Podcast
Questions and Answers
What type of joint is the Carpometacarpal Joint (CMC)?
What type of joint is the Carpometacarpal Joint (CMC)?
Which finger has a CMC joint articulation with the trapezium?
Which finger has a CMC joint articulation with the trapezium?
Which phalange is represented as D3 in the nomenclature?
Which phalange is represented as D3 in the nomenclature?
In making a tight fist, which MCP joints remain stationary?
In making a tight fist, which MCP joints remain stationary?
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What is the more distal aspect of the metacarpal referred to as?
What is the more distal aspect of the metacarpal referred to as?
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Which metacarpal joint combination allows for slight mobility?
Which metacarpal joint combination allows for slight mobility?
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What describes the mobility and stability of the 2nd and 3rd CMC joints?
What describes the mobility and stability of the 2nd and 3rd CMC joints?
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Which of the following describes the relationship between metacarpals and phalanges?
Which of the following describes the relationship between metacarpals and phalanges?
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What type of joint is the interphalangeal joint (IP)?
What type of joint is the interphalangeal joint (IP)?
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Which motion is NOT associated with the metacarpophalangeal (MCP) joints?
Which motion is NOT associated with the metacarpophalangeal (MCP) joints?
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Which fingers are involved when the middle finger is the point of reference for abduction?
Which fingers are involved when the middle finger is the point of reference for abduction?
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What structure helps prevent hyperextension at the MCP joints?
What structure helps prevent hyperextension at the MCP joints?
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What type of joint is found at the base of the thumb?
What type of joint is found at the base of the thumb?
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How many interphalangeal joints does the thumb have?
How many interphalangeal joints does the thumb have?
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Opposition of the thumb involves which combination of movements?
Opposition of the thumb involves which combination of movements?
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What is the function of the flexor retinaculum?
What is the function of the flexor retinaculum?
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What is the primary function of the extrinsic muscles of the hand?
What is the primary function of the extrinsic muscles of the hand?
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Which structure is associated with the function of allowing various grasp patterns?
Which structure is associated with the function of allowing various grasp patterns?
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What is the innervation of the Flexor Digitorum Superficialis muscle?
What is the innervation of the Flexor Digitorum Superficialis muscle?
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Which muscle is responsible for flexing all joints of the thumb?
Which muscle is responsible for flexing all joints of the thumb?
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What does the Extensor Pollicis Brevis muscle primarily extend?
What does the Extensor Pollicis Brevis muscle primarily extend?
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Which two nerves innervate the Flexor Digitorum Profundus muscle?
Which two nerves innervate the Flexor Digitorum Profundus muscle?
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Which muscle's action is primarily radial abduction of the thumb?
Which muscle's action is primarily radial abduction of the thumb?
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What is the origin point of the Flexor Digitorum Superficialis?
What is the origin point of the Flexor Digitorum Superficialis?
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What is the primary role of the palmar carpal ligament?
What is the primary role of the palmar carpal ligament?
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Which ligaments blend distal fibers together?
Which ligaments blend distal fibers together?
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What passes through the carpal tunnel formed by the transverse carpal ligament?
What passes through the carpal tunnel formed by the transverse carpal ligament?
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Where does the extensor retinaculum attach laterally?
Where does the extensor retinaculum attach laterally?
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How many compartments does the extensor retinaculum divide into?
How many compartments does the extensor retinaculum divide into?
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What muscle is associated with the first dorsal compartment?
What muscle is associated with the first dorsal compartment?
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What shape does the palm assume when relaxed?
What shape does the palm assume when relaxed?
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Which structure is known as the extensor hood?
Which structure is known as the extensor hood?
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What is the primary action of the Extensor Indicis?
What is the primary action of the Extensor Indicis?
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Which tendons form the anatomical snuff box?
Which tendons form the anatomical snuff box?
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What is the primary action of the Extensor Digiti Minimi?
What is the primary action of the Extensor Digiti Minimi?
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Which nerve innervates the Extensor Digitorum?
Which nerve innervates the Extensor Digitorum?
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How many joints comprise the thumb?
How many joints comprise the thumb?
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Which of the following describes the location of the anatomical snuff box?
Which of the following describes the location of the anatomical snuff box?
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What is the action of the Flexor Pollicis Longus?
What is the action of the Flexor Pollicis Longus?
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What is the origin of the Flexor Digitorum Superficialis?
What is the origin of the Flexor Digitorum Superficialis?
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What is an intrinsic muscle?
What is an intrinsic muscle?
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Explain the difference between the thenar muscles and hypothenar muscles. Provide an example of each.
Explain the difference between the thenar muscles and hypothenar muscles. Provide an example of each.
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What hand muscle does not have a bony attachment? To what two tendons does it attach?
