Injuries to the muscles, bones, and joints of high-level athletes are extremely common and may be responsible for prolonged periods of competitive inactivity. The implications of these injuries sometimes have detrimental effects not only to the athlete, but to their team, coach, and affiliated organizations as well. Medical imaging plays a critical role in providing accurate diagnostic and prognostic information regarding the management and treatment of athletic injuries. Any improper diagnoses could cause a delayed return to play or progress into a more serious injury. Several imaging techniques are widely available, however magnetic resonance imaging (MRI) is currently one of the most prevalent imaging exams utilized in examining sports-related injuries.
Sports Exercise Medicine
When a sports-related injury occurs, the main goal of the sports exercise medicine (SEM) physician is to return the athlete to competition as soon as possible. This goal is balanced against the need to prevent the injury from worsening or reoccurring. A SEM physician is usually responsible for managing a multidisciplinary team of specialists, working to ensure that the most effective management plan is delivered to the patient.
A key member of the SEM team is the radiologist. The radiologist will provide significant input regarding the use of appropriate imaging to confirm an accurate diagnosis, information regarding the management of the injury, decisions on return to play, various screening and preparticipation assessments, and technical assistance with certain procedures.1
Sport-related injuries can be broadly divided into acute and chronic injuries. An injury that occurs suddenly, such as a sprained ankle due to an awkward landing, is an acute injury. A chronic injury develops because of repeated overuse of muscle groups or joints.2 Some of the most common sports-related injuries include:
- Sprain- A sprain is abnormal stretching or tearing of a ligament that supports a joint.3
- Muscle strain- A muscle strain refers to damage to a muscle or its attaching tendons, usually in the form of a partial or whole tear to the muscle fibers.4
- Joint damage- Common joint injury occurs in the knees, ankles, wrists, and shoulders. The joints swell and suffer from inflammation, making them immobile and limiting their range of motion.5
- Fracture- A fracture is a broken bone, ranging from a thin crack to a complete break.6
The diagnosis of any sports-related injury is usually established after taking a thorough assessment of the patient’s health history and performing a careful clinical examination of the injured area. When the SEM physician requires additional information before establishing a diagnosis, a medical imaging examination will be ordered.
Why is MRI the Preferred Modality?
The complex nature of some athlete’s injuries and the need for a rapid diagnosis has increased the demand for accuracy and urgency in medical imaging modalities. The specific modality used depends on the range of pathologies and the injured tissues. Selecting the most appropriate imaging test is essential to minimizing patient risk, expediting diagnosis and treatment of the patient, and limiting health care costs.
With soft tissue injuries being very common, many physicians use ultrasound to avoid any exposure to harmful radiation. However, MRI also has an extremely high yield in soft-tissue injuries, including documenting the extent of muscle damage, and the ability to identify intra-articular lesions such as meniscal and articular cartilage injuries. An MRI exam is particularly useful in identifying bone stress as well. The quality of output generated by MRI is often considered the “gold standard”, because of the modalities’ exquisite soft tissue contrast, multiplanar capabilities, and noninvasive procedure.7
While an MRI is not necessary to diagnose an injury, it is an important tool used to confirm a diagnosis or rule out a competing one, especially when the history and physical examination are unable to reliably establish a diagnosis. Furthermore, MRI is commonly used before orthopedic surgery, because the information gained from an MRI can provide the surgeon with a “map” of the injured area, helping to guide the surgery and improve the outcome.
Muscle, tendon, and joint injury, as well as stress fractures are some of the most common sports injuries that may require an MRI scan.
Imaging Injured Muscles
Muscle injuries account for up to one third of all sports-related injuries, representing a major challenge for many athletes. MRI is considered the preferred imaging modality when assessing the morphology of muscles. This is because of an MRI’s ability to visualize soft tissues with excellent contrast and provide high spatial-resolution and multiplanar assessment. Furthermore, when compared to ultrasound, MRI is capable of confirming and evaluating the extent and severity of muscle injuries and can better assess muscle injuries located deep in muscle compartments.9
The majority of muscle injuries occur around the myotendinous junction, the weakest point in the musculotendinous unit. Muscles that are prone to strains typically cross two joints, have a high percentage of fast-twitch muscle fibers, and have a propensity for eccentric contraction.7 These strains commonly occur in the groin and hamstring in many athletes.
