Phalanges Flashcards
The thumb is rotated almost __ degrees to the other digits. The metacarpal of the thumb is also positioned well _____ to the other metacarpals
90; anterior or palmar
What depend on the thumb flexing in plane that intersects (versus parallels) the plane of the flexing finger?
Optimal prehension
What are the arches of the hand?
- proximal transverse arch
- Distal transverse arch
- Longitudinal arch
Where does the proximal transverse arch pass through? what is its keystone? is it static or mobile?
- distal row of carpal bones
- Capitate is the keystone.
- This arch is static
Where does the distal transverse arch pass through? what is its keystone? is it static or mobile?
- the Metacarpal phalangeal (MCP) joints
- Keystone: central (2nd and 3rd) metacarpals
- Sides are mobile
Where does the longitudinal arch pass through? what is its keystone? is it static or mobile?
- Follows the general shape of the second and third rays.
- Keystone is the second and third MCP joints.
What are the transverse arches of the hand joined together by? what is its purpose?
a “rigid tie-beam” provided by the second and third meta carpals
- reinforces the entire arch system
a special term describing the movement of the thumb across the palm, making direct contact with the tip of any finger
opposition
Does the 3rd finger adduct or abduct?
No, it ulnar and radially deviates
What plane is flexion and extension in for the thumb? adduction and abduction?
frontal plane; sagittal plane
What are the two phases of opposition of the thumb?
- abduction
2. flexion and medially rotates across the palm toward the small finger
What is the closed pack position for the thumb CMC joint?
full opposition
What muscle guides the thumb into opposition?
opponens pollicis
Full opposition incorporates ____ degrees of medial rotation of the thumb
45-60
What digits form a stable pillar? what is this pillar called?
2nd and 3rd; central pillar
What does the stability of the 2nd and 3rd CMCs and the mobility of the 1st, 4th, and 5th CMCs allow?
the concavity of the palm to firmly fit around many objects
All CMC joints of the finger are surrounded by articular capsules and strengthened by multiple dorsal, palmar, and interosseous ligaments. Which ones are particularly well developed?
dorsal ligaments, especially around the middle CMC
Which digits have complex saddle joints?
2nd and 3rd
Which digits have flat to slightly convex and articulate with a slightly concave articular surface of the hamate?
4th and 5th
which metacarpal heads move while clenching a fist?
4th and 5th
What allow the thumb to fully oppose, thereby easily contacting the tips of the other digits?
saddle shape
Is the CMC of the thumb relatively loose or fixed? how many ligaments does it have?
loose; 5
Abduction and adduction are based on the [convex/ concave] articular surface of the thumb MC moving on the fixed [convex/ concave] diameter of the trapezium
Convex; concave
Flexion and extension are based on the [convex/ concave] articular surface of the thumb MC moving on the fixed [convex/ concave] diameter of the trapezium
concave; convex
What shape are the MCP joints of the fingers?
Large, ovoid articulations
What is embedded within the capsule of each MCP joint that provide mechanical stability?
- radial and ulnar collateral ligs (cord [dorsal] and accessory parts [fan-shaped fibers attach distally along the edge of the palmar plate])
- palmar plates
form tunnels (or pulleys) for the extrinsic finger flexors and are attached to the palmar side of the plates
Fibrous digital sheaths
What is the primary function of the palmar plate?
strengthen the structure of the MCP joints and limit extremes of extension
What attaches between the palmar plate of each MCP joint and help interconnect them?
three deep transverse MC ligaments
What forms the concave component of the MCP joint?
- The articular surface of the proximal phalanx
- the collateral ligaments
- the dorsal surface of the palmar plate
- 3 sided receptacle accès the heads of the metacarpals
What reinforces the palmar plate in hyper extension?
Check-rein ligament
The arthrokinematics at the MCP joint are based on the [convex/ concave] articular surface of the phalanx moving against the [convex/ concave] metacarpal head
Concave; convex
- note: first dorsal interosseus muscle directs the arthrokinematics & stabilizes
What is the closed pack position of the MCP joint? loose pack?
CP = 70 degrees flexion OP = 20 degrees flexion
Is there more abduction/ adduction when the MCP is flexed or extended?
extended
- collateral ligaments are near taut in full flexion and the articular surface contacts the palmar part of the metacarpal heads in flexion
What does proper splinting in closed pack position (for the fingers) reduce?