What hand muscle does not have a bony attachment? To what two tendons does it attach?
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The flexor pulley system consists of only annular pulleys.
The flexor pulley system consists of only annular pulleys.
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What is the primary function of the flexor tendon pulley system?
What is the primary function of the flexor tendon pulley system?
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What is a mallet finger?
What is a mallet finger?
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What characterizes a swan neck deformity?
What characterizes a swan neck deformity?
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What causes De Quervain’s Disease?
What causes De Quervain’s Disease?
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Which of the following injuries is characterized by a common hand injury among athletes involving an acute tear?
Which of the following injuries is characterized by a common hand injury among athletes involving an acute tear?
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What symptoms are associated with Carpal Tunnel Syndrome?
What symptoms are associated with Carpal Tunnel Syndrome?
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The ulnar claw is characterized by an inability to extend all digits.
The ulnar claw is characterized by an inability to extend all digits.
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What is the primary function of the Flexor Digitorum Superficialis?
What is the primary function of the Flexor Digitorum Superficialis?
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Which joint type do the Carpometacarpal joints belong to?
Which joint type do the Carpometacarpal joints belong to?
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How many bones comprise one thumb?
How many bones comprise one thumb?
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What is the main function of extrinsic muscles of the hand?
What is the main function of extrinsic muscles of the hand?
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What does CMC stand for in joint nomenclature?
What does CMC stand for in joint nomenclature?
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Which muscle primarily abducts the thumb?
Which muscle primarily abducts the thumb?
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Which ligaments form the carpal tunnel?
Which ligaments form the carpal tunnel?
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The joint type for Interphalangeal joints is _____ hinge joint.
The joint type for Interphalangeal joints is _____ hinge joint.
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What is the anatomical snuffbox?
What is the anatomical snuffbox?
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Which nerve innervates the majority of intrinsic muscles of the hand?
Which nerve innervates the majority of intrinsic muscles of the hand?
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Which of the following is an intrinsic muscle of the hand?
Which of the following is an intrinsic muscle of the hand?
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The middle finger can perform adduction.
The middle finger can perform adduction.
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What movements occur at the thumb CMC joint?
What movements occur at the thumb CMC joint?
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What is the purpose of the Volar plate?
What is the purpose of the Volar plate?
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Study Notes
Hand Nomenclature
- Thumb = D1
- Index (Pointer) = D2
- Long (Middle) = D3
- Ring = D4
- Small = D5
Bones of the Hand: Ray
- Metacarpal base is more proximal
- Metacarpal head is more distal
- Metacarpal neck is below the head
Joint Structures
-
Carpometacarpal Joint (CMC)
- Articulation between metacarpal and carpal bones
-
Metacarpophalangeal Joint (MCP or MP)
- Articulation between metacarpal and proximal phalanx
-
Interphalangeal Joint (IP)
- Proximal IP (PIP)
- Distal IP (DIP)
CMC Joints
- Non-axial plane (irregular) synovial joint
- Thumb CMC: articulation between trapezium and 1st metacarpal. High Mobility, Low Stability.
- Index CMC: articulation between trapezoid and base of 2nd metacarpal. Low Mobility, High Stability.
- Long CMC: articulation between capitate and base of 3rd metacarpal. Low Mobility, High Stability.
- Ring CMC: articulation between hamate and base of 4th metacarpal. Slight Mobility, High Stability.
- Small CMC: articulation between hamate and base of 5th metacarpal. Slight Mobility, High Stability.
- The 5th CMC joint is the most mobile of the fingers and allows for a small amount of finger opposition.
“Knuckles” (MCP Joints)
- Biaxial Condyloid Joints
- Rounded metacarpal heads articulate with concave base of phalanges
- Motions: Flexion/Extension/Hyperextension/Abduction/Adduction
- Volar plate prevents hyperextension
MCP Joints: Motions
- Middle finger is reference point for abduction and adduction
- Abduction: fingers move away from the middle finger.
- Adduction: fingers move towards the middle finger.
Interphalangeal Joint (IP)
- Uniaxial Hinge Joints
- Motions: Flexion/Extension
- Digit 1 (Thumb): 1 IP Joint
- Digits 2-5: 2 IP Joints (PIP and DIP)
Thumb CMC Joint
- Trapezium articulates with 1st metacarpal
-
Saddle Joint (Concave & Convex)
- Note: Sometimes described as a modified ball and socket joint, which implies motion in all three planes.
- Rotation at the CMC joint with opposition is involuntary and occurs due to joint shape. It is considered an accessory motion.
Thumb CMC Joint: Motions
- Flexion/Extension: Occurs in frontal plane.
- Palmar Abduction/Adduction: Occurs in sagittal plane.