Muscle strains are clinically graded as first, second, or third-degree strains, and an MRI examination can visualize the extent of the injury. A first-degree strain is characterized on an MRI as an edema surrounding the myotendinous junction without a hematoma. Second-degree strains show partial-thickness tears of the myotendinous junction, manifested by edema, hematoma and partial disruption. A third-degree strain is document in an MRI as the complete disruption of the myotendinous margins and retracted muscle. In addition, MRI can also differentiate tendon avulsions and myotendinous rupture, which is essential when considering if a patient requires surgery.7
To accurately evaluate morphology and the extent of muscle injuries, multiplanar acquisitions are required of the long and short axes of the involved muscles. In addition, pulse sequences must include fat-suppressed fluid-sensitive techniques, allowing for the detection of edematous changes around the myotendinous and myofascial junctions, as well as for the delineation of intramuscular or perifascial fluid collections or hematomas. Fluid-sensitive techniques include fat-suppressed spin-echo T2-weighted, proton density-weighted, intermediate-weighted sequences, and the short tau inversion recovery (STIR) technique.9
Imaging Injured Joints
Tendons, ligaments, and joints are also common areas of injury among athletes. In fact, MR imaging of the knee joint has become the most commonly performed musculoskeletal MRI exam. In a study of 6.6 million knee injuries presenting to emergency departments in a 10-year period, approximately 50% of the injuries were sports-related.10 An MRI provides the most comprehensive imaging assessment of the knee joint, and when performed early enough after injury, is both cost-effective and can aid in predicting which patients need further treatment.
An injury commonly experienced in the knees of the athletic population is an acute meniscal tear, and well-established imaging criteria exists in the diagnosis of this injury. This includes abnormal intrameniscal signal intensity on short-echo-time pulse sequence images extending to an articular surface on at least two sections, alteration of meniscal morphology, or identification of displaced meniscal fragments. The combined sensitivity and specificity of MRI for medial meniscal tears is 93% and 88% respectively, and 79% and 95% respectively for a lateral meniscus tear.10 MRI can further classify a meniscal tear by its orientation, whether it occurred due to trauma, and what parts of the knee the tear is affecting. The location of the tear within the meniscus is significant, as it influences the type of meniscal repair required.
Standard MRI studies of the knee when obtaining a global assessment are typically acquired in three orthogonal planes with a combination of proton density, intermediate-weighted, and T2-weighted pulse sequences with and without fat suppression. Many radiologists prefer spectral fat suppression when acquiring fat-suppressed images, due to the superior signal-to-noise ratio in comparison with inversion recovery techniques. In addition, three-dimensional isotropic acquisitions performed on a 3.0T scanner have been found to have improved spatial resolution and are routinely used as a problem-solving tool when examining the knee.10
Imaging Fractures in Bones
MRI for imaging bones has surpassed other imaging modalities, with a sensitivity of 100% and specificity of 85%. An MRI exam can provide better anatomical detail and more precisely depict the tissues involved.11 Common sports-related bone injuries seen in many runners and jumpers are medial tibial stress syndrome (shin splints) and stress fractures. These injuries are both caused by repeated over use and stressful impact on the bones.
An MRI can easily detect minor stress reactions, such as bone contusions on a STIR sequence or a fat-suppressed T2-weighted fast-spin-echo sequence. It is also sensitive enough to detect further malignant entities causing a marrow replacement, which makes the bone prone to insufficiency fracture.14
In a study conducted by Takeo Mammoto et. al, 33 patients with exercise-induced tibial pain were evaluated. High-resolution MR axial images were obtained using a microscopy surface coil on a 1.5T MR system. All 33 patients showed abnormal signals in the periosteal tissue, and 26 patients also showed abnormal signals in the bone marrow. This study concluded that bone marrow abnormalities might predict later periosteal reactions, leading to shin splints or stress fractures.12
Another study cited by the American Journal of Roentgenology examined 26 asymptomatic male collegiate basketball players. All 26 players were imaged before their season began, and 14 were imaged at the end of the season. The MR imaging was done on a 1.5T system and included axial turbo spin echo (TSE) proton density-weighted images, axial gradian recalled echo T2-weighted images, and axial TSE fat-suppressed T2-weighted images. The results documented abnormal signals of the periosteum, bone marrow, and cortical bone, as well as edema along fascial structures and involving muscle.
The study resulted in 12% of 52 feet showing a signal indicating bone marrow edema in the metatarsals. The MRI exams were able to depict bone marrow edema in the feet before a fracture became evident, implying that identification of this edema may reveal stress changes early on, allowing early treatment and prevention of potentially debilitating stress fractures.13 In fact, it has become well documented that MRI is able to show even minor stress changes in bone at a much earlier stage than that of the actual stress fracture, providing athletes with valuable information regarding the management of injury.
