Biomechanics of the wrist

1. B Y :
SUMANA RASHID NASEERI
BPT 4TH YEAR
BIOMECHANICS OF THE WRIST

2.  The wrist is the distal joint of the upper limb and
allows the hand to assume the optimal position for
prehension.

3.  The articular complex of
the wrist contain joints:-
 THE RADIO-CARPAL
JOINT between the radial
head and the proximal row
of carpal bones.
 THE MID-CARPAL JOINT
between the proximal and
distal rows of carpal
bones.(figure 1)
ARTICULAR COMPLEX OF THE WRIST
Wrist Joint(figure 1)

4. RADIO-CARPAL JOINT
 RADIO-CARPAL
JOINT is an ellipsoidal
joint and the carpal
aspect presents two
convexities transverse
convexity and antero-
posterior convexity
(figure 2)..

5. THE LIGAMENTS OF THE RADIO-CARPAL
JOINT ARE THE:-
 COLATERAL LIGAMENTS(LATERAL AND
MEDIAL)
 ANTERIOR LIGAMENTS (ATTACHED TO THE
ANTERIOR EDGE OF THE DISTAL SURFACE OF
THE RADIUS AND NECK OF THE CAPITATES)
 POSTERIOR LIGAMENT(FORMS A STRAP
POSTERIORLY)

6. Action of the ligaments:-
 During adduction-abduction the medial and
lateral ligaments are active.Starting from the
rest position.
Adduction lateral ligament is
stretched,medial slackened.
Abduction vice versa.
 During flexion-extention the anterior and
posterior ligaments are most active.
Flexion posterior ligament stretched.
Extension anterior ligament stretched.

7. MOTION MUSCLE
WRIST FLEXION
ASSIST WRIST
FLEXION
WRIST EXTENSION
 FLEXOR CARPI
ULNARIS
 FLEXOR CARPI
RADIALIS
 PALMARIS LONGUS
 EXTENSOR CARPI
RADIALIS LONGUS
 EXTENSOR CARPI
RADIALIS BREVIS
 EXTENSOR CARPI
ULNARIS
MUSCLES OF THE WRIST

8. MOTION MUSCLE
WRIST ULNAR
DEVIATION
WRIST RADIAL
DEVIATON
FLEXOR CARPI
ULNARIS
EXTENSOR CARPI
ULNARIS
FLEXOR CARPI
RADIALIS
EXTENSOR CARPI
RADIALIS LONGUS
MUSCLES OF THE WRIST(CONTD..)

9. SYNERGIST AND STABILIZING ACTION
OF THE MUSCLE OF THE WRIST:-
EXTENSOR MUSCLES of the wrist act
synergistically with the flexors of the
fingers. E.g. during extension of the
wrist the fingers are automatically flexes
and ,to extend the fingers in this position
,a voluntary movement is required.
FLEXOR MUSCLES of the wrist act
synergistically with the extensors of the
fingers. When the wrist is flexed ,
extension of the proximal phalanx
follows automatically.

10. KINEMATICS
 The articular complex of the wrist has
basically two degree of freedom.When
these compounded with pronation and
supination,i.e. rotation of the forearm
around its axis,the hand can be oriented
at any angle to grasp or hold an object.
 Movement of the wrist occur around two
axes:-
 TRANSVERSE AXIS
 ANTERO-POSTERIOR AXIS

11. KINEMATICS(CONTD..)
 1.TRANSVERSE AXIS:-
Transverse axis takes
place in SAGITTAL
PLANE with movement:
1. FLEXION the anterior
palmar surface of the
hand moves towards
the anterior aspect of
the forearm.
2. EXTENSION the
posterior dorsal
surface of the hand
moves towards the
posterior aspect of the
forearm(figure 3)

12. KINEMATICS(CONTD..)
 2.ANTERO-
POSTERIORAXIS:-Takes
place in the frontal plane
with movements:
1. ADDUCTION or ULNAR
DEVIATION :The hand
moves toward the axis of
the body and its
medial(ulnar) border
forms an obtuse angle with
the medial border of the
forearm.
2. ABDUCTION or RADIAL
DEVIATION:The hand
moves away from the axis
of the body and its
lateral(radial)border
forms an obtuse angle with
the lateral border of the
forarm.(figure 4)

13. MOVEMENTS
ROM(RANGE OF
MOTION)
 RADIAL DEVIATION
 ULNAR DEVIATION
 FLEXION
 EXTENSION
0-20 DEGREE
0-30 DEGREE
0-80 DEGREE
0-70 DEGREE
RANGE OF MOTION OF WRIST.

14.  Movement of circumduction(combination of
the movement of
flexion,extension,adduction,and abduction)
takes place in two axes of wrist.

15. THE STABILIZATION FUNCTION OF THE
LIGAMENT

16. 1.STABILIZATION IN THE FRONTAL PLANE:
• In the frontal plane
ligaments are
essential,because the distal
surface of the radius faces
distally and medially,so that
as a whole it can be
represented by a plane
running obliquely proximo-
distally and medio-laterally.
• Under the pull of
longitudinally muscles,carpus
in the neutral position tends
to slip proximally and
medially(figure 5)

17. THE STABILIZATION FUNCTION OF THE
LIGAMENT(CONTD..)
 When the wrist is
adducted to aproximately
30,the pull of the muscle
now act perpendicular to
the plane of the
slippage,as a result the
carpal bones are pushed
back into the cavity and
the carpus is
stablized.(figure 6)

18. THE STABILIZATION FUNCTION OF THE
LIGAMENT(CONTD..)
 When the wrist is
abducted,the pull of the
long muscles accentuate
the instability and tends
to displaced the carpal
bones proximally and
medially.(figre 6)

19. 2.STABILIZATION IN THE SAGITTAL PLANE
 In the sagittal plane
roughly similar events
takes place.Because the
distal surface of the
radius points distally and
interiorly(lateral
view),the carpal bones
tend to slip proximally
and interiorly,i.e.in a
plane parallel to that of
the distal surface of the
radius.(figure 7)

20. STABILIZATION IN THE SAGITTAL
PLANE(CONTD..)
 When the wrist is flexed
30 to 40,the muscular
pull tends to displace the
carpal bones in a plane
perpendicular to that of
the distal surface of the
radius,thus repositioning
and stabilizing these
bones.(figure 8)

21. STAILIZATION IN THE SAGITTAL
PLANE(CONTD..)
 During extension,the tendency of the carpal bones to
be displaced proximally and anteriorly is
reinforced.(figure 9)