The hand - anatomy and diseases of the hand

The hand (manus) forms the lower part of the arm and serves as a gripping tool. There are a total of 27 bones in the human hand, which are connected to each other by joints with their capsules and ligaments.

The hand

The hand and forearm together form a functional unit and are connected via the wrist. Hand movements are largely triggered by muscles that come from the forearm. Only the slender tendons of the muscles are located directly in the hand. Some of the tendons are surrounded by tendon sheaths that protect them and reduce friction.

The three large hand nerves are the radial nerve (Nervus radialis), median nerve (Nervus medianis) and ulnar nerve (Nervus ulnaris).

The three areas of the hand

Three areas of the hand can be distinguished:

The carpus with 8 carpal bones (ossa carpi, carpalia):

The carpal bones are connected to each other by ligaments and arranged in two rows:

• Carpal bones in the proximal row: scaphoid bone (Os scaphoideum), lunate bone (Os lunatum), triangular bone (Os triquetrum), pea bone (Os pisiforme)
• Carpal bones in the distal row: trapezium bone (Os trapezium), trapezoid bone (Os trapezoideum), capitate bone (Os capitatum), hook bone (Os hamatum).

The metacarpal (metacarpus) with 5 metacarpal bones (ossa metacarpi):

The metacarpal bones are connected to the distal row of carpal bones via joints. The base, shaft and head of these tubular bones can be distinguished.

The 5 fingers (digiti manus) with 14 phalanges:

The five fingers are called the thumb (pollex), index finger (index), middle finger (digitus medius), ring finger (digitus anularis) and little finger (digitus minimus). The fingers (with the exception of the bipartite thumb) consist of the proximal phalanx (proximal phalanx), middle phalanx (middle phalanx) and distal phalanx (distal phalanx).

Like the metacarpal bones, the phalanges are tubular bones with a base, shaft and head. The thumb is connected to the carpal bone by the thumb-saddle joint and can therefore assume an opposition position (opposability) to the other fingers, which makes the pincer grip possible. The remaining four fingers have three finger joints with collateral ligaments.

The wrist

The wrist contains partial joints that work together as a functional unit. The human wrist consists of the proximal wrist joint between the radius and the proximal row of carpal bones and the distal wrist joint between the proximal and distal row of carpal bones.

Diseases and injuries of the hand

Common diseases of the hand are Dupuytren's disease(Dupuytren's contracture - a disease of the connective tissue of the palm of the hand in which lumps and cords appear on the inner surface of the hand) and carpal tunnel syndrome (carpal tunnel syndrome). Carpal tunnel syndrome is one of the nerve compression syndromes (bottleneck syndromes); in this case, the metacarpal nerve is trapped in the flexor-sided wrist canal (carpal tunnel).

Another condition that can occur in the hand is Raynaud's syndrome, in which the fingers or toes suddenly become cold or numb. The fingers are more frequently affected. Due to disorders in the small blood vessels, the blood supply to the limbs is reduced in this condition.

Frequent fractures in the hand area are the scaphoid fract ure, which often occurs when a fall is intercepted with an outstretched hand, but is then often misinterpreted by the patient as a sprain, and the fracture of the radius near the hand(radius fracture).

Nerve injuries to the hand and forearm are also not uncommon. They are usually caused by cuts. Tendon disorders are also common in the hand(snapping finger or tendovaginitis de Quervain, a special form of tendon sheath inflammation).

The hand can be affected by arthrosis (especially thumb saddle joint arthrosis or rhizarthrosis) as well as rheumatism.