Metacarpal 5

Metacarpal 5 Bone

Figure 1

2425435

Melisa Gray

CA41001

Contents

07. References

04. Muscle Attachments

01. General Information

02. Features & Function

05. Identification

06. Siding

03. Articulations

Figure 2

01. General Information

Metacarpal 5 Bone

• The MC5 is an important part of the metacarpus (a group of five bones of the hand between the phalanges and the carpus). It is also known as the metacarpal bone of the little finger or pinky finger.

• Most medial and one of the smallest of the metacarpus bones.

• Located on the ulnar side of the hand.

• It is a long, slender bone with little curvature. It has an extended, cylindrical shaft with a base at one end and a rounded head at the other.

Figure 3

02. Features & Function

Figure 4

Figure 5

Did you know... The MC5 bone is the most common bone to be injured when throwing a punch!

• The fifth finger's flexion, extension, abduction and adduction are all important hand movements that rely on the MC5 bone. The animation above illustrates this.

• Plays an essential role in giving the hand structural support, facilitating little finger mobility, and helping the hand grasp and hold items.

• Attached to the MC5, the flexor digiti minimi brevis and abductor digiti minimi muscles perform crucial roles in regulating the motions of the fifth digit. This balance of muscle function is crucial for precise and coordinated motions.

03. Articulations

• Proximal articulation with the hamate bone. This ensures stability.

• At the proximal end, MC5 articulates with the fifth carpometacarpal joint. This joint connects the MC5 bone to the hamate bone at the base of the hand.

• It forms joints with the proximal phalanx of the fifth finger at the distal end, allowing for flexion and extension motions.

• The lateral portion of MC5 is non-articular and contains a tubercle for the extensor carpi ulnaris muscle attachment.

Figure 7

Figure 6

04. Muscle Attachments

Abductor Digiti Minimi: -Abducts the fifth digit.

• Attaches to the base of MC5 on the medial side.

Flexor Digiti Minimi Brevis: -Flexes the fifth digit.

• Attaches to the base of the fifth metacarpal bone, specifically on the palmar/anterior surface.

Extensor Carpi Ulnaris: -Extension and adduction of the wrist

• Attaches to the base of mc5

Interosseous Muscles: -Adducts fingers, and assists in flexing metacarpophalangeal (MCP) joints while extending the interphalangeal joints.

• The fourth palmar interossei muscles attach to the distal part of the lateral surface.

Opponens Digiti Minimi: -Flexion, lateral rotation and opposition of the fifth digit

• Attaches along the anterior surface of MC5.

Figure 8

FACT OF THE DAYWhen the neck of the MC5 is fractured, it is known as 'Boxer’s fracture'.

05.

Identification

Shape and Length:

• Metacarpal 5 is slender and elongated compared to the other metacarpals.
• It is one of the smallest metacarpal bones.

Articulation:

• The proximal end articulates with the hamate bone of the carpus. This articulation is a unique feature.

• The distal end interfaces with the base of the fifth proximal phalanx. This junction is crucial for precise movements of the fifth digit.

Tuberosity:

• On the palmar surface of the base, there is a prominent tubercle (bony prominence) for the insertion of the tendon of the extensor carpi ulnaris muscle.

06.

Siding

• The base's medial aspect features a tubercle positioned similarly to articulations found on other metacarpals. This placement aids in the straightforward process of siding.

• On the dorsal surface of the base, there is a prominent tubercle for the insertion of the tendon of the extensor carpi ulnaris muscle. This is a specific landmark for orientation.

• MC5 is located on the medial side of the hand, adjacent to the fourth metacarpal bone.

• The proximal end articulates with the carpal bones and can be identified by its articular surface for the hamate bone. The distal end forms the knuckle of the little finger.

• The base is the wider end that connects to the carpals of the wrist. The head is the narrower end that connects to the proximal phalanx of the little finger. The base is typically flatter and broader compared to the head.

Figure 9

07. References

Figure 9 - File: Metacarpal Bones (left hand) 01 palmar view with label.png. Available at: https://commons.wikimedia.org/wiki/File:Metacarpal_bones_(left_hand)_01_palmar_view_with_label.png (Accessed: 19 October 2023). Figure 1&8 - Pinterest. Available at: https://www.pinterest.co.uk/pin/810436895469294279/ (Accessed: 19 October 2023). Bones of the hand: Carpals, metacarpals and phalanges (no date) TeachMeAnatomy. Available at: https://teachmeanatomy.info/upper-limb/bones/bones-of-the-hand-carpals-metacarpals-and-phalanges/ (Accessed: 18 October 2023). Figure 2&5 - Category: animated GIF files (no date) Wikimedia Commons. Available at: https://commons.wikimedia.org/wiki/Category:Animated_GIF_files (Accessed: 19 October 2023). Figure 4&7 - Fifth metacarpal bone (2023) Wikipedia. Available at: https://en.wikipedia.org/wiki/Fifth_metacarpal_bone (Accessed: 15 October 2023). Janis Savlovskis, K.R. (no date) Metacarpal Bones (Ossa Metacarpalia), Bones of the Hand: Metacarpal Bones. Available at: https://www.anatomystandard.com/Upper_Limb/Hand_Bones/Metacarpals.html (Accessed: 14 October 2023). MD, J.V. (2023) Metacarpal Bones, Kenhub. Available at: https://www.kenhub.com/en/library/anatomy/the-metacarpal-bones# (Accessed: 15 October 2023). Metacarpal (no date) Encyclopædia Britannica. Available at: https://www.britannica.com/science/metacarpal (Accessed: 14 October 2023). Figure 6 - The metacarpophalangeal joint (no date) TeachMeAnatomy. Available at: https://teachmeanatomy.info/upper-limb/joints/metacarpophalangeal/ (Accessed: 17 October 2023). Figure 3 - Sports medicine advisor index (no date) Jason Pirozzolo, D.O., C.S.C.S. Available at: http://www.jasonpirozzolo.com/patientinfo/sma_index.htm (Accessed: 16 October 2023).

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