PT 762 - Wrist

What is the name of the anatomical feature that separates the tendons of EPL and ECRB and where is it found?

Dorsal tubercle (listers tubercle) of the distal radius

Is the articular surface of the distal radius convex or concave?

Concave

What is the name of the anatomical feature on the lateral side of the distal radius?

Styloid process of the radius

What is the name of the anatomical feature on the posterior medial distal ulna?

Styloid process of the ulna

What are the two biomechanical configurations of the articular surface of the distal radius?

Angled 25 degrees medial (ulnar tilt)

Angled 10 degrees palmar direction (palmar tilt)

What is the clinical significance of the two biomechanical configurations of the distal radius in terms of range of motion?

More range of motion in wrist flexion and ulnar deviation than extension and radial deviation

The proximal row of carpal bones are tightly or loosely bound?

Loosely joined

The distal row of carpal bones are tightly or loosely bound?

Tightly bound

Why are the distal row of carpal bones tightly bound?

To provide a rigid base of articulation with MC bones

The proximal pole of the scaphoid is convex or concave and articulates with what?

It is convex and articulates with the radius

The distal pole of the scaphoid is convex or concave and articulates with what?

Convex and articulates with the trapezium and trapezoid

The distal medial surface of the scaphoid is convex or concave and accepts what?

Concave and accepts lateral head of capitate

The medial surface of the scaphoid not only contacts the capitate but also contacts what?

Small medial facet contacts lunate

Where do most fractures of the scaphoid occur along?

The "waist" of the scaphoid

Fractures of the scaphoid are associated with what?

Tenderness in the anatomic "snuff box"

What happens is a scaphoid fracture is left untreated?

Avascular necrosis of the proximal pole

What is the central bone of the proximal row of carpal bones?

Lunate

The proximal surface of the lunate is convex or concave and articulates with what?

Convex and articulates with the radius

The distal surface of the lunate is convex or concave and articulates with what?

Concave and articulates with the medial head of capitate and part of apex of hamate

How did the lunate bone get its name?

The concave distal surface gives it a crescent moon shape

Which carpal bone is in the most ulnar position of the wrist or medial to the lunate?

Triquetrum

The lateral surface of the triquetrum articulates with which other carpal bone?

Hamate

The pisiform is a sesamoid bone meaning it is inside the tendon of a muscle, which muscle tendon is it inside of?

The FCU

Which other carpal bone does the pisiform articulate with?

The palmar surface of the triquetrum

The pisiform also serves as an attachment site for what?

Muscles and ligaments

What is the largest carpal bone in the wrist?

Capitate

What does the proximal head of the capitate articulate with?

Scaphoid and lunate

The capitate and third metacarpal function as what together in wrist movement?

A single column serving as axis of rotation for all wrist movement

What does the proximal surface of the trapezium articulate with and is it convex or concave?

Articulates with the scaphoid and is concave

What does the distal surface of the trapezium articulate with and is it convex or concave?

Articulates with base of 1st metacarpal and is both convex and concave (saddle joint)

What is the name of tubercle that is located on both the trapezium and scaphoid and what does this serve as an attachment site for?

The palmar tubercle serving as an attachment site for the lateral side of the transverse carpal ligament

Which carpal bone is wedged tightly between the capitate and trapezium?

Trapezoid

The proximal surface of the trapezoid is convex or concave and articulates with what?

Concave and articulates with scaphoid

The distal surface of the trapezoid articulates with what?

Articulates with base of 2nd metacarpal

What anatomical feature is unique to the hamate that is not found on the other carpal bones?

A hook

The proximal apex of the hamate contacts what?

Lunate

The distal surface of the hamate articulates with what?

Bases of fourth and fifth metacarpal

The hook of hamate and pisiform serve as an attachment site for what?

The medial side of the transverse carpal ligament

The floor of the carpal tunnel is convex or concave and formed by what?

Concave and formed by carpal bones

The roof of the carpal tunnel is what?

