Anatomy of the wrist: overview, rough anatomy, natural variants (2023)

The anatomical connection between the distal forearm and the hand consists of 15 bones: 8 carpal bones, the distal radius and ulna, and the base of the 5 metacarpals.

carpal bones

The carpal bones are divided into two groups, a proximal row and a distal row. The proximal row is at the level of the distal carpal crease and includes the scaphoid, lunate, triquetrum, and pisiform bone. The second row of carpal bones, the distal row, consists of the trapezium, trapezoid, capitate, and hamate; The distal row articulates with the bases of the 5 metacarpal bones. The bones of the proximal carpal row represent an intermediate segment, as they are not attached to any tendons.[10]Because of this, their movements are entirely dependent on mechanical forces from surrounding joints.

The bones in the distal row are closely attached to each other via intercarpal ligaments (see images below). These bones are also closely related to the metacarpal bones that make up the carpometacarpal (CMC) joint. In particular, the ligamentous connection between the trapezium and capitate to the index finger (second finger) and middle finger (third finger), respectively, is so stiff that the distal carpal row has been considered part of a fixed hand unit that moves in response to muscle-tendon forces exerted starting from the forearm.[11]

Wrist ligaments, rear view.

If medieval galleries

Volar wrist ligaments.

If medieval galleries

The wrist is surrounded by a fibrous capsule and is held together by a series of ligaments that provide stability at the carpal joint by connecting the bones both dorsally and volarly (see images below). These carpal ligaments are divided into two groups: intrinsic ligaments, which arise from and insert into the carpal bones, and external ligaments, which connect the carpal bones to the radius or metacarpal bones.[12]

Ligaments in the wrist, palmar view.

If medieval galleries

Ligaments of the wrist, posterior (dorsal) view.

If medieval galleries

outer ligament, volar

Volume of the Radioscaphocapitum

The radioscaphocapitate ligament, located ulnar to the radial collateral ligament, arises from the radial styloid process, passes below the waist of the navicular bone, and inserts at the capitate, creating a loop to support the navicular bone.[1]

Long radiolunar band

The long radiolunar band arises at the distal radius of the volar aspect of the scaphoid fossa. The proximal attachment is partially overlapped by the radioscaphocapitate ligament. It inserts radially at the distal surface of the lunate bone and at the volar segment of the scapholunate interosseous ligament without directly attaching to the scaphoid. The long radiolunar band provides stability to prevent ulnar or distal translocation of the lunate. Poirier's space represents an area of ​​weakness between the long radiolunate and radioscaphocapitate ligaments at the level of the heel of the metatarsus.[1]

Short radiolunar band

The short radiolunate ligament arises at the distal radius at the ulnar and volar margins of the lunate fossa and inserts into the volar aspect of the lunate fossa. Its insertion is proximal to the insertion of the ulnolunar ligament. The short radiolunar band may play a role in lunar stabilization.[1, 13]

Radioscapholunate Band

The radioscapholunate ligament is located between the long and short radiolunate ligaments of the distal radius in the region spanning the scaphoid and lunate fossa. The radioscapholunate ligament inserts distally between the volar and proximal segments of the scapholunate interosseous ligament on both the navicular and lunate bones.

This ligament is not considered a true ligament because it consists of vascular and nerve elements and no ligamentous tissue.[13]Because of this, it doesn't offer any significant mechanical support.[1]

ulnolunar ligament

The origin of the ulnolunate ligament is radial to the ulnocapitate ligament at the base of the ulnar styloid process. It inserts distally on the ulnar side of the lunate, distal to the insertion of the short radiolunate ligament.[1]

Ulnocapitatum-Band

The ulnocapitate ligament is attached proximally to the fovea of ​​the ulnar head, with its insertion attached distally to the proximal and volar regions of the capitate (see figure below).[1]

Volar carpal joints and bones. AIA = anterior interosseous artery; C = head; CH = capitohamate; H = hamate; L= crazy; LRL = long radiolunar band; P = small form; PRU = palmar radioulnar band; R = radius; RA = radial artery; RSC = radioscapholunate band; S = scaphoid; SC = scaphocapitate ligament; SRL = short radiolunar band; T = triquetrum; TC = triquetrocapitate ligament; Td = trapezoid; TH = triquetrohamate band; Tm = trapezoid; TT = trapezius band; U = ulna; UC = ulnocarpal ligament; UL = ulnolunate ligament; UT = ulnotriquetral ligament.

