Imaging Of Supraspinatus And Infraspinatus Rotator Cuff
Tears
The rotator cuff tendons surround the humeral head
and are attached to the lesser tuberosity (subscapularis) and the greater
tuberosity (supraspinatus and infraspinatus tendons and teres minor). Between
the two tuberosities is the bicipital groove through which is the long head of
the biceps tendon (see Plate 1-4).
Rotator cuff tears can be either
partial or full thick- ness. Partial-thickness tears involve only a superficial
surface of the tendon and may extend into the tendon substance but are not
through-and-through defects. A full-thickness defect involves the full
thickness of the tendon and may involve more than one tendon.
Tendon tear size is defined as either
partial thickness or full thickness and is also defined by the size in
centimeters of involvement as well as the tendons involved (e.g.,
supraspinatus, infraspinatus). When a large tendon tear is present, often
involving more than one tendon such as the supraspinatus and infraspinatus,
there is retraction of the tendon from its insertion site. When a tear is
present for a substantial period of time, the muscle tissue in the area of the
involved tendons undergoes muscular atrophy and fatty infiltration. These
changes are often seen on MR images and are important prognostic factors with
respect to the ability of the tendon to be repaired or the potential for
healing of the repaired tendon. Larger tears result in loss of both active
forward flexion and external rotation.
Imaging of the rotator cuff can
include ultrasonography, MRI, and CT. Ultrasonography provides a simple and
cost-effective means of assessing the presence of a both partial and
full-thickness tears of the rotator cuff. The efficacy of ultrasonography is
improved with dynamic assessment and recording of the images and should be done
by an experienced radiologist. Many health care systems have not developed the
same expertise with the use of ultrasound when compared with CT arthrography or
MRI with or without the use of contrast enhancement of the images. Contrast
arthrography is performed by injection of a liquid contrast material into the
glenohumeral joint. When there is a full-thickness tear of the rotator cuff,
the contrast material will leak out of the joint through the defect in the
rotator cuff and be seen on plain radiographs, CT scans, or MR images as fluid
in the subacromial space. Use of plain radiographs will give a two-dimensional
view of the shoulder; but when taken in multiple planes, radiographs can give a
more clear definition of the size and location of the tear. Much more
information is available with thin slice tomographic imaging available with CT
and MRI. In addition, an assessment of the muscle atrophy and amount of fatty
infiltration of the muscle can been seen with CT and MRI. For most clinicians,
MRI is preferred as the study providing the most information related to cuff
tear size, location of the tear, degree of tendon retraction, and the changes
in the muscle associated with the location of the tear.