- Opposition/Reposition: Opposition (flexion and abduction with rotation) is a combination of motions. Reposition is the return to anatomical position.
Bones and Landmarks
- 5 MCPs
- 5 Proximal Phalanges
- 4 Middle Phalanges
- 5 Distal Phalanges
- Proximal end of metacarpal/phalanx: base
- Distal end of metacarpal/phalanx: head
Ligaments and Other Structures
- Flexor retinaculum: fibrous band spanning the anterior wrist, holds tendons close to the wrist during flexion and prevents carpal bone separation.
- Splits into: Palmer Carpal Ligament and Transverse Carpal Ligament
Ligaments and Other Structures: Carpal Tunnel
- Median nerve
- FDS
- FDP
- FPL
Ligaments and Other Structures: Extensor Retinaculum
- Fibrous band crossing dorsal side of wrist
- Attaches medially to the ulnar styloid and laterally to the triquetrum, pisiform, and radius
- Function: Holds extensor tendons close to wrist during extension.
- Divided into 6 sections (tunnels) called dorsal compartments.
Ligaments of the Hand and Other Structures: Dorsal Compartments
- 1st Compartment: Abductor Pollicis Longus (APL), Extensor Pollicis Brevis (EPB)
- 2nd Compartment: Extensor Carpi Radialis Longus (ECRL), Extensor Carpi Radialis Brevis (ECRB)
- 3rd Compartment: Extensor Pollicis Longus (EPL)
- 4th Compartment: Extensor Digitorum Communis (EDC), Extensor Indicis Proprius (EIP)
- 5th Compartment: Extensor Digiti Minimi (EDM)
- 6th Compartment: Extensor Carpi Ulnaris (ECU)
Ligaments of the Hand and Other Structures: Extensor Expansion Ligament
- “Extensor Hood”
- Triangular aponeurosis covering dorsal and sides of proximal phalanx of fingers
Arches of the Hand
- Longitudinal Arch: Starts at wrist and goes to finger tips.
- Transverse Arch: Distal - Metacarpal Heads, Proximal - CMC Joints.
- Function: Allow for high level of function with various grasp patterns.
Creases
- Distal Palmar Crease
- Proximal Palmar Crease
- Thenar Crease
- Distal Wrist Crease
- Proximal Wrist Crease
Extrinsics
- Muscles with origin above the wrist and insertion inside the hand.
- Cross the wrist and hand joints.
- Primary Function: Finger motion
- Secondary Function: Wrist motion
Extrinsic Muscles
- Anterior: Flexor Digitorum Superficialis (FDS), Flexor Digitorum Profundus (FDP), Flexor Pollicis Longus (FPL).
- Posterior: Abductor Pollicis Longus (APL), Extensor Pollicis Brevis (EPB), Extensor Pollicis Longus (EPL), Extensor Digitorum Communis (EDC), Extensor Indicis (EI), Extensor Digiti Minimi (EDM).
Flexor Digitorum Superficialis
- Origin: Medial epicondyle of humerus, coronoid process, medial collateral ligament.
- Insertion: Anterior margin of base of 2nd-5th middle phalanx.
- Action: Flexion of PIP; secondary MCP flexion (2nd-5th Digits).
- Nerve: Median nerve.
Flexor Digitorum Profundus
- Origin: Medial olecranon, anterior and medial ulna, interosseous membrane.
- Insertion: Base 2nd-5th distal phalanges
- Action: Flexion of DIP, secondary MCP and PIP flexion (2nd-5th Digits).
- Nerve: Median nerve (2nd and 3rd), Ulnar nerve (4th and 5th).
Relationship of Profundus and Superficialis Insertions
- Profundus tendons pass through the superficialis tendons.
Flexor Pollicis Longus
- Origin: Radius, anterior surface, interosseous membrane
- Insertion: Distal phalanx of thumb
- Action: Flexion of all thumb joints
- Nerve: Anterior Interosseous (Median)
Abductor Pollicis Longus
- Origin: Posterior radius, interosseous membrane, middle ulna
- Insertion: Base of thumb metacarpal
- Action: Radial abduction of thumb
- Nerve: Radial nerve
Extensor Pollicis Brevis
- Origin: Posterior distal radius
- Insertion: Base of proximal phalanx of thumb
- Action: Extends MCP joint of thumb
- Nerve: Radial nerve
Extensor Pollicis Longus
- Origin: Middle posterior ulna and interosseous membrane
- Insertion: Base of distal phalanx of thumb
- Action: Extension of thumb IP joint.
