Hand Part 1

Bones & Bony Landmark

A. distal end of radius

B. wrist “meniscus”

C. carpals, especially the pisiform, trapezium, scaphoid, hamate, and lunate

D. metacarpal bases & heads

E. anatomical snuff box

anatomical snuff box

- space at the dorsal surface of the base of the thumb

- contains the scaphoid bone & a branch on the radial artery

Palmar aponeurosis

analogous to the plantar aponeurosis

Where does the Palmar aponeurosis attach?

- provides attachment for the palmaris longus muscle

- longitudinal slips attach to the dermis of the palmar surface of the fingers

Dupuytren’s contracture

inflammation & thickening of the longitudinal bands, causing a claw like hand (draws the fingers into flexion)

- most common in older adults and etiology is typically unknown

Extrinsic hand structures of the hands

tendons of FDS & FDP

Where does the FDS, FDP, and Bursa insert into?

- recall that tendons of FDS insert into the middle phalanx

- recall that tendons of FDP insert into the distal phalanx

- recall that the ulnar bursa follows these tendons into the palm of the hand

Ruptures of the FDP tendons at insertions

- typically occur when a flexed finger is forcibly extended

- results in a DIP joint stuck in extension (“Jersey finger”)

Jersey Finger

More common in the FDP (where the DIP joint is located) than the FDS

Ruptures of the FDS tendons at insertions

- similar MOI

- results in permanent flexion of the PIP joint

What do the FDS and FDP stabilize?

IP joints

Abduction

opens the hand

Flexor

flexes fingers

Opponens

Power grip, bring the thumb to the pinky

Thenar compartment

base of the thumb

Three muscles:

A. Abductor Pollicis Brevis m.

B. Flexor Pollicis Brevis m.

C. Opponens Pollicis m. – this muscle is key in grip strength

What is innervated by the thenar compartment

all innervated by the median nerve

What does the thenar compartment mirror?

The Hypothenar

Hypothenar compartment

Three muscles:

A. Abductor Digiti Minimi m.

B. Flexor Digiti Minimi Brevis m.

C. Opponens Digiti Minimi m. – this muscle works with the OP in grip strength

What is the hypothenar compartment innervated by?

all innervated by the ulnar nerve

Trouble opposing pinky to thumb vs thumb to pinky. What n. is injured?

Trouble with pinky to thumb - ulnar n.

Trouble with thumb to pinky - median n.

Lumbrical muscles

four small muscles that originate from the tendons of FDP m. in the palm of the hand

Lumbrical muscles are responsible for

these muscles are responsible for extension of the IP joints

Innervation of the lumbrical muscles 1 & 2

lumbrical muscles 1 & 2 are innervated by the median nerve

- this has implications for diagnosing carpal tunnel syndrome

Innervation of the lumbrical muscles 3 & 4

lumbrical muscles 3 & 4 are innervated by the ulnar nerve

- this has implications for diagnosing ulnar nerve injuries

Interosseous muscles

there are palmar and dorsal interosseous muscles

palmar interosseous muscles…

ADDUCT the fingers toward midline (PAD)

dorsal interosseous muscles

ABDUCT the fingers away from midline (DAB)

The interosseous muscle actions are the quickest way screen for what?

An ulnar nerve injury

Adductor pollicis muscle innervation

innervated by ulnar nerve

Median nerve

- pathway through the flexor forearm is in the middle

- found at the wrist slightly lateral to palmaris longus muscle tendon

- goes through carpal tunnel

- emerges onto palmar surface of the hand and immediately splits into sensory and motor branches

Median n. sensation:

1. the lateral surface of the palm,

2. the first 3 ½ digits on the palmar surface,

3. plus their dorsal tips

Median n. motor to:

1. APB muscle

2. FPB muscle

3. OP muscle

4. first two lumbrical muscles

If you have trouble with the lumbrical m, how will the fingers present?

The fingers are stuck in flexion

What does the hand look like in carpal tunnel syndrome then?

• paresthesia, progressing to dysesthesia, on the lateral surface of the palm, the first 3 ½ digits and their dorsal tips

• diminished grip strength

• PIP and DIP joints of digits 2 & 3 may be stuck in flexion

ulnar nerve is a pathway for what?

pathway from the flexor forearm is on the medial surface with the ulnar a.

- at the wrist, it is located lateral to the FCU tendon

Where does the ulnar n. enter?

- enters the palm of the hand with the ulnar artery, superficial to the carpal tunnel

- passes through the Tunnel of Guyón

- breaks into motor & sensory branches

Ulnar n. is sensation to what?

- the medial surface of the palm, the medial surface of the dorsum, and

the last 1 ½ digits on both the palmar and dorsal surfaces

Ulnar n. is motor to what?

1. ADM muscle

2. FDMB muscle

3. OPM muscle

4. last two lumbrical muscles

5. interosseous muscles

6. adductor pollicis muscle

What does the hand look like in an ulnar nerve injury?

• paresthesia and/or dysthesia in the medial palm, medial dorsum, and all aspects of the last 1 ½ digits

• diminished grip strength

• PIP and DIP joints from the last two digits may be stuck in flexion

Ulnar n. testing

a. testing palmar interossei (ulnar n.)

b. testing dorsal interossei (ulnar n.)

testing palmar interossei (ulnar n.)

Put a piece of paper between the index finger and the middle finger. Have the patient adduct while you are pulling out

testing dorsal interossei (ulnar n.)

Push the index and middle fingers together while the patient maintains abduction