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11 Articles in Volume 7, Issue #4
Cervical-Medullary Meningioma
CES in the Treatment of Depression
Deep Penetration Therapeutic Laser
Fibromyalgia Patient Insights
Invoking the Placebo Effect
Multidimensional Ultrasonography
Paradigm Shift in Cancer Pain Management
Prolotherapy for Low Back Pain
Sedation Levels for Intraspinal Injections
Self-Protection Against “Off-label” Lawsuits
Viewpoint: Methadone Successes and Cautions

Multidimensional Ultrasonography

Research now supports the use of diagnostic ultrasound imaging (DUI) for more subtle shoulder lesions including partial thickness rotator cuff tears.

To date, soft-tissue scanning has relied on standard 2-dimensional scanners which do not provide any depth or volume measurement. The latest improvements—including high frequency transducers and much improved image resolution capabilities of ultrasound scanners—have dramatically improved multidimensional ultrasonography and has demonstrated it’s ability in the detection of shoulder rotator cuff (RTC) tears.

Epidemiology of Shoulder Pain

There are only a few areas of the body whose biological dysfunction can cause greater personal and societal costs than the shoulder. Pain in the shoulder is a common condition in America and is responsible for an enormous human burden. In 2000, the direct costs for the treatment of shoulder pathology totaled in excess of 7 billion dollars.1 The economic burden, at a societal level, is surpassed only by low back pain as the most costly condition to treat. Persistent shoulder pain can be related to numerous causes including bursitis, arthritis, tendonitis, capsulitis, impingement, and rotator cuff disease among the more common reasons for shoulder pain and/or weakness. Some of these conditions have complex etiologies but a differential diagnosis is possible when clinicians combine medical history, physical examination, and diagnostic imaging data.

Rotator cuff disorders are the most common cause of shoulder pain with an estimated prevalence of approximately 10%.2 It is estimated that, in general, non-specific shoulder pain has a one year prevalence estimate in some countries between 20-50%, with many community-based study estimates of having shoulder pain within a lifetime at between 14-21%.3 Sport-specific rates of shoulder injury are also available and indicate that certain sports, such as football, have significantly higher rates of shoulder trauma. Using the NFL injury surveillance system, the rate of shoulder injuries in quarterbacks between the time period 1984 and 2001 was estimated to be 15.2% and represented the second most injured region of the body.4 Injuries were classified as either trauma or repetitive strain related, with rotator cuff syndrome (tendonitis) being the most common shoulder problem reported. In collegiate players, rotator cuff injury is also not uncommon. In a recent cohort study of 336 elite college players, approximately 50% had a history of shoulder injuries with the most problematic positions being quarterbacks and defensive backs. Rotator cuff injuries represented about 12% of the total injuries reported by the players.5

With shoulder injury rates being so significant in the U.S. general population, workforce, and sporting milieus, it is not surprising that the clinical community has sought to develop innovative and cost-effective ways in which to image the shoulder and rotator cuff in general. The use of MRI as a means of viewing shoulder anatomy and pathology is well recognized. Magnetic resonance imaging has proven to be a very useful tool in determining the presence or absence of trauma or disease to the various shoulder structures. MRI has been used to estimate the severity of rotator cuff tearing and the general integrity of the rotator mechanism.6 Having said that, not all hospitals and medical centers have access to an MRI—not to mention the high cost, patient inconvenience, and recognized contraindications (metallic implants/pacemakers) to MRI. The high incidence of shoulder pain, specifically rotator cuff dysfunction, has led to the search for more cost-effective means of evaluating key shoulder structures such as the RTC conjoint tendon which seems to be implicated in many cases of shoulder pain.

Shoulder Anatomy

The shoulder is a complex structure that is actually comprised of four separate articulations including; glenohumeral, acromioclavicular, sternoclavicular, and scapulothoracic joints. Motion of the arm on the trunk involves coordinated movements of all these joints. For the purposes of this report, the important muscular elements forming the rotator cuff are the four muscles that converge into the cuff tendon itself. The subscapularis arises from the deep surface of the scapula and inserts onto the lesser tuberosity. The supraspinatus, infraspinatus, and teres minor arise from the posterior surface of the scapula and insert onto the greater tuberosity, from superior to inferior respectively.

When a detailed view of the rotator cuff tendon is seen, it becomes apparent as to how the RTC can be damaged during a fall, overuse, and/or age-related degenerative changes (delamination). The RTC tendon is a relatively flat structure that passes under the bony acromion and rigid coracromial ligament arch. With prolonged and repetitive upper extremity activities, there is cuff irritation leading to possible tendon hypertrophy (swelling) within a normally very narrow space, that being under the coracromial arch. The resultant microtrauma to the cuff can lead to shoulder pain.7 Unfortunately, tendons do not have a very good blood supply and such is the case with the RTC common tendon whose watershed area (region of greatest vascularity) is typically that portion of the tendon lying directly below the acromion. This is the site most likely to be damaged and subject to the subsequent morphological alterations (fibrosis) that follow. Chronic irritation of the RTC tendon has been known to cause more permanent structural changes in the tendon including atrophy, fibrosis, calcification, and impingement leading to RTC tearing.

Multidimensional Ultrasound Imaging

The use of diagnostic ultrasound imaging (DUI) for the detection of rotator cuff disorders and disease has become increasingly popular as studies performed using higher resolution scanners have more consistently demonstrated very good overall accuracy rates.

