Hand Anatomy Flashcards
How many metacarpals
5
How many carpal bones?
8- scaphoid, lunate, triquetrum, pisiform, trapezium, trapezoid, capitate, hamate
How many phalanges?
14- proximal, middle & distal for digits 2-5, only proximal and distal for 1st phalange
What kind of joints are in the hand?
- Metacarpal-phalangeal (MCP): synovial joints, condyloid, allows flex-extension & adduction-abduction
- Interphalangeal (IP): synovial joints, PIPs (proximal interphalangeal joint) and DIPs (distal interphalangeal joint), bi-condyloid facets allow flexion-extension and little adduction-abduction
What are the ligaments of the fingers?
- Palmar (volar)- thickened anterior portions of the joint capsules of MCP & IP joints
- Deep Transverse- interconnects MCP joints EXCEPT for the thumb, allows for greater mobility of the thumb
- Collateral ligaments- CT bands on each side of joint, support all MCP & IP joints, at MCP joints: flexion tautens collateral ligaments which limits adduction-abduction, extension relaxes ligaments which permits adduction-abduction
What are the 2 important aspects of the palm?
- Palmar aponeurosis: protective covering over tendons
* Superficial transverse ligament: across palmar side of MCP joints
What are tendon coverings made up of?
- Fibrous flexor sheaths which enclose flexor tendons in fingers
- Synovial sheaths around tendons
- Flexor retinaculum= transverse carpal ligament, it is the ‘roof’ of the carpal tunnel
- All are made of fibrous CT
- Makes fluid that cuts down friction
What are synovial sheaths?
- Wrap around the tendon to reduce friction
- Lined with 2 types of synoviocytes:
1. Type A are marcophage-like
2. Type B secrete hyaluronic acid, which increases the viscosity, consists of hylauronic acid, lubricin, proteinases & collagenases - Synovial fluid also transports oxygen, nutrients, CO2 and waste products
- Has thixotropic characteristics
Movements of the thumb
- Abduction-Adduction are perpendicular to the palm
* Flexion-Extension are parallel to the palm
Movements of the fingers
*Abduction-Adduction are referenced from the middle finger
DAB & PAD
- Dorsal abduct
- Palmar adduct
- Dorsal and palmar interossei are antagonists of each other
Importance of finger ligaments
- Fibrous flexor sheaths act as a pulley system to assist action of flexor muscles/tendons on phalanges
- Link ligaments provide a connection between flexor tendon sheaths and dorsal expansions to coordinate movements
- Holds tendons close to each other and close to the bone
Trigger finger
Occurs when chronic irritation causes a nodule to form along the flexor tendon, this nodule prevents smooth action of the tendon and may even lock finger in flexed position
Bowstring phenomenon
- What happens if tendon sheath ruptures
* Will see the tendon essentially pulling off the bone
Swan neck
- Starts as mallet finger
* Brings PIP into extension
Boutonniere
Extensor tendon disrupted= collateral ligament slips under axis of joint= PIP inflection because no opposing force, but collateral ligament pulls up and give extension of DIP
Median nerve
- Cutaneous: 3 1/2 digits and thenar eminence
- Forearm muscles: pronator teres, palmaris lonus, flexor carpi radialis, flexor digitorum superificialis and 1/2 of profundus, pronator quadratus, flexor pollicis longus
- Hand muscles: all thenar muscles except the adductor pollicis, lumbricals 1, 2
- Power grip: muscles provide forceful grip
Carpal Tunnel
- Space formed by flexor retinaculum/transverse carpal ligament spanning across carpal bones (flexor retinaculum lies deep to palmar aponeurosis)
- Structures in the carpal tunnel: median nerve, flexor digitorum superficialis, flexor digitorum profundus, flexor pollicis longus
- Structures NOT in the carpal tunnel: ulnar nerve, radial and ulnar arteries, palmaris longus, flexor carpi ulnaris, flexor carpi radialis
Carpal Tunnel Syndrome
- Median nerve is compressed
- Carpal tunnel size is reduced due to local inflammation or tenosynovitis, fluid overload, dislocation of carpal bones, arthritis
- Often associated with diabetes mellitus, which also compromises nerve function
- Symptoms include loss of sensation over median nerve distribution, loss of function of thenars and lumbricals 1, 2, thenar wasting (ape hand)
Testing the median nerve
- Tinel’s or Phalen’s test
- Sensory testing- tunin fork, 2-point discrimination
- Strength testing- thenar musculature
- It is possible to have a negative electromyograph and still have carpal tunnel syndrome (CTS)
Ulnar nerve
- Cutaneous: 1 1/2 digits, ulnar side of palm and dorsum of hand
- Forearm muscles: flexor carpi ulnaris, 1/2 of flexor digitorum profundus
- Hand muscles: hypothenars, adductor pollicis, lumbricals 3 & 4, dorsal and palmar interossei
- Precision grip: intrinsic hand muscles produce fine movement of the fingers (b/c many more hand muscles innervated by ulnar)
Tunnel of Guyon or Ulnar Tunnel
- Space between pisiform and hook of hamate, interconnected by pisohamate ligament (extension of flexor carpi ulnaris tendon)
- Floor of tunnel is the flexor retinaculum
- Roof of tunnel is the palmar carpal ligament (extension of forearm deep fascia)
- In the tunnel: ulnar nerve (splits into deep and superficial branches), ulnar artery and veins
Ulnar nerve entrapment
- Claw hand due to lack of MCP flexion and IP extension in fingers, 2 fingers remain extended b/c 2 of the lumbricals are innervated by the median nerve
- Atrophy of interossei
- Cutaneous loss of 1 1/2 digits
Testing the Ulnar nerve
- Tinel’s over the Tunnel of Guyon
- Sensation testing over ulnar nerve distribution
- Instruct patient to cross one’s fingers; this requires intact interossei function
- Can do EMG and nerve conduction studies
Testing the radial nerve
- Wrist and elbow extension
- Sensation around dorsum of thumb
- Nerve conduction studies
- Doesn’t innervate anything intrinsically in the hands
- ‘Waiters’ hand
