Why Use Diagnostic Musculoskeletal Ultrasound?
Musculoskeletal ultrasound is an imaging tool which uses high-frequency sound waves to produce images of soft tissues and bony surfaces. While the first report of the use of diagnostic ultrasound for musculoskeletal purposes dates to the 1950’s (Dussik et al., 1958), its use within orthopaedics has accelerated over the past 10-15 years due to its accessibility and image resolution capabilities.
The purpose of this blog post is to evaluate the evidence pertaining to the use of diagnostic ultrasound in sports medicine and orthopaedics.
Diagnostic applications of musculoskeletal ultrasound include evaluation of:
Tendons (tendinopathy, partial tears, full tears)
Muscles (strains, contusion)
Nerves (entrapment)
Ligaments (sprains, tears)
Joint (effusions)
Figure 1 - Normal rotator cuff supraspinatus tendon (Jacobson 2018)
Figure 2 - Abnormal rotator cuff supraspinatus tendon with partial-thickness articular-sided tear (Jacobson 2018)
Figure 3 - Cross-sectional view of enlarged median nerve at carpal tunnel (Koenig et al., 2009)
Figure 4 - Elbow ulnar collateral ligament (van Duijn et al., 2016)
Musculoskeletal Ultrasound is Excellent at Imaging Superficial Structures
The accuracy of diagnostic ultrasound in evaluating rotator cuff conditions has been studied. A 2010 systematic review and meta-analysis of 23 studies by Ottenheijm et al. strongly recommended the use of musculoskeletal ultrasound in patients for whom conservative treatment fails to:
Rule in or rule out full-thickness rotator cuff tears
Rule in partial-thickness rotator cuff tears
Diagnose tendinopathy, subacromial bursitis, and calcific tendinopathy
| Sensitivity | Specificity | |
|---|---|---|
| Full-thickness RC tears | 95% | 96% |
| Partial thickness RC tears | 72% | 93% |
| Subacromial bursitis | 79-81% | 94-98% |
| Tendinopathy | 67-93% | 88-100% |
| Calcific tendinopathy | 100% | 85-98% |
Figure 6 - Sensitivity and specificity of ultrasound for evaluation of various subacromial pathologies (Ottenheijm et al., 2010)
The diagnostic accuracy of ultrasonography, MRI, and MR arthography in the evaluation of rotator cuff disorders was evaluated by Roy et al. via a 2015 systematic review and meta-analysis of 82 studies. The study results found:
For any rotator cuff tear: US, MRI, and MRA are all reasonable imaging modalities
For full-thickness rotator cuff tears: US, MRI, and MRA are all reasonable imaging modalities
For partial-thickness rotator cuff tears: US, MRI, and MRA are all specific, but US and MRI may be limited by lower sensitivity than MRA
| Ultrasound | MRI | MRA | ||||
|---|---|---|---|---|---|---|
| Sensitivity | Specificity | Sensitivity | Specificity | Sensitivity | Specificity | |
| Partial or full thickness RC tears | 91% | 86% | 90% | 90% | 90% | 90% |
| Full thickness RC tears | 91% | 93% | 90% | 93% | 90% | 95% |
| Partial thickness RC tears | 68% | 94% | 67% | 94% | 83% | 93% |
| Tendinopathy | 79% | 94% | ||||
Figure 7 - Comparison of sensitivity and specificity of ultrasound, MRI, and MRA for subacromial pathologies (Roy et al., 2015)
Value of Dynamic Imaging
Musculoskeletal ultrasound enables real-time dynamic imaging that helps correlate pathology with symptom-producing motions. Examples of dynamic ultrasound imaging in sports medicine include:
Rotator cuff impingement (image and video below)
Elbow ulnar collateral ligament (UCL) injury
Wrist extensor tendon subluxation
Snapping hip (internal or external)
Enhanced visualization of hamstring tendon tear and retraction
Enhanced visualization of Achilles tendon tear and retraction
Peroneal tendon subluxation or dislocation
Figure 8 - Video showing evaluation for subacromial rotator cuff impingement (Original video by Dr. Rajiv Verma, DO RMSK)
Post-Operative Imaging
Ultrasound carries minimal metal artifact compared to MRI. A review article from the American Journal of Roentgenology found the presence of metallic implants in MRI can cause substantial imaging artifacts, including signal loss, failure of fat suppression, geometric distortion, and bright pile-up artifacts, all of which can result in failure of many MRI mechanisms (Hargreaves et al., 2011). While there are methods to help avoid or reduce MRI artifacts, ultrasound may be a good alternative.
Ease of Comparison
An advantage of ultrasound compared to MRI is the ability to compare one side of the body to the other. For instance, if an abnormality is found in one shoulder but is of questionable clinical relevance, ultrasound enables the physician to evaluate the unaffected shoulder within a matter of seconds to make a comparison. Obtaining an MRI for the unaffected shoulder for comparison would be highly costly, time-intensive, and likely not covered by insurance.
Patient Interaction During Examination
The patient and physician are both able to view the ultrasound screen during an in-office ultrasound evaluation. This allows the physician to point out normal and abnormal findings to the patient and explain the clinical relevance of the findings in real-time. The combination of verbal and visual explanation can enhance a patient’s understanding of their condition and rationale for treatment options.
