Proximal phalanx is the one which is closest to the palm of hand. It is attached to the metacarpals (bones of the palm of hand) and makes metacarpophalangeal joint. Middle Phalanx is absent in the thumb and is only present in the fingers. It is attached to proximal phalanx at one end and to distal phalanx at other end. The joints made by these phalanges are known as interphalangeal joints. Each phalanx has articular surfaces at both ends and a middle shaft in between. The distal phalanges often carry nails so they are termed as ungual phalanges.

Each phalanx has got three got three parts: body, proximal extremity and distal extremity.

• The body of each phalanx has got flat structure on either sides. It has two surfaces i.e. palmar and dorsal surface. Palmar surface is concave and dorsal surface is convex in architecture.

• The proximal extremities of all three layers of phalanges i.e. first, second and third layer, present articular facets (features indicating the articulation of phalanges with other bones). In the first row of bones, these facets are oval and concave in architecture. However, these facets have similar structure in the second and third row of phalanges. In these rows these facets are double concave that separated from each other by the means of a median ridge.

• The distal extremities of only the first and second layer of phalanges present articular facets. The distal extremities of the third layer of bones are free and smooth, since this end of bones is free. Generally, the distal extremities of the phalanges of hands are smaller than the proximal extremities. All the distal extremities end into two knuckles (condyles) that are separated by a shallow groove. The articular facets of these bones tend to extend more on the palmar surface than on the dorsal surface. This feature is more marked in the first row of phalanges.

FUNCTION 

• The function of phalanges is to produce fine and skilled movements of the hands.
• They allow the hands to grip, hold, write and perform all those movements due to which humans are considered at higher level than other mammals.
• Distal phalanges support the muscles which are rich in nerve supply and produce sensitive feelings of touch which are transmitted to the brain.
• Terminal phalanges also contain the apical tufts, which support the fingernails.

CLINICAL SIGNIFICANCE 

• Fingers are at higher risk of injuries than other parts of hands, that is why phalanges are often fractured.

• Distal phalanx is the most fractured bone in the hand.

• Nail bed injuries are also common in the fractures of the distal phalanx.

• Conditions such as osteoporosis and malnutrition are important causes of the fractures of phalanges.

• Defects in the formation of phalanges are present sometimes by birth. These are termed as congenital deformities in which shape and size of the finger is usually abnormal.

• Sometimes there are more than five digits present by birth, it is termed as polydactyly.