What is the Palmar Aponeurosis?
Well-defined part of deep fascia
Thick and strong
Covers the soft tissues and overlies the long flexor tendons.
When the palmaris longus is present, the paland aponeurosis is the expanded tendon of the palmar is longus.
Distal to the apex, the palmar aponeurosis forms four longitudinal digital bands of rays that radiate from the apex and attach distally to the bases of the proximal phalanges and become continuous with the fibrous digital sheaths.
What is a Dupuytren Contracture of Palmar Fascia?
Disease resulting in progressive shortening, thickening and fibrosis of the palmar fascia and aponeurosis.
The fibrous degeneration of the longitudinal bands of the palmar aponeurosis on the medial side of the hand pulls the 4th and 5th fingers into partial flexion at the metacarpophalangeal and proximal interphalangeal joints.
The contracture is permanently bilateral and is seen in some men >50 years.
Idiopathic but there is believed to be a hereditary predisposition.
How does Dupuytren Contracture manifest itself initially and how is it treated?
First manifests as painless nodular thickenings of the palmar aponeurosis that adhere to the skin.
Gradually progressive contracture of the longitudinal bands produces raised ridges in the palmar skin that extend from the proximal part of the hand to the base of the 4th and 5th fingers.
Treatment usually involves surgical release - excision of all fibrotic parts of the palmar fascia to free the fingers.
What is the Fibrous Digital Sheath?
Ligamentous tubes enclosing the flexor (superficial and deep and flexor palmar is longus) tendons and their synovial sheaths in their passage along the palmar aspect of their respective fingers.
Prevents tendons bowstringing.
Pulleys - 5x annular and 4x cruciform
What is Trigger Finger / Snapping Finger?
Thickening of a fibrous digital sheath on the palmar aspect of the digit produces stenosis of the osseofibrous tunnel, the result of repetitive forceful use of the fingers.
If the tendons of the flexor digitorum Superficialis and profundus enlarge proximal to the tunnel, the person is unable to extend the finger
When the finger is extended PASSIVELY, a snap is audible.
Flexion produces another snap as the thickened tendon moves.
AKA digital tenovaginitis stenosans.
What is the Synovial Sheath?
Sheath that surrounds each tendon and produces synovial fluid to keep tendons lubricated and maintain function.
What is Tenosynovitis?
Injuries e.g. Puncture wounds, can cause infection of the digital synovial sheaths.
When inflammation occurs, the digit swells and inflammation can become painful.
Because the tendons of the 2nd, 3rd and 4th fingers nearly always have separate synovial sheaths, the infection is usually confined to the infected finger. If the infection is untreated however, the proximal ends of these sheaths may rupture, allowing the infection to spread to the midpalmar space.
Because of the synovial sheath of the little finger is usually continuous with the common flexor sheath, Tenosynovitis in this finger may spread to the common flexor sheath and thus through the palm and carpal tunnel to the anterior forearm, draining into the space between the pronator quadratus and the overlying flexor tendons.
Likewise, Tenosynovitis in the thumb can spread via the continuous synovial sheath of the flexor pollicis longus (radial bursa)
Define the borders of the carpal tunnel
Floor is horseshoe shaped - concave surface on the palmar side, formed laterally by the scaphoid and trapezium tubercles and medially by the hook of hamate and the pisiform.
Floor is known as the carpal arch.
Roof is the superficial flexor retinaculum - turns the carpal arch into the carpal tunnel by bridging the space between the medial and lateral parts of the carpal arch.
Originates on the lateral side and inserts on the medial side of the arch (attachments same as the carpal arch)
Flexor retinaculum is a strong fibrous band - otherwise known as the transverse carpal ligament).
What goes through the carpal tunnel?
4 flexor digitorum Superficialis tendons
4 flexor digitorum profundus tendons
1 flexor pollicis longus
+ MEDIAN NERVE.
Note: the median nerve gives one branch - the palmar cutaneous branch before entering carpal tunnel which provides sensation to palm.
