triquetral bone

{{Infobox bone

| Name = Triquetral bone

| Latin = os triquetrum, os pyramidale

| Image = Triangular bone (left hand) 01 palmar view.png

| Caption = Left hand anterior view (palmar view). Triquetral bone shown in red.

| Image2 = Gray223.png

| Caption2 = The left triquetal bone

| Origins =

| Insertions =

| Articulations = Articulates with three bones:
lunate laterally
pisiform in front
hamate distally
triangular articular disk which separates it from the lower end of the ulna.

}}

The triquetral bone ({{IPAc-en|t|r|ai|'|k|w|E|t|r|@l|,_|-|'|k|w|i:|-}}; also called triquetrum, pyramidal, three-faced, and formerly cuneiform bone) is located in the wrist on the medial side of the proximal row of the carpus between the lunate and pisiform bones. It is on the ulnar side of the hand, but does not directly articulate with the ulna. Instead, it is connected to and articulates with the ulna through the Triangular fibrocartilage discManaster, B. J., Julia Crim "Imaging Anatomy: Musculoskeletal E-Book" Elsevier Health Sciences, 2016, p. 326. and ligament, which forms part of the ulnocarpal joint capsule.{{cite web |url=https://radiopaedia.org/articles/ulnotriquetral-ligament?lang=us |title=Ulnotriquetral ligament |last=Feger |first=Joachim |website=radiopedia.org |access-date=September 28, 2022}} It connects with the pisiform, hamate, and lunate bones. It is the 2nd most commonly fractured carpal bone.

Structure

The triquetral is one of the eight carpal bones of the hand. It is a three-faced bone found within the proximal row of carpal bones. Situated beneath the pisiform, it is one of the carpal bones that form the carpal arch, within which lies the carpal tunnel.

{{cite book|last=Drake|first=Richard L.|title=Gray's anatomy for students|year=2005|publisher=Elsevier/Churchill Livingstone|location=Philadelphia|isbn=978-0-8089-2306-0|author2=Vogl, Wayne |author3=Tibbitts, Adam W.M. Mitchell |author4=illustrations by Richard |author5= Richardson, Paul }}{{rp|708}}

The triquetral bone may be distinguished by its pyramidal shape, and by an oval isolated facet for articulation with the pisiform bone. It is situated at the upper and ulnar side of the carpus. To facilitate its palpation in an exam, the hand must be radially deviated so that the triquetrium moves out from under the ulnar styloid process. The triquetrum may be difficult to find, since it also lies under the pisiform.

The triquetral bone has nutrient foramina for entering the nutrient vessels into the bone which comes from branches of the radial, ulnar, and interosseous arteries.{{cite journal |last1=balci |first1=aybegum |title=The morphologic and morphometric features of the triquetrum |journal=Hand Surgery and Rehabilitation |date=1 November 2022 |volume=42 |issue=1 |pages=40–44 |doi=10.1016/j.hansur.2022.11.002}}

Ossification

The triquetral bone ossifies between 9 months and 50 months (4 years and 2 months).{{cite journal|last1=Balachandran|first1=Ajay|last2=Kartha|first2=Moumitha|last3=Krishna|first3=Anooj|last4=Thomas|first4=Jerry|last5=K|first5=Prathilash|last6=TN|first6=Prem|last7=GK|first7=Libu|last8=B|first8=Krishnan|last9=John|first9=Liza|title=A Study of Ossification of Capitate, Hamate, Triquetral & Lunate in Forensic Age Estimation|journal=Indian Journal of Forensic Medicine & Toxicology|date=2014|volume=8|issue=2|pages=218–224|doi=10.5958/0973-9130.2014.00720.8|url=http://www.indianjournals.com/ijor.aspx?target=ijor:ijfmt&volume=8&issue=2&article=052|access-date=18 August 2014|issn=0973-9130|url-access=subscription}}

=Surfaces=

The superior surface presents a medial, rough, non-articular portion, and a lateral convex articular portion which articulates with the triangular articular disk of the wrist.

The inferior surface, directed lateralward, is concave, sinuously curved, and smooth for articulation with the hamate. The dorsal surface is rough for the attachment of ligaments.

The volar surface presents, on its medial part, an oval facet, for articulation with the pisiform; its lateral part is rough for ligamentous attachment.

The lateral surface, the base of the pyramid, is marked by a flat, quadrilateral facet, for articulation with the lunate.

The medial surface, the summit of the pyramid, is pointed and roughened, for the attachment of the ulnar collateral ligament of the wrist.

=In animals=

In reptiles and amphibians, the bone is instead referred to as the ulnare, since (at least in the most primitive fossils) it articulates with the ulna.

Function

The carpal bones function as a unit to provide a bony superstructure for the hand. {{rp|708}}

Fracture

Triquetral fractures can occur due to forceful flexion of the wrist, causing an avulsion of the dorsal aspect of the bone that is often hidden on anterior radiographs, but can be seen as a tiny bone fragment on lateral views.

Etymology

The etymology derives from the Latin triquetrus which means "three-cornered." Therefore, it is sometimes also called the triangular bone or os triangulare. However, os triangulare may also refer to a nearby accessory bone.

Additional images

File:Triangular bone (left hand) - animation01.gif|Triquetral bone of the left hand (shown in red). Animation.

File:Triangular bone (left hand) - animation02.gif|Triquetral bone of the left hand. Close up. Animation.

File:Triquetral bone.jpg|Triquetral bone.

File:RightHumanPosteriorDistalRadiusUlnaCarpals - Triquetral bone.png|Right hand posterior view (dorsal view). Thumb on bottom.

File:RightHumanAnteriorDistalRadiusUlnaCarpals - Triquetral bone.png|Right hand anterior view (palmar view). Thumb on top.

File:Gray219 - Triangular bone.png|Bones of the left hand. Palmar surface. Triquetral shown in yellow.

File:Gray220- Triangular bone.png|Bones of the left hand. Dorsal surface. Triquetral shown in yellow.

File:Ospoignet - Triquetral bone.png|Cross section of wrist (thumb on left). Triquetral shown in red.

File:Dorsale Triquetrumabsprengung - CT VRT with arrow.png|Triquetral fracture indicated by the white arrow.

File:TriQFracture.PNG|Triquetral fracture as seen on lateral view of a radiograph.