Unlike lab-based testing, where established sensitivity and specificity values might be considered fixed properties of a test, diagnostic orthopedic testing is inherently different. In orthopedic testing, the tests are performed differently by different examiners across the country. This adds greater variability to those factors that eventually determine the derived values of the Bayesian model. This individual psychomotor aspect to diagnostic testing—combined with variation within scanners (man-machine interaction)—will heavily influence the final outcome of diagnostic accuracy. As a result, global reports on the validity of DUI reflect variance in sensitivity, specificity, positive and negative predicitive values.

The use of DUI in detection of RTC pathology is well accepted in research venues, but continues to be underutilized clinically due to early reports of high operator dependency associated with this form of imaging. While the earlier studies seem to agree that although DUI had good potential for identifying full thickness RTC tears, there was some question as to whether the more difficult partial thickness tears could reliably be detected. With the advent of high frequency transducers and much improved image resolution capabilities of ultrasound scanners, the research now supports the use of DUI for more subtle shoulder lesions including partial thickness rotator cuff tears.8,9 As far as the operator expertise required to use ultrasound imaging, there have been some recent studies supporting a very high diagnostic accuracy rate of ultrasound imaging by both orthopedic surgeons,10 and non-physician medical staff.11

Diagnostic Accuracy

In one study of 332 consecutive patients who underwent surgery after being preoperatively scanned for size and location of RTC tears, ultrasound imaging concurred with surgical findings in all but 12 cases (sensitivity 98%, specificity 93%, accuracy 97%). Size and location of tear were accurately predicted in 69 of 96 cases or 87% accuracy.12 In another study that examined 98 patients who were preoperatively scanned and later underwent arthroscopic surgery to their shoulders, ultrasonography correctly identified all 65 full thickness tears of the RTC with an overall accuracy of 96%.13 Both studies found that full thickness tears were more accurately identified than smaller partial thickness lesions, although accuracy rates for partial thickness tears were well within acceptable ranges and superior to non-imaging diagnostic tests commonly used for detecting the presence of RTC tears.14

The use of MRI for diagnosing post-surgical shoulder pain has historically been a problem due to suture-anchor artifact. In a study of 44 patients who had undergone arthroscopic shoulder surgery along with diagnostic ultrasound scanning but continued to have shoulder pain, ultrasound imaging correctly diagnosed 40/44 patients, posting an accuracy rate of 89%.15 Finally, in another study involving 190 consecutive shoulder patients, diagnostic ultrasound correctly identified 118 of 124 large rotator cuff tears, posting an accuracy rate of 95%. Partial (small) tears were identified in 24 out of 30 patients who had true partial thickness tearing, again posting an accuracy rate of 95%.16

Technology Discussion

The majority of studies to date have utilized the standard 2-dimensional ultrasound scanners which do not provide any depth or volume measurement. The development of 3-dimensional units have added an additional level of understanding versus that of the typical 2D image. The 3D units create static ultrasound images in different planes which —when computer-enhanced and rendered in 3D view—allows the clinician to estimate the volumetric property of a lesion. This three dimensional image creation depends on multiplanar image construction technology similar to that used in MRI. Similarly, the latest 4D units are dynamic, real time multidimensional imaging devices capable of producing very high resolution depictions of human musculo-skeletal anatomy.

“The 3D units create static ultrasound images in different planes which—when computer-enhanced and rendered in 3D view— allows the clinician to estimate the volumetric property of a lesion.”

The use of 3D imaging has already found a niche in obstetric and gynecology practices around the country. While the use of 2D ultrasound in OBGYN has been the convention, it is quickly being replaced by the more “functional” 3D and 4D versions. Multidimensional ultrasound imaging has been shown to accurately depict volume and size characteristics of internal organs such as the gall bladder and lesions such as thyroid nodules.

However, the cost factor in purchasing a multidimensional scanner is significant at this time. A much cheaper alternative is reconstruction software that organizes and manages 2D ultrasound data from exising 2D scanners and creates a 3D image that could otherwise only be achieved with a 3D scanner. An example of such software is Sonocubic by Medge Platforms.

Examples of before and after visualization of a forearm—demonstrating the software transformation of 2D data into a 3D view—is illustrated in Figures 1 and 2, respectively. While Figure 1 is a conventional 2 dimensional image of a forearm mass that provides only width and length dimensions, Figure 2 allows a more complete visualization in 3D by adding a depth element that better estimates the lesion volume and provides a more accurate depiction of overall size or mass. Further, the 3D rendering detected a second smaller but similar lesion in this forearm which was not clearly seen in 2D. The round, dark (hypoechoic) areas are the lesions in both 2D and 3D. The resulting 3D image allows for much improved intra substance visualization of soft tissue structures and subtle soft tissue lesions. Regarding the primary focus of this article, it is clear that this technology will more accurately detect shoulder lesions and partial thickness RTC tears.

Figure 1. 2D ultrasound image of forearm soft tissue structures, with lesions showing as round, dark (hypoechoic) areas.

Figure 2.3D rendering from multiple 2D untrasound images of the forearm providing better visualization of the lesions (round hypoechoic areas).

Conclusion

Clinicians should expect to see a greater dependency on diagnostic ultrasonography for soft tissue scanning in areas such as the shoulder and knee since the diagnostic yield of multidimensional sonography appears to rival the more costly MRI. Alternately, sonographers and clinicians—using specialized software to reconstruct a volume of 2D images at multiple orthogonal planes into a 3D image—can readily render multidimensional views of lesions such as partial thickness tearing in RTC disorders.

Acknowledgement

I wish to thank George Stration of American Medical Systems of Livonia, MI for providing us with the opportunity to test the sonocubic software allowing 2D to 3D image conversion. Further information is available at www.sonocubic.com.

Last updated on: December 13, 2011
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