Flashcards in The Elbow, Forearm, Wrist and Hand Deck (26):
FUNCTION OF THE ELBOW, WRIST, AND HAND
Modification of hand position relative to body
• Load modifier (adaptation of lever length for lifting / pushing)
• Shock absorbing
• Hand positioning
• Manipulation of objects
3 JOINTS IN THE ELBOW COMPLEX
• Superior radioulnar
Generally with increased effort, more muscles are recruited to assist.
• This may include even fairly distant muscles being recruited
Nervous system generally prefers to activate/control one muscle if possible
• e.g., elbow flexion and supination – biceps brachii
• Body can adapt if there is injury, and use a combination of other muscles
to perform the actions
• e.g., elbow flexion and supination – brachioradialis and supinator
• OR elbow flexion with NO pronation/supination required: brachioradialis • Use of biceps would require the additional use of pronator muscles to
THUS SYNERGY CHANGES WITH DEMANDS
Muscle/s selected for a task tends to be the most efficient.
• Brachialis – always active in flexion
• Brachioradialis – purely a flexor particularly if in mid-position
• Supinator – same for all elbow angles
• Biceps brachii – shoulder and elbow flexion, forearm supination.
most effective as supinator if elbow flexed at 90 degrees.
Muscle roles alter according to demands
Can be agonist/synergist/antagonist:
depends on task, task complexity, force required etc.
Radial Nerve Injury / C6 Spinal Cord Injury.
Triceps paralysed - can extend from elbow flexion in sitting = eccentric biceps controls.
Can’t push down to cut food, lift body, i.e. can’t produce concentric contraction
Musculocutaneous nerve lesion & some muscular dystrophies. Biceps & Brachialis paralysed.
Weak elbow flexion - only with Brachioradialis (+ ECRL/B & Pron. Teres). Poor ability to flex when elbow extended, therefore:
Swing arm to get momentum to start movement, can hold at 90 deg. F using other secondary flexors.
Median Nerve Injury – (proximal to the elbow.)
- Paralysis of pronator teres
Force of pronation reduced
Hard to use a key
Hard to hold a glass
WRIST AND HAND
Hand placement and stability depends initially on trunk, shoulder, elbow and wrist control.
• As form a fist - long finger flexors (FDP & FDS) are activated but they also would flex the wrist.
• Must use wrist extensors (ECRL, ECRB, ECU) to stabilise wrist for efficient & effective grasp.
FINGER FLEXION WITH WRIST FLEXION IS WEAK.
CAN’T CLOSE FIST FULLY.
Active insufficiency of the finger flexors.
Passive insufficiency of the extensors.
In grasp, when FDP acts it tractions/pulls the proximal lumbrical attachment.
Flexion of the IP joints stretches the intrinsics producing MCP flexion.
Paralysis of intrinsics produces a claw hand. Can flex fingers but not grip.
Dorsal interossei do not assist with F/E of the MCP joint.
Palmar interossei & lumbricals produce MCP flexion (and lumbricals also = IP extension).
Lumbricals less involved in grip. Interossei more used in gripping and pinching.
With the hand relaxed:
WRIST FLEXION > FINGERS EXTEND
WRIST EXTENSION > FINGERS FLEX
due to tenodesis - Stabilizing a joint by anchoring the tendons that move the joint.
The Rheumatoid Hand
The “Intrinsic plus” position is produced where MCPs are flexed and IPs are extended.
Paralysis of the interossei and lumbricals; MP hyperext. and ips flexed
This produces the “Intrinsic minus” resting position of the CLAW HAND.
Radial Nerve Paralysis
Lose the wrist extensors and long extensors of the digits plus extensors and APL of thumb. Produces a characteristic wrist drop.
A splint is used to allow effective use of the flexors which are functioning. (Must ensure they don’t get shortened as they are unopposed.)
- wrist maintained in 20-30˚ flexion
Ulnar Nerve Paralysis
FDP, IO, lumbricals of D4&5 and the hypothenar muscles are affected.
The 4th and 5th fingers are most affected. Characteristic position with these fingers flexed at the IP joints. The MCPs are held in hyperextension. Known as Bishop’s Hand or Benediction Hand Deformity - referring to the “at rest” deformity.
Ulnar Nerve Lesion
Marked wasting of hypothenar muscles
Flexed PIP D4 and D5 with MCP hyperextension
Median Nerve Paralysis
Affects most of the flexors, radial side.
Affects grasp. Lose flexion and opposition of the thumb. Thenar muscles atrophy. Thumb acts in plane of palm.
May adduct. Leads to characteristic “Ape hand” deformity.
WITH NERVE INJURY THERE WILL NOT ONLY BE MOTOR LOSS BUT ALSO SENSORY LOSS.
THIS WILL RESULT IN DECREASED
ACCURACY AND POWER OF MOVEMENT DUE TO POOR FEEDBACK FOR CONTROL
Osteoarthritis of hand joints
Deformity, restriction of joint motion,
e.g. 1st CMC jt, DIPs
Thumb fixed in F, Opp. position Unable to extend fully and limited abduction.
prehension patterns - power grip
– uses fingers, thumb, palm. Thumb is adducted to hold object against curled fingers. E.g., holding a hammer.
prehension patterns - precision grip
uses pinch between thumb and one or more fingers. Thumb is abducted and opposed. E.g., holding a pin.
Types of power grips
Hook - Bucket handle (doesn’t require thumb)
Cylindrical- Can, drinking glass
Fist - Tennis racquet, Hammer
Spherical - Ball - throwing, bowling