Hand & Prehension

OT 5761
Vicki Kaskutas, OTD, OT/L
 Skin & fascia of the hand
• dorsal fascia is thin and loose
• dorsal skin is mobile and subject to avulsion
injury and edema
• palmar fascia has thick fibers connecting
the skin to the ligaments, fascia, & muscles
• fibers stabilize the palm skin and account
for the palmar creases
 Skin creases
• correspond directly to underlying joints
indicating where motion occurs in the hand
• palmar creases are fixated to underlying
fascia
• distal palmar crease corresponds to level of
the MP joints
 Skeletal arches of the hand
• carpal arch (proximal transverse arch):
transverse concavity formed by the distal
carpal bones
• transverse arch (distal transverse arch):
transverse concavity formed by the heads of
metacarpals 2-5
• longitudinal arch: longitudinal concavity
formed by the carpals, metacarpals and
phalanges
 Transverse arches
• Proximal transverse arch is maintained
whether fingers are flexed or extended due
to the immobile nature of the distal carpals

• Distal transverse arch is decreased when

fingers extend and increased when fingers
flex as metacarpals 4 and 5 are mobile
 Distal transverse arch
• metacarpals 2 & 3 provide a stable base for
the hand and axis for the other metacarpals
• metacarpals 4 & 5 flex and extend to
conform to objects for tight grasp and bring
fingertips towards thumb for manipulation
• metacarpal 1 is very mobile to conform to
many size objects in various planes of
motion
 Longitudinal arch

• row of metacarpal heads is the highest point

in arch
• arch is longest at metacarpal 2 and shortest
at metacarpal 5 due to the different lengths
of the metacarpals
• segments contributing to arch allow 280
degrees of combined motion
 Finger ROM
• finger flexion ROM is greater in fingers on
the ulnar side of the hand

• this additional range angles the ring and

small fingers toward the center of the wrist
 What is the role of increasing
CMC motion and MP flexion on
the ulnar side of the hand?
 Finger Movement Agonists

• MP flexion – lumbricals, DI, VI, FDS, FDP

• MP extension – ED
• PIP flexion – FDS, FDP
• PIP extension – lumbricals, DI, VI
• DIP flexion – FDP
• DIP extension – lumbricals, DI, VI
 Thumb opposition
• ability to touch little finger & thumb
• thumb pad is reoriented to touch finger pad
• combination of movements of abduction,
flexion, and medial rotation of CMC joint
• occurs in almost all forms of prehension

• Reposition – returning the thumb to

anatomical position
 Prehension
• the grasping or taking hold of an object
between any two surfaces in the hand
• thumb participates in most prehension
• number of ways objects can be grasped is
infinite and varies between individuals
• general classification into
– power grip
– precision handling
 Power grip
• a forceful act of flexion at all finger joints
• amount of flexion varies with object
• thumb stabilizes in adduction between fingers
and most commonly palm (if used)
– result of opening the hand
– positioning the fingers
– approaching fingers to object
– maintaining a static phase
– proximal joints move object through space
 Precision handling
• the skillful placement of an object
between finger(s)&thumb (2-jaw chuck)
• palm is not involved
• fine motor control & intact sensation needed
– result of opening the hand
– positioning the fingers
– approaching fingers to object
– grasping the object
– manipulating object in hand with fingers
Comparing power grip &
precision handling
power grip precision
handling
palm used yes no
thumb used maybe yes
fine coordination no yes
gross strength yes no
Types of power grips
Hook

Spherical

Cylindrical
 Types of precision handling

Tip to tip prehension

Pad to pad prehension

Pad to side prehension

Lateral pinch
 What muscles are used for the
various prehension patterns?