- Nerve: Radial nerve
Anatomical Snuff Box
- Deep depression on dorsal base of thumb
-
Borders:
-
Radial (Lateral) Side:
- Abductor Pollicis Longus
- Extensor Pollicis Longus
-
Ulnar (Medial) Side:
- Extensor Pollicis Brevis
-
Radial (Lateral) Side:
- Bone found in depression: Scaphoid bone
Extensor Digitorum
- Origin: Lateral epicondyle of humerus
- Insertion: Base of middle and distal phalanx of 4 fingers (extensor mechanism)
- Action: Extension of all 3 joints of fingers.
- Nerve: Radial nerve.
Extensor Indicis
- Origin: Distal Ulna
- Insertion: Base of distal phalanx of 2nd finger
- Action Extension of MCP joint of 2nd finger
- Nerve: Radial nerve
Extensor Digiti Minimi
- Origin: Lateral epicondyle of humerus
- Insertion: Base of proximal phalanx of small finger
- Action: Extension of MP joint of 5th finger
- Nerve: Radial nerve
Sensory Innervations
- Median Nerve: Palmar surface of thumb, index, middle, and radial half of ring finger.
- Ulnar Nerve: Palmar surface of small finger and ulnar half of ring finger, dorsal surface of all fingers except thumb.
- Radial Nerve: Dorsal surface of the thumb, index, middle, and radial half of ring finger
Review Questions
- 1. Which thumb and finger motions occur in the frontal plane? Flexion/Extension of the fingers and thumb.
- 2. Which thumb and finger motions occur in the sagittal plane? Palmar abduction/adduction of the thumb.
- 3. Which thumb and finger motions occur in the transverse plane? Thumb rotation during opposition.
- 4. How many bones comprise a thumb? 4
- 5. How many bones comprise a finger? 3
- 6. How many joints comprise the thumb? 3 (CMC, MCP, IP)
- 7. How many joints comprise a finger? 3 (MCP, PIP, DIP)
- 8. Which thumb opposition motion is considered an accessory motion? Rotation
- 9. Which tendons and nerve run through the carpal tunnel? FDS, FDP, FPL, and Median nerve
- 10. What is an extrinsic muscle? A muscle that originates outside the hand.
- 11. What is the “anatomical snuff box”? Which muscles act as the borders of this area? It's the depression between the tendons of Abductor Pollicis Longus, Extensor Pollicis Brevis, and Extensor Pollicis Longus.
Flexor Digitorum Superficialis
- Origin: Medial epicondyle of humerus, coronoid process of ulna, and radial tuberosity.
- Insertion: Base of middle phalanx of digits 2-5.
- Action: Flexion of PIP joints
- Nerve: Median nerve
Flexor Digitorum Profundus
- Origin: Medial and anterior ulna, coronoid process, medial olecranon, and interosseous membrane.
- Insertion: Base of distal phalanxes 2-5.
- Action: Flexion of DIP joint.
- Nerve: Median nerve (2nd and 3rd) and ulnar nerve (4th and 5th).
Flexor Pollicis Longus
- Origin: Interosseous membrane, anterior surface of radius.
- Insertion: Base of distal phalanx of thumb.
- Action: Flexion of thumb at all joints.
- Nerve: Anterior Interosseous (Median) nerve.
Bones of the Hand: Ray
- Metacarpals: Each finger has one metacarpal bone.
- Metacarpal Base: The more proximal aspect of the metacarpal.
- Metacarpal Head: The more distal aspect of the metacarpal.
- Metacarpal Neck: Located below the metacarpal head.
Carpometacarpal Joints (CMC)
- Type of Joint: Non-axial plane (irregular) synovial joint.
- Articulation: The CMC joints connect the proximal end of a metacarpal to the distal row of carpal bones.
- Thumb CMC: High mobility, low stability.
- Index, Long, Ring, and Small CMC: Low mobility, high stability.
- The 5th CMC joint: The most mobile of the finger CMC joints, allowing for a small amount of opposition.
Metacarpophalangeal Joints (MCP or MP)
- Type of Joint: Biaxial condyloid joints.
- Articulation: The MCP joints connect the distal ends of metacarpals with the proximal phalanges.
- Motions: Flexion, extension, hyperextension, abduction, and adduction.
Interphalangeal Joints (IP)
- Type of Joint: Uniaxial hinge joints.
- Motions: Flexion and extension.
- Digit 1 (Thumb): Has 1 IP joint.
- Digits 2-5: Have 2 IP joints (Proximal IP [PIP] and Distal IP [DIP]).
Thumb CMC Joint
- Articulation: Trapezium articulates with the base of the 1st metacarpal.
- Type of Joint: Saddle joint (sometimes described as a modified ball and socket joint).
- Motions: Flexion/extension, palmar abduction/adduction, opposition/reposition.
Ligaments and Other Structures: Flexor Retinaculum
- Location: A fibrous band stretching across the anterior wrist in a mediolateral (horizontal) direction.
-
Functions:
- Holds tendons close to the wrist during flexion.
