Anatomy of the hand

dorsal palmar

•the skin of the palm is thick and anchored.

•the flexure lines associated with cutaneous movement (which do not necessarily indicate the sites of joints)

the skin of the dorsum is thin and mobile(allowing accumulation of fluid subcutaneously)

•The subcutaneous fat that constitutes the tips of the fingers is loculated by fibrous septa and occupies a closed pulp space which is liable to infection ( whitlow) from a penetrating wound.

•the fingerprints, and the nails.

whitlow

This may be followed by the damageto the distal phalanx

owing to the interruption of its blood supply

Palmar aponeurosis

• Thickened deep fascia.• Triangular with the apex

continuous with palmaris longus.

• Splits into 4 processes to the medial 4fingers.

• Protects the tendons,blood vessels and nerves that lie deep to it

In the olden days, the palm is said to be containing a mid palmar space and a thenar space where pus can be accumulated. This view is discarded now.

“Dupuytren's contracture” of one or more fingers, especially the little and ring fingers, is commonly attributed to thickening and shortening of the palmar aponeurosis.Its causation is not really understood.

Transverse section at the wrist

Synovial sheaths

• As the digital flexor tendons pass through

• the carpal tunnel they are all enclosed in a single (common) synovial sheath.(ulnar bursa)

• The FPL has its own synovial sheath.(radial bursa)

Note the continuity between th little finger’s digital sheath with the common sheath

Space of parona

• The common synovial sheath extends in to the lower forearm into a space called “space of parona”

Untreated infection of the synovial sheaths can impair hand function

infection of the synovial sheaths of the thumb or little finger may spread readily into the palm and even into the forearm(space of parona)

Fibrous flexor sheaths

• Thick fibrous arches with cruciform ligaments convert the concavity of metacarpals and phalanges into tunnels and protect the flexors tendons from slipping.

• Inside these tunnels the tendons are enclosed in synovial sheaths.

• (digital synovial sheaths)

Insertion of FDS• Each tendon splits at

base of the middle phalanx to be inserted in to the sides of it.

• This splitting is necessary to allow the passage of FDP to the distal phalanx.

FDP

• Has 4 tendons like FDS.• From these 4 tendons, 4

lumbricals take origin• FDP is inserted in to the

distal phalanx• Hence it is capable of

flexing the both I-P joints• (FDS can flex only

proximal I-P joint)

lumbricals

• 4 small muscles originate from tendons of FDP and insert into the dorsal digital expansion.

• 1st and 2nd are supplied by median nerve.

• 3rd and 4th are by ulnar nerve.

Interossei

• 4 palmar and 4 dorsal interossei

• Palmar interossei produce adduction of fingers (PAD)

• Dorsal interossei produce abduction of fingers(DAB)

• Middle finger is the reference point

• (axis finger)

• Palmar interossei are 4 in number but the fingers are 5.

• How to distribute?

•Middle finger does not have palmar interosseous.

Dorsal interossei are 4 in number and fingers are 5.How to distribute?

Middle finger has 2.(index 1,ring finger 1)

Thumb and little finger do not have any.

Extensor expansion (dorsal digital expansion)

Problems occur when the central slip is damaged, as can happen with a tear.

1.Ulnar nerve 2.Median nerve 3.Radial nerve

The dorsum of the hand, sensory innervation

1.Ulnar nerve 2.Median nerve 3.Radial nerve

The palm of the hand, sensory innervation

The Z-position of the hand, produced by the interossei and lumbricals

Claw hand, due to paralysis of the interossei and lumbricals (following section of the ulnar nerve). The unopposed extensor and flexors produce the opposite of the Z-position.(extension at M-P joint and flexion atI-P joints)

(Flexion at M-P joints and extension at I-P joints)

Hand at rest