Metatarsal

The metatarsal bones are a group of five long bones located in the midfoot, connecting the tarsal bones of the hindfoot to the phalanges of the toes. They play a crucial role in supporting body weight, maintaining foot arches, and enabling locomotion. Understanding their anatomy and function is essential for diagnosing and managing foot disorders.

Anatomy of the Metatarsals

General Structure

Each metatarsal bone consists of three main parts: the base, shaft, and head. The base articulates with the tarsal bones, the shaft forms the elongated middle portion, and the head connects with the proximal phalanges.

• Base: Articulates proximally with tarsal bones and has ligamentous attachments
• Shaft: Cylindrical and slightly curved, providing structural support
• Head: Distal expanded end forming the metatarsophalangeal joint
• Articular surfaces: Oriented to allow smooth articulation and weight transfer
• Variations: The first metatarsal is shorter, thicker, and more robust than the lateral metatarsals

Individual Metatarsals

Each metatarsal has specific characteristics that relate to its position and function within the foot.

• First metatarsal: Shortest and thickest, supports the great toe and bears significant weight
• Second metatarsal: Longest metatarsal, central position contributes to stability
• Third metatarsal: Slightly shorter than the second, articulates with the cuneiform bones
• Fourth metatarsal: Lateral position, contributes to lateral column stability
• Fifth metatarsal: Contains a prominent tuberosity at its base for tendon attachment, prone to fractures

Muscular and Ligamentous Attachments

The metatarsal bones serve as attachment points for several muscles and ligaments, which are essential for foot movement and stability. These attachments contribute to both dynamic motion and maintenance of the foot arches.

• Muscle insertions:
  • Flexor hallucis brevis inserts on the first metatarsal head
  • Flexor digitorum brevis and lumbricals attach to lateral metatarsals
  • Dorsal and plantar interossei attach to adjacent metatarsals to facilitate toe abduction and adduction
• Ligamentous connections:
  • Plantar ligaments connect metatarsal heads and contribute to the longitudinal arch
  • Metatarsophalangeal joint capsules stabilize the distal ends
  • Dorsal ligaments reinforce the dorsal aspect of metatarsal joints
• Role in foot arches:
  • Medial longitudinal arch relies on first metatarsal alignment
  • Lateral column stability depends on fourth and fifth metatarsals

Vascular and Neural Supply

Proper blood flow and innervation are crucial for metatarsal health, supporting bone metabolism, repair, and sensory function.

• Arterial supply:
  • Dorsal metatarsal arteries branch from the dorsalis pedis artery
  • Plantar metatarsal arteries branch from the lateral plantar artery
• Venous drainage:
  • Dorsal venous network drains into the great and small saphenous veins
  • Plantar venous network drains into deep plantar veins
• Nerve supply:
  • Medial and lateral plantar nerves provide sensation to the plantar surfaces
  • Deep peroneal nerve supplies the dorsal surface of the first interspace
  • Proprioceptive fibers contribute to balance and gait coordination

Biomechanics

The metatarsal bones play a pivotal role in weight distribution, locomotion, and maintenance of foot arches. Their structural arrangement allows for efficient transfer of forces during standing, walking, and running.

• Weight-bearing: The first metatarsal bears the greatest load during the push-off phase of gait
• Force distribution: Lateral metatarsals help stabilize the foot and prevent collapse of the transverse arch
• Arch contribution: Medial longitudinal arch relies on first through third metatarsals; lateral longitudinal arch involves fourth and fifth metatarsals
• Gait mechanics: Metatarsals flex and extend to accommodate uneven surfaces and absorb impact

Clinical Significance

Common Injuries

Metatarsals are prone to various injuries, often resulting from trauma or repetitive stress.

• Fractures: Stress fractures and acute fractures such as Jones fracture of the fifth metatarsal
• Dislocations: Rare, usually associated with severe trauma
• Metatarsalgia: Pain in the metatarsal region due to overuse, improper footwear, or structural abnormalities

Deformities

Structural deformities involving metatarsals can lead to functional impairment and pain.

• Bunion (hallux valgus): Lateral deviation of the first metatarsal contributing to medial eminence enlargement
• Claw toes and hammer toes: Altered metatarsal-phalangeal alignment affecting toe posture

Surgical Considerations

Surgical intervention may be required for severe fractures, deformities, or chronic pain unresponsive to conservative management.

• Osteotomies to correct malalignment or relieve pressure
• Internal fixation techniques for fractures and non-unions
• Postoperative rehabilitation focusing on gait restoration and strengthening

Imaging and Diagnostic Evaluation

Accurate assessment of metatarsal bones is essential for diagnosing fractures, deformities, and other pathologies. Various imaging modalities provide detailed anatomical and structural information.

• X-ray evaluation: Standard anteroposterior, lateral, and oblique views to detect fractures, dislocations, and degenerative changes
• Computed Tomography (CT): Offers high-resolution images for complex fractures or preoperative planning
• Magnetic Resonance Imaging (MRI): Useful for assessing soft tissue involvement, bone marrow edema, and stress injuries
• Ultrasound: Evaluates superficial tendons, ligaments, and vascular structures around metatarsals

Development and Variations

The metatarsal bones undergo a specific developmental timeline and can exhibit anatomical variations that have clinical implications.

• Ossification timeline: Primary ossification centers appear prenatally; secondary centers at the distal ends during childhood
• Congenital variations: Bipartite metatarsals, accessory bones, and variations in length or curvature
• Sexual dimorphism and population differences: Variations in metatarsal length and robustness between sexes and among populations
• Clinical relevance: Developmental anomalies may predispose to stress fractures, deformities, or gait abnormalities

References

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3. Coughlin MJ, Mann RA, Saltzman CL. Surgery of the Foot and Ankle. 9th ed. Philadelphia: Elsevier; 2014.
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5. Clough TM, Bhatia M. Metatarsal fractures and injuries. Orthop Trauma. 2018;32(1):21-30.
6. Robbins J, Yao D. Biomechanics of the metatarsals in gait and load distribution. Foot Ankle Int. 2017;38(12):1350-1358.
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