Benefits of 3.0T MR vs. 1.5T when Examining the Musculoskeletal System
High-field MRI of 3.0T is quickly gaining clinical acceptance and experiencing widespread use. The increased signal-to-noise ratio (SNR) is fundamentally responsible for improved image quality compared to a 1.5T system. While the superiority of 3.0T imaging has been clearly demonstrated for neurological imaging, what is the impact of 3.0T imaging of the musculoskeletal system?
Wong, Scot et al performed a comparative study of 3.0T versus 1.5T of the knee joint in 2009. The intent was to compare MR imaging at 1.5 and 3.0T in the same patients, regarding image quality, visualization of cartilage pathology, and to assess diagnostic performance. 26 patients were identified in the study, and standard MR protocols included T1-weighted and fat-saturated intermediate-weighted fast spin-echo sequences in three planes.
Four radiologists reviewed each study independently, scored image quality, and analyzed pathological findings. The results showed that each radiologist scored the 3.0T images higher than those obtained at 1.5T in visualizing anatomical structures and abnormalities. In addition, diagnosis of cartilage abnormalities was improved at 3.0T with higher sensitivity, accuracy, and correct grading of cartilage lesions. Furthermore, SNR at 3.0T was approximately two times higher than at 1.5T. These results not only demonstrated improved image quality, but also documented improved diagnostic confidence when using 3.0T compared to 1.5T when imaging the musculoskeletal system.15
As technology continues to advance, the powerful capabilities of MRI and the value that this imaging modality brings to the clinical setting continues to grow as well. For high-level athletes, these advances mean earlier detection of injury and improved management plans; ultimately alluding to a more successful athletic career.
1. McCurdie, I. "Imaging in sport and exercise medicine: "a sports physician's outlook and needs". PMC. NCBI, August 2012. Web. 08 August 2018. <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3495580/>.
2. "Sports Injuries". Better Health Channel. Victoria State Government, August 2015. Web. 08 August 2018. <https://www.betterhealth.vic.gov.au/health/HealthyLiving/sports-injuries>.
3. Wedrob, Benjamin. "Sprains and Strains." MedicineNet.com. 06 July 2018.Web. 08 August 2018. <https://www.medicinenet.com/sprained_ankle/article.htm>.
4. "Muscle Strain." WebMD. Web. 08 August 2018. <https://www.webmd.com/fitness-exercise/guide/muscle-strain#1>.
5. "Common Joint and Muscle Injuries." Elastoplast. Web. 08 August 2018. <https://www.elastoplast.com.au/injury-advice/muscle-and-joint-pain/common-joint-and-muscle-injuries>.
6. "Fracture". healthline. Web. 08 August 2018. <https://www.healthline.com/health/fracture>.
7. Lischuk, A.W., et al. "Imaging of Sports-Related Hip and Groin Injuries." PMC. NCBI. May 2010. Web. 08 August 2018. <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3445100/>.
8. Finanger, Erika L., et al. "Use of skeletal muscle MRI in diagnosis and monitoring disease progression in Duchenne Muscular dystrophy." PMC. NCBI. 14 December 2011. Web. 08 August 2018. <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3561672/>.
9. Guermaze, Ali, et al. "Imaging of Muscle Injuries in Sports Medicine: Sports Imaging Series." Radiology. RSNA. 20 February 2017. Web. 08 August 2018. <https://pubs.rsna.org/doi/full/10.1148/radiol.2017160267>.
10. Naraghi, Ali M., White, Lawrence M. "Imaging of Athletic Injuries of Knee Ligaments and Menisci: Sports Imaging Series." Radiology. RSNA. 19 September 2016. Web. 08 August 2018. <https://pubs.rsna.org/doi/full/10.1148/radiol.2016152320>.
11. Berger, Ferco, et al. "Stress fractures." Radiology Assistant. 23 May 2007. Web. 08 August 2018. <http://www.radiologyassistant.nl/en/p4615feaee7e0a/stress-fractures.html#i4625327aa3e45>.
12. Mammoto, Takeo, et al. "High-resolution axial MR imaging of tibial stress injuries." PMC. NCBI. 10 May 2012. Web. 08 August 2018. <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3411460/>.
13. Major, Nancy M. "Role of MRI in Prevention of Metatarsal Stress Fractures in Collegiate Basketball Players."American Journal of Roentgenology. ARRS. January 2006. Web. 08 August 2018.
14. Sinha, Partha. "Stress Fracture Imaging." Medscape. 12 January 2016. Web. 08 August 2018. <https://emedicine.medscape.com/article/397402-overview>.
15. Wong, Scot, et al. "Comparative study of imaging at 3.0T versus 1.5 T of the knee." PMC. NCBI. 07 April 2009. Web. 08 August 2018. <https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2704948/>.