In fact, previous literature concluded “Ultrasound performed by the physician provides an excellent opportunity for patient education and to explain the rationale for treatments” (Borg et al., 2008).
Radiation
There is no radiation involved in the use of musculoskeletal ultrasound.
Portability
Ultrasound systems vary in size from units larger than a desktop computer to units that are small enough to be compatible with smartphones and carried in a briefcase. While the image quality of ultrasound machines varies, the portability of ultrasound enables utility in the clinic and on the sidelines during game coverage. Furthermore, given the steep learning curve associated with performing musculoskeletal ultrasound, portable machines allow physicians to practice their ultrasound skills outside of clinic.
Lower Cost Relative to MRI
A 2008 study by Parker et al. evaluated Medicare use, costs, and potential for cost substitution in musculoskeletal imaging. 3621 musculoskeletal MRI’s from 1996 to 2005 were evaluated and used to project musculoskeletal imaging costs from 2006 to 2020. The study results found:
Musculoskeletal MRI usage increased 353.5% from 1996 to 2005.
Projected musculoskeletal imaging costs in 2020 were $3.6 billion, of which $2.0 billion would be for MRI.
45.4% of primary diagnoses and 30.6% of all diagnoses could have been made with musculoskeletal ultrasound.
Potential savings of $6.9 billion in the period from 2006 to 2020.
The study data underscores that substantial cost savings can be realized by using ultrasound in lieu of MRI, when appropriate.
Contraindications
There are no specific contraindications to having an ultrasound evaluation performed.
Limitations
While there are several advantages to using ultrasound for musculoskeletal ultrasound, there are also limitations which must be acknowledged.
First, ultrasound examinations are operator dependent. Musculoskeletal ultrasound evaluation requires a detailed understanding of normal anatomy, abnormal anatomy, and how the anatomy appears on ultrasound imaging. Acquiring this knowledge involves a long, steep learning curve and ongoing continuing education to refine current skills and learn new techniques.
Second, deep structures can be more difficult to evaluate compared to superficial structures due to the limited penetration of ultrasound beams. For instance, a structure deep in the hip may be more difficult to adequately visualize than a structure in the hand or wrist which is close to the skin surface.
Third, ultrasound has a limited field of view, about the size of the edge of a credit card. The ultrasound probe is moved to evaluate the area of interest more completely which helps offset this limitation. That being said, MRI provides a wider field of view than ultrasound.
Fourth, ultrasound beams cannot penetrate through bone. Consequently, structures within joints such as an ACL or meniscus or labrum are difficult to completely evaluate. MRI is superior for evaluating structures inside joints.
Finally, the quality of ultrasound imaging depends upon the quality of the equipment being used. Some older machines may have less image clarity while some newer machines have exquisite detail. It is notable that MRI machines have the same image quality variability that is dependent on the quality of the MRI machine.
Conclusions
Diagnostic ultrasound in sports medicine and orthopaedics has a strong evidence basis favoring its use. Diagnostic ultrasound can and should be utilized as an initial imaging modality prior to MRI when the history, physical examination, and available resources deem it appropriate.
– Rajiv Verma, DO RMSK
References
Dussik KT, Fritch DJ, Kyriazidou M, Sear RS. Measurements of articular tissues with ultrasound. Am J Phys Med 1958;37:160–5.
Jacobson, Jon. Fundamentals of Musculoskeletal Ultrasound. 3rd ed., El Sevier, 2018.
Koenig RW, Pedro MT, Heinen CP, et al. High-resolution ultrasonography in evaluating peripheral nerve entrapment and trauma. Neurosurg Focus. 2009;26(2):E13.
van Duijn AJ, Felton SD. Ultrasound Imaging of Ulnar Collateral Ligament Injury. J Orthop Sports Phys Ther. 2016;46(12):1086. doi:10.2519/jospt.2016.0420
Ottenheijm RP, Jansen MJ, Staal JB, et al. Accuracy of diagnostic ultrasound in patients with suspected subacromial disorders: a systematic review and meta-analysis [published correction appears in Arch Phys Med Rehabil. 2010 Dec;91(12):1962-3]. Arch Phys Med Rehabil. 2010;91(10):1616-1625.
Roy JS, Braën C, Leblond J, et al. Diagnostic accuracy of ultrasonography, MRI and MR arthrography in the characterisation of rotator cuff disorders: a systematic review and meta-analysis. Br J Sports Med. 2015;49(20):1316-1328. doi:10.1136/bjsports-2014-094148
Hargreaves BA, Worters PW, Pauly KB, Pauly JM, Koch KM, Gold GE. Metal-induced artifacts in MRI. AJR Am J Roentgenol. 2011 Sep;197(3):547-55.
Borg F, Agrawal S, Dasgupta B. The use of musculoskeletal ultrasound in patient education. Ann Rheum Dis. 2008; 67:419.
Parker L, Nazarian LN, Carrino JA, et al. Musculoskeletal imaging: medicare use, costs, and potential for cost substitution. J Am Coll Radiol. 2008;5(3):182-188.