Rotator cuff anatomy
Fonte- http://www.jouefct.com/rotator-cuff-anatomy-gallery-download-top-10/rotator-cuff-anatomy-gallery-download-top-10-shoulder/
The shoulder is a synovial articulation in which the shallow glenoid is deepened an additional 50% by the fibrocartilaginous labrum that forms a rim around the perimeter of the glenoid (1).
Four muscles attach as tendons onto the proximal humerus and make up the rotator The supraspinatus,
subscapularis,
infraspinatus,
and teres minor are the componentes of the rotator cuff and have insertion on the greater tuberosity of the proximal humerus,
the lesser tuberosity of the proximal humerus the posterior aspect of the greater tuberosity and the greater tuberosity respectively.
At the distal aspect of the rotator cuff,
the supraspinatus and infraspinatus tendons splay out and interdigitate,
forming a common continuous insertion on the middle facet of the humeral greater tuberosity.
To a lesser extent,
the supraspinatus and subscapularis tendons demonstrate contiguity,
with interwoven fibers from these two tendons envel- oping the biceps tendon.
The greater tuberosity consists of three facets the superior,
middle and inferior.
The supraspinatus has a widht of approximately 23 mm in width and the infraspitatus of approximately 22 mm (3).
The rotator interval is a space between the anterior part of the supraspinatus tendon and the superior edge of the subscapularis tendon.
Fonte- http://everydayphysio.tumblr.com/post/117162766266/the-rotator-cuff-interval-the-rotator-interval
In this space,
the long head of the biceps brachii tendon becomes intraarticular as it courses toward the supraglenoid tubercle of the scapula.
The rotator interval also allows a direct communication between the glenohumeral joint and the subscapularis recess.
There are several other anatomic structures about the shoulder that deserve mention.
Some strutctures deserve special mention namely,
the acromioclavicular joint,
which is also a synovial articulation.
A fibrocartilage disc is located in the acromioclavicular joint,
which degenerates (4).
Another anatomic structure is the subacromial-subdeltoid bursa,
primarily located between the supraspinatus tendon and the coracoacromial arch.
The coracoacromial arch is located over the supraspinatus tendon and subacromial-subdeltoid bursa and consists of the coracoid,
the coracoacromial ligament,
and the acromion.
Rotator Cuff Function
Muscle
|
Origin
|
Insertion
|
Joint actions
|
Infraspinatus
|
Scapula
|
Humerus
|
Stabizer,
lateral rotation and abduction
|
Supraspinatus
|
Scapula
|
Humerus
|
Abduction; stabilizer
|
Subscapularis
|
Scapula
|
Humerus
|
Medial rotation,
stabilizer
|
Teres Minor
|
Scapula
|
Humerus
|
Lateral Rotatiol,
abduction (small part)
|
The rotator cuff is important in shoulder movement
- Initiation of shoulder abduction – supplied by the supraspinatus muscle and tendo,
which if not functional mandates a significant increase in the force exerted by the middle segment of the deltoid muscle.
The infraspinatus muscle is the main external rotator in the shoulder,
whereas the subscapularis muscle is an important internal rotator.
The infraspinatus,
subscapularis,
and latissimus dorsi muscles act as stabilizers during flexion (5),
thesubscapularis muscle acts as a stabilizer during external rotation (6),
and the subscapularis and supraspinatus muscles work together as stabilizers during extension.
One approach suggested to compensate for laxity of the joint capsule and ligaments is strengthening the rotator cuff muscles to compensat
There are many causes of shoulder pain related to impingement (6)
-Rotator cuff disease
-Acromial spurs
-Subacromial-subdeltoid bursal inflammation
-Coracoacromial ligament thickening
Findings at MR imaging may also help determine if surgery is contraindicated.
MR Imaging of Rotator Cuff Tears
Typical protocol
Fonte-https://essr.org/content-essr/uploads/2016/10/shoulder.pdf
Rotator cuff Tears
MR imaging can provide information about rotator cuff tears (7)
- Tear dimensions
- Tear depth or thickness
- Tendon retraction
- Tear shape
Classification of RTC tears(Ellman)-location of full thickness tear
|
Classification of RTC tears (Ellman)-largest dimensiono of the tears
|
Classification of RTC tears (Cofield et al ) Grading of full thickness tear
|
Supraspinatus
|
Less than 2 cm
|
Less than 1 cm
|
Infraspinatus
|
2-4 cm
|
1-3 cm
|
Subscapularis
|
More than 5 cm
|
3-5 cm
|
Teres Minor
|
Cuff artrhopaty
|
More than 5 cm
|
Classifications of RTC tears (Ellman)
|
Location
|
Grading
|
Articular
|
Less than 3 mm
|
Bursal
|
3-6 mm
|
Interstitial
|
More than 3 mm
|
This factors influence treatment selection and help determine the prognosis.
