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Flashcards in Intrinsic Hand Deck (41)
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Importance of Thumb in ADLs

Performs 50% of movement of hand!


% of Motor Cortex of Brain Devoted to Hand Muscles

About 25%!


Numbering of Fingers

Thumb considered Digit #1, then index finger is #2.... pinky is #5.


5th Carpometacarpal (CMC) Joint

Considered the most mobile metacarpal joint, as it allows pinky to oppose thumb.


CMC Joints of Digits 2-5

Index Finger (#2): Trapezoid articulates with 2nd metacarpal (MC)
Middle Finger (#3): Capitate articulates with 3rd MC
Ring Finger (#4) and Pinky (#5): Hamate articulates with 4th/5th MCs


Functional Groups of Intrinsic Hand Muscles

1) Thenar Group
2) Hypothenar Group
3) Interossei Group
4) Lumbrical Group


Thenar Group of Intrinsic Hand Muscles

Thumb muscles that originate at Thenar Eminence (fat part of base of thumb).
1) Abductor Pollicis Brevis* (CMC abduction)
2) Flexor Pollicis Brevis* (CMC flexion)
3) Opponens Pollicis* (CMC opposition)
4) Adductor Pollicis** (CMC adduction)
*Innervated by Median Nerve (C6-7)
**Innerv. by Ulnar Nerve (C8, T1)


Hypothenar Group of Intrinsic Hand Muscles

Pinky muscles that originate in Hypothenar Eminence (fat part on ulnar side of palm). All innervated by Ulnar Nerve (C8, T1).
1) Opponens Digiti Minimi (pinky opposition)
2) Abductor Digiti Minimi (MCP abduction)
3) Flexor DIgiti Minimi Brevis (MCP/PIP/DIP flexion)


Interossei Group of Intrinsic Hand Muscles

Abductors/Adductors of MCP joint of fingers. Innervated by Ulnar Nerve (C8, T1).
1) Palmar Interossei (“PAD”=Palmar adduct)
2) Dorsal Interossei (“DAB”=Dorsal abduct)


Lumbrical Group of Intrinsic Hand Muscles

Unique to body, no bony attachments; proximal attachment to tendons of flexor digitorum profundus; distal attachment to extensor digitorum communis.
• There are 4 total lumbricals.
• Flex MCP and Extend DIP/PIP
• Causes “Intrinsic Plus” position of hand when activated.


Radial Nerve

• Terminal branch of brachial plexus.
• Innervates posterior muscles—most extensors.
• Injury/palsy causes wrist drop


Median Nerve

• Terminal branch of brachial plexus.
• Innervates palmar side of thumb, digits 2-3, and radial half of digit 4. (Intrinsic anterior muscles)
• Considered “nerve of function” due to palmar innervation.
• Injury causes “ape hand” (thumb kept in plane of hand)


Ulnar Nerve

• Terminal branch of brachial plexus
• Innervates ½ of 4th digit, and digit #5; intrinsic anterior muscles
• Injury causes “claw” hand of 4th-5th digits (loss of lumbricals; or “intrinsic minus” position)


“Intrinsic Plus” vs. “Intrinsic Minus”

Positions of hand.

Plus: When lumbricals are activated. Extended wrist, flexed MCP (knuckles). Ideal position for healing injuries. Like holding a book by its binding.

Minus: When ulnar nerve compromised and lumbricals not working. “Claw hand” of 4th and 5th digits. Affects other fingers due to shared ligaments.


Functional Hand Position

Ideal position for strength and precision.
• Wrist extended 20˚
• Fingers slightly flexed at all joints
• Thumb in opposition with MCP and IP flexed



Flexion of fingers due to passive insufficiency of extrinsic finger flexor muscles.
• Wrist extension naturally causes fingers to close/flex
• Used as functional grip for quadriplegics due to SCI below C6 (C7 injuries)


Wrinkles in Hands

Caused as function of nerves. If nerve is cut, skin stops wrinkling/is unable to sweat.