If medieval galleries

Outer ligaments, dorsal

intercarpal ligaments

The intercarpal ligaments are secondary stabilizers of the scapholunate.[1]

radiocarpal ligaments

The radiocarpal ligament arises in the ulnar and dorsal part of the distal radius between the radial dorsal tubercle (Lister) and the crest between the scaphoid and lunate fossa. It inserts distally at the proximal and dorsal tubercles of the triquetrum and lunate.[1]

Own ligaments, volar

Lunotriquetrales Band

The lunotriquetral ligament arises on the ulnar side of the lunate bone and inserts on the triquetrum distal to the insertion of the ulnolunate ligament and radial to the lunotriquetral interosseous ligament.[1]

Trapeziotrapezoidband

The trapezoid ligament inserts on the ulnar side of the trapezium and runs ulnar to the radial edge of the trapezium.[1]

Scaphotrapezialband

Consisting of two branches, a radial branch and an ulnar branch, both branches of the scaphotrapezial ligament are attached to the radial and volar aspect of the scaphoid tubercle. The two branches move distally and diverge in a V-shape. The radial branch inserts on the radial side of the trapezius, while the ulnar branch inserts on the proximal side.[1]

Scapotrapezoidband

Together with the scaphotrapezial ligament, the scaphotrapezial ligament supports the scaphotrapezial joints. It is attached to the distal and volar aspect of the scaphoid tuberosity and inserted distally at the proximal border of the trapezium.[1]

A ligament of the scaphocapita

The scaphocapitate ligament inserts radially on the ulnar and volar aspect of the distal pole of the scaphoid and ulnarly on the radial and volar aspect of the capitate.[1]

Capitotrapezband

The capitotrapezoid ligament arises on the ulnar and volar aspects of the trapezium and spans the trapezium to insert on the radial and volar aspects of the capitate.[1]

Capitohamatband

The ligamentum capitohamum inserts at the ulnar region of the os capitatum and runs ulnar to the radial border of the hamate.[1]

The trigeminal ligament

The triquetrocapitate ligament inserts proximally at the volar and radial border of the triquetrum and distally at the ulnar and volar border of the capitate.[1]

Triquetrohamatband

The triquetrohamate ligament inserts proximally at the distal border of the triquetrum and distally at the dorsal border of the hamate. There are three types of relationships between the triquetrocapitate and triquetrohamate bands:

  • Type A: Triquetrocapitate bands separate from triquetrohamate bands

  • Type B: Triquetrocapitate ligaments overlap triquetrohamate ligaments

  • Type C: The triquetrocapitate ligament has an additional ligament from the triquetrum to the proximal pole of the hamate

Inner ligaments, dorsal

Interkarpales Band

The intercarpal ligament overlaps the dorsal portion of the scapholunate interosseous ligament, with its origin being at the distal and radial portion of the dorsal tubercle of the triquetrum. The dorsal intercarpal and dorsal radiocarpal ligaments form a lateral "V" configuration with the apex toward the triquetrum that provides indirect dorsal stability to the scapholunate complex during wrist movement.[14]Together with the radiocarpal ligament, the intercarpal ligament provides stability and alignment of the carpal bone while preventing dorsal intercalated segment instability (DISI) and volar intercalated segment instability (VISI) deformities.[1]

Trapeziotrapezoidband

The trapezoid ligament is located at the ulnar edge of the trapezium and runs ulnar to the radial edge of the trapezium.[1]

Capitotrapezband

The capitotrapezoid ligament is attached to the ulnar border of the trapezoid and runs ulnar to the distal and radial part of the capitate.[1]

Capitohamatband

The distal component of the capitohamate ligament consists of distal and proximal ligaments and arises on the distal aspect of the ulnar border of the capitate and inserts on the distal aspect of the radial border of the hamate. The proximal ligament arises at the ulnar border of the capitate and inserts at the proximal aspect of the radial border of the hamate.[1]

Triquetrohamatband

The triquetrohamatus ligament attaches proximally to the distal and radial border of the triquetrum and inserts distally to the proximal and volar border of the hamate.[1]

interosseous ligaments

scapholunate ligament

The scapholunate ligament connects the scaphoid and lunate bone along the proximal articular surface and is the primary stabilizer of the scapholunate joint. It consists of 3 structures: (1) a volar portion, (2) a dorsal portion, and (3) a proximal portion. The dorsal portion is the thickest of the three structures and is the most critical stabilizer of the shoulder joint.[15, 16]The disruption of the ligament allows the lunate to expand when the scaphoid flexes, resulting in a dorsal intercalated segment instability (DISI) deformity (see figure below).[1, 17]

Dorsal/volar intercalated segmental instability (DISI/VISI).

If medieval galleries

Lunotriquetrales Band

The lunotriquetral ligament connects the lunate bone and the triquetrum along the proximal articular surface. Similar to the scapholunate interosseous joint, this ligament has three distinct structures: (1) a volar portion, (2) a dorsal portion, and (3) a proximal portion. Damage to the lunotriquetral ligament allows flexion of the lunate bone with the scaphoid normally aligned, creating a volar intercalated segmental instability deformity (VISI) (see figure above).[1, 17]

Trapeziotrapezoidband

The trapeziotrapezoid ligament connects the trapezius and trapezium. It resides entirely within the trapezoid joint, inserting on the volar aspect of the ulnar aspect of the trapezoid and traveling ulnar to the distal radial border of the trapezoid.[1]

Capitotrapezband

Like the interosseous trapezoid ligament, the capitotrapezoid ligament is located in the joint space. It attaches the head to the trapezius. This ligament runs from the central area of ​​the ulnar aspect of the trapezoid to the distal, radial aspect of the capitate.[1]

Capitohamatband

The capitohamic ligament runs from the mid-ulnar side of the capitate bone to the radial side of the hamate. This ligament is entirely within the joint.[1]

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