Where is the fifth metatarsal metaphyseal-diaphyseal junction located?

Fifth Metatarsal Metaphyseal-Diaphyseal Junction Location

The fifth metatarsal metaphyseal-diaphyseal junction is located at the proximal portion of the fifth metatarsal, specifically at the transition zone between the metaphysis and diaphysis, approximately 1.5 cm distal to the tuberosity.

Anatomical Landmarks and Characteristics

The fifth metatarsal can be divided into distinct anatomical regions:

1. Proximal Region (Base/Tuberosity)

   • Contains the tuberosity (styloid process) which is the most proximal and lateral projection
   • Articulates with the cuboid bone proximally and fourth metatarsal medially
   • Receives insertion of the peroneus brevis tendon

2. Metaphyseal-Diaphyseal Junction

   • Located just distal to the tuberosity (approximately 1.5 cm distal)
   • Represents a transition zone between the wider metaphysis and the narrower diaphysis
   • Corresponds to the area where Jones fractures occur
   • Has unique vascular characteristics that affect healing potential

3. Diaphysis (Shaft)

   • The long, narrow portion of the bone extending distally
   • Contains the medullary canal

Vascular Supply Significance

The metaphyseal-diaphyseal junction has clinical importance due to its vascular anatomy:

• The tuberosity receives blood supply from numerous metaphyseal vessels in a radiate pattern 1
• The diaphysis is primarily supplied by a nutrient artery with longitudinal intramedullary branches 1
• The junction between these two vascular territories occurs at the metaphyseal-diaphyseal junction 1
• This creates a watershed area with relatively poor blood supply, explaining the high risk of delayed union and nonunion of fractures in this region 1, 2

Clinical Relevance

The metaphyseal-diaphyseal junction is clinically significant because:

• Fractures at this location (Zone 2 in Lawrence and Botte classification) have higher rates of delayed union and nonunion compared to tuberosity fractures 2
• The intraosseous diameter at this junction averages 6.475 mm in the dorsal-plantar dimension and 4.6 mm in the medial-lateral dimension 3
• This area corresponds to the location of Jones fractures, which often require surgical intervention 2, 4
• Pedal osteomyelitis occurs most frequently around the fifth metatarsophalangeal joint, which is distal to this junction 5

Imaging Considerations

When evaluating the fifth metatarsal metaphyseal-diaphyseal junction:

• Plain radiographs can identify fractures but may not fully characterize the vascular status
• MRI provides superior soft tissue contrast and can identify bone marrow edema, which may indicate stress reactions before frank fractures occur
• CT can provide detailed bony anatomy and is useful for surgical planning

Management Implications

Understanding the location and vascular characteristics of the fifth metatarsal metaphyseal-diaphyseal junction is crucial for:

• Proper classification of proximal fifth metatarsal fractures
• Predicting healing potential based on fracture location
• Guiding treatment decisions between conservative and surgical management
• Selecting appropriate fixation methods when surgery is indicated

The relatively poor blood supply at this junction explains why fractures in this area often benefit from early surgical intervention, particularly in athletes or active individuals 2, 6.