Wrinkles on backs of finger knuckles are “dimples” where skin attaches to tendons.



Device used for grip testing.
• Client must sit with shoulder adducted, neutrally rotated, elbow flexed 90˚, forearm neutral, wrist betw 0-30˚ extension, and betw 0-15˚ ulnar deviation.
• 3 trials are taken of each hand
• Examiner must hold/support dynamometer (or rest on something) to prevent dropping. Very heavy!
• Uninvolved hand used as comparison for dominant/non-dominant.
• Normative data used, with variables considered such as age


Pinch Gauge

Used to test pinch strength.
• Use same seating position as dynamometer.
• 3 trials obtained, bilaterally
• 3 types of pinches evaluated:
1) 2-point pinch (thumb/index)
2) lateral pinch
3) 3-point pinch (thumb tip to tips of index/middle)


Swan Neck Deformity

Finger with hyperextended PIP joint and flexed DIP joint. Conditions that loosen PIP and allow it to hyperextend can produce this, such as RA.


Boutonniere Deformity

Occurs when disease/injury causes PIP joint to become flexed and DIP joint is pulled up into too much extension (hyperextension).
• Can be caused by a ligament tear.


Mallet Finger

AKA: Baseball Finger; Dropped Finger; Extensor Tendon Injury
• Injury to extensor digitorum tendon at DIP joint. Causes DIP to be flexed.
• Usually occurs when a ball, while being caught, hits outstretched finger and jams it, creating ruptured/stretched extensor digitorum tendon.


Trigger Finger

AKA: Stenosing Tenosynovitis
• A finger or thumb gets stuck in bent position, and snaps when straightened. If it’s severe, finger may become locked in bent position and requires surgical release.


Dupuytren’s Contracture

Thickening of fibrous tissue layer under skin of palm/fingers. Painless, but tightening (contracture) can cause fingers to flex. Creates a “cord” in the palm at base of finger.


Kapandji Scoring Tool

Measures end stage of opposition; to assess opposition of thumb. Based on where client can touch tip of thumb. Scores 1-10 based on how far reach goes.
1=radial side of index proximal phalanx
10=distal palmar crease


Rheumatoid Arthritis (RA) of Hand and Thumb

Autoimmune arthritis. Cause unknown. Women 20-50. Hands, wrists, elbows, shoulders, hips, ankles. Fatigue, joint pain, inflammation, edema, warmth, redness. Causes progressive joint destruction, deformity, disability.
Hand: Ulnar deviation of MCP joints; swan neck or boutonniere deformities, or zigzag pattern of hand. May require “MCP joint implant arthroplasty” (silicone spacers replace MCP joint).
OT: Conservative mgmt. or postop after joint replacement; prevention of further deformity; energy conservation; joint protection; assistive devices; pain control; strength maintenance


Osteoarthritis (OA) of Hand and Thumb

Caused by wear and tear on joints. Overuse or trauma. Pain and stiffness. More prevalent in females 50+. Common in PIP/DIP, CMC of thumb, cervical/lumbar spine, shoulders, knees, and hips. Similar treatment to RA.
• CMC of thumb most common site for surgical reconstruction. Removal of trapezium and a tendon used as arthroplasty (joint replacement).



Thickening and inflammation of synovial lining of joints. Can accompany RA. Can cause ligament and tendon destruction, leading to laxity and possible rupture.


Repetitive Stress Injuries (RSIs) of Hand and Thumb

AKA: Cumulative Trauma Disorders (CTDs)
• Affect wrist, hand, thumb more often than anywhere else in body
• Carpal Tunnel Syndrome (CTS)
• Tendinitis
• Trigger Finger



Irritation or inflammation of tendon. Prevalent in hand/wrist; can be precursor to other RSIs (ie: could lead to CTS).
• Microscopic tears in tendons can occur, especially at musculotendinous junction (where tendon and muscle join).
• Pain, swelling.
• Most common in: Flexor and extensor tendons of wrist; Extensor tendons of thumb