- Prevents the separation of the carpal bones.
- Components: Divided into the palmar carpal ligament and the transverse carpal ligament.
Ligaments and Other Structures: Palmar Carpal Ligament
- Location: More proximal and superficial.
- Attachments: Connects to the styloid processes of the radius and ulna, crossing over the flexor muscles.
- Distal fibers: Blend with the transverse carpal ligament.
Ligaments and Other Structures: Transverse Carpal Ligament
- Location: Deeper and more distal.
- Attachments: Connects to the pisiform and hook of the hamate on the medial side, and the scaphoid and trapezium laterally.
- Function: Forms a tunnel through which the median nerve and 9 extrinsic flexor tendons pass.
Ligaments of the Hand and Other Structures: Extensor Retinaculum
- Location: Fibrous band crossing the dorsal side of the wrist.
- Attachments: Connects to the ulnar styloid medially and the triquetrum, pisiform, and radius laterally.
- Function: Holds extensor tendons close to the wrist during extension.
- Divisions: Divided into six sections (tunnels) called dorsal compartments.
Ligaments of the Hand and Other Structures: Dorsal Compartments
- Compartment 1: Abductor Pollicis Longus (APL) and Extensor Pollicis Brevis (EPB).
- Compartment 2: Extensor Carpi Radialis Longus (ECRL) and Extensor Carpi Radialis Brevis (ECRB).
- Compartment 3: Extensor Pollicis Longus (EPL).
- Compartment 4: Extensor Digitorum Communis (EDC) and Extensor Indicis Proprius (EIP).
- Compartment 5: Extensor Digiti Minimi (EDM).
- Compartment 6: Extensor Carpi Ulnaris (ECU).
Ligaments of the Hand and Other Structures: Extensor Expansion Ligament
- Nickname: “Extensor Hood”.
- Location: A small, triangular, flat aponeurosis covering the dorsum and sides of the proximal phalanx of the fingers.
Arches of the Hand
- Longitudinal Arch: Starts at the wrist and extends to the fingertips.
- Transverse Arch: Distal – Metacarpal heads; Proximal – CMC joints.
- Function: Allows for a high level of function with various grasp patterns.
Creases
- Distal palmar crease: Most distal horizontal crease in the palm.
- Proximal palmar crease: Middle horizontal crease in the palm.
- Thenar crease: Diagonal crease across the thenar eminence.
- Distal wrist crease: Most distal transverse crease on the wrist.
- Proximal wrist crease: Most proximal transverse crease on the wrist.
Extrinsic Muscles of Thumb & Fingers
- Origin: Above the wrist.
- Insertion: Inside the hand.
-
Functions:
- Primary: Finger motion.
- Secondary: Wrist motion (weak).
Anterior Extrinsic Muscles
-
Flexor Digitorum Superficialis (FDS):
- O: Medial epicondyle of humerus (common flexor origin), coronoid process, and medial collateral ligament.
- I: Anterior margin of the base of the 2nd-5th middle phalanges.
- A: Flexion of PIP joints; secondary MCP flexion (2nd-5th digits).
- N: Median nerve.
-
Flexor Digitorum Profundus (FDP):
- O: Medial olecranon, anterior and medial ulna, and interosseous membrane.
- I: Base of the 2nd-5th distal phalanges.
- A: Flexion of DIP, secondary MCP and PIP flexion (2nd-5th digits).
- N: Median nerve (2nd and 3rd) and ulnar nerve (4th and 5th).
-
Flexor Pollicis Longus (FPL):
- O: Radius, anterior surface, and interosseous membrane.
- I: Distal phalanx of thumb.
- A: Flexes all joints of the thumb.
- N: Anterior interosseous (median) nerve.
Posterior Extrinsic Muscles
-
Abductor Pollicis Longus (APL):
- O: Posterior radius, interosseous membrane, and middle ulna.
- I: Base of the thumb metacarpal.
- A: Radial abduction of thumb.
- N: Radial nerve.
-
Extensor Pollicis Brevis (EPB):
- O: Posterior distal radius.
- I: Base of the proximal phalanx of thumb.
- A: Extends MCP joint of thumb.
- N: Radial nerve.
-
Extensor Pollicis Longus (EPL):
- O: Middle posterior ulna and interosseous membrane.
- I: Base of distal phalanx of thumb.
- A: Extension of thumb IP joint.
- N: Radial nerve.
-
Extensor Digitorum Communis (EDC):
- O: Lateral epicondyle of humerus.
- I: Base of middle and distal phalanx of 4 fingers (extensor mechanism).
- A: Extension of all three joints of fingers.
- N: Radial nerve.
-
Extensor Indicis (EI):
- O: Distal ulna.
