Shoulder Flashcards
What is the main cause of RTC injuries in patients under 40yo?
What imaging is gold standard?
trauma injuries
MRI
What does the shoulder girdle consist of?
clavicle, scapula and humerus
What does 1/3 of the humeral head sit in that gives the joint its mobility?
the glenoid fossa
What are the RTC muscles?
Where do 3/4 of these muscles originate and insert?
supraspinatus, infraspinatus, teres minor, subscapularis
originates on posterior scapula, inserts on greater tubercle of humeral head (except subscap)
Why is the supraspinatus the most frequently injured shoulder tendon?
because it runs under the AC joint and under the humeral head (creates friction and pinch points)
The teres minor tendon almost never fails, but why would the muscle be evaluated?
the muscle can be scanned in comparison to the infra to look for evidence of long standing tears
How many muscles and tendons does the subscap have?
4 muscles and 4-6 tendons that insert on the lesser tuberosity of the humeral head
Which head of the biceps cannot be evaluated and why?
Which head is evaluated on every scan and where is it seen?
short head: inserts on coracoid process and isn’t seen
long head: sits in bicipital groove and inserts on the superior glenoid labrum
What is the RTC interval? why is it important to evaluate this area?
separation of subscap by supra by the biceps tendon
can be used to differentiate between pathology of the supra from the subscap
What is the glenoid labrum?
fibrocartilaginous ring lining outer glenoid fossa
- deepens the socket, posterior glenoid labrum is evaluated for fluid
What is another potential space for fluid accumulation in a supra tear?
AC joint
What are bursae?
What is the main bursa in the shoulder (largest in body)?
small thin sacs that contain small amounts of synovial fluid to reduce friction where tendons and muscles cross joint capsules
subacromial-subdeltoid bursa (essentially 2 but evaluated as 1)
What age will patients typically experience RTC failure?
which fail first etc?
over 40yo, incidence increases with age and can be asymptomatic (often incidental findings)
supra, then infra and subscap when the original tear extends
What causes acute tears?
trauma, falls, ruptures or dislocations
What causes chronic tears?
occur as a cumulative progression of an injury from overhead activities that cause microtraumas due to impingement
Where do partial thickness tears typically begin?
usually in the critical zone: found in anterolateral supra tendon, 1cm from insertion on greater tuberosity
may involve articular surface (most common) or bursal surface (2nd)
How does a partial thickness tear appear?
anechoic defect in tendon fibers (acute)
or hyperechoic area due to blood and bursal granulation tissue within the frayed tendon (chronic)
What are secondary indicators of partial thickness tears?
diffuse thickening and bone irregularities
Explain the difference in articular surface tears and bursal surface tears
(appearance and symptom)
1- typically presents as fluid in the biceps tendon sheath
2- tender to palpation
What is a complete tear?
involving full thickness and full width
retraction occurs with a separation of 2-4cm between torn tendon ends
What do full thickness tears demonstrate that partial tears dont?
communication between glenohumeral joint and subacromial bursa, leads to a large amount of fluid in SASD bursa
List the most common to rare tendon tears in the shoulder
supra, infra, subscap, teres
What are some signs that indicate a full thickness tear?
cartilage interface sign: echogenic line on anterior surface of humeral head cartilage
naked tuberosity sign: deltoid muscle in direct contain with humeral head
double effusion sign: fluid in SASD bursa and biceps tendon sheath
also deltoid muscle or SASD bursa herniation into RTC
Explain calcific tendinosis
process that can affect any RTC tendons
calcium aggregates can be solid, paste or liquid
What happens when calcium bursts out of the tendon into the SASD bursa?
what can be seen in painful calcs?
acute and painful synovitis
increased CD signals
What is subluxation of biceps tendon?
dislocation outside of the bicipital groove
due to a problem with the transverse humeral ligament that holds the tendon in place, abnormally shallow bicipital grooves or subscap tears
What is the most common site for subluxation of the biceps tendon?
What is the sonographic appearance?
medical and deep to the subscap
empty groove, possibly filled with granulations and fibrous tissue and seeing the biceps tendon over the lesser tuberosity
tendon sheath may be filled with fluid
What is subacromial impingement syndrome?
lateral shoulder pain that occurs during elevation of the arm above 180*
defined as compression of the RTC and/or SASD bursa by the overlying coraco-acromial arch
What can cause subacromial impingement syndrome?
can be caused by osteophytes on the acromion, SASD bursitis or RTC tear
