Wrist (Part II) Flashcards
How many degrees of freedom does the wrist have? What are they?
Two
- Flexion/extension
- Ulnar/radial deviation
*NOT circumduction (combination of the above movements)
Flexion is ____ than extension and ulnar deviation is ___ than radial deviation
greater
greater
Extension tends to occur with ____ deviation whereas flexion tends to occur with ____ deviation.
radial
ulnar
The natural path of motion for the wrist follows what type of path?
oblique (dart thrower)
Axis of rotation for wrist movements passes through head of what bone? Why?
capitate
The firm articulation between the capitate and base of 3rd metacarpal bone causes rotation of capitate to direct osteokinematic path of entire hand
During flexion and extension where does the axis of rotation run?
in nearly a medial-lateral line
During radial and ulnar deviation where does the axis of rotation run?
in nearly an anterior-posterior line
The wrist rotates in sagittal plane about ___°-___°. How much is attributed to flexion and how to extension?
130°-160°
Flexion = 70° - 85°
Extension = 60° - 75°
What limits end-range extension?
- Stiffness in thick palmar radiocarpal ligaments
- Large palmar tilt of distal radius may limit extension range
The wrist rotates in frontal plane about ___°-___°. How much is attributed to radial deviation and how to ulnar deviation?
50° - 60°
Ulnar Deviation = 35° - 40°
Radial Deviation = 15° - 20°
Why does ulnar deviation normally double radial deviation?
Because of the ulnar tilt of the distal radius
What is the “average” position of function for the wrist?
About 10°-15° of extension and 10° of ulnar deviation
Carpal kinematics are typically described as a double-joint system, why?
Movement occurs simultaneously at both radiocarpal and midcarpal joints
What does the “central column” of the wrist consist of?
The distal radius, lunate, capitate, and 3rd metacarpal
3 articulations of the central column of the wrist
Radiocarpal (between radius and lunate)
Midcarpal (between lunate and capitate)
Carpometacarpal (between capitate and 3rd metacarpal)
The distal end of the radius is con__ and the proximal surface of the lunate is con___.
concave
convex
Describe the arthrokinematics at the radiocarpal joint during extension
The convex surface of the lunate rolls dorsally and slides palmarly
Describe the arthrokinematics at the radiocarpal joint during flexion
The convex surface of the lunate rolls palmarly and slides dorsally
The distal surface of the lunate is con__ and the proximal surface of the capitate is con___.
concave
convex
Describe the arthrokinematics at the midcarpal joint during extension
The head of capitate rolls dorsally on lunate and slides in palmar direction
Describe the arthrokinematics at the midcarpal joint during flexion
The head of capitate rolls palmarly on lunate and slides in dorsal direction
In order for full wrist extension and flexion to occur what must happen at the radiocarpal and midcarpal joints?
They must work as a unit
What is the close-packed position for the wrist and why?
Full extension because it elongates palmar radiocarpal ligaments and all muscles that cross on palmar side of wrist which help to stabilize it
Which joints attribute to most of the movement during ulnar deviation?
midcarpal joint and radiocarpal joint
Describe the arthrokinematics at the radiocarpal joint during ulnar deviation
The scaphoid, lunate, and triquetrum roll ulnarly and slide radially majorly
Describe the arthrokinematics at the midcarpal joint during ulnar deviation
The capitate rolls ulnarly and slides radially slightly
During full range of ulnar deviation what does the triquetrum come into contact with?
the articular disc
Describe the mechanism that occurs to stabilize the wrist for activities that require large gripping forces
The hamate compresses against the triquetrum which pushes the proximal row of carpal bones against the styloid process of the radius
Describe the arthrokinematics at the radiocarpal joint during radial deviation
The scaphoid, lunate, and triquetrum roll radially and slide ulnarly
Describe the arthrokinematics at the midcarpal joint during radial deviation
The capitate rolls radially and slides ulnarly slightly
What limits the amount of radial deviation at the radiocarpal joint?
The carpus impinges against the styloid process of the radius
Does more radial deviation occur at the radiocarpal or midcarpal joint?
midcarpal joint
2 Common Forms of Carpal Instability
- Rotational collapse of wrist
- Ulnar translocation of carpus
A rotational collapse of the wrist is aka what?
“zigzag” deformity
There are 2 types of zigzag deformities: DISI and VISI. What do each stand for?
- Dorsal intercalated segment instability
- Volar intercalated segment instability
What occurs during dorsal intercalated segment instability (DISI)?
During a fall onto an outstretched hand the lunate dislocates so its distal articular surface faces dorsally
What occurs during volar intercalated segment instability (VISI)?
Dislocation of the lunate so that its distal articular surface faces volarly (palmarly)
Which ligament is typically damaged with a VISI?
lunotriquetral ligament
The distal end of the radius angles towards the ulnar at an angle of about __°. This
25°
A wrist with an ulnar tilt of 25° has an ulnar translation force of __% of total compression force that crosses wrist
42
Describe the “Double-V” System of wrist ligaments
In a neutral position, four ligaments appear as two inverted Vs
The distal inverted V is formed by what 2 ligaments?
medial and lateral legs of palmar intercarpal ligament
The proximal inverted V is formed by what 2 ligaments?
the lunate attachments of palmar ulnocarpal and palmar radiocarpal ligaments
During ulnar deviation what ligaments of the “double-V” system are stretched?
The lateral leg of the palmar intercarpal ligament and fibers of the palmar ulnocarpal ligament
During radial deviation what ligaments of the “double-V” system are stretched?
The medial leg of the palmar intercarpal ligament and fibers of the palmar radiocarpal ligament
What are the 3 primary wrist extensor muscles?
- Extensor carpi radialis longus
- Extensor carpi radialis brevis
- Extensor carpi ulnaris
What are the 4 secondary wrist extensor muscles?
- Extensor digitorum
- Extensor indicis
- Extensor digiti minimi
- Extensor pollicis longus
What role do wrist extensor muscles play in grip?
They maintain optimal length of finger flexors and block wrist flexion tendency caused by activated finger flexor muscles
Maximal grip force occurs at about __° of extension
30°
What are the 3 primary wrist flexor muscles?
- Flexor carpi radialis
- Flexor carpi ulnaris
- Palmaris longus
What are the 5 secondary wrist flexor muscles?
- Flexor digitorum profundus
- Flexor digitorum superficialis
- Flexor pollicis longus
- Abductor pollicis longus
- Extensor pollicis brevis
What is the joint angle of peak torque for wrist flexion?
40° of flexion
What are the 7 radial deviators of the wrist?
- Extensor carpi radialis longus
- Extensor carpi radialis brevis
- Extensor pollicis longus
- Extensor pollicis brevis
- Flexor carpi radialis
- Abductor pollicis longus
- Flexor pollicis longus
What are the 4 ulnar deviators of the wrist?
- Extensor carpi ulnaris
- Flexor carpi ulnaris
- Flexor digitorum profundus and superficialis
- Extensor digitorum
What carpal bone is the axis of rotation for radial and ulnar deviation?
the capitate
