Feature article

MRI Options for Imaging Rotator Cuff Damage

One of the most common injuries encountered in an orthopedic practice is injury to the shoulder. In recent years, physicians have been seeing an increase to the number of shoulder injuries, specifically among young athletes and  patients over 40 years old. Damage to the muscles and tendons of shoulder joints occurs due to repetitive of over use or natural wear and tear as one ages. This damage often results in a tear in the rotator cuff, which can cause a great deal of pain and discomfort. There are many approaches to treating rotator cuff damage, in the hopes that the pain will subside, and a patient will fully recover from the injury.  

Anatomy of the Rotator Cuff

Your shoulder is a complex system of muscles, ligaments and bones, capable of extensive motions. The shoulder joint is made up of three bones: the humerus (upper arm bone), the scapula (shoulder blade), and the clavicle (collarbone). The shoulder is a ball-and-socket joint, meaning that the head of the upper arm bone fits into a shallow socket in the shoulder blade. The humerus is held securely into the shoulder socket by the rotator cuff.

The rotator cuff is a series of  muscles and tendons that surround the shoulder joint, stabilizes the bones, and helps to lift and rotate the arm.1 This structure allows the bones of the shoulder to move in more directions than any other joint in the body. The group of muscles that make up the rotator cuff are known as the teres minor, supraspinatus, infraspinatus, and subscapularis.2 Generally, when a rotator cuff tear occurs, it involves the supraspinatus tendon incurring gradual damage.

Why does the Rotator Cuff Tear?

Rotator cuff damage can be caused by:

  • Repetitive motions and overuse
  • Degeneration as you age
  • Injury or accident

The majority of rotator cuff tears happen as a result of a wearing down of the tendon that occurs gradually and naturally as we age. The major cause of shoulder pain in patients older than 40 is rotator cuff damage. In fact, it is estimated that 20-50% of people 60 years or older have a rotator cuff tear, and 65% of individuals older than 70 years have an asymptomatic rotator cuff tear.3 Several factors contribute to degenerative rotator cuff tears:

  • Repetitive stress- Repeating the same shoulder motions again and again puts stress on your muscles and tendons. Sports such as baseball, tennis, and volley ball are examples of activities that put you at risk for a tear. Many jobs that require lifting heavy objects can cause overuse as well.
  • Lack of blood supply- As we age the blood supply in our rotator cuff tendons decreases, inhibiting the body’s ability to repair minor tendon damage and leading to a tendon tear.
  • Bone spurs- As we get older bone spurs often develop on the underside of the acromion bone. When we lift our arms, the spur rubs on the rotator cuff tendon, weakening it and making it more likely to tear. This condition is known as an impingement.1

When damage or a tear occurs to the rotator cuff tendons, shoulder movement becomes very painful and the arm may become weak. Many people with rotator cuff tears experience pain when lifting their arm overhead, and have difficulty completing daily tasks such as putting on a shirt or brushing their hair. In addition, this injury also causes a great deal of pain when you are sleeping, often making it impossible to sleep on the damaged shoulder.2

If pain and weakness in the shoulder persists for more than two weeks, it is important that you contact an orthopedic expert. Damaged or torn tendons cannot heal themselves, and if they are not treated properly the muscles around the shoulder may atrophy and no longer be functional.

How to Examine Rotator Cuff Damage

The most common exam that a physician will use to diagnose a rotator cuff tear is a magnetic resonance imaging (MRI) test. An MRI scanner uses a powerful magnetic field, radio frequency pulses, and a computer to produce a highly detailed image of organs, soft tissue, bone, and other structures within the body. This test is used to assess injuries and conditions, detect any abnormalities, and determine treatment plans.

 An MRI of the shoulder will provide detailed images of the structures within the shoulder joint from multiple angles, providing a radiologist with up-to-date and accurate visual depictions of the joint. In addition, unlike an X-ray or CT scan, an MRI does not use any potentially harmful ionizing radiation, and it is an entirely painless procedure. Furthermore, with the development of new arthroscopic techniques for examining rotator cuff tears, MRI is playing an increasingly important role in determining which patients may benefit from surgery.

MRI Arthrogram

An MRI arthrogram is a two-part procedure that shows more details of a joint than an MRI alone. During the arthrogram, a contrast agent is injected into the targeted joint. Injecting contrast assists the radiologist in easily differentiating between normal and abnormal tissue. The radiologist will use a fluoroscope to inject the contrast in exactly the right place. A fluoroscope is an X-ray machine that allows a radiologist to view X-ray images live, without having to take and develop X-ray photographs.4 Once the contrast is injected, the patient will undergo an MRI exam.

