Hand Flashcards
Radial Collateral Ligament (1st CMC)
Thick strong ligament
-Resists flexion, opposition, and abduction
Stabilizes when opposing thumb = PRIME STABILIZER during opposition
Ulnar Collateral (1st CMC)
-Resists abduction and extension
More on palmar side (enmeshed with transverse ligament -> ligament over carpal bones)
Anterior (palmar) oblique (1st CMC)
Thin, weak ligament
- stressed with full extension (up and down fibers -> resists extension)
Posterior oblique (1st CMC)
Similar to Radial Collateral
mainly resists opposition
Arthrokinematics of 1st CMC
FLEXION
Ulnar (medial) roll and slide of 1st MC on trapezium
CVS FES
Arthrokinematics of 1st CMC
EXTENSION
Radial (lateral) roll and slide of 1st MC on trapezium
CVS FES
Arthrokinematics of 1st CMC
ABDUCTION
Palmar roll, dorsal slide of 1st MC on trapezium
VCO AAO
Arthrokinematics of 1st CMC
ADDUCTION
Dorsal roll, palmar slide of 1st MC on trapezium
VCO AAO
MCP Collateral Ligament
Dorsal Cord
- thicker and stronger
- more longitudinal
Accessory Portion
- fan shaped, not as strong
- attaches to volar plate
taut during extension, collateral cord loose
loose during flexion, collateral taut
Volar Plate
Dense fibrocartilage on palmar aspect -> adds to jt stability
Blends with joint capsule
Resists extremes of hyperextension
Deep Transverse metacarpal Ligaments
- 3 ligs that merge into one flat wide lig
- Help to bind 2-5th MCs
MCP Athrokinematics
FLEXION
Palmar roll and slide of proximal phalanx on MC
Created by: Flexor Digitorum Profundus FDP
- Dorsal capsule and CORD portion of radial collateral ligament are taut
MCP Athrokinematics
EXTENSION
Dorsal roll and slide of proximal phalanx on MC
Created and Controlled by: Extensor Digitorum and intrinsic muscles
- Volar plate and accessory portion of collateral ligament are taut, cord portion loose
MCP Athrokinematics
ABDUCTION
CVS
Proximal phalanx rolls and slides in same direction
Depends on which digit…
2nd digit
- roll and slide radially
5th digit
- roll and slide ulnarly
Created by: dorsal interossei
- Full abduction: ulnar collateral ligament is taut, radial collateral is loose
Check rein ligaments
only in PIP not DIP
- resists Hyperextension along with volar plate (why PIPs do not allow a lot of Hyperextension)
-> not in DIP allow more Hyperextension
Volar/Palmar Plate
Mobile, thickened fibrocartilaginous structure
restrains Hyperextension at IP joints
- Improves mechanical advantage of flexor tendons optimizing initiation of PIP flexion (increases MA)
- Increases surface area allowing for greater ROM
Arthrokinematics of PIP and DIP
FLEXION
PIP
-palmar roll and slide of concave base of middle phalanx
DIP
- palmar roll and slide of concave base of distal phalanx
More flexion in each jt as you more ulnarly
- As you move into full flexion, the passive tension in the dorsal capsule helps to guide motion but also increases stability
Flexor Pulleys
Annular pulleys
A1-A5 numbered bottom to top
- Major pulleys: A2 & A4
- Minor pulleys: A1 A3 A5
- Severe or overstretching of major pulleys will significantly alter the MA and line of pull of the flexor tendons
-> makes the line of pull more compressive and losing Y rotary component
Cruciate pulleys
C1-C3 numbered top to bottom
Pulleys…
Prevent bowstringing
Ensure proper line of pull for optimum motion
Distribute pressure on tendons
Cylindrical Grip
Wrist in neutral or slight extension and UD
-Uses extrinsic finger flexors to maintain grasp
Ex: holding a cup
Spherical Grip
Relies heavily on extrinsic muscles
- Span the fingers to contour around object
Ex: holding a baseball
Hook Grip
NEVER includes the thumb
- FDP and FDS provide most of muscle activity
-> Usually hook grip your arms at your side, so not much extensor torque to counteract (bc the line of pull is WITH gravity)
Pad to pad prehension
Pulp pinch
- like using tweezers
Tip to tip prehension
Tip pinch
- like holding a pencil
Pad to side prehension
Key grip/lateral pinch
- like holding a key
What does the Central Band do?
Part of Extensor Mechanism
- serves as the “backbone” of the extensor mechanism
- Transmits extensor force from the ED across the PIP jt
What do the Lateral bands do?
Part of Extensor Mechanism
- Transmit extensor force from the ED, lumbricals, and interossei across the PIP and DIP jts
What does the Dorsal Hood do?
Part of Extensor Mechanism
Transverse fibers
- stabilize the ED tendon over the dorsal aspect of the MCP jt
- Form a sling around the proximal end of the proximal phalanx, assisting the RD in extending the MCP joint
Oblique fibers
- Transfer force from lumbricals and interossei to the lateral bands of the extensor mechanism, assisting with the extension of the PIP and DIP jts
What does the Oblique retinacular ligament do?
Part of extensor mechanism
Helps coordinate movement between the PIP and DIP jts of the fingers
What are the Opposing Thumb Muscles?
Opponens Pollicis (OP)
- predominant with light opposition to all fingers and firm opposition to 4th and 5th digits
Flexor Pollicis Brevis (FPB)
- predominant action with firm opposition to 2nd and 3rd fingers
Abductor Pollicis Brevis
- not as active during opposition
What is Intrinsic Plus Position?
Flexion at MCP and Extension at IPs
- Simultaneous contraction of lumbricals and interossei WITHOUT any extrinsic finger muscle activity produces intrinsic plus position
What is Intrinsic Minus Position?
Extension at MCP and Flexion at IPs
- combo of ED, lumbricals, and interossei
-> torque of ED overcomes lumbricals and interossei torque
Activity of extrinsic finger flexors and extensors WITHOUT concomitant activity of intrinsic muscles produces Intrinsic minus position
What is Optimal Grip?
30-35 degrees extension
Gripping Muscles
FDS and FDP
Activation of EDRL, ECRB, ECU
-> extensors prevent unwanted flexion during gripping
