Week 8 Elbow Biomechanics and Common Conditions Flashcards
joints of elbow complex (elbow joint, forearm)
elbow joint:
humeroradial joint
humeroulnar joint
forearm:
superior (proximal) radioulnar joint
inferior (distal) radioulnar joint
classification of the elbow joint
compound synovial modified hinge joint
modified hinge joint = ulna rotates about its own longitudinal axis in flexion and extension
alignment 對齊 - coronal plane of elbow joint
coronal plane = front/ back
‘carrying angle’ = normal valgus (10-15 degrees)
excessive cubitus valgus = >20 degrees
cubitus varus = < 5 degrees
observe in supination forarm
alignment - sagittal plane of elbow joint
sagittal plane = left/ right
humeroulnar joint - encouraging flexion
alignment: anterior curvature of distal humerus and proximal ulna allow ROM flexion and limit extension
What stabilise elbow joint?
- humeroulnar joint
- MCL
- LCL
stability - humeroulnar joint
50% bony shape
:
- olecranon: prevent anterior dislocation
- coronoid process: prevent posterior dislocation
50% ligaments and passive restraints
:
- MCL, LCL, capsule
- the ratio varies depending on degree of flexion/ extension
- any muscle activity will also provide a joint compressive force that increases joint stability 任何肌肉活動也會提供關節壓縮力,進而增加關節穩定性
ligamentous stability - MCL
medial (ulnar) collateral ligament
- resists valgus forces
- anterior fibers (band) taut in full E
- posterior fibers (band) taut in full F
- in 20-120 degrees flexion, MCL are main limit to valgus stress – In flexed positions,
overstretching may cause medial instability
在彎曲位置時,過度伸展可能會導致內側不穩定
ligamentous stability - LCL
lateral (radial) collateral ligament
- less defined than MCL
- two fibre bundles: radial/ ulnar
- resist varus force at elbow
- blends with (supports) annular ligament
- stabilises head of radius
- provides posterolateral stability to elbow complex
- provides some resistance to longitudinal distraction
Both collateral ligaments dense with 密集著 sensory receptors – aid 幫助 proprioceptive and detect safe passive tension in ligaments and capsule 偵測韌帶和關節囊的安全被動張力
degrees of elbow ROM: flexion/ extension
normal AROM: 145/ -5 degrees
PROM up to 150-160 degrees
functional ROM less
what limits the extension of elbow
- close packed position full extension
- olecranon in olecranon fossa
- anterior bands MCL
- tension/ shortening of biceps
what limits the flexion of elbow
AROM:
- soft tissue opposition
- tricpes/ biceps
- swelling/ pain limiting ROM
PROM:
- coronoid process in coronoid fossa
- soft tissue apposition
- posterior capsule
- posterior LCL/ MCL
- passive length triceps
factors that contributing to ROM of elbow
1. type of motion (active/ passive)
2. position of forearm (supinated/ pronated)
- forearm pronated –> ROM of flexion decreased
3. position of shoulder (flexion/ extension)
- length of 2 joint muscles (LH of triceps, both heads of biceps)
4. presence of increased intra-articular pressure 關節內壓力增加 (effusion)
- extra fluid in the joint stretches the capsule and limits full ROM
radioulnar joints
in supination? in pronation?
supination:
- radius & ulna parallel
pronation:
- radius crosses over the ulna
- ulna remains stationary
radioulnar joint kinematics
proximal and distal joint
proximal joint: spinning of radial head within the fibro-osseous ring
distal joint: concave
surface of the ulnar notch of radius
slides around the convex
ulnar head
can refer back to nettler’s atlas plate 425 carpal articular surface
what is the function of interosseous membrane of radioulnar joint
ensures the radius and ulna do not splay apart
/ stabilises both proximal & distal radioulnar joints