Anatomy of Hand and Wrist in a Nutshell

Anatomy of Hand and Wrist

3 sets of bones:

• Carpals (wrist – true bones of wrist) 8 aligned in 2 rows, form a concave shape in palmar view. # I-V
• Metacarple (bones of palm of hand) I-V
• Phalanges (bones of fingers). Only 2 on thumb, proximal and distal. On 2-5, have proximal, middle, and distal phalanges.
• Digits: I-V, with I being thumb (pollicis) and little finger = minimi / quinti.

Note: Flexor digitorum superificialis inserts at base of middle phalanx of 2-5.

Flexor digitorum profundus inserts at tip of distal phalanx of 2-5.

Wrist:

Palmar view: proximal and distal rows of carpals are separated into 4 and 4.

• Proximal: (radius to ulnar side)

1. • Scaphoid – from word for “skiff” / Boat.
   • Lunate – head is quarter moon shape.
   • Triquetrum – 3 cornered hat
   • Pisiform (remember flexi carpi ulnaris attaches here)

Distal:

• Trapezium – trapezoid sape
• Trapezoid – ‘’
• Capitate– has a fairly large / prominent articular surface that looks like a head.
• Hamate – “hook” – refers to process that protrudes toward palmar side that is the “hook of the hamate”

Pnemonic: “some lovers try positions that they cannot handle”

Articulation:

The ulna is separted from the triquetrum / lunate by broad space compared to radial end where articulation is tight.  Clinically = when you fall on hand,  scaphoid fracture is very common due to tight articulation between radius and scaphoid.  The blood supply to the scaphoid is lost in facture→get necrosis of that joint with ulna (proximal portion of scaphoid)→lose motion.

Motion:

Wrist – extension (back hand), flexion (smack). Abduction = radial deviation

Adduction = ulnar deviation.

Fingers: Distinct from thumb (which is set at right angles to other fingers).

• Midline of hand runs through middle finger. Away from this line = abduction, toward this line = adduction.
• Metacarpophylangeal joint (MP joint) allows extension / flexion.
• PIP / DIP (proximal / distal interphalangeal joint) allows extension / flexion as well.

Thumb:

• Reach to grab bar / open hand to choke someone = abduction, moving thumb toward palm to actually grab bar / choke someone = adduction. Thus reference of motion is palm.
• Opposition = touch thumb across palm to pinky, finger tips touch.
• Neutral position (obvious)
• Flexion / extension: flexor has similar motion to opposition motion.

Superficial structures:

• Palmaris longus inserts into palmar aponeurosis. The skin of the palm is attached tightly here.
• Palmaris brevis: origin in skin (?) inserts into palmar aponeurosis as well. On medial aspect near wrist.
• Around each of the long tendons in the fingers = have fibrous digital sheath. Inside this – have synovial sheath which permits free motion (similar to bursae).
• Proximal to this: synovial sheath passes through wrist underneath the Flexor retinactulum (a bracelet of CT around wrist that holds long forearm tendons against wrist). The synovial sheaths that pass under here are all joined together, thus, an infection in one finger may spread to others as they pass through wrist.
• Carpal tunnel: very confined space, if infection of synovial sheaths occurs, nerve may be affected etc. Median nerve passes under the flexor retinaculum, but superficial to the synovial sheeth. Thus, compression of the relatively superficial median nerve is a large component of carpal tunnel syndrome.

Intrinsic hand muscle: Superficial group.

• 3 hypothenar muscles – for little finger = innervated by ulnar nerve deep branch. The superficial branch of the ulnar is cutaneous.
  • Opponens digiti minimi
  • Flexor digiti minimi (brevis)
  • Abductor digiti minimi
• 3 thenar muscles – for thumb = innervated by median nerve recurrent branch. As median nerve passes through carple tunnel, a small branch pass recurrently into thenar muscles.
  • Opponens pollicis – the deepest of these muscles
  • Flexor pollicis brevis – starts almost on palm, pulls thumb toward palm. Has dual innervation (superficial head = median nerve, deep head = ulnar nerve).
  • Abductor pollicis brevis

Innervation: Radial nerve is only cutaneous, no muscle innervation in the dorsal hand.

Deeper in hand:  vast majority are by ulnar nerve.

Interosseous muscles: 4 dorsal / 3 palmar.