- collateral ligaments becoming taut
- extrinsic extensor muscles elongated
- volar/palmar plate determine how splinting occurs because creep will not revert
What special articulation helps guide IP joints into flexion and extension as it restricts axial rotation?
tongue-in-groove articualation
What do the PIP joints have (which DIP joints lack) that strengthen the palmar plate and resist hyper extension?
Check-reign ligaments
What are the accessory ligaments that reinforce the IP joints?
collateral ligaments
What is the ROM at the PIP joint?
100- 120 degrees
What is the ROM at the DIP joint?
70-90 degrees
- up to 30 degrees of hyperextension
what is the close-pack position of the IP joints?
near full extension
- during immobilization of the hand, IP joints are in near or full extension
- Places a stretch on the palmar plates, collateral ligaments, and extrinsic finger flexor muscles, reducing the likelihood of flexion contracture of these joints
What is the primary action of the FDS?
Flex the PIP joints
- can be controlled independently
- splits at PIP to allow passing of FDP tendon
What is the sole flexor of the DIP joint?
FDP
- limited independent digit action
- people who can independently flex DIP tend to have hyperextension at PIP palmar plate
What is the sole flexor at the IP joint of the thumb?
Flexor pollicis longus
The extrinsic flexor tendons of the digits travel to their distal attachment in protective fibs-osseous tunnels known as ________.
fibrous digital sheath
Embedded within each digital sheath are discrete bands of tissue called _____.
Flexor pulleys
- 5 annular pulleys
- 3 less distinct cruciate pulleys
Flexor tendons and surrounding synovial membrane may become inflamed. Associated swelling limits the space within th sheath and there restricts gliding action of the tendons; tendons may develop a nodule and become wedged within the stenosis region of the sheath, thereby blocking movement of the digit. With additional force, the tendon may suddenly slip through the constriction with a snap. what is this condition?
Trigger finger
The extrinsic digital flexors act on multiple joints, from the DIP joint to the elbow. What is required to neutralized undesired actions of digital flexors?
wrist extensor and digital extensor muscles
-produces a lot of compression forces
Actively extending the wrist produces a passive flexion of the fingers and thumb because of the increased passive tendon in the stretched flexor muscles. this generation of passive movement at other joints is referred to as _________
tenodesis action
What do people with C6 quadriplegia (paralyzed finger flexors and extensors) used in order to grasp objects?
tenodesis
What are the extrinsic extensors of the fingers?
- extensor digitorum
- extensor indices
- extensor digiti minimi
A small slip of the EDC tendon attaches to the base of the dorsal side of the proximal phalanx. the remaining tendon flattens into _____, forming the “backbone” of the extensor mechanism to each finger. Where does this portion of the tendon attach?
Central band; dorsal base of the middle phalanx
Before crossing the PIP joint, two __________ diverge from the central band of the EDC. More distally, these fuse into a single terminal tendon that attaches to
lateral bands; the dorsal base of the distal phalanxe
What do the multiple attachments of the extensor mechanism into phalanges allow the EDC to do?
Transfer extensor force distally throughout the entire finger
What important connections allow the intrinsic muscles to assist the EDC with extension of the PIP and DIP joints?
The transverse and oblique fibers of the dorsal hood
- interossei and umbricals attach into these fibers
What does isolated contraction of the EDC cause?
Hyperextension of the MCP joints
- requires intrinsic m’s for fully extended PIP and DIP joints
What are the extrinsic extensors of the thumb?
- Extensor pollicis longus
- Extensor pollicis brevis
- Abductor pollicis longus
- create the “Anatomic Snuffbox”
Despite their relatively small size, the intrinsic muscles are essential for fine control of the digits. What are the 4 sets of intrinsic muscles?
- Muscles of the thenar eminence
- Muscles of the hypothenar eminence
- Two heads of the adductor pollicis
- The lumbricals and Interossei
What are the muscles of the thenar eminence?
- Abductor pollicis brevis
- Flexor pollicis brevis,
- Opponens pollicis
If there is a disruption of the median nerve, we lose all muscles of the thenar eminence. What will you see?
muscle atrophy; flattening out of the eminence with loss of muscle bulk
What are the muscles of the hypothenar eminence?
