Imaging of Muscle Injuries In Sports Medicine - Benefits and Assessment

Introduction:

In sports medicine, doctors must help injured athletes return to competition while preventing further harm. Muscle injuries can occur from direct trauma (like a direct blow) or indirect trauma (excessive force along the muscle-tendon-bone axis), resulting in different types of injuries like contusion, muscle strain, and tendon avulsion. Knowing the injury's prognosis, or likely outcome, is crucial, and imaging plays a significant role in this. Doctors use diagnostic tools like ultrasound and MRI to confirm and evaluate the extent of muscle injuries. This helps them decide on the best treatment and predict how long recovery might take. This is especially useful when the injury is unclear, healing takes longer than expected, or surgery might be needed.

How Are Muscle Injuries Classified According to Their Severity?

The British Athletics Muscle Injury Classification provides a grading system for muscle injuries based on severity. Here is a simplified explanation of each grade:

• Grade 0: No detectable muscle injury on MRI. It may be general muscle soreness or normal discomfort after exercise (DOMS).

• Grade 1: Small tear in the muscle with some swelling and bleeding. The tear is less than 10% of the muscle's cross-sectional area and less than 5 cm long. There is some disruption of the muscle fibers, which can extend from the muscle covering (fascia).

• Grade 2: Moderate tear in the muscle with more swelling and bleeding. The tear is 10 to15 percent of the muscle's cross-sectional area and 5 to15 cm long. The fiber disruption can occur within the muscle or at the junction between the muscle and tendon (MTJ).

• Grade 3: Extensive tear in the muscle with significant swelling and bleeding. The tear involves more than 50 percent of the muscle's cross-sectional area and is longer than 15 cm. The fiber disruption can extend into the tendon.

• Grade 4: Complete tear of the muscle or tendon. The entire muscle is torn, or there is a complete tendon tear.

In simple terms, the grading system helps classify muscle injuries based on their size, extent of swelling and bleeding, and degree of fiber disruption. The higher the grade, the more severe the injury.

What Imaging Methods Are Used to Diagnose Muscle Injuries in Sports Medicine?

There are different ways to take pictures of muscle injuries in sports medicine, including MRI, CT scans, Ultrasound, and X-rays. Two standard methods are ultrasound and magnetic resonance imaging (MRI). These are the techniques most often used by doctors to look inside the body and see what's happening with the muscles. MRI is an effective method for evaluating muscle injuries in athletes. It provides detailed visualization of soft tissues and high-resolution images to assess muscle morphology. It is beneficial for diagnosing and assessing the severity of muscle injuries, especially traumatic damage. Ultrasound is another valuable tool for assessing muscle injuries in athletes. It is cheaper and more widely available than MRI, and it allows for dynamic imaging while moving the injured limb, which can help detect muscle fiber disruption and assess healing. Ultrasound can also be used to guide treatments in athletes.

How Is Muscle Damage in Athletes Assessed Using an MRI?

During an MRI for muscle assessment, a dedicated surface coil is used, typically on the affected limb. Multiplanar properties (axial, coronal, and sagittal) are necessary for accurate evaluation. Fluid-sensitive techniques detect oedematous changes, such as fat-suppressed spin-echo T2-weighted or proton density-weighted sequences.T1-weighted spin-echo sequences help assess subacute hemorrhage, hematoma, atrophy, fatty infiltration, and scar tissue in chronic injuries.

Muscle injuries often occur at the myotendinous junction. MRI can reveal different grades of muscle strains:

• Grade 1: shows oedematous changes

• Grade 2: involves partial fiber disruption with hematoma

• Grade 3: represents complete disruption with a visible gap and retraction. Avulsion injuries, where the myotendinous unit is torn from its bony attachment, are also considered grade 3 injuries.

MRI findings have clinical relevance in predicting recovery time and the risk of re-injury.

• A negative MRI is associated with faster recovery.

• The extent of injuries measured using MRI correlates with longer recovery times.

• Disruption of the central tendon is associated with longer recovery times.

• Advanced MRI techniques, such as T2 mapping, diffusion-tensor imaging (DTI), proton MR spectroscopy, and MR elastography, provide detailed information about muscle composition, microstructure, and function.

Therefore, MRI is the reference imaging method for assessing muscle injuries in athletes. It provides crucial information for treatment and predicting recovery times. Advanced MRI techniques offer additional insights, but their practicality in clinical practice currently needs to be improved.

What Are the Benefits of Using Ultrasound for Imaging Muscle Injuries in Sports Medicine?

Before using ultrasound, the doctor will ask the athlete about their symptoms and examine the injured muscle by feeling it with their hands. High-frequency probes are used to assess the injury and examine different muscle angles. Doppler imaging can show increased blood flow associated with acute injuries. Ultrasound can show similar findings to MRI in different grades of muscle strain:

Grade 1: Strains may not show abnormalities or may have areas of increased echogenicity (brightness) or focal tears within the muscle.

Grade 2: Strains show partial fiber disruption and may have intramuscular hematomas (blood collections).

Grade 3:

• Strains show complete disruption of the muscle and retraction of the ends.

• The clinical relevance of ultrasound findings in muscle injuries is still being studied. One study showed that the location and extent of injuries seen on ultrasound were associated with longer recovery times in hamstring injuries. Factors such as the size and length of the injury were related to longer recovery times. However, MRI was found to be a better predictor of recovery time based on the length of the injury.

In conclusion, ultrasound is a useful tool for assessing muscle injuries in athletes. It is more accessible and allows for real-time imaging during movement. It can show similar findings to MRI and may help predict recovery times, although MRI is still considered a better predictor in some instances.

How Are the Healing and Post-Injury Assessed at MRI and Ultrasound Imaging?

• During muscle injury healing, changes can be observed on MRI and ultrasound.

• Decrease in fluid-like signal intensity and formation of scar tissue are common findings.

• Scar tissue appears as areas of low signal intensity on MRI, making it challenging to diagnose new injuries accurately.

• Residual scarring can be present even after recovery, increasing the risk of reinjury.

• Follow-up imaging may show changes in signal intensity, such as increased fluid-like signal intensity or the development of fibrous tissues.

• Ultrasound findings depend on the severity of the initial injury, with minor injuries showing increased echogenicity that gradually decreases during healing.

• More substantial injuries may appear as hypoechoic regions indicating fluid accumulation.

• Ultrasound is less sensitive than MRI in detecting morphological changes after muscle injury.

• Routine imaging follow-up for muscle injuries is unnecessary, but it may be helpful in persistent symptoms after grade 2 injuries or suspected re-injuries.

• Imaging can provide additional information about the healing process and guide further management.

Conclusion:

Muscle injuries in sports are common and affect an athlete's performance. Superior Imaging techniques, like the British classification, help guide treatment and predict better outcomes. MRI is preferred for assessing muscle injuries, while ultrasound is helpful for diagnosis and monitoring recovery. Advanced imaging techniques provide further information but are limited by cost and availability in professional sports.