In this presentation we are talking about the side determination and the landmarks which is present on Trapezoid and the muscles and ligaments attachments and its origin and insertion on the Trapezoid bone Video lecture available on https://youtu.be/EfcHKMWvoAA?si=Q5ofWDPfQVocY8W8

1. 1 TRAPEZOID

2. SHAPE AND
STRUCTURE
• The trapezoid bone is a small,
irregularly shaped bone located in
the distal row of the wrist, positioned
between the scaphoid and second
metacarpal bones. It exhibits a
wedge-like form, its broad dorsal
surface resembling a triangular
plane. Conversely, its volar surface
presents a concave, quadrilateral
configuration. The trapezoid bone
measures approximately 20 mm in
length, 15 mm in width, and 10 mm
in height, making it the smallest
carpal bone

3. Surface Features
Each side of the trapezoid bone presents
distinct articular surfaces that facilitate its
interactions with neighboring bones:
1.Dorsal surface: The dorsal surface is convex
and triangular, articulating with the scaphoid
bone.
2.Volar surface: The volar surface is concave
and quadrilateral, articulating with the
capitate bone.
3.Radial surface: The radial surface is convex
and triangular, articulating with the trapezium
bone.
4.Ulnar surface: The ulnar surface is concave
and triangular, articulating with the base of
the second metacarpal bone.

4. Articulations The trapezoid bone forms four crucial articulations with
its neighboring bones:
1.Proximal articulation: The trapezoid bone articulates
with the scaphoid bone, the largest bone in the
proximal row of the wrist. This articulation is non-
synovial, meaning it lacks a fluid-filled space
between the articulating surfaces.
2.Distal articulation: The trapezoid bone articulates
with the grooved base of the second metacarpal
bone, the second bone in the proximal row of the
hand. It is triangular, convex transversely and concave at
right angles This articulation is synovial,
characterized by a fluid-filled space that facilitates
smooth movement.
3.Lateral articulation: The trapezoid bone articulates
with the trapezium bone, the bone immediately
adjacent to it radially. This articulation is synovial,
facilitating smooth movements between the two
bones.
4.Medial articulation: The trapezoid bone articulates
with the concave facet with the distal part of capitate
bone, the largest bone in the distal row of the wrist.
This articulation is synovial, allowing for intricate
movements between the two bones.
5. Palmar surface : It has a rough palmar surface that is

5. Bone Markings
The trapezoid bone exhibits two
significant bone markings that serve as
attachment points for muscles and
ligaments:
1.Tuberosity: A small, rounded elevation
on the volar surface, the trapezoid's
carpal tunnel side. It provides
attachment for the flexor retinaculum, a
fibrous band that supports the tendons
passing through the carpal tunnel.
2.Groove: A shallow groove adjacent to
the tuberosity, it serves as an
attachment point for the thenar
muscles, which control thumb
movement.

6. Dorsal Intercarpal Ligament
The dorsal intercarpal ligament is a thick, Y-shaped
ligament that attaches to the dorsal aspect of the
trapezoid bone and extends to the dorsal aspect of
the capitate bone. It is divided into two bands: the
proximal band and the distal band. The proximal
band attaches to the proximal margins of the
trapezoid and capitate bones, while the distal band
attaches to the distal margins of the trapezoid and
capitate bones. The dorsal intercarpal ligament
helps to stabilize the carpal joint by limiting
dorsiflexion and palmar flexion of the wrist.

7. Volar Intercarpal
Ligament
The volar intercarpal ligament is a
thick, broad ligament that attaches to
the volar aspect of the trapezoid
bone and extends to the volar aspect
of the capitate bone. It helps to
stabilize the carpal joint by limiting
hyperextension and flexion of the
wrist.

8. Dorsal
Radiocarpal
Ligament
The dorsal radiocarpal ligament is a
broad, fan-shaped ligament that
attaches to the dorsal aspect of the
distal radius and extends to the
dorsal aspect of the scaphoid, lunate,
triquetrum, and trapezoid bones. It
helps to stabilize the wrist joint by
limiting dorsiflexion of the wrist.

9. Volar
Radiocarpal
Ligament
The volar radiocarpal ligament is a
broad, fan-shaped ligament that
attaches to the volar aspect of the
distal radius and extends to the volar
aspect of the scaphoid, lunate,
triquetrum, and trapezoid bones. It
helps to stabilize the wrist joint by
limiting palmar flexion of the wrist.

10. Trapeziometacarpal Ligament
The trapeziometacarpal ligament is a thick, Y-shaped
ligament that attaches to the radial aspect of the trapezoid
bone and extends to the base of the second metacarpal
bone. It is divided into two bands: the proximal band and the
distal band. The proximal band attaches to the proximal
margin of the trapezoid bone and the distal margin of the
second metacarpal bone, while the distal band attaches to
the distal margin of the trapezoid bone and the base of the
second metacarpal bone. The trapeziometacarpal ligament
helps to stabilize the trapeziometacarpal joint by limiting
abduction and adduction of the second metacarpal bone.
Stabilizing Ligaments of the trapeziometacarpal joint. a:
Anterior view, b: Posterior view. Abbreviations: IML,
intermetacarpal ligament; UCL, ulnar collateral ligament;
AOL, anterior oblique ligament; TCL, transverse carpal
ligament; POL, posterior oblique ligament; DRL,
dorsoradial ligament; APL, abductor pollicis longus.

11. Scaphotrapezial
Ligament
The scaphotrapezial ligament is
a thick, triangular ligament that
attaches to the distal margin of
the scaphoid bone and extends
to the proximal margin of the
trapezoid bone. It helps to
stabilize the scaphotrapezial joint
by limiting abduction and
adduction of the first metacarpal
bone.

12. Trapezocapitate Ligament
The trapezocapitate ligament is a thick, triangular
ligament that attaches to the distal margin of the
trapezoid bone and extends to the proximal margin
of the capitate bone. It helps to stabilize the
trapezocapitate joint by limiting abduction and
adduction of the third metacarpal bone.

13. Blood Supply
The trapezoid bone receives its blood supply from branches of
the dorsal and anterior intercarpal arteries, which originate from
the radial and ulnar arteries, respectively. These arteries supply
the bone with oxygenated blood, crucial for its nourishment and
function.

14. Function
The trapezoid bone plays a vital role in the
wrist's intricate movements and overall
stability:
1.Force transmission: The trapezoid bone
acts as a link between the proximal and
distal rows of the wrist, facilitating the
transmission of force from the radius
and ulna to the second metacarpal bone
during hand movements.
2.Stability: The trapezoid bone, along with
other carpal bones, forms the wrist
joint's articular surface. It contributes to
the overall stability of the wrist by
providing support and preventing
excessive movement, ensuring smooth
and controlled movements.

15. Clinical
Significance
• Fractures of the trapezoid bone are
relatively uncommon, accounting for
approximately 1% of all carpal bone
fractures. However, they can occur due
to direct trauma or forceful impact to
the wrist. Fractures of the trapezoid
bone can cause pain, swelling, and
limited wrist movement. Treatment
typically involves immobilization of the
wrist with a cast or splint, followed by
physical therapy to regain range of
motion and strength.

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By Aniket Mishra