Sagittal and frontal plane movements Rotary motion Flexion Extension and Hyperextension Radial Deviation Ulnar Deviation

1. Biomechanics of wrist & Hand

2. Outline
 Introduction of hand
 Types of grasp
 Arches of the hand
 Functional position of the hand
 Joints of the hand
 Mechanism for finger flexion
 Mechanism for finger extension; the extensor mechanism
 Muscles that transmit force to the extensor mechanism
 How does the extensor mechanism work?
 Clinical appearance of peripheral nerve injuries in the hand
 Internet links related to the hand

3. Movements of the Wrist
Sagittal and frontal plane movements
Rotary motion
Flexion
Extension and Hyperextension
Radial Deviation
Ulnar Deviation

4. Joint Structure of the Hand
Carpometacarpal (CM)
Metacarpophalangeal (MP)
Interphalangeal (IP)

5. Common Injuries of the Wrist and Hand
Sprains and strains fairly common
Metacarpal fractures and football
Ulnar collateral ligament and hockey
Wrist fracture and skate/snowboarding
Wrist in non-dominant hand for golfers
Carpal tunnel syndrome

6. Types of grasp
Two types of grasp are differentiated according
to the position and mobility of the thumb's CMC
and MP joints.
1. Power grasp
2. Precision grasp

7. POWER GRASP
(The adductor pollicis stabilizes an object against the palm; the hand's
position is static.)
 cylindrical grip (fist grasp is a small diameter cylindrical grasp)
 spherical grip
 hook grip (MP extended with flattening of transverse arch; the person
may or may include the thumb in this grasp)
 lateral prehension (this can be a power grip if the thumb is adducted,
a precision grip if the thumb is abducted).

8. Prehension of hands

9. PRECISION
(Muscles are active that abduct or oppose the thumb; the
hand's position is dynamic.)
 palmar prehension (pulp to pulp), includes 'chuck' or
tripod grips
 tip-to-tip (with FDP active to maintain DIP flex)
 lateral prehension (pad-to-side; key grip)

10. Three arches balance stability and
mobility in the hand.
 The proximal transverse arch is
rigid, but the other two arches are
flexible, and are maintained by
activity in the hand's intrinsic
muscles.

11. 1. PROXIMAL TRANSVERSE ARCH
 a stable bony arch that forms the posterior border of the carpal
tunnel.
 The arch's integrity is maintained by a soft tissue "strut" formed by
the flexor retinaculum or transverse carpal ligament (also called
the volar carpal ligament). This ligamentous strut connects the
scaphoid and
trapezium on the arch's radial side with the
hamate on its ulnar side, and forms the
anterior border of the carpal tunnel.

12. 2. DISTAL TRANSVERSE ARCH
It is also call metacarpal arch, because it is formed
by the metacarpal heads; metacarpals 2 and 3 are
stable while 4 and 5 are relatively mobile. You can
observe the arch's combination of "radial" stability
and "ulnar" mobility by loosely closing your fist, then
squeezing more tightly, when you will observe
movement in the more mobile fourth and fifth
metacarpals.

13. 3. LONGITUDINAL ARCH
Observe this arch's behavior as you loosely close your fist.
The arches provide a balance between stability and mobility
for grasping. For instance, we produce the so-called "chuck
grasp" by using the more stable second and third
metacarpals, instead of the more mobile fourth and fifth
metacarpals.
Therapeutic splints must support these three arches.

14. Functional position of the hand
•Wrist
• extended 20 degrees
• ulnarly deviated 10 degrees
•Digits 2 through 5
• MP joints flexed 45degrees
• PIP joints flexed 30-45 degrees
• DIP joints flexed 10-20 degrees
•Thumb
• first CMC joint partially abducted and opposed
• MP joint flexed 10 degrees
• IP joint flexed 5 degrees

15.  When therapists immobilize a patient's hand,
they often position it this way. During a
period of immobilization, the resting lengths
of the hand's ligaments and muscles
change. This hand position provides the
best balance of resting length and force
production so the hand can function when
the patient mobilizes it again.

16. JOINT STRUCTURE AXIS MOTION
CLOSE-PACKED
POSITION
Metacarpo-
phalangeal (MP)
biaxial
(condylar)
lateral
A-P
flexion/extension
abduction/adductio
n
first: extension
2nd-5th: flexion
Proximal
Interphalangeal
(PIP)
uniaxial lateral flexion/extension extension
Distal
Interphalangeal
(DIP)
uniaxial lateral flexion/extension extension
Joints of the hand

17. Mechanism for finger flexion
 FDP: flexor digitorum profundus (the deeper of the two)
 FDS: flexor digitorum superficialis (the more superficial muscle)
Although the FDP is deep to the FDS over most of its course, it
attaches to the skeleton more distally, because it passes through a
'split' in the FDS tendon.

18. Mechanism for finger extension
 We can extend the PIP and DIP joints without also extending the MP
joints.
 But we can't extend the PIP joint without extending the DIP joint at the
same time.
 Flexing only the DIP joint without also flexing the PIP joint is difficult.
 Full (active or passive) flexion of the PIP joint prevents active
extension of the DIP joint.

19. Force Transmission
• 80-90% through Radius & 10-20% - Ulna
• Peak pressures are higher through Scaphoid fossa than
lunate fossa
• 50% of load applied through distal Carpus is transmitted
through the Capitate to the scaphoid & lunate

20. Force Transmission
Pattern of force transmittal depends on:
• Wrist position
• Capsuloligamentous integrity
• Articular surface
• Congruity

22. PERIPHERAL NERVE INJURIES IN
THE HAND
Median nerve:
 Often due to carpal tunnel syndrome.
 Wasting of thenar eminence
 Decreased thumb function, especially
opposition.
 Thumb moves into plane of palm.

23. Ulnar nerve
 Damage to ulnar nerve can occur with trauma to elbow region.
Ulnar neuropathy is a frequent complication of diabetes mellitus
 Wasting of web space and interosseous spaces.
 Affects strength of intrinsic muscles of hand, so person can't hold
a piece of paper between extended but adducted fingers
 Affects adductor pollicis and ulnar head of FPB. A person who
lacks strength in these muscles cannot grasp with the thumb
unless he or she flexes the IP joint by substituting with the flexor
pollicis longus.

25. Radial nerve injury
 Associated with gunshot or stab wounds, fracture of
humerus, "Saturday night palsy."
 person demonstrates a "dropped wrist," and cannot
reposition thumb.
 lack of wrist extension may cause hand grip to be
weak.

27. Thanks