Dorsal – Abduction    Palmar – adduct (DAB / PAD)

Dorsal interosseous muscles:

• First dorsal interosseous muscle – inerts first metacarple. Pull #2 toward thumb.
• No interosseous on medial side of little finger = it is abducted by abductor digiti minimi.

Adductor Pollicis: takes origin from 3^rd metacarple and capitate bone.  Broad muscle belly that converges onto insertions at base of proximal phalanx in thumb and onto Sesamoid bone (floating within tendon).  Has oblique and transverse heads.  Between these two heads is the deep branch of the radial arteryà gets to the hand by passing through adductor pollicis.  Innervated by ulnar nerve.

4 lumbricals:

• I and II are on radial side, III and IV are on ulnar side. These are the wave bye bye muscles (flex MP, extend IP joints)
• I and II = median nerve
• III and IV = ulnar nerve.
• Note that #s are not in sync with digit #s.
• Origin of each = tendon of flexor digitorum profundus for each muscle. The insertion is on the extensor hood (expansion). Extensor digitorum tendon is flattened into hood.  Muscles on the palmar side (lumbrical) cross MP joint and attaches to the edge of this hood. Make 2 attachments:
• Can flex the MP joint and extend the IP joints.

Muscles attaching to hood:

• Lumbricals
• Interosseal
• Abductor digiti minimi
• Tumb = adductor pollicis / abductor pollicis (brevis).

These muscles are thus given an extension quality as well (think of piano playing).

Vessels of hand:

Arteries:

• Radial / ulnar artery approach hand on anterior side. Radial artery is used for taking pulse at wrist.
• Largest part of radial passes behind the thumb and into the palm of the hand deep to adductor pollicis)→ arches over to join up with a smaller branch of the ulnar = forms the Deep palmar arch. This is “radial artery dominant”.
• The ulnar artery approaches the wrist and remains mostly superficial)→ arches over to join small branch of radial artery = forms the superficial palmar arch. Thus, the superficial arch is “ulnar artery dominant”
• Upon superimposition of these arches: notice that superficial arch is just deep to the palmar aponeurosis. The deep arch is almost on the bones)→ beneath many extrinsic muscles.
• The deep arch is proximal, the superficial arch is more distal.
• Off of the superficial arch: have 2 sets of arteries that supply the fingers: palmar digital artery (common))→ proper digital arteries for the fingers.
• Thumb / index finger have special arteries: Radialis indicis for index finger (radial side of index finger) and the princeps pollicis artery for the thumb. These are all branches of either the radial / ulnar arteries.

Allen Test: deals with arterial patency (openness of the arteries in the hand).  Pump fist a few times)→ open to see perfusion.

Innervation of the hand:

• Ulnar nerve: as it approaches the handà divides into superficial and deep branches. Superficial branch = all cutaneous / sensory for the medial 1 ½ digits. Deep branch = motor
• Median nerve: passes through carpal tunnel→recurrent branch to thenar muscles. Fleshy tips of the index / middle / ring finger / thumb are supplied by median nerve. Also innervates posterior tips of thumb / index / middle finger / lateral ring finger.
• Radial nerve: related to anatomical snuff box. It does supply the edge of the palm beneath thumb (related to thenar muscles). Also the dorsal lateral portion of the hand but not the tips.

Carpal tunnel:

Flexor retinaculum with deep portion = transverse carple ligament. Attaches to trapezium, scaphoid (radial side) à pisiform, hamate (ulnar side)

Tendons for numerous muscles travel in this tunnel:

• Flexor pollicis longus
• 4 from flexor digitorum superficials
• 4 from flexor digitorum profundus
• Median nerve passes as well.

Related to this tunnel but not inside it: Flexor carpi radialis is slightly outside the tunnel to insert 2^nd metacarple.

Also related: ulnar nerve / ulnar artery. They travel together through a gap in the flexor retinaculum called the Canal of Guyon, do not pass through carpal tunnel.

Anatomical snuff box:

Between tendons of: Extensor pollicis longus and extensor pollicis brevis. Longus goes to distal phalanx.  Brevis inserts proximal phalanx.

Tendon of abductor pollicis longus is close to EPB and attaches to 1^st metacarple.

Structures:

1. Superficial branch of radial nerve – branches over snuff box and onto dorsal side of hand / skin over thenar muscles (sensory only).
2. Radial artery – deep inside anatomical snuff box, find the deep branch of the radial artery→forms most of deep arch. Passes through the 2 heads of the first dorsal interosseous muscle.

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