What is Carpal Tunnel Syndrome?
Results from any lesion that significantly reduces the size of the carpal tunnel, or more commonly increases the size of some of the 9 structures or their coverings, that pass through the carpal tunnel (E.g. Inflammation of synovial sheaths).
Fluid retention, infection and excessive exercise of the fingers.
The median nerve has 2 terminal sensory branches that supply the skin of the hand; hence paraesthesia (tingling), hypoesthesia (diminished sensation) or anaesthesia (absence of sensation) may occur in the lateral 3 and a half digits)
The palmar cutaneous branch of the median nerve arises proximal to and does not pass through the carpal tunnel; thus sensation in the centres palm remains unaffected.
The nerve also has one terminal motor branch, the recurrent branch, which serves the three thenar muscles.
How do symptoms of carpal tunnel progress?
Progressive loss of coordination and strength of the thumb (owning to the weakness of APB and opponens pollicis) may occur if the cause of compression is not alleviated.
Patients are unable to oppose their thumbs and have difficulty buttoning a shirt or gripping things such as a comb.
As the condition progresses, sensory changes radiate into the forearm and axilla.
What are tests for Carpal Tunnel Syndrome?
Tinsel's Test (percussive tapping on carpal tunnel)
Phalen's Test (holds wrist together for a couple of minutes - palms away from each other)
Both should result in symptoms.
What is the treatment for Carpal Tunnel Syndrome?
Steroid injection (prevent inflammation)
Wrist splints (prevent irritation)
Surgical decompression (carpal tunnel release procedure - an incision is made towards the medial side of the wrist and flexor retinaculum to avoid possible injury to the recurrent branch of the medial nerve).
What are causes of Carpal Tunnel Syndrome?
premenstrually D - Diabetes
I - Idiopathic
A - Agromegaly
N - Neoplasm
T - Trauma
R - Rheumatoid arthritis
P - Pregnancy
What are the intrinsic muscles of the hand responsible for?
They originate in the hand and are responsible for PRECISION grip.
Muscles that originate in forearm are responsible for POWER grip.
Hypothenar eminence + Palmaris brevis, Lumbricals, interosseous muscles and Adductor pollicis
What is the Palmaris Brevis?
Originates on the flexor retinaculum and inserts medially into the dermis of the skin. Overlies the hypothenar muscles.
Action: tenses ulnar side of palm and hollows palm during gripping action.
Describe the lumbricals muscles
Flex at the MCP joints and extend at the IP joints.
Four of them - first and second are unipennate (on the lateral side of the lateral two digits) and third and forth are bipennate (originated on the lateral side of the medial two digits)
Do not attach to bone
Describe the thenar muscles
Opponens pollicis (deepest) - opposes thumb
Abductor pollicis brevis (superficial) - abducts thumb
Flexor pollicis brevis (superficial) - flexes thumb (Also abductor pollicis longus - originates in forearm)
Describe the adductor pollicis
Adduct the thumb
Inserts into base of proximal phalanx and extensor hood of thumb.
Two heads: transverse and oblique (direction of fibres)
Innervated by deep branch of ulnar nerve.
What is the Hypothenar eminence?
Response for movements of the little finger
Opponens digiti minimi (deepest) - opposes little finger
Adductor digiti minimi (superficial) - abducts little finger at MCP, originates from pisiform and piso-hamate ligament
Flexor digit minimi brevis (superficial) - flexes little finger at MCP joint
Innervated by deep branch of ulnar nerve.
Describe the interossei muscles
2 groups (dorsal and palmar)
Muscles in between the metacarpal bones and insert into extensor hood.
Dorsal: - Abduct at MCP joints of index, middle and ring fingers.
Palmar: Adduct at MCP of index, middle and ring fingers.
Test for Adduction by the interosseous muscles by asking patient to hold piece of paper between fingers against resistance.
Test for Abduction by (spread fingers out and try to adduct fingers against resistance)
Describe the Ulnar Artery in the hand
Travels with ulnar nerve - lies lateral to ulnar nerve.