- I: Base of distal phalanx of 2nd (index) finger and dorsal expansion.
- A: Extension of MCP joint of 2nd (index) finger.
- N: Radial nerve
-
Extensor Digiti Minimi (EDM):
- O: Lateral epicondyle of humerus.
- I: Base of proximal phalanx of small (5th) finger and dorsal expansion.
- A: Extension of MP joints of 5th finger.
- N: Radial nerve.
Anatomical Snuff Box
- Location: Deep depression on the dorsal base of the thumb.
-
Borders:
- Radial (Lateral) Side: Abductor Pollicis Longus and Extensor Pollicis Longus.
- Ulnar (Medial) Side: Extensor Pollicis Brevis.
Intrinsic Muscles of the Hand
- Origin: Within the hand.
- Insertion: At or distal to the carpal bones.
-
Functions:
- Motion of thumb and fingers.
- Responsible for precision and fine motor control.
Intrinsic Muscles of the Hand - Thenar Muscles
- Location: Form the thenar eminence.
- Function: Act to move the thumb.
Intrinsic Muscles of the Hand - Hypothenar Muscles
- Location: Form the hypothenar eminence.
- Function: Act primarily on the little finger.
Intrinsic Muscles of the Hand - Deep Palm Muscles
-
Function:
- Act to move the lumbricals and interossei, as well as one thumb muscle.
- Located between the thenar and hypothenar eminences.
Intrinsic Muscles of the Hand (Thenar)
-
Flexor Pollicis Brevis (FPB):
- O: Trapezium and flexor retinaculum.
- I: Proximal phalanx.
- A: Flexion of the MCP joint of the thumb.
- N: Median nerve.
-
Abductor Pollicis Brevis (APB):
- O: Scaphoid, trapezium, and flexor retinaculum.
- I: Proximal phalanx.
- A: Abducts the thumb.
- N: Median nerve.
-
Opponens Pollicis (OP):
- O: Trapezium and flexor retinaculum.
- I: First metacarpal.
- A: Opposes the thumb.
- N: Median nerve.
Intrinsic Muscles of the Hand (Hypothenar)
-
Flexor Digiti Minimi (FDM):
- O: Hamate and flexor retinaculum.
- I: Base of proximal phalanx of the 5th finger.
- A: Flexes the CMC and MCP of the 5th finger.
- N: Ulnar nerve.
-
Abductor Digiti Minimi (ADM):
- O: Pisiform and tendon of flexor carpi ulnaris.
- I: Proximal phalanx of the small (5th) finger.
- A: Abducts the MP of the 5th finger.
- N: Ulnar nerve.
-
Opponens Digiti Minimi (ODM):
- O: Hamate and flexor retinaculum.
- I: 5th metacarpal.
- A: Opposition of the small (5th) finger.
- N: Ulnar nerve.
Intrinsic Muscles of the Hand (Deep Palm)
-
Adductor Pollicis (AP):
- O: Capitate, base of the 2nd metacarpal, and palmar surface of the 3rd metacarpal.
- I: Base of the proximal phalanx of the thumb.
- A: Adducts the thumb.
- N: Ulnar nerve.
-
Dorsal Interossei (DAB):
- O: 2 metacarpal bases - adjacent.
- I: Base of proximal phalanx and dorsal apparatus and EDC.
- A: Abduct fingers at MCP, flex MP joint, extend PIP.
- N: Ulnar nerve.
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Palmar Interossei (PAD):
- O: Base and shaft of a metacarpal.
- I: Base of proximal phalanx, dorsal expansion, and EDC.
- A: Adduct fingers at MCP.
- N: Ulnar nerve.
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Lumbricals:
- O: Tendon of flexor digitorum profundus.
- I: Tendon of extensor digitorum muscle
- A: Flex the MCP, extend IP.
- N: Median nerve (1st & 2nd), Ulnar nerve (3rd & 4th).
Flexor Ligamentous Structures
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Collateral ligaments: Located on the lateral aspect of the DIP, PIP, and MCP joints.
- Radial Collateral Ligaments: Stabilizes laterally.
- Ulnar Collateral Ligaments: Stabilizes medially.
Pulley System
- Location: A fibro-osseous tunnel on the palmar aspect of the hand through which the deep and superficial flexor tendons pass.
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Components:
- Palmar Aponeurosis Pulley
- Five Annular Pulleys (A1 to A5)
- Three Cruciform Pulley
- Function: Maintain flexor tendons close to the joint’s axis of motion and prevent bowstringing.
- Thumb: Only has 2 pulleys (A1 and A2).
