ARTICLES ON HUMAN ANATOMY, BONES OF THE UPPERLIMB (PHALANGES)

INTRODUCTION

The phalanges are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones.

The type of bones which form the skeleton of digits i.e. the fingers and toes of the body are primarily known as phalanges bones. The human body has a total of fifty-six phalanges, with three phalanges for each finger and toes except for two phalanges per thumb and large toes in feet. The phalanges are normally linked with each other at hinge-like inter-phalangeal joints which is for extension purpose. In many cases, the phalange bones are fused with each other. 

Structure

The phalanges are the bones that make up the fingers of the hand and the toes of the foot. There are 56 phalanges in the human body, with fourteen on each hand and foot. Three phalanges are present on each finger and toe, with the exception of the thumb and large toe, which possess only two. The middle and far phalanges of the fourth and fifth toes are often fused together (symphalangism). The phalanges of the hand are commonly known as the finger bones. The phalanges of the foot differ from the hand in that they are often shorter and more compressed, especially in the proximal phalanges, those closest to the body.

A phalanx is named according to whether is are proximal, middle, or distal and its associated finger or toe. The proximal phalanges are those that are closest to the hand or foot. In the hand, the prominent, knobby ends of the phalanges are known as knuckles. The proximal phalanges join with the metacarpals of the hand or metatarsals of the foot at the metacarpophalangeal joint or metatarsophalangeal joint. The intermediate phalanx is not only intermediate in location, but usually also in size. The thumb and large toe do not possess a middle phalanx. The distal phalanges are the bones at the tips of the fingers or toes. The proximal, intermediate, and distal phalanges articulate with one another through interphalangeal articulations.

Bone anatomy

Each phalanx consists of a central part, called the body, and two extremities.

• The body is flat on either side, concave on the palmar surface, and convex on the dorsal surface. Its sides are marked with rough areas giving attachment to fibrous sheaths of flexor tendons. It tapers from above downwards.
• The proximal extremities of the bones of the first row present oval, concave articular surfaces, broader from side to side than from front to back. The proximal extremity of each of the bones of the second and third rows presents a double concavity separated by a median ridge.
• The distal extremities are smaller than the proximal, and each ends in two condyles (knuckles) separated by a shallow groove; the articular surface extends farther on the palmar than on the dorsal surface, a condition best marked in the bones of the first row.

In the foot, the proximal phalanges have a body that is compressed from side to side, convex above, and concave below. The base is concave, and the head presents a trochlear surface for articulation with the second phalanx. The middle are remarkably small and short, but rather broader than the proximal. The distal phalanges, as compared with the distal phalanges of the finger, are smaller and are flattened from above downward; each presents a broad base for articulation with the corresponding bone of the second row, and an expanded distal extremity for the support of the nail and end of the toe.

Distal phalanx

In the hand, the distal phalanges are flat on their palmar surface, small, and with a roughened, elevated surface of horseshoe form on the palmar surface, supporting the finger pulp. The flat, wide expansions found at the tips of the distal phalanges are called apical tufts. They support the fingertip pads and nails. The phalanx of the thumb has a pronounced insertion for the flexor pollicis longus (asymmetric towards the radial side), an ungual fossa, and a pair of unequal ungual spines (the ulnar being more prominent). This asymmetry is necessary to ensure that the thumb pulp is always facing the pulps of the other digits, an osteological configuration which provides the maximum contact surface with held objects.

In the foot, the distal phalanges are flat on their dorsal surface. It is largest proximally and tapers to the distal end. The proximal part of the phalnx presents a broad base for articulation with the middle phalanx, and an expanded distal extremity for the support of the nail and end of the toe. The phalanx ends in a crescent-shaped rough cap of bone epiphysis — the apical tuft (or ungual tuberosity/process) which covers a larger portion of the phalanx on the volar side than on the dorsal side. Two lateral ungual spines project proximally from the apical tuft. Near the base of the shaft are two lateral tubercles. Between these a V-shaped ridge extending proximally serves for the insertion of the flexor pollicis longus. Another ridge at the base serves for the insertion of the extensor aponeurosis. The flexor insertion is sided by two fossae — the ungual fossa distally and the proximopalmar fossa proximally.

Development

The number of phalanges in animals is often expressed as a "phalangeal formula" that indicates the numbers of phalanges in digits, beginning from the innermost medial or proximal. For example, humans have a 2-3-3-3-3 formula for the hand, meaning that the thumb has two phalanges, whilst the other fingers each have three.

In the distal phalanges of the hand the centres for the bodies appear at the distal extremities of the phalanges, instead of at the middle of the bodies, as in the other phalanges. Moreover, of all the bones of the hand, the distal phalanges are the first to ossify.

Function 

The distal phalanges of ungulates carry and shape nails and claws and these in primates are referred to as the ungual phalanges.

CLINICAL SIGNIFICANCE

Usual accidents or traumas can cause clinical fractures which can cause temporary to permanent impairment in these areas. The common injuries to proximal phalanges range from fractures related to connecting limbs or dislocation of connecting joints. They are most commonly treated with plaster of Paris bandages for stability and recovery of the original condition of the bone structures and links and are also treated with screw insertions wherever necessary. The usual screw Insertion surgeries include the usage of anesthetics and analgesics to reduce pain in the injured area. The area is usually suspended to immobilization till the original alignment of the said bone is not fully recovered.

A fracture can be of numerous types ranging from a hairline fracture to a dislocation or a complete breakage of a single phalangeal digit based upon your accidental injury to the digital skeleton. Based on the level of injury, your orthopedic surgeon will immobilize your injured area with a plaster of paris base bandage and will tell you about the possible recovery period. This can range from a couple of weeks to a couple of months totally dependent on your injury and recovery capability of your body. But we assure that you don’t have a reason to worry at all. 

An injury to your phalanges can be fatal and can possibly leave you immobilized permanently. It is best to visit an orthopedic surgeon to get yourself diagnosed and treated if you face an injury. They usually prescribe a screening test from a range of X-Ray to MRI (Magnetic Resonance Imaging) depending upon the type of your injury. Generally, people find it scary to undergo these screening tests due to the fear of exposure of oncogenic X-Rays but once in a whole exposure to these rays doesn’t really cause a harm. Besides, they are important to get your diagnosed.

Not all the pains in the fingers and toe areas are a result of phalangeal injury but ignoring them can be fatal for your locomotion and movement. They can also be a resit of muscle injury but the pain can cause inflammation your tendons which in turn connects to your phalanges, so an appointment with an orthopedic surgeon would be the best option to medically recover from the pain.