What is the Capitate Bone?
The capitate bone, also known as Os capitatum in Latin, is one of the eight carpal or wrist bones in the human hand [1]. It is categorized as a short bone [2] and holds the distinction of being the largest among all the carpal bones [3].
The upper part of the capitate, which is situated toward the metacarpals, is referred to as the head, while the lower part, toward the proximal row, forms the body, with the middle part called the neck [4]. Its name is derived from the Latin word ‘caput’, meaning ‘head’ [5] due to this particular shape.
Where is the Capitate Situated?
The capitate bone is positioned as the third bone from the thumb in the distal carpal row, wedged between the trapezoid on the radial side and the hamate bone on the ulnar side [1]. It is found right in the center of the human wrist [6].
Capitate Bone
Development and Ossification Process
Ossification of this bone begins when a baby is 1-3 months old, making it the first carpal bone to become visible on an x-ray [6].
Capitate Bone X-Ray
Capitate Bone Structure and Anatomy
Surfaces and Joint Connections
Due to its central position, the capitate bone articulates with a total of seven carpal and metacarpal bones, namely the hamate, lunate, scaphoid, trapezoid, and the third metacarpal. It also forms slight connections with the second and fourth metacarpals [7].
Capitate Bone Anatomy Surfaces and Articulations
The medial surface is oval and concave, forming a connection with the hamate [8].
The proximal surface of the head of the carpal forms a convex facet that fits into a hollow formed by the concave facets of the lunate and scaphoid [1, 7].
The lateral surface connects with the trapezoid bone [9].
The distal or inferior surface is divided into three separate facets by two bony ridges. The largest of these facets connects with the base of the third metacarpal, while the other two facets form connections with the second and fourth metacarpals [4].
The dorsal surface is flattish yet rough, being the largest nonarticular surface [8]
The narrow palmar surface is rough and rounded for muscular and ligament attachments [4].
Occasionally, the wrist may exhibit radial deviation (in some individuals), which may cause the proximal medial border of the capitate to connect with the triquetrum [7].
Muscular Attachments
The palmar surface of the capitate bone, together with the bases of the second and third metacarpals, is the primary origin point of the oblique head of the adductor pollicis muscle [8, 10]
Ligament Attachments
This carpal bone has multiple ligament connections, with the principal ones including the radioscaphocapitate, ulnocapitate, scaphocapitate, capitotrapezoid, capitohamate, and the triquetrocapitate ligaments [7].
The radioscaphocapitate ligament connects with the capitate in a way that it creates a flexible sling that supports the scaphoid [11].
Blood Supply
The primary blood supply of the capitate bone is from the dorsal basal metacarpal and dorsal intercarpal arches. Additionally, the joining points (anastomoses) of the palmar intercarpal and ulnar recurrent arches provide minor, yet important vasculature [7].
Functions: Role of the Capitate Bone
With the highest number of articulations among all the carpal bones, the capitate bone plays a crucial role in shaping the carpal rows and maintaining the movements of the wrist. As it is located at the center of the wrist, the axis of rotation for any wrist motion passes through the capitate [12]
Common Injuries and Associated Conditions
The capitate bone, surrounded by the adjacent carpal and metacarpal bones, is well-protected within the carpus, making it one of the rarely fractured bones here [1]. Avascular necrosis, a common condition affecting some of the wrist bones, is also rare in this bone due to its rich blood supply.
Arthritis of the surrounding bones may sometimes affect the capitate, with treatment involving medication and surgical intervention in severe cases.
References
- https://www.healthline.com/human-body-maps/capitate-bone
- https://www.visiblebody.com/learn/skeleton/types-of-bones
- https://www.ncbi.nlm.nih.gov/pubmedhealth/PMHT0023129/
- https://www.bartleby.com/107/54.html
- https://clinanat.com/100-mtd/325-capitate
- http://sketchymedicine.com/2016/01/carpal-bone-ossification/
- https://radiopaedia.org/articles/capitate
- https://www.earthslab.com/anatomy/capitate-bone/
- https://www.kenhub.com/en/library/anatomy/carpal-bones
- https://rad.washington.edu/muscle-atlas/adductor-pollicis/
- https://emedicine.medscape.com/article/1899456-overview?pa=Up%2BygdTtO%2FzQ9GvDrRyYQjmnWPro9UiuzqUZx3xRksn4pSlZEM%2BUSgQI%2FoDi%2BlgI56MI7dGTgNawPfsOtJla9Q%3D%3D#showall
- https://musculoskeletalkey.com/structure-and-function-of-the-wrist/
