Session 4: The Hand (14.01.2020) Flashcards
Names of the digits
Thumb (I) Index finger Middle finger Ring finger Little finger (V)
(1->5 in anatomical position)
What are the bones of the wrist and hand?
- The Radius
- The Ulna
- The Carpus (carpal bones);
- Proximal row – scaphoid, lunate, triquetrum, pisiform
- Distal row – trapezium, trapezoid, capitate, hamate
- The metacarpal bones
- The phalanges
Bones of the wrist and articulation
The distal ends of the radius and ulna articulate with the proximal row of carpal bones, with the exception of pisiform (a sesamoid bone) and with the articular disk.
How is the skin of the hand different? Why?
- Skin in palm of the hand and foor is different (thick skin)
- no hair
- histologically outer layer much thicker than in the rest of the skin of the body
- palms and soles of feet exposed to much more
Fascia of the palm
Palmar fascia
Palmar aponeurosis
- overlies the long flexor tendons of the hand
- proximally continuous with the flexor retinaculum
- distally continuous with the fibrous digital sheaths
Fibrous digital sheaths
- contain the flexor tendons and their synovial sheaths
Flexor retinaculum
= transverse carpal ligament
-> forms the roof of the carpal tunnel
Compartments of the hand
- Septa – medial and lateral
- Septa ; from palmar apponeurosis to
- medially : to little finger metacarpal
- laterally : to middle finger metacarpal - Hypothenar compartment
- Central compartment
- Thenar compartment
- Adductor compartment
Connective tissue and septae of the hand
x
Muscles of the region (summary)
Anterior compartment of the forearm (revision)
- Superficial compartment
- Deep compartment
Posterior compartment of the forearm (revision)
Intrinsic muscles of the hand
- thenar compartment
- adductor compartment
- hypothenar compartment
- interossei and lumbricals
Forearm muscles in terms of hand
- The hand and wrist are operated by “remote control” by the forearm muscles
- The forearm muscles attach at the distal humerus as well as the radius and ulna
- Flexors (and pronators) anteriorly
- Extensors (and supinators) posteriorly
- in the upper forearm - you don’t want muscle bulk in the wrist area
What are forearm muscles acting across the wrist called?
- carpi
but not to the digits
Carpi muscles
Muscles acting across the wrist - the “carpi” muscles.
Digitorum muscles
Muscles acting on the digits – the “digitorum” muscles and long muscles of thumb, index finger (extensor) and little finger
What are muscles acting on the digits called?
Muscles acting on the digits – the “digitorum” muscles and long muscles of thumb, index finger (extensor) and little finger
-> thumbs: pollicis
Which muscles are in the deep anterior compartment of the forearm?
Flexor digitorum profundus (FDP) Flexor pollicis longus (FCP) Pronator quadratus (PQ)
x
x
Intrinsic muscles of the hand
Thenar muscles
- abductor pollicis brevis
- flexor pollicis brevis
- opponens pollicis
Adductor muscle
- adductor pollicis
Hypothenar muscles
- abductor digiti minimi
- flexor digiti minimi
- opponens digiti minimi
Interossei and lumbricals
- lumbricals – flex the MCP’s, extend the IPJs
- palmar interossei – adduct the digits (“PAD”)
- dorsal interossei – abduct the digits (“DAB”)
=> very precise movements of the hand, the small muscles are involved in precise movements of the hand (e.g. picking up something small of the table)
Muscles that move the thumb - which muscles do it?
Abduction
-> APL, APB
Adduction
-> Adductor pollicis, first dorsal interosseous
Extension
->EPL, EPB, APL
Flexion
-> FPL, FPB
Opposition
->Opponens pollicis
What is the hand subdivided into?
- wrist (carpus)
- metacarpus
- the digits (five fingers incl. thumb)
anterior and posterior surface of the hand
anterior: palm
dorsal: dorsum of hand
Carpals mnemonic
Some - scaphoid Lovers - lunate Try - triquetrum Position - pisiform That - trapezium They - trapezoid Cannot - capitate Handle - hamate
How many metacarpals and phalanges are there?
metacarpals - 1 in each digit
- 3 phalanges in each digit except thumb (proximal (middle) distal)
What is the palmar aponeurosis?
- it is a triangular condensation of deep fascia that covers the palm and is anchored to the skin in distal regions.
- the apex of the tendon is continuous with the palmaris longus tendon, when present.
- from there, fibers radiate to extensions at the bases of the digits that project into each of the index, middle, ring and little fingers and to a lesser extent the thumb.
- transverse fibers interconnect the more longitudinally arranged bundles that continue into the digits.
- vessles, nerves and long flexor tendon lie deep to the palmar aponeurosis.
Fibrous digital sheaths
- after exiting the carpal tunnel, the tendon of the FDS and FDP muscles cross the palm and enter fibrous sheaths on the palmar aspects of the digits.
- begin proximally, anterior to the MCP-J and extend to the distal phalanges
- formed by fibrous arches and cruciate ligaments which are attached posteriorly to the margins of the phalanges and to the palmar ligaments associated with the metacarpophalangeal and interphalangeal joints
- hold the tendons to the bony plane and prevent the tendons from bowing when digits are flexed.