The transverse carpal ligament

What are the functions of the transverse carpal ligament?

Serves as an attachment site for muscles and restrains tendons from "bowstringing"

The transverse carpal ligament converts the concavity of the carpal bones into what? And what passes through this?

The carpal tunnel and the median nerve and extrinsic flexors of the digits pass through this

How many joints of the wrist and hand are there? And what are they?

3 joints:

1) Radiocarpal Joint

2) Midcarpal Joint

3) Intercarpal Joints

The midcarpal joint can be broken down into what?

Two compartment:

Medial and lateral

What are the proximal components of the radiocarpal joint?

Concave distal radius and articular disc (TFC)

What are the distal components of the radiocarpal joint?

Convex scaphoid, lunate and triquetrum

How is the triquetrum considered part of the radiocarpal joint?

In full ulnar deviation the medial surface contacts the disc

The medial compartment of the midcarpal joint has both a convex and concave part. What is the concave part?

The concave recess of the distal surface of scaphoid, lunate, and triquetrum

The medial compartment of the midcarpal joint has both a convex and concave part. What is the convex part?

Convex head of capitate and apex of hamate

The lateral compartment of the midcarpal joint has both a convex and concave part. What is the concave part?

Proximal surface of trapezium and trapezoid

The lateral compartment of the midcarpal joint has both a convex and concave part. What is the convex part?

Distal pole of scaphoid

How many intercarpal joints are there?

13 with joint surfaces varying shape

What is the range of motion of the intercarpal joints and do they contribute to wrist motion?

Small range of motion compared to radiocarpal and midcarpal but they do contribute to wrist motion

What are the functions of ligaments in the carpus?

Maintain natural intercarpal alignment and transfer forces across the carpus

Ligaments of the carpus can be classified in which two ways and how do these differ?

Can intrinsic or extrinsic

Intrinsic has both proximal and distal attachment on carpals

Extrinsic has a proximal attachment outside the carpals (on radius or ulna)

What are the extrinsic ligaments of the carpus?

Dorsal radiocarpal ligament

Radial collateral ligament

Palmar radiocarpal ligament

TFCC (ulnar collateral ligament)

The palmar radiocarpal ligament is composed of what 3 ligaments?

Radioscaphocapitate

Long radiolunate

Short radiolunate

The TFCC is composed of something and which two ligaments?

Articular disc

Ulnar collateral ligament

Palmar ulnocarpal ligament

The intrinsic ligaments of the carpus can be classified into which three ways?

Short ligaments

Intermediate ligaments

Long ligaments

What are the functions of the short intrinsic ligaments of the carpus?

Connect distal row and stabilize to function as a single mechanical unit

What are the intermediate intrinsic ligaments of the carpus?

Lunotriquetral, scapholunate, scaphotrapezial, scaphotrapezoidal

What are the long intrinsic ligaments of the carpus?

Palmar intercarpal and dorsal intercarpal ligaments

How many degrees of freedom does the wrist have? And what are its motions?

2 degrees of freedom:

Flex/Ext

Radial/ulnar deviation

Can the wrist rotate about an axis running through the radius?

No, pronation and supination is in the forearm, but there is passive accessory movement

The AOR for wrist flex/ext and radial/ulnar deviation goes through what?

The capitate

What is the AOR for wrist flex/ext?

Med-lat AOR

What is the AOR for wrist radial/ulnar deviation?

Ant-post AOR

Are the AOR for wrist movement static?

No they migrate through wrist motion

Wrist flex/ext is visualized through articulated central column composed of what?

Distal radius

Lunate

Capitate

3rd metacarpal

Extension at the radiocarpal joint occurs between what two bones uses what arthrokinematic principle in open chain?

Lunate rolling and sliding in opposite directions on the radius

What direction does the lunate roll and slide in during open chain wrist extension at the radiocarpal joint?

Convex lunate rolls dorsally and slides palmarly

During open chain extension of the wrist which bones are moving at the midcarpal joint and in what direction?

