Bones and Joints of Hand

Carpal bones

The wrist bones ( ossa carpi ) are made up of two rows of small bones, each row of four:

• proximal row – (mediolaterally, ulnoradially) pisiform, triquetrum, lunate, scaphoid ;
• distal row – (mediolateral, ulnoradial) os hamatum, capitate, trapezoid, trapezium .

The proximal row participates in the radioulnar articulation. The distal row is attached to the metacarpal bones .

The carpal bones form the bony base of the carpal tunnel , through which the tendons of the flexor digitorum superficialis et profundus muscles and the median nerve pass , which is often compressed here ( carpal tunnel syndrome ). Carpal bones

Proximal row

The pisiform

Pea bone. It is the shape and size of a pea. It develops as a sesamoid bone in the tendon of the ulnar flexor of the wrist .

The triquetrum

Triangular bone. It has the shape of an irregular tetrahedron.

The lunate Bone

The lunate bone. Its shape resembles a crescent moon.

The scaphoid bone

The scaphoid bone (not to be confused with the os naviculare on the tarsus ). Its shape remotely resembles a boat, the depression is turned medially . It is the largest bone of the proximal row. It bears the tuberculum ossis scaphoidei . (unfortunately, the English version of the picture contains the aforementioned error - naviculare x scaphoideum)

Distal row

Hooked mouth

Hamal bone. It has a triangular shape. The hamulus ossis hamati (hook) protrudes prominently from it.

Capped mouth

Capitula. The largest carpal bone. The proximally directed part is called the caput ossis capitati and fits into the proximal row between the lunate and scaphoid bones .

Trapezoidal bone/Polygonal bone less

A small, polygonal, or scarf-shaped bone. Its shape resembles the letter L ( shoe ), and in sagittal cross-section it has the shape of a pyramid with its base turned towards the dorsum of the hand .

Trapezoidal face/Major polygonal face

A large polygonal bone. It has a similar shape to the trapezoid bone , but is larger. Laterodorsally, there is a prominent saddle-shaped surface for articulation with the first (thumb) metacarpal bone.

Metacarpal bones

Metacarpals of the left hand Metacarpal fracture

The skeleton of the hand ( metacarpus ) is made up of five bones ( ossa metacarpi ). These bones are similar in shape to long bones, but are short bones (about 10 cm). They are located between the carpal bones (carpus) and the phalanges, where they are connected to both the carpal bones and the phalanges. All joints are strengthened by ligaments on both sides. Each of the bones has its own characteristic feature, for example, the os metacarpi I is the shortest. We distinguish three parts:

• basis – proximal widened end with articular fossa, attaches to the carpus ;
• corpus – body (corresponds to the diaphysis);
• caput – distal extension of the bone, on which the ossa digitorum attach.

All bones are well palpable from the dorsal side. They are numbered from I. to V. in the radioulnar direction.

Finger bones

Ossa digitorum – finger bones

Ossa digitorum – finger bones

The skeleton of the fingers is made up of the ossa digitorum (manus) or phalanges , the joints of the fingers (hand), which are two on the thumb and three on the other fingers. Three main sections are distinguished on each joint:

• basis phalangis , base of the joint – wider proximal section,
• corpus phalangis , body of the joint – the middle, slimmer part,
• caput phalangis , the head with which the joint ends distally.

The bases of the joints are transversely widened, on the proximal side there is a concave articular surface for the adjacent bone (see below). The bodies of the phalanges are dorsally slightly convex, palmarly straight to slightly concave. The heads are convex surfaces of the roller joints with a corresponding groove; the corresponding guide rail is on the base of the following joint.

The articles vary depending on the position of the finger:

• Phalanx proximalis (prima) is the longest, the bases of the proximal phalanxes have a proximally oval-shaped fossa for the head of the metacarpal .
• The middle phalanx (secunda) is shorter than the first joint, and has fine ridges on the edges for the attachment of flexor tendons. The thumb does not have a middle phalanx.
• The distal phalanx (tertia) is the shortest; on the palmar side near the base it has a roughened place for the tendon of the long flexor digitorum; distally it ends with an expansion - tuberositas phalangis distalis is a roughening on the palmar side of the final expansion of the distal joints and is attached to a dense ligament that fills the distal end of the fingertip.

All joints are palpable , especially from the dorsal side. Of the distal joints, only the base is palpable.

Hand joints

The articulationes manus include the following joints:

Radiocarpal articulation

• articulating surfaces: facies articularis carpalis radii, proximal row of ossa carpi ( os scaphoideum , os lunatum , os triquetrum ), discus articularis
• The radius articulates directly with the ossa carpi.
• between the ulna and the carpal bone is the discus articularis
• meniscal process

Articulatio mediocarpalis

• articulating surfaces: scaphoid bone, lunate bone, triquetrum bone form a fossa for capitate bone , hamate bone ; trapezium bone , trapezoid bone form a fossa for distal part of scaphoid bone
• horizontal S shape

Pisiform bone articulation

• stiff joint
• articulating surfaces: pisiform bone , triquetrum bone
• The tendon of the flexor carpi ulnaris muscle emerges from the pisiform axis.
• The tendon of the flexor carpi ulnaris muscle divides into 2 ligaments

1. lig. pisohamatum (k hook bone hook)
2. pisometacarpal ligament (to the base of the 4th + 5th metacarpal)

Articulationes intercarpales

• joints with little mobility between the carpal bones of one row
• interosseous intercarpal ligament

Articulationes carpometacarpales

• articulating surfaces: distal row of carpal bones, base of metacarpal bones

Art. carpometacarpal thumb

• saddle joint
• articulating surfaces: basis of metacarpal bone I, trapezium bone
• movements: palmar flexion, dorsiflexion, abduction, adduction, rotation, opposition, reposition

Articulationes intermetacarpales

• joint of the 2nd–5th metacarpal
• interosseous metacarpal ligament

Xray of right hand

References

• ČIHÁK, Radomír.  Anatomy 1.  2nd edition. Prague: Grada, 2001. 516 pp.