CME article 2

Ultrasound of the Shoulder Joint
Dr Rahul Sachdev, New Delhi

 

The differential diagnosis of shoulder pain includes a wide variety of lesions that can produce similar symptoms and signs. Rotator cuff tendinitis, strain and tears can all produce shoulder pain and weakness on elevation of the arm. Since each of these conditions have different treatments, their differentiation is essential.

Pathophysiology

There is an area of relative avscularity a cm proximal to the point of insertion into the greater tuberosity. In addition, there is a relatively avascular area in the biceps tendon. This has been described as a critical zone. Therefore, attrition, chronic irritation, and inflammatory processes could result in weakening of these structures, leading to complete tears. Progressively, as the tendinous portion of the Rotator cuff becomes thin or torn, the Rotators allow the deltiod to pull the humerus against the undersurface of the acromion, thereby leading to more impingement and tearing. In very large and chronic tears, the tendon may be put at risk and is often found deficient at the time of surgery.

Impingement syndrome has been classified into three stages:

Stage I: Edema and hemorrhage

Stage II: Further inflammatory changes with fibrosis and thickening of the biceps tendon

Stage III: Disease eventually evolves into complete thickness tears of the rotator cuff.

 
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Major Criteria:

Non visualization of the cuff

Focal non-visualization of the cuff

Discontinuity

Abnormal echogenecity

 
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Fig 3 (discontinuity) Fig 4 (abnormal chogenecity)
 

Minor Criteria:

Sub-deltoid bursal effusion

Concave sub-deltoid bursal contour

Humeral head elevation

Joint effusion

 
Non visualization of the cuff
In large rotator cuff tears, no cuff tendon will be visualized.

The sub-deltoid bursa will

a) Directly approximate the surface of the humeral head

b) Its contour will be concave downwards

c) It will be thickened, measuring upto 5 mm

Joint and bursal effusion is a common accompaniment to such large tears

 
Focal Non visualization of the cuff
 
Smaller tears will appear as localized absence in the cuff. The sub-deltoid bursa will touch the humeral head. The majority of these tears will occur anteriorly in the supra spinatus area in the critical zone. A small amount of cuff is preserved surrounding the biceps tendon. Tears will be sharply demarcated with abrupt transition from normal to abnormal cuff.
 
Discontinuity
   
This is observed sonographically when smaller cuff defects fill with joint fluid or echogenic reactive tissue. Such defects may be accentuated by placement of the arm in extension and internal rotation.
 
Abnormal Echogenecity
 
This can be diffuse or focal. Diffuse abnormal echogenecity is an unreliable sonographic sign for cuff tears. It may be associated with inflammation or fibrosis. Focal abnormal echogenecity has been associated with full thickness and partial thickness tears. The increased echogenecity is due to granulation tissue, hypertrophied synovium and hemorrhage.
 
Sub Deltoid Bursal Effusion

This is the most reliable secondary finding. This may be the only abnormal sonographic finding in patients with small tears. In the presence of an otherwise normal USG, this should be followed up by arthrography or MRI.

Concave Sub-Deltoid Bursal Contour

This is noted in medium and large tears reflecting the absence of cuff tendon.

Humeral Head Elevation

The humeral head may be elevated relative to the acromion when compared with the normal site, corresponding to plain film findings.

Joint Effusion

Intra-articular effusion has been strongly correlated with cuff pathology. The presence of such fluid should strongly increase the sonographer’s suspicion of full thickness tears.

Echogenic Band

Echogenic foci have been reported as the sign of rotator cuff tears. Surgical correlation in these patients have shown that the areas of increased echogenecity corresponded to granulation tissue that filled in the gap created by rotator cuff tears.

Biceps Tendon

The most important abnormality to identify is the biceps tendon sheath effusion. This appears as an echo-poor halo surrounding the extra-articular portion of the biceps tendon. Transverse views display the biceps tendon sheath effusion more reliably than longitudinal views. 50% of biceps tendon sheath effusions are associated with rotator cuff tears.

Comparison of published results
 
  Mack Crass Middleton
Sensitivity 91% 93% 93%
Specificity 98% 92% 83%
Accuracy 95% 91% 87%
Prevalence 52% 28% 60%
Criteria 1,2,3 1,2,3,4a 1,2,3,5
Gold Standard Surgery Surgery Arthrography
Pathology FT PT/FT FT
Frequency 5 Mhz 10 Mhz 10 Mhz
Equipment LA MS MS
 
Criteria:

1. Nonvisualization

2. Focal nonvisualization

3. Discontinuity

4. Abnormal echogenecity

 
a focal

Pathology

PT partial thickness tear

LT linear array

b diffuse

FT full thickness rotator cuff tear

Equipment

MS Mechanical sector

 
References

1. Middleton WD. USG of the shoulder: Rotator Cuff NA: 1992; 30: 927-40.

2. Mack LA. Sonographic evaluation of the rotator cuff: Rotator Cuff NA: 1988; 26: 161-77.

3. Crass JR. USG of the Rotator Cuff with surgical correlation. JCU 1984; 12: 487-93.

4. Crass JR. USG of the Rotator Cuff. Radiographics 1985; 5: 941-53.

5. Middleton WD. Pitfalls of Rotator cuff sonography. AJR 1986; 146: 555-60.

Contribution

Dr. Rahul Sachdev, BR Diagnostics, GK I, New Delhi.