Elbow & forearm Flashcards
What is the normal “carry angle” for the elbow?
13 degrees
women greater than men
What constitutes cubitus valgus?
greater than 20-25 degrees carry angle
What constitutes cubitus varus?
- forearm angled toward midline
Why does the carrying angle disappear with full elbow flexion?
- the trochlear groove determines path of the forearm
List all the ligaments that surround the elbow joint and their jobs
Medial collateral ligament (UCL):
- Ant. fibers: resists valgus (taut thru ROM)
- post. fibers: resists valgus (taut w/ elbow flexion)
- transverse fibers
Lateral collateral ligament (RCL):
- RCL & lateral ulnar collateral ligament (resist varus)
LUCL forms sling for radial head to protect against excessive ER of proximal forearm
Annular ligament:
- wraps around radial head
What is the axis of rotation for pronation and supination?
- from radial head to ulnar head
What are the arthrokinematics of humeroulnar flexion?
Moving ulna: concave
- rolls and slides anteriorly
Moving humerus: convex
- rolls anterior
- slides posterior
What are the arthrokinematics of humeroulnar extension?
Moving ulna: concave
- rolls and slides posteriorly
Moving humerus: convex
- rolls posterior
- slides anterior
What are the arthrokinematics of humeroradial flexion?
Moving radius: concave
- rolls and slides anteriorly
Moving humerus: convex
- rolls anteriorly
- slides posteriorly
What are the arthrokinematics of humeroradial extension?
Moving radius: concave
- rolls and slides posteriorly
Moving humerus: convex
- rolls posteriorly
- slides anteriorly
What are the arthrokinematics of PRUJ pronation?
Moving radius:
- spin
Moving ulna: concave
- rolls and slides volar (anterior)
What are the arthrokinematics of PRUJ supination?
Moving radius:
- spin
Moving ulna: concave
- rolls and slides dorsal (posterior)
What are the arthrokinematics of DRUJ pronation?
Moving radius: concave
- rolls and slides volar (palmar)
Moving ulna: convex
- rolls volar
- slides dorsal
What are the arthrokinematics of DRUJ supination?
Moving radius: concave
- rolls and slides dorsally
Moving ulna: convex
- rolls dorsal
- slides volar
What are the arthrokinematics of humeroradial pronation/supination?
Moving radius & humerus:
- spin
What are some consequences of a torn interosseous membrane?
- proximal drift of the radius
- bony asymmetry
- will cause wrist pain/loss of function
What are some consequences of a torn TFCC?
- multidirectional joint instability
- pain/difficulty in motions of forearm/wrist
What structures are responsible for stabilizing the DRUJ?
- TFCC
- pronator quadratus
- FCU tendon
- distal oblique fibers of interosseous membrane
Explain the screw home mechanism of the elbow?
- pronator teres compresses radial head against capitulum
What muscles perform elbow flexion?
- brachialis
- biceps brachii
- brachioradialis
- pronator teres
What muscles perform elbow extension?
- triceps brachii
- anconeus
What muscles perform forearm pronation?
- pronator teres
- pronator quadratus
Secondary:
- FCR
- palmaris longus
- brachioradialis (from supinated position)
What muscles perform forearm supination?
- supinator
- biceps brachii
Secondary:
- EPL
- EI
- brachioradialis (from pronated position)
What muscles perform wrist flexion?
- FCU
- FCR
- palmaris longus
Secondary:
- FDP
- FDS
- FPL
- APL
- EPB
What muscles perform wrist extension?
- ECRB
- ERCL
- ECU
Secondary:
- ED
- EDM
- EI
- EPL
What muscles perform radial deviation?
- ECRL/B
- EPL/B
- FCR
- APL
What muscles perform ulnar deviation?
- ECU
- FCU
- FDP/S
- ED
What ROM does elbow flexion have the best torque?
80-90 degrees
What ROM does elbow extension have the best torque?
80-90 degrees
What ROM does wrist flexion have the best torque?
40 degrees
What ROM does wrist extension have the best torque?
30-35 degrees
What ROM does gripping have the best torque?
30-35 degrees wrist ext.
Which positions make the biceps brachii and triceps brachii actively insufficient?
BB: shoulder flexion & elbow flexion
TB: shoulder ext & elbow ext
Which positions make the biceps brachii and triceps brachii passively insufficient?
BB: elbow ext & shoulder ext
TB: shoulder flexion & elbow flexion
What is the best UE positioning for the optimal length-tension relationship of the biceps brachii?
- shoulder ext & elbow flexion
What is the best UE positioning for the optimal length-tension relationship of the triceps brachii?
- shoulder flex & elbow ext
What is the law of parsimony?
- nervous system tends to activate the fewest muscles/fibers possible for control of a given joint action
- this decreases energy expenditure
What is the terrible triad of the elbow?
- dislocation
- radial head fracture
- coronoid fracture
What is posterolateral rotary instability?
- tearing/rupturing of LUCL ligament
- from compression & valgus & supination
- radial head dislocates posteriorly
What is nursemaids elbow?
- radial head dislocates out from the annular ligament
- comes from a sudden pulling from the hand in an upward direction
- common in children due to lack of strength and ligament laxity
How can a person with a C6 lesion transfer from supine to sit?
- tricep is paralyzed so have to use shoulder muscles to help extend the arm
- if wrist is fixed on bed then they can use working elbow flexors to help get from supine to sitting
Explain the pathomechanics of lateral epicondylalgia
- Tennis elbow
- repetitive microtrauma usually involving ECRB
- incomplete reparative process
S & S:
- painful & weak grip
- painful passive wrist flexion & forearm pronation
- TTP over lateral epicondyle
Treatment:
- splinting/bracing
- manual therapy
- ECC training of wrist ext
What are AAOS norms for elbow flexion and extension?
Flexion:
- 150
Ext:
- 0
What are AAOS norms for elbow supination and pronation?
Supination:
- 80
Pronation:
- 80