In addition,
tear extension to adjacent structures,
muscle atrophy,
size of muscle cross-sectional area,
and fatty degeneration have implications for the physiologic and mechanical status of the rotator cuff.
DeOrio and Cofield classified rotator cuff tears on the basis of greatest dimension as either small ( 1 cm),
medium (1–3 cm),
large (3–5 cm),
or massive ( 5 cm) (8).
The di- mensions of rotator cuff tears may have implications for selection of treatment and surgical approach,
postoperative prognosis,
and tear recurrence (9).
Although some studies indicate that there is an association between tear size and surgical outcome,
other studies indicate that tear size has no implications for the success of rotator cuff repair or arthroscopic debridement.
Depth of a Partial-Thickness Tear
Articular-surface partial-thickness rotator cuff tears are common and occur more frequently than bursal-surface partial-thickness tears.
Partial-thickness tears that are not repaired can lead to permanente incapacity.
As the depth of a partial-thickness tear increases,
there is increased strain in the remaining tendon and other rotator cuff tendons.
Articular- surface partial-thickness tears may also propagate to a full-thickness tear Both are graded according to their depth as either
- Grade 1 ( 3 mm)
- Grade 2 (3– 6 mm)
- Grade 3 ( 6 mm)
MR imaging supplies the most complete information about tendon structure.
This important information may influence therapeutic decision making and may include information about pos- sible associated disease related to the labrum.
Tendon thickening may be an indication or repair.
Tear Shape
The shape of a rotator cuff tear is important in the selection of a surgical technique.
Tears can be classified arthroscopically into three basic shapes according to the tear geometry as viewed from the tendon surface: crescentic,
U shaped,
and L shaped .
In crescentic tears,
the tendon pulls away from the greater tuberosity but typically does not retract far medially and therefore can be reattached to bone with minimal tension (9).
U-shaped tears are massive rotator cuff tears that may extend medially to the level of the glenoid fossa (10).
L-shaped tears are massive tears with a lon- gitudinal component along the orientation of the rotator cuff fibers and a transverse component (11)
The ability to identify the tear geometry at arthroscopy diminishes as tear size increases (12).
Massive contracted rotator cuff tears have been classified at MR imaging into two categories: massive crescentic tears (wide anteroposterior dimen- sion) and massive longitudinal tears (spared anterior cuff tissue at the rotator interval) (12).
Tendon Retraction
The degree of tendon retraction is important information obtained with MR imaging.
Optimally,
in primary repair,
the tendon stump should be adjacent to the attachment site so that reattachment is free of tension.
Tear Extension
Supraspinatus tendon tears may extend to adjacent structures,
significantly affecting the mechanics of the glenohumeral joint and having important prognostic implications.
A supraspinatus tendon tear may extend anteriorly to involve the medial aspect of the coracohumeral ligament and superior subscapularis tendon fibers,
a situation that is associated with more severe supraspinatus atrophy and poor prognosis (13).
If the ratio of the cross-sectional area of the supraspinatus muscle to the area of the supraspinatus fossa (occupation ratio) is less than 50% in the sagittal oblique plane,
supraspinatus muscle atrophy is indicated (13).
Rotator Cuff Rupture
On MRI tears of the rotator cuff are visualized in all major planes as fluid fills the gaps in the tendon,
be they superior,
anterior or posterior (14).
Tears most frequently occur in areas of tendinosis near the humeral attachment on the major.
Tendinosis creates increased signal in short TE MRI sequences and may be easier diagnosed if tendon also thickened (14) .
Due to the location,
exposed subacromially,
the supraspinatus tendon is most commonly involved in tendinosis.
Partial tears may also be located within the substance of the tendon,
the so called “intrasubstance” tears .
Biceps pathology is frequently associated with chronic tears of the supraspinatus tendon.
In subscapularis tendon ruptures,
the biceps tendon may subluxate medially into the body of the subscapularis tendon or even completely luxate into the medial joint cavity (15).
Biceps pathology is frequently associated with chronic tears of the supraspinatus tendon.
In subscapularis tendon ruptures,
the biceps tendon may subluxate medially into the body of the subscapularis tendon or even completely luxate into the medial joint cavity.
Massive Rotator Cuff Tear
There is no general agreement regarding the definition of a “massive” rotator cuff tear.
Both functional and anatomic characteristics have been used to classify massive rotator cuff tears.
Despite the different criteria used to define a massive rotator cuff tear,
the result of a massive rotator cuff tear is the destabilization of the glenohumeral joint.