What are the bones that make up the hand?
8 carpal bones, 5 meta carpals, and 14 phalanges
Where is the saddle joint in the hand and what is its purpose
Located between trapezium and metacarpal 1, this saddle joint provides flexibility for the thumb.
Which metacarpals are the most mobile
4 and 5 are more mobile than 2 and 3 because carpal articular surfaces
What is an MCP joint?
Condyloid synovial joint between metacarpal and proximal phalanx
What is an IP
Joint between phalanges with bi-condyloid facets that permit flexion-extention
What is the palmar ligament
Thickened anterior portions of the joint capsules of MCP and IP joints
What is the deep transverse ligament
Ligament that interconnects the MCP joints for added stability, except the thumb
What are the collateral ligaments of the hand
CT bands on each side of an IP or MCP joint
What is the purpose of Collateral ligaments of the hand
Flexion pulls them tight which limits adduction/abduction, extension is the opposite
What is the palmar aponeurosis
Protective CT covering of the flexor tendons
Where is the superficial transverse ligament
Across the MPC joints on the palmar side
What types of synoviocytes line synovial membranes
Type A which is macrophage-like and type B which secretes hyaluronic acid to increase the viscosity
What types of proteins are in synovial fluid
hyluronic acid, lubricin, proteinases, and collagenases
What does synovial fluid transport
Oxygen, nutrients, CO2, and waste products
Where do the thenar muscles originate
The Abductor pollicis brevis, flexor pollicis brevis, and opponens pollicis originate from the flexor retinaculum, scaphoid bone, and the trapezium
Where do the thenar muscles insert
Flexor pollicis brevis and abductor pollicis brevis insert on the proximal phalanx of the thumb. Opponens pollicis inserts onto the 1st metacarpal
What innervates the thenar muscles
median nerve
Where do the hypothenar muscles originate
Abductor digiti minimi originates from the pisiform bone. Opponens digiti minimi and flexor digiti minimi originate from the flexor retinaculum and hook of the hamate
Where do the hypothenar muscles insert
abductor and flexor digiti minimi insert onto the proximal phalanx and the opponents digiti minimi inserts onto the 5th metacarpal
What innervates the hypothenar muscles
Ulnar nerve
What is the origin, insertion, and innervation of the adductor pollicis
Originates: oblique head from the 2nd and 3rd MC and capitate bone, Transverse head from the 3rd MC
Insertion: proximal phalanx of the thumb
Innervation: Ulnar nerve
What are the movements of the thumb
Ab/adduction perpendicular to palm
ext/flexion parallel to palm
What are the movements of the fingers
ab/adduction: away and towards middle finger
ext/flexion: away and towards the palm (respectively)
What is the origin and insertion of the lumbricals
Origin: tendons of flexor digitorum profundus
insertion: dorsal expansions
What is the innervation of the lumbricals
1,2 by the median nerve, 3,4 by ulnar nerve
Why are there only 4 lumbricals
Because the flexor pollicis longus doesn’t have a lumbrical
What is the action of the lumbricals
The “tata” motion; flex MC-P joint, extend IP joints
What is the origin and insertion of the dorsal and palmar interossei
Origin: metacarpals
Insertion: bases of proximal phalanges via dorsal expansions
What is the innervation of the dorsal and palmar interossei
Both are innervated by the ulnar nerve
What is the action of the dorsal interossei
Abduct fingers from midline
What is the action of the palmar interossei
adduct fingers towards midline
What muscles are used to pinch
1st dorsal interosseus and adductor pollicis act to clench the thumb against the index finger for a strong pinch
Where is LI-4 located (acupuncture point)
On the first dorsal interosseus
What is trigger finger
Chronic irritation causes a nodule to form along the flexor tendon. This prevents the smooth action of the tendon and may even lock the finger in a flexed position
What is the bowstring phenomenon
When a fibrous flexor sheath over the flexor tendon breaks, the tendon then pushes agains the skin when in flexion instead of staying on the bone
What is mallet finger injury
injury of the extensor digitorum tendon of the fingers at the distal interphalangeal joint (DIP) that leads to a permanent flexion of the distal phalanx
What is Boutonniere’s finger
Flexion deformity of the PIP joint is due to interruption of the central slip of the extensor tendon such that the lateral slips separate and the head of the proximal phalanx pops through the gap like a finger through a button hole (thus the name, from French boutonnière “button hole”)
What is the function of link ligaments
Provide a connection between dorsal expansions and flexor tendon sheaths to coordinate movement
What is the function of fibrous flexor sheaths
- Act as a pulley system to assist action of flexor muscles on phalanges 2. Keep the tendon against the bone for better pull and protection
What is the cutaneous innervation of the median nerve in the hand
First 3.5 digits and thenar eminence
What is the muscular innervation of the median nerve in the hand
Thenar muscles except the adductor pollicis, lumbricals 1,2
What is the carpal tunnel
Space formed by flexor retinaculum spanning across carpal bones
What 10 things are in the carpal tunnel
median nerve, flexors digitorum superficialis and profundus, flexor pollicis longus
What hand structures are NOT in the carpal tunnel
Ulnar nerve, radial and ulnar arteries, palmaris longus, flexors carpi ulnaris and radialis
What causes carpal tunnel syndrome
compression of the median nerve due to a reduction in the carpal tunnel space
What causes a reduction in the size of the carpal tunnel
local inflammation or tenosynovitis, fluid overload, dislocation of carpal bones, arthritis
What are the symptoms of carpal tunnel syndrome
loss of sensation over median nerve distribution, loss of function of thenars and 1,2 lumbricals, thenar wasting (ape hand)
What causes thenar wasting in carpal tunnel syndrome
Muscles are constantly receiving nerve signals. When a muscle stops receiving nerve signals it starts to atrophy
What is the flick sign
Ask your patient what they do when their pain gets too great and if they flick their wrist there is a 91% chance they have carpal tunnel syndrome
How do you test the median nerve
Tinel’s or Phalen’s test, Sensory test with tuning fork or 2 point discrimination, strength testing, EMG
What is the cutaneous innervation of the Ulnar nerve in the hand
digits 5 and 1/2 of 4, ulnar side of both palm and dorsum
What hand muscles does the ulnar nerve innervate
hypothenars, adductor pollicis, lumbricals 3,4 dorsal and palmar interossei
What is the tunnel of Guyon
Space between pisiform and hook of hamate, interconnected by pisohamate ligament
what forms the floor and roof of the tunnel of Guyon
Floor: flexor retinaculum
Roof: palmar carpal ligament
What goes through the tunnel of Guyon
Ulnar nerve, Ulnar artery and vein
What happens to the hand if the ulnar nerve is damaged
Claw hand due to lack of MCP flexion and IP extension in fingers (Benediction hand), atrophy of interossei, cutaneous loss of 1.5 digits
How does one test the ulnar nerve
Tinel’s test, sensation testing, have patient cross his finger, EMG and nerve conduction tests
How does one test the radial nerve
Wrist and elbow extension, sensation around dorsum of the thumb, nerve conduction studies
