detailed but relatively concise presentation of hand anatomy

1. Anatomy of The Hand
Prepared by
Mahmoud Elsayed Gouda Mohamed
Plastic Surgery Unit – Zagazig University

2. Agenda
Part 1 Part 2
• Terminology & Hand Motion
• Skin
• Fascia
• Musclo-Tendious Unit
• Embryology
• Bones & joints
• Neurovascular Unit
• Carpal tunnel
• Nail bed

3. Terminology
• Forearm and Hand
Radial and ulnar, dorsal and volar (or palmar). Avoid medial/lateral, anterior/posterior
• Digits
Thumb
Index finger
Long or middle finger
Ring finger
Small or little finger
• Palm
Thenar eminence
Hypothenar eminence
Midpalm: Area between thenar and hypothenar eminences

5. • Thumb
• Abduction:
• Movement out of plane of palm (i.e., volar abduction)
or in plane of palm (i.e., planar or radial abduction)
• Abduction occurs at the CMC joint and refers to
metacarpal motion.
• Flexion/extension: Occurs at MP joint or IP joint of
thumb—it is important to specify (i.e., IP joint extension)
• Opposition: Combination of movements, including CMC
joint rotation, resulting in the thumb pulp directly opposing
the pulp of another finger
Hand Motion

7. Fingers
• Abduction: Movement is away from the long
finger.
• Adduction: Movement is toward the long finger.
Occurs at MP joints during Extension.
(reference point is sagittal line through third ray)
Flexion/extension/Hyperextension: Occurs at MP
joints and IP joints

8. Wrist
• Flexion, extension, radial and ulnar deviation:
at mdicarpal and radiocarpal joints
• Pronosupination: at distal radioulnar joint

11. • Volar skin is thicker, less mobile, and has papillary ridges for
grasping.
• Dorsal skin is thinner and more mobile, and the subcutaneous
tissue contains veins and lymphatics.
Skin

12. Surface Anatomy

13. Skin incisions
• Surgical incisions should:
• Be extensible
• Provide access to deep structures
• Provide vascularized skin flaps (avoid very long, narrow flaps)
• Avoid formation of scar contractures. Straight incisions across
flexor creases (digits, palm, wrist,) lead to scar contracture.
• Avoid unnecessary dissection (leading to oedema and scarring)
• Scars should be placed on the non-dependent sides of the
digits (e.g. radial side of little finger) where possible.

14. (A, B) Schematic representation of the joint axes. The longitudinal dimensions in the
midpalmar and middorsal aspect of the digits change maximally. The midaxial line
through the three joint axes does not change in length with flexion and extension.
Palmar incisions placed longitudinally produce contracture if they pass across the
palmar diamonds delineated by lines joining the joint axes (after Littler). Transverse
incisions avoid the occurrence of flexion scar contractures. The same principle
applies at the wrist.

15. • Dorsal
Straight incisions are used on the dorsum of the wrist, hand and
digits. These preserve longitudinal veins, and provide well
vascularized skin flaps with good access.
Horizontal incisions across the MCPj heads may be used for
access to the MCPjs or intrinsic insertions into the extensor hood.
Zig-zag incisions on the dorsum of the hand are unsightly and
may create ischaemic skin flaps if the base is too narrow.
Lazy S or tri-radiate (wine glass) incisions to approach the DIPj.
Types of incision

16. • Mid-lateral
This runs along the side of the digit, dorsal to the neurovascular
bundle, and therefore safe.
It is designed by
flexing the fingertip into the palm,
and marking dots at the apices
of the DIPj, PIPj and MCPj creases.
The digit is then extended and a line drawn connecting the dots.

17. Palmar
Bruner: These zig-zag type incisions are used in the volar aspect of
the palm and digits. In the digits, they run from the mid-lateral line
across the span of a phalanx to the contralateral mid-lateral line. In
the palm they should be 1-2cm long, zig-zagging between palmar
creases
Half Bruner: These are similar to Bruner incisions, but zig-zag
across half of the width of the digit.

19. Incisions for Hand infection

20. Incisions for Hand Fasciotomy

21. Incisions for vascular exposure

22. • Volar fascia
• Anchors volar skin to bone for grasping, in contrast to loose skin
on dorsum.
• The deep fascia :covers the interosseous muscles and is not
involved in Dupuytren’s disease .
• Superfcial volar fascia: Triangular-shaped fascia attached
proximally to PL tendon; composed of longitudinal fibers, vertical
fibers, transverse fibers.
Fascia of The Hand:

23. The longitudinal fibers
course superfcial to the flexor retinaculum, forming pretendinous
bands. These bands travel distally and insert into the deep surface
of the dermis at the distal palmar crease,
bifurcate around the flexor tendon sheath to insert on the radial
and ulnar sides of the MCP joint

25. The transverse fibers are characterized by two distinct bands, one
proximal and one distal.
• The proximal transverse fibers, located at the level of the distal
palmar crease, course deep to the longitudinal pretendinous
bands and are not typically affected by Dupuytren’s disease.
Radially, these fibers form the proximal commissural ligament
of the frst webspace.

