Biomechanics of the Wrist and Hand

Question 1

Biomechanics

The distal radius shows an ulnar tilt of how many degrees? This tilt allows increased motion into which deviation?

Wrist and Hand

Answer 1

25 degrees
Ulnar > Radial

Question 2

Biomechanics

Radial deviation of the wrist is limited by the carpals running into what process?

Wrist and Hand

Answer 2

The Styloid Process

Question 3

Biomechanics

The distal radius shows an palmar tilt of how many degrees? This tilt allows for increased motion into which direction?

Wrist and Hand

Answer 3

10 degrees
Flexion > Extension

Question 4

Biomechanics

Axis of rotation for wrist movements passes through head of what bone?

Wrist and Hand

Answer 4

The capitate.

The firm articulation between the capitate and base of 3rd metacarpal bone causes rotation of capitate to direct osteokinematic path of entire hand.

Question 5

Biomechanics

What is the “average” position of function for the wrist?

Wrist and Hand

Answer 5

About 10°-15° of extension and 10° of ulnar deviation.

Question 6

Biomechanics

Describe the arthrokinematics at the radiocarpal joint during wrist extension.

Wrist and Hand

Answer 6

The convex surface of the lunate rolls dorsally and slides palmarly

Question 7

Biomechanics

Describe the arthrokinematics at the radiocarpal joint during ulnar deviation.

Wrist and Hand

Answer 7

The scaphoid, lunate, and triquetrum roll ulnarly and glide radially.

Question 8

Biomechanics

What role do wrist extensor muscles play in grip?

Wrist and Hand

Answer 8

They maintain optimal length of finger flexors and block wrist flexion tendency caused by activated finger flexor muscles

Question 9

Biomechanics

Maximal grip force occurs at about ____° of extension.

Wrist and Hand

Answer 9

30°

Question 10

Biomechanics

What is the joint angle of peak torque for wrist flexion?

Wrist and Hand

Answer 10

40° of flexion

Question 11

Biomechanics

The trapezium is (Convex or Concave) in the sagittal plane.

Wrist and Hand

Answer 11

Concave

Question 12

Biomechanics

The trapezium is (Convex or Concave) in the transverse plane.

Wrist and Hand

Answer 12

Convex

Question 13

Biomechanics

In the MCP joints the metacarpal is (Convex or Concave) and the proximal phalange is con (Convex or Concave). This means that with all motions roll and glide occur in the ____ direction.

Wrist and Hand

Answer 13

• Convex
• Concave
• Same

Question 14

Biomechanics

How many degrees of freedom are there at the interphalangeal joints? What are they?

Wrist and Hand

Answer 14

One - Flexion/Extension

Question 15

Biomechanics

What is the dart thrower’s motion?

Wrist and Hand

Answer 15

The dart thrower’s motion describes a natural and effective human tendency to accompany radial deviation with wrist extension and ulnar deviation with wrist flexion; as in throwing darts, combing hair, or opening a jar.

Question 16

Biomechanics

Define the following:
(a) positive ulnar variance
(b) negative ulnar variance
(c) ulnar impaction syndrome

Wrist and Hand

Answer 16

(a) when the ulna extends distally ( towards carpals )
(b) when the ulna retracts proximally ( toward elbow )
(c) distal encroachment of the ulna into the TFCC; impaction may progress to inflammation and degeneration of the TFC.

Question 17

Biomechanics

What is the difference between the intrinsic plus position and the extrinsic plus position?

Wrist and Hand

Answer 17

Intrinsic+ : simultaneous contraction of lumbrical and interossei; MCP flexion w/ IP ext.
Extrinsic+ : simultaneous contraction of ED, FDP, FDS; MCP ext. with IP flexion