Annular Ligaments
- A2 and A4 are crucial for preventing the tendons from bowstringing, which is the sideways displacement of tendons
- A1, A3, and A5 over the MP, PIP, and DIP joints respectively, originating from the palmar plate
Cruciform Pulleys
- Prevent the tendon sheath from collapsing or expanding during finger movement
- C1 is located just distal to the A2 pulley
- C2 is located between the A3 and A4 pulleys
- C3 is located distal to the A4 pulley
Trigger Finger Stages
- Stage 1: characterized by tenderness
- Stage 2: characterized by clicking and catching
- Stage 3: characterized by a tendon becoming stuck
Extensor Mechanism
- The extensor mechanism is an extension of the extensor digitorum communis (EDC) tendon on the dorsum of each phalanx
- The extensor indicis (EI) and extensor digiti minimi (EDM) insert into the extensor mechanism of the second and fifth digits, respectively.
- The EDC, central tendon, lateral bands, extensor hood, and oblique retinacular ligament make up the extensor mechanism.
Extensor Mechanism Functions
- The EDC tendon attaches by a tendinous slip to the proximal phalanx, allowing for MP joint extension
- The central tendon (slip) attaches to the base of the middle phalanx and allows for PIP joint extension
- The lateral bands run on either side of the dorsal midline and rejoin before attaching to the distal phalanx, extending the DIP joint
- The extensor hood surrounds the MP joint laterally, medially, and dorsally, receiving tendinous fibers from the lumbricals and interossei
- The ORL attaches at the sides of the proximal phalanx and digital tendon sheaths and proceeds to the distal portion of the lateral bands
Extensor Mechanism Dysfunctions
- Mallet finger: Disruption of the terminal extensor tendon distal to the DIP joint causing the finger joint to deform
- Boutonniere deformity: Injury to the central slip leading to PIP joint flexion and DIP joint hyperextension
- Swan Neck Deformity: Laxity of the volar plate or an imbalance of muscle forces (extension > flexion) at the PIP causing hyperextension at the PIP and flexion at the DIP
- Intrinsic Minus Hand: Weakness of the intrinsic muscles of the hand
Flexor Pollicis Brevis
- Originates from the flexor retinaculum and trapezium
- Inserts into the proximal phalanx of the thumb
- Action: Flexes the thumb at the MCP joint
- Innervation: Median nerve
Abductor Pollicis Brevis
- Originates from the trapezium, scaphoid, and flexor retinaculum
- Inserts into the proximal phalanx of the thumb
- Action: Abducts the thumb
- Innervation: Median nerve
Opponens Pollicis
- Originates from the flexor retinaculum, trapezium, and scaphoid
- Inserts into the lateral surface of the proximal phalanx of the first metacarpal
- Action: Opposes the thumb
- Innervation: Median nerve
Flexor Digiti Minimi
- Originates from the hamate and flexor retinaculum
- Inserts into the base of the distal phalanx of the 5th finger
- Action: Flexes the 5th finger at all joints, also flexes the CMC and MCP of the 5th finger
- Innervation: Ulnar nerve
Abductor Digiti Minimi
- Originates from the ligament tendon of the flexor carpi ulnaris, hamate, lunate, and pisiform
- Inserts into the base of the proximal phalanx of the 5th finger
- Action: Abducts the MP of the 5th finger
- Innervation: Ulnar nerve
Opponens Digiti Minimi
- Originates from the lunate, hamate, and flexor retinaculum
- Inserts into the 5th metacarpal
- Action: Opposes the 5th finger
- Innervation: Ulnar nerve
Adductor Pollicis
- Originates from the capitate, base of the 2nd metacarpal, and lateral surface of the 3rd metacarpal
- Inserts into the proximal phalanx of the thumb
- Action: Adducts the thumb
- Innervation: Median nerve
Dorsal Interossei
- Originates from the adjacent bases between the metacarpals
- Inserts into the proximal bases of the phalanx, dorsal expansion, and EDC
- Action: Abducts the metacarpals of digits 2-5
- Innervation: Radial and Ulnar nerves
Palmar Interossei
- Originates from the lateral surface of metacarpals 4 and 5 and the medial surface of 1st metacarpal, base, and shaft of the metacarpal
- Inserts into the base of the proximal phalanx of digits 2, 4, and 5, the dorsal apparatus, and the EDC
- Action: Adducts the metacarpals for digits 2, 4, and 5
- Innervation: Median and Ulnar nerves
Lumbricals
- Originates from the tendon of the flexor digitorum profundus
- Inserts into the tendon of the extensor digitorum
- Action: Flexes the MCP joint and extends the PIP and DIP joints of digits 2-5
- Innervation: Median (2 and 3 digits) and Ulnar (4 and 5 digits)
Functional Position
- MCP joints are flexed 50-70 degrees and the IP joints are slightly flexed
- Allows for optimal position for the wrist and hand, improving strength and precision
- The most effective position for hand use
Hand Functional Types
- Grasp: the primary function of the hand, holding and manipulating objects.
