9/30 - Shoulder Instability Non-Op Flashcards
what direction is the GH joint deeper in
superior-inferior
describe the GH joint’s set up
least constrained joint in body
glenoid surface 1/4 surface area of humeral head
- 1/3 of humeral head in contact w fossa at any given time
bony congruence limited
what is the significance of limited bony congruence in the GH joint
relying on other structures to stay centered
describe how the quality of the glenoid articular cartilage changes
thicker peripherally
GH laxity
ability to translate humeral head on glenoid fossa
GH instability
unwanted and excessive translation of humeral head on glenoid fossa causing alteration in comfort and/or function
subluxation
complete separation of articular surfaces w spontaneous reduction
dislocation
complete separation of articular surfaces without spontaneous reduction
- remains dislocated until maneuver or force
how is time crucial when it comes to relocation of a dislocation
longer it takes, higher the risk of neurovascular injury
- tension and load on brachial plexus and vascular
- longer it’s there, harder to come back (esp for nerves)
this factors into our goals
important to ask if dislocation how long it was out of place for
where do you see the biggest difference in ROM in normal laxity vs normal shoulder w no laxity
inferior slightly more in normal laxity
- anterior and posterior will be pretty much the same as a normal shoulder
what structures provide stability for the shoulder (7)
labrum
ligaments & capsule
biceps
rotator cuff
scapula
neuromuscular control
negative intra-articular pressure
if someone had a shoulder dislocation, what should you assess next
if any of the stability structures were damaged
- labrum
- ligaments & capsule
- biceps
- rotator cuff
- scapula
- neuromuscular control
- negative intra-articular pressure
what is the labrum
fibrocartilage surrounding glenoid rim
what functions does the labrum provide (3)
- attachment site for glenohumeral capsule and ligaments
- chock-block effect that limits translation
- inc depth of glenoid fossa by 50%
what happens if the labrum is damaged
back to a shallow glenoid fossa w poor bony congruence and stability
what is the function of ligamentous structures and capsule
provide stability at end ranges of motion
what ligamentous structures are involved in the shoulder
coracohumeral ligament
superior GH ligament
middle GH ligament
inferior GH ligament
- anterior and posterior bands
what ligament of the shoulder has a hammock effect? what does this mean?
inferior GH ligament
- anterior and posterior band
as bring arm up to ABD 90 there is tension in inferior; anterior and posterior will come up to hug front and back
how are the ligaments of the shoulders structured
thickenings of capsule
what is the circle of stability concept
what happens if one is damaged depends on integrity of other structures there
ex: cut anterior capsule
whether it dislocates anterior:
- dependent on posterior capsule integrity
- inc translation or subluxation
what provides primary restraint in early ROM
negative intra-articular pressure
what provides primary restraint in mid-range
muscle function
what provides primary restraint in end range
capsule
- no tension on passive structures prior to this range
what is the structure of the long head of biceps
blends w superior glenoid labrum
origin of long head of biceps function (3)
stabilizes arm in ABD and ER
generates joint compressive forces
dec anterior, superior, and inferior translation of humeral head when taut
if seeing an overuse injury in biceps but not an event to cause overuse, what should you think and why
might be bc of hypermobility
- if underlying shoulder hypermobility, will work harder to create stability via compressive forces»_space; leading to some biceps irritation
what is the primary role of the rotator cuff
provides dynamic stabilization by compressing humeral head into glenoid
where do RC ms insert into and why is this important
blend w capsule & creates dynamic ligament tension
if laxity in ligamentous structures, the RC ms working can create stability via dynamic ligament tension
what is the function of scapula upward rotation
provides stable environment of joint contact
what other motions do you see at the scapula during upward rotation/elevation
ABD and tilts posteriorly
what is required for distal mobility
proximal stability
what is proximal stability needed for
distal mobility
what are the advantages to exercises done in the scapula plane (4)
inc stability w joint congruence
- good bony stability
- good stability of capsular ligamentous
minimal capsular tightness
functional plane of motion
ideal position for RC strengthening
what is the scapula plane referring to
position of the glenoid
what are components contributing to neuromuscular control
efferent/motor responses to afferent/sensory info
proprioception
awareness of joint position
kinesthesia
awareness of joint motion
why are we concerned if a person w an unstable shoulder has poor proprioceptive and kinesthetic sensation
when brain doesn’t know where joint is in space, inc risk for injury
- won’t tell you when in an end range injury provoking situation and won’t enact protective measures (ie late cocking phase)
what is negative intra-articular pressure
creates sealed compartment
vacuum effect b/w articular surfaces
- compresses head of humerus
why is negative intra-articular pressure lost w surgery and why is this important
surgery cutting thru capsule, will be venting it
- inc mobility, 40-60% inc in translation
why are AMBRI joints best served by a PT intervention instead of surgery
if tighten structures in surgery, likely stretch back out over time
what are considerations for instability (8)
severity
direction
etiology
frequency (# of episodes)
+/- underlying soft tissue laxity or connective tissue disorder
concomitant path
end-range NM control
premorbid activity level
what about the severity of the instability should be considered
subluxation
- physiologic integrity exceeded
dislocation
- physiologic & anatomic integrity exceeded
direction of instability possibilities?
unidirectional
multidirectional (MDI)
etiologies for instability
traumatic
atraumatic
frequencies for instability
primary
recurrent
why does it take less for a subsequent dislocation or subluxation
load on passive structures will stretch out
won’t take as much load for same things to happen
what are concomitant pathologies for instability
SLAP lesion
bankart lesion
SLAP vs Bankart
SLAP - superior labrum anterior posterior
Bankart - anterior inferior damage
what is a commonly associated w a hill-sachs lesion? why?
associated glenoid bone loss
HOH rolls over rim of glenoid when dislocates
- compressive forces that damage the glenoid (bone and cartilage loss)
why is there value to imaging if a dislocated shoulder has already been relocated
see integrity of the bone
- if there is bone loss, can continue to waste away
what is a SLAP lesion
disruption of superior labral-biceps complex involving tearing, separation or both of the superior labrum beginning posterior to biceps tendon insertion and then extending anteriorly
what is the peel back mechanism
ABD & ER in late cocking phase of throwing
twisting at base of biceps
transmits torsional force to anchor
what is a concern w traumatic anterior instability
brachial plexus injuries (esp axillary n.)
- humerus comes out the front
- that is where the NM structures are
what is a negative to the use of slings
minimize strength and motor control from disuse
- more for comfort usually