• Cylindrical
• Spherical
• Hook
• Tip to tip
• Tip to pad
• Pad to side
Synergistic function of the hand
required for prehension
• Muscles of the wrist and hand work
synergistically during prehension
• Wrist extensors stabilize the wrist in neutral to direct
extrinsic flexor tendon pull to the fingers

• Wrist ulnar deviators work with thumb long

flexors to put thumb in line with the forearm

• Intrinsics work with long flexor tendons to keep

MP’s in neutral abd/add while long flexors act
• Long flexors work to hold object while
interossei abduct/adduct to manipulate object
 Without this synergistic activity,
active insufficiency could interfere
• extrinsic finger flexors can’t flex fingers to
grasp if wrist is in flexion
• so wrist extensors stabilize wrist in neutral
• can you hold your pen tightly with wrist
flexed?
• when long flexors this short they produce
minimal force
 Passive insufficiency can assist
with prehension through tenodesis
• Tenodesis – using wrist extension to close the
fingers & wrist flexion to open the fingers
• Passive tension develops in the extrinsic finger
flexors with wrist extension
• This tension pulls the MP & IP joints of the fingers
and thumb into flexion – pad to side & cylindrical
prehension patterns can result
• As wrist flexes the extrinsic flexors are slack and the
extrinsic extensors are stretched
• This tension pulls the MP & IP joints of the fingers
and thumb into extension
 C6 segmental innervation
required for tenodesis grasp
• Wrist extensors are innervated by C6 & C7
• Individual with C6 functioning will usually have
good strength in the wrist extensors
• So even though the finger muscles are not
working as they are innervated below C6, the
individual may have some prehension
• Must do ROM in manner to encourage this passive
insufficiency
– Wrist extension with fingers flexed
– Wrist flexion with fingers extended
But could this individual with segmental
innervation absent below C6 feel the
object he was grasping or manipulating?
Which peripheral nerves innervate
muscles that are important for these
types of prehension patterns?
• hook
• cylindrical
• spherical
• tip-to-tip prehension
• pad-to-pad prehension
• pad-to-side prehension
What peripheral innervation is required to
perform these prehension patterns?

Cylindrical
Median nerve
Spherical
Hook
Tip to tip
Tip to pad
Pad to side
 Nerve injuries
• Nerves can be injured due to trauma that is:
– Close to a bone that is fractured
– Close to the surface of the skin that is lacerated
– Contusion, compression, crush, or viral
infections.
• Muscles that receive their innervation
proximal to the nerve injury will function
• Muscles that receive their innervation distal
to the nerve injury will NOT function
• Sensory innervation presents similarly
radial
 What will the appearance of
the hand be following a radial
nerve injury?

It depends where the

laceration is…
RADIAL NERVE
How will prehension
patterns look with a
radial nerve injury?
What type of a splint may
improve hand function?
What will the appearance of the
hand be following a median
nerve injury?
MEDIAN
NERVE
How will prehension patterns look
with a median nerve injury?
What type of a splint may
improve hand function?
Ulnar Nerve

C7,8
T1
ULNAR
NERVE
What will the appearance of
the hand be following an
ulnar nerve injury?
How will prehension patterns look
with a ulnar nerve injury?
• Atrophy of the
dorsal interossei,
especially 1st

• Loss of thumb
adduction
Froment’s sign
• Froment’s sign –
laterally pinches with
flexor pollicis longus
as adductor pollicis
not innervated

• Extensor digitorum
attempts to extend
digits, but leads to
hyperextension of MP
joints and clawing in
digits 4 & 5
 Intrinsic muscle importance
• lumbricals/interossei flex MPs & extend IPs
• long extensors will hyper-extend MP unless
MP stabilized in neutral
• intrinsics correct this hyperextension
without causing IP flexion
• absence of these muscle lead to intrinsic
minus hand (claw hand)
What type of a splint may
improve hand function?
 Assessment for
nerve injury
• Symptom report/history
• Appearance: posturing and
muscle wasting
• Phalen’s sign - prolonged wrist
flexion
• Tinel’s sign - percuss nerve
• Manual compression of nerve
• Prolonged stretching of nerve
• MMT
• EMG-NCV
 Close-pack
position
MP joint flexed
• joint surfaces maximally
congruent
• ligaments stretched
• flexion at MP joints 2-5
• extension at IP joints
• extension at thumb MP
IP joints extended
• extension at wrist
 Splinting of the hand
• If splint is to prevent deformity, the forearm
and hand is splinted in the closed packed
position to keep the structures on a stretch
– wrist extension
– maximum MP flexion
– full IP extension
– thumb in abduction
 Disorders of the
Extensor Mechanism
Boutonniere deformity
Swan neck deformity
 Intrinsic minus

Intrinsic tightness testing

Intrinsic plus
Lateral epicondylitis