- within each tunnel, the tendons are surrounded by a synovial sheath -> in the thumb and little finger these sheaths are continuous with the sheaths associated with the tendons in the carpal tunnel.
In what categories can muscles of the forearm be subdivided into?
- extensors/flexors (posterior and anterior compartment respectively)
- muscles that act on the wrist (carpi) and muscles that act on the digits (digitorum) and long muscles of thumb, index finger (extensor) and little finger.
Which muscles are in the superficial anterior compartment of the forearm?
Pronator teres (PT) Flexor carpi radialis (FCR) Palmaris longus (PL) Flexor digitorum superficialis (FDS) Flexor carpi ulnaris (FCU)
(everything except FDS from common flexor tendon)
Intrinsic muscles of the hand - which are the thenar muscles? What are their functions? What is their innervation?
- abductor pollicis brevis
- flexor pollicis brevis
- opponens pollicis
=> all of them are innervated by the median nerve (recurrent branch of the median nerve, C8,T1)
Muscles of the posterior compartment of the forearm
x
Intrinsic muscles of the hand - which is the adductor muscle? What is its function functions? What is their innervation?
Adductor pollicis
- innervated by the deep branch of the ulnar nerve
- adducts the thumb
Intrinsic muscles of the hand - which are the hypothenar muscles? What are their functions? What is their innervation?
Abductor digiti minimi
- abducts the little finger at the MCPJ
Flexor digiti minimi (brevis)
- flexes the little finger at the MCPJ
Opponens digiti minimi
- laterally rotates metacarpal V
=> all innervated by the deep branch of the ulnar nerve (C8-T1)
Intrinsic muscles of the hand - which are the interossei muscles? What are their functions? What is their innervation?
palmar interossei – adduct the digits (“PAD”)
dorsal interossei – abduct the digits (“DAB”)
=> innervated by the ulnar nerve (C8,T1) deep branch
Intrinsic muscles of the hand - which are the lumbrical muscles? What are their functions? What is their innervation?
lumbricals – flex the MCP’s, extend the IPJs
Innervation:
- medial 2: deep branch of ULNAR nerve
- lateral 2: digital branches of MEDIAN Nerve
Adductor pollicis
- a “pollicis” muscle supplied by the ulnar nerve
(the thenar muscles are supplied by the median nerve). - in the adductor compartment
- broad attachment to the metacarpal of middle finger; also: base of proximal phalanx and extensor hood of the thumb.
What movement do dorsal and palmar interossues muscle cause?
Palmar: Adduction of the digits (PAD)
Dorsal: Abduction of the digits (DAB)
Dorsal: tendons attach towards the axial line (if between 1 and to they go towards middle metacarpal) -> they will abduct the fingers
Palmar: adduct fingers, move fingers towards midline
Anterior Tendinous Anatomy of the Hand
- Fibrous digital sheath
- Osseo-fibrous tunnels
- In the tunnels run the long flexor tendons and their synovial sheaths
- Annular and cruciform pulleys
Journey of FDP and FDS
- anterior forearm muscles
- FDP and FDS tendons pass in the carpal tunnel beneath the flexor retinaculum
- …enter a common synovial sheath - common flexor sheath
- …enter a digital synovial sheath, within its own fibrous digital sheath
- Little finger and thumb sheaths continuous with the sheath coming from the carpal tunnel;
- FDS splits around FDP
- FDS to middle phalanx, FDP to distal phalanx
Posterior tendinous anatomy of the hand
- Extensor retinaculum (at the wrist, holds tendons down)
- Synovial tendon sheaths
- Inter-tendinous bands
- Extensor expansions
- Lumbricals and interossei attach to the expansions
- Extensor digitorum, EI, EDM
- sometimes there are connections between the digit tendons (intertendinous connection)
What causes flexion at the metacarpophalangeal joint?
- lumbricals: flex metacarpophalangeal joint while extending interphalangeal joints
- flexor pollicis brevis for the thumb
What are the joints in that region?
- distal radio-ulnar joint
- wrist joint
- intercarpal joints
- carbo-metacarpal and inter-metacarpal joints
- metacaro-phalangel
- Interphalangeal joints (PIPJ and DIPJ)
Movements of the wrist joint
Flexion
FCR and FCU – important
Long flexors of thumb and fingers
(PL, APL)
Extension
ECRL, ECRB, ECU – important
Long extensors of the thumb and fingers
Radial deviation
APL, FCR, ECRL, ECRB
Ulnar deviation
ECU, FCU
=> act as groups of muscles, not individual muscles
Intercarpal joints
Joints between the proximal row
scaphoid, lunate, triquetral, pisiform
Joints between the distal row
trapezium, trapezoid, capitate, hamate
Joints between the proximal and distal rows
the midcarpal joint
-> “gliding occurs at these joints”
Carpometacarpal and Intermetacarpal Joints
CMC of the thumb – clinically important (trapezium to thumb metacarpal)
CMC of digits
Movements are:
- flexion and extension
- radial deviation and ulnar deviation
- circumduction (circumduction at CMC!!)