Convex capitate rolling and sliding in opposite directions on the concave lunate

What direction does the capitate roll and slide in during open chain wrist extension at the midcarpal joint?

Convex capitate rolls dorsally slides palmarly on concave lunate

Which ligament and muscles becomes taut during full wrist extension?

Palmar radiocarpal ligament and wrist/finger flexors

Which ligament and muscles becomes taut during full wrist flexion?

Dorsal radiocarpal ligament and wrist/finger extensors

During open chain flexion of the wrist which bones are moving at the radiocarpal joint and in what direction?

Convex lunate is rolling palmarly and sliding dorsally on concave radius

During open chain flexion of the wrist which bones are moving at the midcarpal joint and in what direction?

Convex capitate is rolling palmarly and sliding dorsally on concave lunate

Wrist ulnar deviation occurs between which bones at the radiocarpal joint? And which are concave and convex?

Convex scaphoid, lunate, triquetrum

Concave radius

What direction are the roll and slide in during open chain wrist ulnar deviation at the radiocarpal joint?

Convex scaphoid, lunate, and triquetrum roll ulnarly and slide radially on concave radius

Open chain ulnar deviation occurs between which bones at the midcarpal joint? And which is convex and which is concave?

Convex capitate and concave scaphoid and lunate

What direction are the roll and slide in during open chain ulnar deviation at the midcarpal joint?

Convex capitate rolling ulnarly and sliding radially on concave scaphoid and lunate

Open chain radial deviation occurs between which two bones and in what direction at the radiocarpal joint?

Convex scaphoid and lunate roll radially and sliding ulnarly on concave radius

Open chain radial deviation occurs between which two bones and in what direction at the midcarpal joint?

Convex capitate rolling radially and sliding ulnarly on concave scaphoid and lunate

What action does a muscle do when its line of pull is anterior/posterior to the med-lat axis?

Anterior to the med-lat axis is flexion

Posterior to the med-lat axis is extension

What action does a muscle do when its line of pull is medial/lateral to the ant-post axis?

Medial to the ant-post axis is ulnar deviation

Lateral to the ant-post axis is radial deviation

If one muscle has two actions how do you determine which torque is stronger for the movements?

If the internal moment arm is greater for one movement than the other than it creates a stronger pull for that movement

How do you compare the relative torque of two muscles?

Look and cross sectional area (size of square in photo) and internal moment arm (distance from axis of rotation)

When two muscles act combined they neutralize opposite torques and move in the direction of the same torque (neutralizing and assisting synergists). Give an example of this.

Flexor carpi ulnaris and flexor carpri radialis both create the same torque in wrist flexion (assisting synergists) and eliminate opposite torques of radial and ulnar deviation (neutralizing synergists)

What is the difference between primary and secondary muscles of the wrist?

Primary muscles act on the wrist only, while secondary act on the wrist and hand

Which muscles are the primary extensors of the wrist, and which produces the greatest torque?

ECRL, ECRB, ECU

ECRB produces greatest torque for wrist extension (central with greatest moment arm)

Which muscles are the secondary extensors of the wrist?

ED, EI, EDM, EPL

Which muscles are the primary flexors of the wrist, and which produces the greatest torque?

FCR, FCU, PL

FCU produces greatest torque (greatest CSA x IMA)

Which muscles are the secondary flexors of the wrist?

FDP, FDS, FPL, APL, EPB

Which muscles perform radial deviation of the wrist?

ECRL

ECRB

EPL

EPB

FCR

APL

FPL

Which muscles perform ulnar deviation of the wrist?

ECU

FCU

FDP

FDS

ED

What is the resting length of the wrist to produce the greatest force in grip?

30 degrees of extension

How does the wrist being in 30 degrees of extension create the strongest grip force?

Extensors contracting and placing the wrist in 30 degrees of extension creates an optimal length tension relationship of long finger flexors (FDS/FDP) for making a fist