shoulder biomechanics and pathos

SLAP lesion type I

fraying/degeneration of inner margin, associated with rotator cuff patho, biceps anchor attached, still stable

SLAP lesion type II

detachment of labrum and biceps tendon anchor, loss of stabilizing effect of labrum and biceps
most common, little gap but biceps still attached

SLAP lesion type III

bucket-handle tear, remaining labrum and biceps intact

SLAP lesion type IV

bucket handle tear extends into biceps tendon, portions of labrum and biceps tendon displaced into GHJ

symptomatic multi-directional instability (MDI)

onset may be related to microtrauma in presence of MDI or hypermobility, scapular dyskinesis, poor RC control, weakness, fatigue, inadequate glenoid concavity, collagen disorders

AMBRI

atraumatic (general congenital capsular laxity)
multidirectional (MDI)
bilateral
responds to rehab
if needs surgery: has inferior capsular shift (ant stabilization procedure)

TUBS

traumatic
unilateral (also unidirectional)
bankart lesion
surgery needed

shoulder dislocation

ant/ant inf most common (98%), MOI abd, ER
post MOI trauma in flex position, FOOSH
inferior MOI hyperabd force

bankart lesion

avulsion ant inf labrum from glenoid rim, requires surgical stabilization
can also have reverse bankart on post inf labrum

Hill sachs lesion

compression defect on posterior humeral head at site where glenoid rim impact humeral head, larger notch in humerus

AC sprain type I

tenderness and mild pain, painful arc, resisted add/ext painful, painful PAM but normal motion, immobilize

AC sprain type II

mod to severe local pain, PROM all painful at end range, horizontal add most painful, immobilize

AC sprain type III

deformity, AROM painful
may do well with sling, can also have surgery

AC joint sprain type IV, V, VI

require surgical fixation and sling

distal clavicle osteolysis

resorption of subchondral bone in distal clavicle, repetitive microtrauma, OA developing

scapular plane

35 degrees forward from frontal plane, where functional movement between pure sagittal and frontal motion occurs, allows increased humeral elevation
upward tilt, 30-40 deg ant to frontal plane

manubrium

attaches axial skeleton to appendicular skeleton

angle of inclination

135

retroversion

30, orients humeral head in scapular plane for articulation, increases congruency and places bicipital groove in anterior direction

retrotorsion

potential adaptation, twist happens at shaft instead of head (distal to GHJ)
people who need a lot of ER

SC joint

basilar joint (convex on concave one direction, concave on convex other)
highly stable and highly congruent with articular disc
OA rare here, link between axial and appendicular

SC joint dynamic stability

secondary, used as stabilizer for other things

SC kinematics

elevation/depression, protraction/retraction, axial rotation
clavicle moving on sternum, important for all GHJ motion
primary facilitator clavicle motion

arthrokinematics SC elevation/depression

elevate: roll superior, glide inferior
depress: roll inferior, glide superior

arthrokinematics SC axial rotation

during final degrees of abd or flex clavicle rotates post 20-35 degrees
linked to motions, cannot do voluntarily

AC joint

plane joint, not highly congruent (risk of dislocation), stability from ligaments
fine tuner of motion

AC arthrokinematics

flex/abd: post glide
ext/add: ant glide

AC joint injury

MOI is medial force causing shear, clavicle moves lat and AC joint separated
from tensile forces causing dislocation, piano key sign

scapulothoracic articulation

movement is direct result of movement from SC and AC joints
similar to sesamoid bone floating in space
resting position: ant tilt 10, upward rotation 5-10, IR 30-40

role of scapula

stable BOS between UE and trunk, allow for lots of motion of UE, attachment for muscles and stabilizers

ST arthrokinematics

elevation/depression, protraction/retraction, upward/downward rotation
upward rot important to keep head of humerus in fossa, lat tightness can limit elevation

scapulohumeral rhythm

2:1 ratio
distribute motion between 2 joints, increase ROM with less compromise stability, maintain congruency

GHJ

sacrifice stability for mobility, relies on dynamic stabilization

glenoid labrum

most effective mid-ROM, deepens glenoid fossa to increase contract surface, buttress effect/chock block mechanism
tears common with dislocation

capsulo-ligamentous complex

reciprocal tightening and loosening of the capsule limits humeral translation
wringing effect provides joint stability at end ranges of motion

intra-articular pressure

negative pressure gradient, if lost causes increased inferior migration (with tears)
if there is a capsule tear resting position changes, shoulder may be elevated

rotator cuff muscles

provide joint compression through range to minimize humeral translation
muscles working together to overcome deltoid
capsule tensioned with rotator cuff contraction to further stabilize

long head biceps brachii

tendon is intracapsular, restricts anterior and superior translation of humeral head

rotator cuff interval

region between supraspinatus and subscapularis not covered by rotator cuff
reinforced by LH biceps, ligaments
common site for anterior dislocation of GHJ

dynamitization

rotator cuff tendons blend into joint capsule to increase stability, contraction tenses the capsule

deltoid

opposes force of rotator cuff, has longer lever arm making it stronger
if rotator cuff cannot overcome will see shrug with elevation

net force GHJ

combination of rotator cuff, applied force, dynamic tensioning, negative pressure, etc
as long as net force centered in glenoid shoulder is stable, disruption to stabilizers changes net force and decreases stability

axillary pouch

allows humeral inferior glide to increase mobility of GHJ

arthrokinematics flexion/extension

humeral head spins
tension in posterior capsule may cause slight ant translation at extremes of flexion

arthrokinematics IR/ER

IR: roll anterior, glide posterior, can be limited if post capsule tight
ER: roll posterior, glide anterior
posterior glides often help with muscular pathos/rounded shoulders

arthrokinematics abd/add

abd: roll superior, glide inferior
add: roll inferior, glide superior (abuts acromion)

scapular winging

weakness of serratus anterior (upward rotator), decreased motion with elevation