The hand (from Latin manus) is located at the end of the upper limbs. It has a role in the gripping and handling of objects and the sense of touch.

The hand is at the end of the forearm, articulated to the latter by the wrist. It has five fingers: the thumb, index, middle, ring and little fingers (little finger). It has a palmar face (the palm) and a dorsal face on which we find nails at the end of each finger.

The bones of the hand are 27 in number and are divided into three categories: carpal bones, metacarpals and phalanges.

The 8 carpal bones form the region commonly referred to as the wrist. The 8 bones are placed in two rows of 4 bones:

• The first row, made of the scaphoid, semi-lunar, pyramidal, and pisiform, articulates with the radius and ulna of the forearm.
• The second row, articulates with the metacarpals, and includes the trapezius, the trapezoid, the great bone and the hooked bone.

All these bones are articulated between them by ligaments which limit their movements.

The metacarpals form the palm of the hand. They are five, numbered I to V from the thumb to the little finger. When you clench your fist, the bony heads of the metacarpals stand out: these are the joints that are generally called joints.

The hand has 14 phalanges: three per finger (proximal, middle and distal) except for the thumb which contains only two (proximal and distal).

There are two categories of muscles that affect hand movements: extrinsic muscles, which are located in the forearm, and intrinsic muscles, which are located in the hand.

Intrinsics are inserted into the bones of the hand through tendons. On the palmar surface, we find the flexor tendons, most of which pass through a canal at the wrist, the carpal tunnel. On the dorsal side run the extensor tendons. In general, the names of the muscles indicate their activity: for example, the flexor carpi radialis muscle and the flexor digitorum superficialis muscle act on flexion of the fingers and wrist, respectively.

Intrinsic muscles allow precise movements of the fingers. We can distinguish the interosseous muscles, located between the metacarpals, which allow the fingers to be separated and brought together. On the palmar face, under the thumb, there is a rounded area: this is the thenar eminence, a muscle group dedicated to thumb movements. On the opposite side is the hypothenar eminence which groups together muscles for the mobilization of the little finger.

The hand is innervated by three main nerves: the median nerve, the radial nerve, and the ulnar nerve. The blood supply is provided mainly by the external radial artery and the internal ulnar artery which meet in the palm.

The hand, thanks to its agility and dexterity, has several roles:

• Gripping and handling function of objects.
• Exploration function of the surrounding world.
• Sensitivity function: involved in the sense of touch, it allows tact (passive) and touch (active or voluntary).
• Expression function: dumb people communicate using sign language and blind people can read braille. In sighted and hearing people, gestures and facial expressions often accompany a speech.
• Food function: the fact of carrying your hand to the butcher allows you to eat.

Carpal tunnel syndrome : manifests as numbness and tingling in the fingers, and loss of muscle strength in the affected wrist and hand. Symptoms result from compression of the median nerve in the wrist at the level of the carpal tunnel.

Arthritis : Formerly called rheumatism, it literally designates inflammation of the joints. There are two main forms:

• Osteoarthritis (or osteoarthritis): this is the most common form of arthritis. It is a chronic condition that manifests as persistent pain in the joints caused by abnormal wear and tear of the cartilage and the entire joint. Osteoarthritis of the fingers (digital osteoarthritis) is also very common, especially in women.
• Rheumatoid arthritis: it is an inflammatory disease of the joints that swell, become painful and are limited in their range of motion. Left untreated, these joints tend to gradually deform over time. The joints of the hands, wrists and feet are often the first to be affected.

Trigger finger : frequent pathology which results in a blockage of the finger when it is in flexion. It is the consequence of the thickening of a flexor tendon in the channel through which the tendon passes through the phalanges to reach the end of the fingers. The tendon becomes cramped and becomes blocked. The person then feels pain and then a blockage. The jump, a spring phenomenon, occurs when the finger is extended.

This condition can be caused by tendonitis or be the consequence of overuse of the finger during repetitive activity (gardening for example). Diabetes is a risk factor.

