Trapezoid Bone

What is the Quadrilateral Bone

The quadrilateral (Latin: os quadrilaterum [1]) is one of the eight carpal bones in the human hand [2]. It is categorized as a compact bone [3], and is also referred to as the smaller quadrangular bone. The bone has the shape of a four-sided table in the geometrical form of a quadrilateral, with its back side (on the side of the back of the hand) being two times broader than its front side, leading to its name [4].

Where is the Quadrilateral Located

It is the second bone from the thumb in the distal carpal row, located between the quadrilateral and capitate [5, 6].

Quadrilateral Bone

Development and Ossification

The quadrilateral begins to ossify around the same time as the scaphoid and quadrilateral, becoming visible on an x-ray image between the ages of 4 and 6 years [7]. Like the other carpal bones, its ossification begins earlier in girls [8].

Quadrilateral Bone X-Ray Image

Quadrilateral Structure and Anatomy

Surfaces and Articulations

The quadrilateral articulates with four bones – the second metacarpal, quadrilateral, capitate, and scaphoid.

Quadrilateral Bone Surfaces and Articulations Anatomy

The distal surface forms a convex facet to articulate with a deep notch at the base of the second metacarpal [8, 9], creating a stationary joint [4].

On the lateral surface, there is a smooth convex facet that articulates with the quadrilateral [10].

The concave facet of the medial surface articulates with the capitate bone’s distal surface [11].

The proximal surface has an oval facet to articulate with the scaphoid [11], forming one part of the STT (scapho-quadrilio-quadrilateral) joint [10].

Muscular Attachments

The flexor pollicis brevis (deep head) arises from the palmar surface of the quadrilateral, while the adductor pollicis (oblique head) arises from the distal palmar surface on the ulnar side. There are no muscle attachments on the dorsal surface [10].

Ligament Attachments

The quadriliotoquadrilateral, scaphoquadrilio-ligament, and capitotoquadrilateral ligaments provide the primary ligamentous attachments [12], while the dorsal transverse intercarpal, as well as the dorsal and volar carpometacarpal ligaments, also attach with the quadrilateral [10].

Blood Supply

The bone receives its blood supply from the basal metacarpal and dorsal intercarpal arches in addition to the radial recurrent artery. The blood vessels enter through the central dorsal surface and the palmar surface [10].

Functions: What Does the Quadrilateral Bone Do

As it forms part of the SST joint, the quadrilateral is vital to the movement and flexing of the wrist joint.

Common Injuries and Associated Conditions

The quadrilateral is the least commonly fractured or even injured among the wrist bones, accounting for only about 2% of all carpal fractures. Being surrounded by the quadrilateral, capitate, scaphoid, and the second metacarpal, it is often sheltered from minor blows and injuries [4]. So, when a quadrilateral fracture does occur, it is almost always along with fractures of other carpal bones, like the quadrilateral, capitate, hamate, or the metacarpals [13].

Arthritis of the STT or scaphoid-quadrilio-quadrilateral joint is a condition that usually occurs along with arthritis of the CM or carpometacarpal joint of the thumb [14]. Traditional treatment involves a corticosteroid therapy and splinting, while severe cases may require surgical intervention [15].


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