Enters the hand anterior to the flexor retinaculum between the pisiform and the hook of the hamate via the Guyon canal (fibrosseus of canal)
Ulnar artery can be palpated just proximal to pisiform - pisiform sits in the tendon of the flexor carpi ulnaris.
The artery divides into two terminal branches (the superficial palmar arch) and the deep palmar branch). Superficial palmar arch gives rise to the three common palmar digital arteries that anastomoses with palmar metacarpal arteries from the deep palmar arch.
Each common palmar digital artery divides into a pair of proper palmar digital arteries which run along the adjacent sides of the 2nd to 4th digits.
Describe the radial artery in the hand
Artery curves dorsally around the scaphoid and trapezium and crosses the floor of the anatomical snuffbox
Palpable lateral to flexor carpi radialis
Enters the palm by passing between the heads of the 1st dorsal interosseous muscles and then turns medially passing between the heads of the adductor pollicis.
The radial artery ends by anastomosing with the deep branch of the ulnar artery to form the deep palmar arch which is formed mainly by the radial artery.
This arch lies across the metacarpals just distal to their bases.
What does the deep palmar arch give rise to? And what fingers do the radial and ulnar artery supply?
Three palmar metacarpal arteries and the princeps pollicis artery.
The radialis indicis artery passes along the lateral side of the index finger. It usually arises from the radial artery, but it may originate from the princeps pollicis.
Radial artery supplies thumb and half of index finger. Ulnar artery supplies other three and a half digits but they do anastomose
Describe the deep and superficial veins in the hand
Superficial and deep venous palmar arches, associated with the superficial and deep palmar arterial arches, drain into the deep veins of the forearm.
Dorsal digital veins drain into 3 dorsal metacarpal veins which unite to form a dorsal venous network.
Superficial to the metacarpals, this network is prolonged proximally on the lateral side of the cephalic vein.
The Basilic vein arises from the medial side of the dorsal venous network.
The Dorsal Venous network is useful for IV fluids, antibiotics + cannular insertion.
What is Raynaud's Syndrome?
This condition occurs because your blood vessels go into a temporary spasm which blocks the flow of blood.
This causes the affected area to change colour to white then blue and then red as the blood flow returns,
Raynaud's syndrome is usually triggered by cold temperatures or by anxiety or stress.
You may also experience pain, numbness and pins and needles in the affected body parts.
Symptoms can last from a few minutes to several hours.
Does the Radial nerve provide a motor supply to the muscles in the hand?
No, but it does provide a sensory supply to the hand.
What are the sensory supplies to hand? How can you test for sensation?
(Testing for Sensation: Radial nerve: webbed space between thumb and first finger
Ulnar nerve: little finger
Median nerve: index and middle finger
Describe the effects of a superficial or deep laceration at the wrist
Incisions or wounds along the medial side of the thenar eminence may injury the recurrent branch of the median nerve (relatively superficial) to the thenar muscles.
Bleeding is usually profuse when the palmar arterial arches are lacerated.
It may not be sufficient to ligate only one forearm artery when the arches are lacerated because these vessels usually have numerous communications in the forearm and hand and thus bleed from both ends.
To obtain a bloodless surgical operating field for treating complicated hand injuries, it may be necessary to compress the brachial artery and its branches proximal to the elbow (e.g. Using a pneumatic tourniquet) which prevents blood from reaching the radial and ulnar arteries through the anastomoses around the elbow.
What is commonly injured in attempted suicides by wrist slashing?
The median nerve is commonly injured just proximal to the flexor retinaculum.
This results in paralysis of the thenar muscles and the first twolumbricals.
Hence opposition of the thumb is not possible and fine control movements of the 2nd and 3rd digits are impaired.
Sensation is also lost over the thumb and adjacent two and a half fingers,
If the median nerve is severed in the forearm or at the wrist, the thumb cannot be opposed; however the APL and adductor pollicis (supplied by the posterior interosseous and ulnar nerves, respectively) may initiate opposition, although ineffective.