540 Exam 3

Distal Row of Carpal Bones (thumb→pinky)

trapezium, trapezoid, capitate, hamate

Proximal Row of Carpal Bones (thumb→pinky)

scaphoid, lunate, triquetrun, pisiform

The __ row of carpal bones is more stable

distal

The __ row of carpal bones is more mobile, serving a mechanical function, gliding during motion.

proximal

The __ row of carpals articulates with the metacarpals

distal

The axis of all wrist motion passes through the ___

capitate

Radiocarpal Joint

• biaxial, condyloid joint

• articulation between the convex radius and concave carpals (scaphoid, lunate, triquetrum)

Does the ulna directly contact the carpal bones?

no—it is separated by an articular disc (TFCC)

At the radiocarpal joint, the radius articulates with the…

scaphoid, lunate, triquetrum

Midcarpal Joint

joint between the proximal and distal carpal rows

Wrist Motion requires movement of what two joints?

radiocarpal and midcarpal

Proximal Carpals

scaphoid→lunate→triquetrum→pisiform

• serves as the mobile mechanical link between radius and distal carpals

Biomechanics of Proximal Carpal Row

instead of being pulled by muscles, the proximal row functions as a mechanical unit between the forearm and rest of wrist

The proximal carpals have few/no direct muscle attachments. What is the one exception?

FCU’s tendon attaches to the pisiform (associated with the ulnar volar wrist) and influences the proximal row

Wrist movement does not occur at one joint alone. The radiocarpal and midcarpal joint work together with the proximal carpal bones serving as an important mechanical link. During flexion and extension, how many degrees are performed by each joint?

• 40-50 at radiocarpal joint

• 23-35at midcarpal

Many ADLs require __% of full wrist motion

50-80%

During wrist flexion, the proximal row glides ___

posteriorly

During wrist extension, the proximal carpals glide ___

anteriorly

During wrist radial deviation, the proximal carpals glide ___

ulnarly

During wrist ulnar deviation, the proximal row glides ___

radially

Anterior Wrist Flexors

1. Flexor Carpi Ulnaris (FCU)

2. Palmaris Longus

3. Flexor Carpi Radialis (FCR)

Flexor Carpi Ulnaris (FCU) Function

flexes and ulnarly deviates wrist

Flexor Carpi Ulnaris (FCU) origin, insertion, nerve

• O: medial epicondyle

• I: pisiform, 5th metacarpal

• N: ulnar

The Flexor Carpi Ulnaris (FCU) is innervated by the ___

ulnar nerve

Palmaris Longus Function

assists with wrist flexion

Palmaris Longus origin, insertion, nerve

• O: medial epicondyle

• I: palm

• N: median

The Palmaris Longus is innervated by the ___

median nerve

Flexor Carpi Radialis (FCR)

flexes and radially deviates the wrist

Flexor Carpi Radialis (FCR) origin, insertion, and nerve

• O: medial epicondyle

• I: 2nd/3rd metacarpals

• N: median

The Flexor Carpi Radialis (FCR) is innervated by the ___

median nerve

The FCU and FCR are synergists for what motion?

wrist flexion

The FCU and FCR are antagonists for what motions?

radial/ulnar deviation

Posterior Wrist Muscles

1. Extensor Carpi Radialis Longus (ECRL)

2. Extensor Carpi Radialis Brevis (ECRB)

3. Extensor Carpi Ulnaris (ECU)

Extensor Carpi Radialis Longus (ECRL) Function

wrist extension and radial deviation

Extensor Carpi Radialis Longus (ECRL) origin, insertion, nerve

• O: distal humerus

• I: base of 2nd metacarpal

• N: radial

The ECRL is innervated by the ___

radial nerve

Extensor Carpi Radialis Brevis (ECRB) Function

wrist extension

ECRB origin, insertion, nerve

• O: lateral epicondyle

• I: base of 3rd metacarpal

• N: radial nerve

The ECRB is innervated by the ___

radial nerve

The ECRL and ECRB insert at the base of the 2nd metacarpal and at the base of the 3rd metacarpal. WHich one inserts at the 2nd metacarpal?

ERCL

Extensor Carpi Ulnaris (ECU) Function

wrist extension and ulnar deviation

ECU origin, insertion, nerve

• O: lateral epicondyle

• I: 5th metacarpal

• N: radial

grip is strongest when?

35 degrees of wrist extension

Do the wrist flexors or extensors have more torque? What does this cause?

wrist flexors (FDP and FDS) have 70% > torque, thus the extensors must work hard to maintain the wrist position so the flexors don’t become actively insufficient

Why are the FDP and FDS “bullies”?

they have about 70% greater torque than the extensors, so the extensors must work hard to maintain the wrist position so the flexors font become actively insufficient

Flexor Reticulum

strong band of connective tissue that crosses the anterior side of the wrist

• transverse carpal ligament (distal and deep)

• palmar carpal ligament (proximal and superficial)

Transverse Carpal Ligament

distal and deep portion of the flexor reticulum

Palmar Carpal Ligament

proximal and superficial portion of the flexor reticulum

Flexor Reticulum Function

holds the flexor tendons close to the wrist to prevent bowstringing; helps maintain carpal stability

Carpal Tunnel

passage way of the wrist with the flexor reticulum serving as the roof and the carpal bones serving as the sides and floor.

