.
People are often aware that MRI gives a really good view of a person’s anatomy and pathology, so this is often the scan people want their doctor to send them for! As we have seen for the choosing wisely campaign, radiographs and MRI are not indicated for people with acute, non-specific low back pain without red flags. Although we want to know, it is not indicated, and may even have a negative effect. The reason it may have a negative effect is threefold:
- Significant numbers of pain-free people have MRI findings such as disc bulging and degenerative changes. We might be more likely to have surgery or recommendations based on imaging that might not have been necessary. One example is a 2016 case study in the New England Journal of Medicine1. that showed an MRI of a large lumbar disc herniation and then a repeat MRI 5-months later that showed it had spontaneously (i.e. no surgery) resolved. We see this in people who have a degenerative meniscal tear diagnosed by MRI, have a knee scope and the statistics show are no better off at two years than if they had not had surgery and worse find they will end up having knee replacement sooner (see our blog on this!).
- There is actually a significant variability in the reading of an MRI. This paper2 found that a lady with back and leg pain was sent to 10 different imaging centers over a week and there was large variability in the findings/readings of the scans!…Among the 10 reports, there were 49 distinct findings, and not one was found in all 10 reports! On average, each radiologist made about a dozen errors, seeing one or two things that weren’t there and missing about ten things that were! In the UK I saw many more scans and am by no means an expert in interpreting them, but I have caught miss-readings myself and been in hospital rounds where surgeons have disagreed with the radiologists’ findings.
- The nocebo effect – When you are told something about your body it can be positive (placebo), or negative (nocebo). If you are told that you have spinal degeneration that can negatively affect your beliefs about your spine. For this reason, there are actually descriptors that might be more beneficial to use, e.g. “We saw nothing more than the equivalent of wrinkles of the spine on your scan”.
When it is appropriate, MRI is a superb imaging option. In the US, physical therapy programs teach image interpretation, but there are very few situations (military being one) that PTs can order them. In the UK, after the requisite courses, PTs can order all types of imaging and I have been on the side of ordering images out of concern of cancers, fracture, ligament and tendon rupture, which has led to appropriate treatment.
Seeing inside the body is amazing and under the right circumstances, it is very necessary. However, we do not always need to see inside. What a patient tells us provides most of a diagnosis, the physical examination confirms things and imaging is only needed when something more concerning is going on that needs some type of intervention (surgery, chemotherapy, radiotherapy, etc). In many cases, even in the case of imaging findings that we might call a pathology, physical therapy can be successful in helping people return to activity and resolve pain. If you have an issue, don’t be too eager to jump to imaging, consider if physical therapy might help. Feel free to contact (e-mail, or phone) me to see if physical therapy would be a good option to consider.
- Hong J, Ball PA. IMAGES IN CLINICAL MEDICINE. Resolution of Lumbar Disk Herniation without Surgery. N Engl J Med. 2016;374(16):1564.
- Herzog R, Elgort DR, Flanders AE, Moley PJ. Variability in diagnostic error rates of 10 MRI centers performing lumbar spine MRI examinations on the same patient within a 3-week period. Spine J. 2017;17(4):554-561.
- Beattie KA, Duryea J, Pui M, et al. Minimum joint space width and tibial cartilage morphology in the knees of healthy individuals: a cross-sectional study. BMC Musculoskelet Disord. 2008;9:119.
- Kurklu M, Ozboluk S, Kilic E, Tatar O, Ozkan H, Basbozkurt M. Stress fracture of bilateral tibial metaphysis due to ceremonial march training: a case report. Cases J. 2010;3:3.
- Flanigan DC, De smet AA, Graf B. Magnetic resonance imaging in traumatic hip subluxation. Indian J Orthop. 2011;45(3):272-5.
- Fornaro J, Keel M, Harders M, Marincek B, Székely G, Frauenfelder T. An interactive surgical planning tool for acetabular fractures: initial results. J Orthop Surg Res. 2010;5:50.
- Awh MH, Stadnick ME. MRI challenge. Sports Health. 2009;1(2):180-3.