Intermetacarpal joints
Metacarpophalangeal and interphalangeal joints
MCPs = knuckles
- flexion and extension
- abduction and adduction
- ulnar collateral ligament of the thumb
Interphalangeal (IP) joints
- Flexion and extension only
- Proximal Interphalangeal PIP
- Distal Interphalangeal DIP
- IP (thumb)
- volar plate
Arteries of the hand
Ulnar Artery Beside FCU at the wrist Interosseous arteries in the forearm Superficial palmar arch – palmar digital arteries Deep palmar branch
Radial Artery Under brachioradialis and beside FCR at the wrist Anatomical snuff box Deep palmar arch Palmar metacarpal arteries
Veins of the region
Superficial and deep systems
Cephalic vein (superficial) runs up lateral border of arm
Basilic vein (superficial) runs up the medial border of arm
Basilic veins joins venae comitantes to form the axillary vein in the arm
Cephalic vein joins axillary vein in the axilla
Axillary vein becomes the subclavian vein at the level of the first rib
-> deep veins run with the arteries, comitantes (usually 2, sometimes even 3 or 4)
Is the median cubital vein always present?
NO
The median cubital vein, linking the basilic and cephalic veins, is not always present.
Which are the main nerves of the forearm?
Ulnar nerve (C8T1) Median nerve (C678T1) Radial nerve (C5678T1)
What are the nerves of the hand?
Median nerve
- Main nerve of the anterior compartment of forearm
- Some supply to hand intrinsic muscles
Ulnar nerve
- Main nerve of the hand
- Some of anterior compartment (FCU, half of FDP)
Radial nerve
- Posterior compartment of the forearm
- Some sensory component to the hand
Motor: mostly Ulnar N. but some also median (thenar)
Digital nerves
- Purely sensory
- Often damaged
- there aren’t really muscles in the digits so there aren’t; really nerves except sensory.
- Sensation in the digits is important in the function and actions of the hand, can be damaging.
Median Nerve
- C678T1
- At the wrist lies between FDS and FDP, deep to PL
- Enters the carpal tunnel with FDP, FDS and FPL
- Motor to: Thenar muscles (APB, FPB, OP) and lumbricals II and III
- Sensory to: Palmar surface of thumb, IF, MF and half of RF; Some of the dorsal surface of those digits
Ulnar Nerve
- C8T1
- At the wrist lies by FCU
- Runs over (not under) the flexor retinaculum, lateral to the pisiform
- Divides into;
- Superficial branch, sensory to: palmar surfaces of LF and half of RF
- Deep branch, motor to;
hypothenar muscles, adductor pollicis, lumbricals III and IV, all the interossei
Radial nerve
- C5678T1
- Divides just above the level of the elbow into;
- Deep branch – the posterior interosseous nerve (motor)
- Superficial branch – the superficial radial nerve (sensory)
- No motor supply in the hand
- Sensory supply to the dorsum of the hand
Innervation of the intrinsic muscles of the hand
Intrinsic hand muscle innervation:
- Median supplies thenar muscles and the lateral 2 lumbricals (Little purple brach: supplies sensation to the palmar region, branches off a bit before the tunnel)
- Ulnar supplies all of the other intrinsic hand muscles
The carpal tunnel - what are the borders?
Bony attachments
- Scaphoid, trapezoid, pisiform, hamate
- Form a gutter
Roof is the flexor retinaculum
What are the contents of the carpal tunnel?
Median nerve FPL tendon 4 tendons of FDP 4 tendons of FDS (= 2 sets of four tendons, FPL tendon and median nerve)
What are the types of grip?
Power Grip
long flexors of the fingers and thumb
intrinsic muscles of the palm
extensors of the wrist joint!
Precision Grip
the wrist and fingers are held rigidly by the long flexors and extensors
the intrinsic muscles of the hand carry out the fine movements needed
Hook Grip
consumes little energy, mainly involves long flexors of digits; e.g. carrying shopping bag or briefcase
Carpal tunnel syndrome
- entrapment syndrome caused by pressure on the median nerve within the carpal tunnel;
- etiology often obscure but in some instances nerve injury may be a direct effect of of increased pressure on the median nerve caused by overuse, swelling of tendons a d tendon sheaths (e.g. Rheumatoid Arthritis) and cysts from carpal joints.
- increased pressure is thought to cause venous congestion that produces nerve oedema and anoxic damage to the capillary endothelium of the median nerve itself.
- pins and needles sensation in the median nerve area
- weakness and loss of bulk of thenar muscles may also occur
- initially reduce inflammation and remove repetitive insults that produce symptoms.
- possibly surgical decompression of the flexor retinaculum
How does the ulnar nerve enter the hand?
- lateral to pisiform and posteromedially to the ulnar artery
- divides into to branches immediately distal to pisiform”
- deep (mainly motor)
- superficial (mainly sensory)
Guyon’s canal
- a s the deep branch of the ulnar nerve passes across the palm it lies in a fibro-osseous tunnel between the hook of the hamate and the flexor tendons
- occasionally, small outpourings of synovial membrane (ganglia) from the joints of the carpus compress the nerve within this canal producing sensory and motor symptoms