Dupuytren’s disease : pathology named after the surgeon who described it in 1832 which is characterized by retraction of the fingers which limits their extension. This phenomenon is the consequence of a thickening of an aponeurosis of the hand, a thin layer located under the skin and which covers the structures of the hand (bones, tendons, muscles, nerves and ligaments). This thickening causes the appearance of nodules (small balls) and bands (bands of tissue) which, over time, retract and cause flexion of the fingers. The causes of this disease are not known.

Thumb sprain : it is the relaxation or rupture of one of the ligaments of the thumb following a trauma. The most frequent accident is the ski fall: the thumb is retained by the strap which pulls it in an outward movement. The medial lateral ligament is usually the most exposed. It plays an important role in gripping gestures by stabilizing the thumb. In the event of a sprain, the joint therefore becomes unstable and the function of the thumb is impaired. The problem is resolved by immobilization or by surgery if the sprain is serious.

To protect yourself from the possible appearance of symptoms of carpal tunnel syndrome, it is possible to follow some basic preventive measures: rest your hands and wrists regularly while performing repetitive tasks, hold objects with your full hand rather than fingertips or avoiding long use of tools that vibrate strongly are examples.

Regarding osteoarthritis, there are several ways that can reduce its occurrence. Maintaining a healthy weight, for example, avoids putting too much stress on the knee joint, which is vulnerable. On the other hand, very few means are known to prevent rheumatoid arthritis.

Protecting your joints and fingers during manual activities or sports is beneficial. For gardening, for example, it is advisable to choose the right gloves. For board sports, hand and wrist protections are effective.

The most common pediatric surgical emergency is trauma to the fingertips by crushing the last phalanx. Doors or doors are the main causes (75% of cases) (5). The use of door locks or shock absorbers reduce these risks.

Physical examination : carried out by the doctor, it includes the questioning (general then focused on the symptoms that led the patient to consult) followed by the physical examination of the hand and wrist (skin, blood supply, bone structures, sensitivity and motor skills) . This examination should allow the diagnosis to be made.

X-ray : medical imaging technique that uses X-rays. It is the standard reference examination, the first mandatory step and sometimes sufficient for diagnosis.

IRM (magnetic resonance imaging): medical examination for diagnostic purposes carried out using a large cylindrical device in which a magnetic field and radio waves are produced to generate very precise images, in 2D or 3D, of parts of the body or internal organs (here the hand).

Ultrasound : medical imaging technique which is based on the use of ultrasound, inaudible sound waves, which make it possible to “visualize” the interior of the body. It is a complementary examination of the x-ray in case of doubt about the diagnosis. It has the advantage of easily studying the tendons.

Scanner : diagnostic imaging technique which consists of “scanning” a given region of the body in order to create cross-sectional images, thanks to the use of an X-ray beam. The term “scanner” is actually the name of the medical device, but it is commonly used to refer to the exam. We also speak of computed tomography or computed tomography. It is a complementary examination of the x-ray in case of doubt about the diagnosis.

Electromyogramme : complementary examination of the clinical examination, it allows the study of nerves and muscles. It is performed if there is any doubt about the diagnosis of carpal tunnel syndrome.

The hand has been an important symbol in many fields for millennia.

In Christianity, clasped hands refer to the posture of the believer at the time of prayer. It is also the hands of Christ that bear the stigmata of the crucifixion. In Islam, the khamsa (number 5), commonly called the Hand of Fatma (or Fatima) and often worn as a pendant, is seen as a protective hand to ward off attacks from the evil eye (8).

The hand is also a symbol of justice. In France, the hand of Justice was the emblem of the judicial power attributed by God, until 1792, to the kings of France (9).

In the realm of beliefs, seers or fortune tellers read the lines of the hand to predict the future of individuals. The lines designate furrows which run through the palmar face of the hand.

The hand is one of the human organs that has evolved the least. Its mobility and agility were already present in the days of the first small primates which hung from the branches of trees. These abilities were retained but the movement of all the fingers developed (10).

A hand is a kind of identity card. At the fingertips are raised papillary ridges on the skin. They form designs that are unique to each individual. The recognition of these fingerprints is a tool used by forensic scientists to identify criminals (11).