Wrist

Question 1

What joints make up the wrist?

Answer 1

Radiocarpal joint (distal end of radius and proximal row of carpal bones.)
Midcarpal joint (proximal and distal rows of carpal bones.)
(Radioulnar is part of forearm complex).

Question 2

Describe the shape of the proximal joint surface of the radiocarpal joint for the sagittal and frontal planes and identify its specific composition.

Answer 2

Radius–One piece of bone, smooth. It is concave in both medial-lateral and anterior-posterior directions. The ulnar tilt of 25 degrees allows the wrist and hand to rotate farther into ulnar deiation than into radial deviation. Distal radius articulation is angled about 10 degrees in the palmar direction. Palmar tilt allows for greater flexion of the wrist than extension. (articular disc part of TFCC)

Question 3

Describe the shape of the distal joint surface of the radiocarpal joint. What bones constitute the distal surface?

Answer 3

Scaphoid has a convex proximal pole that articulates with the scaphoid facet.
Lunate has a convex proximal surface that articulates into the concave facet on the radius.
Triquetrum (included because at full ulnar deviation its medial surface contacts the articular disc.)

Question 4

What constitutes the medial and lateral compartments of the midcarpal joint?

Answer 4

Medial–convex head of capitate and apex of hamate fitting into the concave recess formed by the distal surfaces of the scaphoid, lunate, and triquetrum.

Lateral–junction of the slightly convex distal pole of scaphoid with slightly concave proximal surfaces of the trapezium and the trapezoid.

Question 5

Describe the general shape of the medial compartment joint surfaces for the midcarpal joint.

Answer 5

Capitate and hamate are convex. Scaphoid, Lunate, and Triquetrum are concave. Trapezoid and trapezius are concave. Scaphoid is convex.

Question 6

Define TFCC and describe it (specifically address the main feature/component)

Answer 6

Triangular Fibrocartilage Complex–5 interconnected tissues. Primarily, (triangular fibrocartilage) aka the articular disc located within both the distal radio-ulnar and radiocarpal joint. Also consists of the Ulnar collateral ligament and palmar ulnocarpal ligament. Meniscus Homologue fills gaps within and immediately medial to the prestyloid recess of the ulnocarpal space. (pg 223)

Question 7

Domonstrate the osteokinematic motions and degrees of freedom for the wrist joint.

Answer 7

2 degrees of freedom. Flexion-extension and Ulnar deviation, radial deviation. Those 2 motions combined = circumduction, frontal, and sagittall plane.

Question 8

Is there any significance to the number of degrees of freedom found at the wrist that relates to the forearm?

Answer 8

Only 2 degrees of freedom at the wrist.
Pronation and supination of the wrist occurs at the forearm. Thus the wrist gets a 3rd degree of functional freedom from the forearm.

Question 9

Name the planes in which each ostekinematic motion takes place.

Answer 9

Flexion/extension–sagittal
Radial/ulnar deviation–frontal plane.
Rotation occurs at distal and proximal radioulnar joints to give rotational motion in transverse plane.

Question 10

Identify the anatomic locations and directions of the axes for wrist motions.

Answer 10

Both medial/lateral (flexion/extension) and anterior/posterior (deviation) axes pierce the capitate bone.

Question 11

What is the central column of the wrist?
What is the technical term for the formation of the column?
Describe arthrokinematics of wrist flexion and extension using the central column of the wrist

Answer 11

1. Alignment of the radius, lunate, capitate and 3rd metacarpal.
2. Intercallation (all in a line) sequence of bony segments. Misalignment can sometimes tell us what’s wrong.
3. Arthrokinematics is the same on both joints because they are shaped the same. Convex moving on concavity, . In extension, roll posterior, glide anterior. Wrist flexion, Roll anterior, glide posterior.

Question 12

Describe arthrokinematics of Radial and Ulnar Deviations (RD/UD)

Answer 12

RD has roll in the radial direction and greater slide in the ulnar direction. (scaphoid)
UD has roll int he ulnar direction and slide in the radial direction. (hamate/capitate???)
These kinematics occur in both the proximal row and distal row of carpal bones.
Convexity on concavity.

Question 13

What are the ROM contributions of the radiocarpal joint to flexion/extension and RD/UD?

Answer 13

Contributes more flexion due to the shape of the radius. Radius extends further distally on the dorsal side at the wrist than the anterior side. The extended end acts like a chalk block.
Proximal row tends to flex and distal row, lateral compartment extends on proximal row during radial deviation.
UD>RD
Flex>Ext.

Question 14

What are the ROM contributions of the midcarpal joint to flexion/extension and RD/UD?

Answer 14

The Midcarpal joint’s contributions to flex/ext and Rd/UD are opposite. of radiocarpal.
Ext>Flex
RD>UD

Question 15

Generally, though there is more to their function, what are the primary function of the wrist extensors as they relate to the wrist and hand?

Answer 15

Wrist extensors extend the wrist.
Positions and stabilizes the wrist during active finger flexion. (When grabbing something, the wrist extensors extend the wrist slightly to optimize length/tension relationship of finger flexors to grip.)

Question 16

Describe the independent and synergistic functions of the FCR, FCU, ECRL/B and ECU in producing osteokinematics motions at the wrist.

Answer 16

All of these muscles not only have their primary responsibility to either flex or extend the wrist, but they also deviate the wrist in either the ulnar direction or radial direction.

FCR-Flexion/RD, FCU Flx/UD, ECRL/B Ext/RD, ECU Ext/UD.

FCR+ECRL/B = RD
FCR + FCU = FLexion
FCU + ECU = UD
ECRL/B + ECU = Ext.

Question 17

Name the 5 components of the TFCC.

Answer 17

Articular disc (triangular Fibrocartilage)
Radio-ulnar joint capsular ligament. 
Palmar ulnocarpal ligament. 
Ulnar collateral ligament. 
Meniscus Homologue.