9/27 - Rotator Cuff NonOp Flashcards
what are 3 different terms that all describe subacromial shoulder pain
subacromial impingement syndrome
rotator cuff tendinopathy
rotator cuff related shoulder pain
scapulohumeral rhythm ratio for 180deg of shoulder elevation
2deg of GH motion for every 1deg of ST motion
180deg shoulder elevation
- 120deg humeral elevation
- 60deg scap rotation
the coordinated effort in scapulohumeral rhythm is important for what function
overhead function
- shoulder elevation
what is the primary function of the rotator cuff
offset force of deltoid
- the ER and IR that it also does is less important
what does the RC provide at the GH joint
dynamic stabilization by compressing humeral head into glenoid
what is the relationship of the RC muscles to the GH joint capsule
RC muscles blend w capsule & create dynamic ligament tension
- since fibers blend, when cuff contracts provides tension in the capsule
what are the force couples at work in the shoulder joint
deltoid - RC
anterior-posterior RC
upper trap - serratus anterior
what happens when there is an unopposed deltoid
superior migration
what ms are included in the anterior and posterior force couple
anterior - subscap
posterior - infra and teres minor
why would an isolated supraspinatus injury have a good prognosis
not part of a force couple
what osteokinematics is the upper trap - serratus anterior force couple responsible for
shoulder elevation
upward rotation of the scap
what are 4 functions of the upper trap - serratus anterior force couple
- optimal position of glenoid
- deltoid length - tension
- prevents impingement
- stable base to recruit scap musculature
how does the upper trap - serratus anterior force couple prevent impingement
creates posterior tipping which inc the subacromial space
what are extrinsic mechanisms behind subacromial impingement
subacromial compression
- acromial arch shape
- posture (more forward, less space)
- ms performance (dec, less upward rotation)
what are intrinsic mechanisms for subacromial impingement
age
- dec vascularity >40yo (healing potential declines)
- tendon degeneration
hypercholesterolemia
DM
smoking
what do all intrinsic mechanisms play a role in? where else does this apply other than non-op cases?
tissue’s ability to heal
relates to post op
- quality of tissue relates to how well do after surgery
what is in the subacromial space? what role do these play in subacromial impingement?
tendons of RC
LHB tendon
subacromial bursa
superior capsule
all can create sx if compressed
how does sub acromial space change w shoulder motion
in a normal shoulder - space gets smaller as you get up and above head
space is 1/2 the size it was w shoulder down when shoulder raised at 90deg
what is a hypothesis for subacromial impingement
dec ST upward rotation inc risk for RC compression d/t dec clearance in subacromial space
what combined motion w shoulder elevation can inc sub acromial clearance if reduced scap upward rotation
max IR
- RC insertions may have passed under lateral acromion at 90deg
what motions inc the acromiohumeral distance at 45deg of elevation
inc ST upward rotation
posterior tilt
what can change the impact of dec ST upward elevation on subacromial space
depends on angle of elevation
how does dec ST upward rotation change the risk of compression
shifts risks to lower angles
the subacromial space is the smallest between what angles
50-70deg
how does the position of the RC change during shoulder elevation? what is the relevance of this when it comes to sx of compression
RC already medial to acromion in most at 90deg elevation
- RC compression at lower angles may become sx in midrange due to inc force production
what would sx >90deg of elevation be related to
internal impingement (RC vs glenoid) or biceps
what was the old school of thought behind the mechanism of impingement? why is this not thought anymore?
a mechanical problem
- run out of space and pinch stuff in between
- true mechanical = compression of tissues
hasn’t been shown in all pts
pts can have nonmechanical impingement
- from tension in musculature
how does mechanical vs nonmechanical impingements differ in treatment plans
they don’t - overall treatment is the same
- interventions for hypomobility and dec strength
what are 5 etiology behind shoulder impingement
- humeral head depressor weakness / fatigue
- GH instability
- posterior capsule tightness
- scap dyskinesia / ms weakness
- subacromial crowding (ie bone spurs, other anatomical changes)
is acute or chronic etiology more commonly seen w shoulder impingement
acute is rare
chronic more common - usually overuse
what are 3 chronic etiologies of shoulder impingement
repetitive microtrauma
throwing sports
vocational demands
how do the presenting sx differ in the late cocking phase on location of path
anterior instability = anterior pain
posterior impingement = posterior pain
what does it mean to have painful arc? when is this typically seen?
hurts starting at 50-70deg and then as get more flexion, starts to feel better
- seen in subacromial pain syndrome
what are sx of subacromial pain syndrome
ant lat shoulder pain
pain >/= 90deg
painful arc
pain worse at night