26. • The distal transverse fibers, alternately referred to as the
natatory ligament, course superfcial to the longitudinal
pretendinous bands and are affected by Dupuytren’s disease.
The natatory ligament extends from the radial border of the
index finger to the ulnar border of the small finger. Ulnarly, the
natatory ligament divides to envelop the abductor digiti minimi
(ADM) and the ulnar neurovascular bundle. Radially, the
natatory ligament is continuous with the distal commissural
ligament of Grapow within the frst webspace.

28. • The vertical fibers connect the superficial palmar aponeurosis to the
deep fascia. These fibers forma series of eight vertical septa on the
radial and ulnar sides of the flexor digital apparatus. These septa
divide longitudinal compartments containing the flexor tendons from
those containing the lumbricals and digital neurovascular bundles.
• Additional vertical fibers connect the superficial palmar fascia
to the overlying dermis, providing resistance to shear forces
within the palm

30. • Retaining ligaments of fingers ( Digital Fascia)
• Stabilize skin and extensor mechanism of digits and support
neurovascular bundles
• more variable in the anatomy
• Grayson’s ligament
• Cleland’s ligament
• Transverse retinacular ligament: originate from the volar capsule of
the PIP joint and course dorsally to insert into the lateral margin of the
extensor mechanism
• Oblique retinacular ligament (ligament of Landsmeer):
Originates on volar aspect of middle phalanx and inserts on dorsal aspect
of distal phalanx. Helps coordinate PIP joint and DIP joint motion

32. Deep Fascial Spaces
• Potential spaces that can be sites of infection
• Midpalmar space
• Thenar space
• Hypothenar space
• Interdigital web space
• Parona’s space

33. Fasciotomy
Ten compartments + Carpal tunnel:
• 7 interossei
• 1 adductor polices
• 1 thenar + 1 hypothenar

34. Synovial sheaths
The synovial sheaths
are closed sacs
around the tendons
composed of a visceral
layer on the tendon
surface and a parietal
layer on the fibrous
sheath surface.

35. • The thumb synovial sheath is continuous from the wrist to the
distal extreme of the flexor pollicis longus.
• The digital synovial sheaths for the index, long, and ring fingers
usually start at the level of the distal palmar crease and extend to
the distal interphalangeal joints.
• Often the little-finger sheath extends more proximally to
communicate with a common sheath around the finger flexors and
then across the wrist to the distal forearm, where tendons pass
through the carpal tunnel.

36. • Gliding
• Nutrition

37. In the thumb and little finger, the infection can spread within the
sheath into the distal forearm because of the continuation of the
sheath (radial bursa around FPL, ulnar bursa around little finger
tendons)

38. Muscle Tendon Units
• Extrinsic Flexors
• Pulley system
• Thenar and Hypothenar Muscles
• Extensor mechanism

39. • There are 12 flexor tendons in the hand and forearm. Common
flexor group arises near the medial epicondyle .
• Nine flexors passes under the flexor retinaculum to reach the hand
• The long flexors to the fingers ( FDP, FDS) are responsible
for flexion of the interphalangeal joints and are supplements
to active flexion of the metacarpophalangeal joints and the
wrist joint

40. Finger flexors
▪ Flexor digitorum superficialis (FDS)
○ Separate muscle belly origin, allowing independent finger
motion
○ Tendons superficial to the flexor digitorum profundus (FDP)
tendons up to their bifurcation into slips at the
metacarpophalangeal (MCP) joint, where they travel around the
FDP tendon, dive deep, rejoin to form Camper's chiasm, and
insert onto the middle phalanx
○ Flexes the proximal interphalangeal (PIP) joint

41. ▪ FDP
○ Common muscle belly origin
♦ Because of this common origin of the middle ,ring and little,
shortening of FDP tendon or overtightening of repair can lead
to decreased grip strength and decreased flexion of the
uninjured digits (“quadrigia” effect).
○ Inserts into the volar aspect of the distal phalanx
○ Flexes the distal interphalangeal (DIP) joint

42. FDP test

43. FDS test

44. FDS test

45. ▪ Flexor pollicis longus (FPL)
○ Arises from the midaspect of the
radial shaft and interosseous
membrane
○ The only tendon inside the flexor
sheath of the thumb; inserts onto
the distal phalanx
○ Flexes the thumb interphalangeal
(IP) joint

48. Zones Of Flexor Tendon Injuries

49. Pulley System

50. • Muscle excursion is defined as the distance a muscle can shorten
and is proportional to fiber length.
• The joint moment arm is the perpendicular distance between the
joint center rotation and the central longitudinal axis of the tendon
• The larger the moment arm, the greater the tendon excursion must
be to produce a given angle of joint rotation

51. Wrist Flexors
Flexor carpi radialis (FCR)
○ Inserts onto the base of the 2nd and 3rd metacarpals
Prime Wrist Flexor
▪ Flexor carpi ulnaris (FCU)
○ Inserts onto the base of the 5th metacarpal, hook of hamate, and
pisiform
Stability of DRUJ
○ Overlies ulnar artery and nerve
♦ Laceration to FCU is concerning for injury to the ulnar a. and n.
▪ Palmaris longus (PL)
○ Absent in ~15% to 20%
○ Ends in the fan-shaped palmar fascia
○ Lies volar to median nerve traveling within carpal canal
○ Lacerations to PL are concerning for median nerve laceration.

53. Thenar and Hypothenar Muscles
of the Hand

57. Questions and Comments

59. Thank You !