- Flexor Digiti Minimi
- Abductor Digiti Minimi
- Opponens Digiti Minimi
- Palmaris Brevis
What is the common function of the hypothenar eminence?
rais and cup the ulnar border of the had
-action deepens the distal transverse arch and enhances digital contact with held objects
What nerve injury can result in complete paralysis of the hypothenar muscles?
ulnar nerve
What do the lumbricals distally blend with?
Oblique fibers of the the dorsal hood
-exert a pull through the central and lateral bands of the extensor mechanism
Position of the hand that produces a combined MCP joint flexion and IP joint extension
intrinsic-plus
- simultaneously contraction of the intrinsic m’s of fingers
Position of the hand that produces MCP hyperextension and IP flexion
extrinsic plus (or intrinsic-minus) - simultaneously contract the extrinsic m's of fingers
What is the indirect effect of the intrinsic muscles of the fingers?
They produce a flexion torque at the MCP joint, preventing the EDC from hyperextending the MCP
- this blocking allows the EC effectively tense the extensor mechanism to completely extend the IP joints
What nerve injury results in “clawing” due to EDC activation causing MCP joints to hyperextend and the IP joint to remain partially flexed?
Ulnar nerve
- intrinsic m’s are inactivated
- called intrinsic minus
Ligament that courses from the palmar side of the PIP to the dorsal side of the DIP and coordinates extension between the two joints
Oblique retinacular ligament
What may cause the oblique reticular ligaments to become tight?
- Arthritis
- trauma
- Dupuytren’s contracture
The wrist flexors offset the large extension potential of the EDC at the wrist. The wrist actually flexes slightly during rapid and complete finger extension. What does wrist flexion help maintain?
Optimal length of the EDC during active finger extension
During active finger flexion the lumbricals are not activated, but still assist the action passively. How does this occur?
They are stretched in a proximal direction owing to the contraction of FDP and at the same time are stretched in a distal direction owing to the distal migration of the extensor mechanism
What is lost if a median nerve injury occurs at the elbow? below the elbow?
At elbow:
- lose forearm pronator/ flexor m’s
- lose thenar eminence and lateral lumbricals
- sensory loss to lateral hand
- ape hand deformity
Below elbow:
- forarm pronator/ flexor muscle will be in tact
Causes pain and paresthesia over median nerve distribution; progression to muscle weakness and atrophy
Carpal tunnel syndrome
What is lost if an ulnar nerve injury occurs at the elbow? below the elbow?
At elbow: - FCU and medial FDP - Adductor Pollicis - Medial lumbricals - Interossei - Bishops hand - Sensory loss to medial hand Below elbow: - FCU and FDP intact
What is lost if a radial nerve injury occurs at the elbow? below the elbow?
Above elbow: - Lose forearm extensors/ supinators - Sensory loss to dorsum of forearm and hand - Wrist drop deformity Below elbow: - No motor loss - Only sensory loss
What muscle activates with a low power fist? high power?
- Almost exclusively the FDP (EDC = consistent activity as well for extension brake at MCP joint)
- FDS
Describes the ability of the fingers and thumb to grasp or to seize, often for holding securing, and picking up objects
prehension
Chronic synovitis; Reduce the tensile strength of the periarticular connective tissues; Forces from muscle contraction and the external environment can destroy the mechanical integrity of a joint.
deformities caused by RA
CMC joint flexion (and adduction), MCP joint hyperextension, and IP joint flexion; Starts with instability of the CMC joint, followed by a flexion and adduction contracture
Zigzag deformity of the thumb
What are the two most common deformities of the MCP?
- Palmar dislocation
2. ulnar drift
The collateral ligaments may rupture because of constant bowstringing force; Over time the proximal phalanx may translate in a palmar direction, resulting in a completely dislocated MCP joint
Palmar dislocation
The contact force of the thumb causes the MCP joint of the index finger to be pushed ulnarly; Increasing the deflection of the EDC; Rupture of the transverse fibers allows the EDC tendon to slip toward the ulnar side of the joint’s axis of rotation
Ulnar drift
Palmer plates overstretched; Lateral bands shift dorsal from overactive intrinsics
Swan-neck deformity
Ruptured central band; Lateral bands slip palmer
Boutonniere deformity