- Prehension: Grasping and manipulating an object
- Power grip: A forceful grasp using an isometric contraction
- Precision grip: Object is manipulated by finger movement
Grasp Patterns
- Spherical: All fingers and thumb abduct around an object. Palm not involved - mostly finger tips. Example: Holding an apple.
- Cylindrical: Fingers flexed around the object with the thumb wrapped around the object. Fingers adducted, object pressed against palm. Example: Holding a hammer.
- Hook fist: 2nd through 5th digits flexed around an object, flexor digitorum profundus and superficialis contracting. Example: Holding a handle.
Precision Grips (Pinch)
- Tripod: Involves thumb and first two digits.
- Pincer/Tip to tip: Pick up small objects
- Lateral prehension (key): Thumb on the lateral side of the index finger, the most powerful
Pediatric Development of Grasp
- Grasp patterns develop gradually as children mature
- Children develop different grasp patterns at different ages
Common Wrist and Hand Pathologies
- Colles' Fracture: Occurs when an elderly person falls on an outstretched hand, causing a transverse fracture of the distal radius and posterior displacement of the distal fragment.
- Smith's Fracture: A fracture of the distal radius caused by a fall on the back of the hand, resulting in an anterior displacement of the distal fragment.
- Greenstick Fracture: An incomplete fracture, more often seen in children. Commonly occurs in the radius, proximal to a Colles' fracture.
- Ganglion Cyst: A benign tumor mass appearing as a bump on the dorsal surface of the wrist, developed along the tendons or joints of the wrist and hand.
- Carpal Tunnel Syndrome: Occurs when the median nerve is compressed within the carpal tunnel, causing numbness, tingling, and weakness in the thumb, index, and middle fingers.
- De Quervain's Disease: An inflammation and thickening of the sheath containing the extensor pollicis brevis and abductor pollicis longus tendons, causing pain on the radial side of the wrist.
- Trigger Finger/Stenosing Tenosynovitis: A disorder affecting the sliding mechanism of a tendon in its sheath. When a nodule or swelling develops, the tendon becomes stuck. The flexor tendons of the middle and ring fingers are most commonly affected.
- Dupuytren's Contracture: A condition where the palmar aponeurosis undergoes nodular thickening. Most common in the palm, affecting the ring and little fingers, leading to flexion contractures.
- Skier's Thumb/Gamekeeper's Thumb: An acute tear of the ulnar collateral ligament of the thumb, often seen in athletes.
Extensor Mechanism Dysfunction Review
- Swan Neck Deformity: Characterized by hyperextension at the PIP joint and flexion at the DIP joint.
- Boutonniere Deformity: Characterized by PIP joint flexion and DIP joint hyperextension.
- Mallet Finger: Caused by a disruption of the terminal extensor tendon distal to the DIP joint, resulting in a deformed finger joint.
Radial Nerve Pathway and Injury
- The radial nerve branches into the posterior interosseous nerve at the supinator muscle.
- The radial nerve is compressed as it spirals around the humerus.
- Saturday Night Palsy: Occurs when the radial nerve is compressed due to someone falling asleep with their arm over the back of a chair. This injury results in loss of wrist extensors.
- Wrist Drop: Loss of wrist extension and weakened ability to release objects due to high radial nerve injury.
Median Nerve Pathway and Injury
- The median nerve gives rise to the Anterior Interosseous Nerve (AIN) at the radiohumeral joint line.
- The AIN supplies motor function to the deep muscles in the anterior forearm: flexor pollicis longus, pronator quadratus, and flexor digitorum profundus (II and III).
- Ape Hand Deformity: Loss of thumb opposition and atrophy of the thenar eminence muscles, caused by median nerve injury.
- Sign of Benediction: MCP and PIP joints of the 2nd and 3rd fingers are extended while the MCP joints of the 4th and 5th fingers are flexed when making a fist, indicating median nerve injury.
- AIN Dysfunction: Inability to form an “OK” sign due to inability to flex the thumb IP joint and the index DIP joint.
Ulnar Nerve Pathway and Injury
- The ulnar nerve supplies the intrinsic muscles of the hand.
- Ulnar Claw: Occurs with the loss of medial two lumbricals, leading to hyperextension of the proximal phalanges and extreme flexion of the middle and distal phalanges of the 4th and 5th fingers when extending all digits.
- Claw Hand: A combination of ulnar and median nerve injuries that results in a claw-like deformity of the hand.
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Description
Test your knowledge on the nomenclature and structural anatomy of the hand. This quiz covers the bones of the hand, various joints including the carpometacarpal and metacarpophalangeal joints, and their articulations. Ideal for students or professionals interested in human anatomy and kinesiology.