• median nerve

• 4 FDS tendons

• 4 FDP tendons

• 1 FPL tendon

Extensor Reticulum

strong horizontal fibrous band of connective tissue located on the posterior wrist that holds extensors down

Extensor Reticulum Function

holds extensor tendons close to the wrist as they cross into the hand; prevents tendons from stringing away from wrist during movement

Main Job of the Wrist Ligaments

stability—hold carpal bones together while still allowing wrist movement

Palmar Ligaments (palmar radiocarpal and palmar ulnacarpal)

• located on the palm side of wrist

• generally stronger and help stabilize the wrist, esp. during loading

Dorsal Ligaments (dorsal radiocarpal and dorsal intercarpal)

• located on posterior wrist

• help provide stability during wrist extension

Radial Collateral Ligaments

• thumb-side of wrist

• helps prevent excessive ulnar deviation

Ulnar Collateral Ligaments

• pinky-side of wrist

• helps limit excessive radial deviation

Injured ligaments cause…

pain, instability, and changes in wrist mechanics

Colles Fracture

distal radius fracture with posterior displacement

• due to FOSH

• common in elderly due to bone fragility

Smith’s Fracture

distal radius fracture with anterior displacement

• due to falls on back of hand

Greenstick Fracture

incomplete fracture, usually at the radius

• more proximal than colles fractures

• common to children due to soft, flexible bones

Ganglion Cysts

common and benign, fluid-filled (synovial fluid) cysts that are generally harmless but can cause discomfort or restrict movement if they press on nearby nerves or structures

• vary in size, may fluctuate over time

• usually appear as bumps on the dorsal wrist

Wrist Sprain

wrist hyperextends, putting stress on the ligaments (which hold bones together) causing them to stretch or tear

• due to FOSH

Carpal Tunnel Syndrome

compression of the median nerve causing numbness, tingling, pain, and weakness that starts gradually and can worsen over time

• (median nerve is crucial for sensation and movt in thumb, index, and middle finger)

Extrinsic vs Intrinsic Muscles

Extrinsic

• originate in the forearm

• tendons travel to the hand

• generate larger movements and force

Intrinsic

• originate in hand

• primarily located in the hand

• support precision and coordination

Extensor Digitorum Function

MCP, PIP, DIP extension; assists with wrist flexion

Extensor Digitorum origin, insertion, nerve

• O: lateral epicondyle

• I: distal phalanges (2-5)

• N: radial

The Extensor Digitorum is innervated by the ___

radial nerve

Flexor Digitorum Superficialis (FDS) Function

MCP and PIP flexion

Extensor Indicis Function

MCP, PIP, DIP extension of index finger

Extensor Indicis origin, insertion, nerve

• O: extrinsic

• I: index

• N: radial

The Extensor Indicis is innervated by the ___

radial nerve

Extensor Digiti Minimi Function

MCP, PIP, DIP extension of pinky

Extensor Digiti Minimi origin, insertion, nerve

• O: lateral epicondyle

• I: 5th distal phalanx

• N: radial

The Extensor Digiti Minimi is innervated by the ___

radial nerve

Flexor Digitorum Superficialis (FDS) Function

MCP and PIP flexion

Flexor Digitorum Superficialis (FDS) origin, insertion, nerve

• O: medial epicondyle

• I: middle phalanges (2-5)

• N: median

The Flexor Digitorum Superficialis (FDS) is innervated by ___

median nerve

Flexor Digitorum Profundus (FDP) Function

MCP, PIP, DIP flexion

Flexor Digitorum Profundus (FDP) origin, insertion, nerve

• O: extrinsic

• I: distal phalanx

• N: median/ulnar

The Flexor Digitorum Profundus (FDP) is innervated by the

median (2,3) and ulnar (4, 5) nerves

Flexor Digiti Minimi Function

MCP flexion of pinky

Flexor Digiti Minimi origin, insertion, nerve

• O: intrinsic

• I: 5th proximal phalanx

• N: ulnar

The Flexor Digiti Minimi is innervated by the ___

ulnar nerve

Lumbricales Function

MCP flexion; PIP/DIP extension

Lumbricles origin, insertion, nerve

• O: intrinsic

• I: extensor digitorum

• N: median/ulnar

THe Lumbricles are innervated by the ___

median (1st-2nd lumbs), ulnar (3rd-4th lumbs)

Dorsal Interossei Functions

MCP abduction; PIP/DIP extension

Dorsal Interossei origin, insertion, nerve

• O: intrinsic

• I: proximal phalanx

• N: ulnar

The Dorsal Interossei is innervated by the ___

ulnar

Palmar Interossei Function

MCP adduction; PIP/DEIP extension

Palmar Interossei origin, insertion, nerve

• O: intrinsic

• I: proximal phalanx

• N: ulnar

The Palmar Interossei are innnervated by the ___

ulnar nerve

Abductor Digiti Minimi Function

MCP abduction of pinky

Abductor Digiti Minimi origin, insertino, nerve

• O: intrinsic

• I: 5th proximal phalanx

• N: ulnar

The Abductor Digiti Minimi is innervated by the ___

ulnar nerve

Opponens Digiti Minimi Function

5th digit opposition

Opponens Digiti Minimi origin, insertion, nerve

• O: intrinsic

• I: 5th metacarpal

• N: ulnar

The Opponens Digiti Minimi is innervated by the ___

ulnar nerve

What are the muscles of the snuff box

EPL, EPB, APL