A French study by Lambert et al found that when detecting a rotator cuff tendon tear requiring surgery, a 3.0T MRI alone has a positive predictive value of 100%. In a follow-up study of 48 patients, when arthroscopy was performed, there was no change in the surgical management determined by the initial MRI.3

When examining using conventional MRI alone, T2-weighted images in the oblique coronal and oblique sagittal planes is the preferred technique for imaging the rotator cuff. Most radiologists have found that fat-suppressed, fast spin-echo, T2-weighted images are the most accurate for detecting rotator cuff tears. A sensitivity of 84-100% and a specificity of at least 77-97% can be expected with this pulse sequence. In addition, research has shown that oblique sagittal images are especially useful for identifying tears involving the anterior edge of the supraspinatus.3

However, there are some advantages to using MRI arthrography. When injecting the contrast agent into the joint, the substance distends the joint, forcing the contrast agent into a small defect. Therefore, T1-weighted images, which are fast to acquire and have a superior signal-to-noise ratio can be used instead of T2-weighted images.3

When a full-thickness tear is present in the rotator cuff, MR arthrography will display the contrast solution extending through the defect in the cuff and  into the subacromial-subdeltoid bursa. When only a partial-thickness tear is present the scan will show an extension of the contrast agent into the substance of the tendon. Several studies have reported that MR arthrography is nearly 100% sensitive and specific for both full-thickness and partial-thickness rotator cuff tears.3

Furthermore, several studies have shown that compared to traditional MRIs of the rotator cuff, tears are better characterized on MR arthrography and there is better correlation with surgical findings. In fact, one study reported that radiologists improved their accuracy for detecting tears from 62-67% with MRI, to 92-96% with MR arthrography. Despite these studies, use of MR arthrography has not been widely accepted. Most radiologists have found that fat-suppressed, fast spin-echo, T2-weighted images obtained with a quality shoulder coil are accurate for most rotator cuff tears, and that conventional MRI is adequate for routine imaging of the shoulder.3

Buyers Guide_950x250.jpg

Treatment of Rotator Cuff Tear

If a rotator cuff tear is detected on the MRI, your physician will recommend a treatment plan. Rotator cuff tears that are left untreated can expand over time and early treatment can prevent symptoms from worsening. In planning your treatment, your physician will consider many individual factors, such as your age, activity level, overall health, and the type of tear.

In about 80% of patients, nonsurgical treatment, such as physical therapy, will relieve pain and improve function in the shoulder.1 Additional nonsurgical options include:

  • rest
  • avoiding activities that cause pain
  • anti-inflammatory medication such as ibuprofen
  • steroid injection.

However, nonsurgical treatment holds the risk of the tear increasing over time and potential limited use of the joint. Surgery to repair a torn rotator cuff involves re-attaching the tendon to the head of the humerus. Surgical treatment may be recommended by your physician if:

  • symptoms have lasted for 6-12 months
  • you have a large tear (more than 3cm)
  • you have significant weakness or loss of function in the shoulder
  • the tear was caused by an acute injury

Rotator cuff repairs account for more than 75,000 surgical repairs performed annually, and research shows that overall patient outcome is positive.5 With accurate imaging provided by both conventional MRI and MRI arthrograms, surgeons have the ability to provide superior treatment for patients on an individual basis. 

 

References:

1. "Rotator Cuff Tears". OrthoInfo. American Academy of Orthopaedic Surgeons. Web. 31 July 2018. <https://orthoinfo.aaos.org/en/diseases--conditions/rotator-cuff-tears/>.

2. "What does rotator cuff pain feel like?". Ascension. Web. 31 July 2018. <http://www.affinityhealth.org/Services/Orthopedics/ShoulderArms/RotatorCuffPain.htm>

3. Tuite, Michael J. "Rotator Cuff Injury MRI". Medscape. 14 March 2018. Web. 31 July 2018. <https://emedicine.medscape.com/article/401714-overview>.

4. "Fluoroscopy Procedure". Health Library. Web. 31 July 2018. <https://www.hopkinsmedicine.org/healthlibrary/test_procedures/orthopaedic/fluoroscopy_procedure_92,P07662>.

5. Allem, AW, Brophy, RH. "Outcomes of rotator cuff surgery: what does the evidence tell us?". NCBI. 31 October 2012. Web. 31 July 2018. <https://www.ncbi.nlm.nih.gov/pubmed/23040552>.