Is increased ossific density at the lateral aspect of the fifth metatarsal (metatarsal bone) base more likely to represent an apophysis (growth plate) rather than an avulsion fracture?

From the Guidelines

The ossific density at the lateral aspect of the fifth metatarsal base is likely an apophysis rather than an avulsion fracture. This distinction is crucial for proper management, as it directly impacts the treatment approach and patient outcomes in terms of morbidity, mortality, and quality of life. An apophysis is a normal growth center that appears during development and eventually fuses with the main bone, whereas an avulsion fracture represents actual bone injury requiring treatment 1. Several features help distinguish between the two: apophyses typically have smooth, well-corticated margins and run parallel to the long axis of the metatarsal, whereas avulsion fractures often have irregular margins and may be displaced.

Key considerations in differentiating between an apophysis and an avulsion fracture include:

• The age of the patient, as the apophysis of the fifth metatarsal typically appears between ages 9-14 and fuses by age 14-18 1
• Clinical presentation, with acute trauma and point tenderness suggesting fracture, while chronic or activity-related pain without specific injury is more consistent with apophysitis
• Radiographic appearance, with apophyses having characteristic smooth margins and alignment with the metatarsal bone

Given the potential for significant differences in management and outcomes, accurate diagnosis is critical, and may involve radiographs from multiple angles and comparison views of the opposite foot in unclear cases 1. Management of fractures may require immobilization or surgery, which can significantly impact morbidity and quality of life, whereas apophysitis typically responds to conservative measures like activity modification and supportive footwear, minimizing the risk of long-term complications and promoting optimal recovery 1.

From the Research

Ossific Density at the Lateral Aspect of the Fifth Metatarsal Base

• The presence of ossific density at the lateral aspect of the fifth metatarsal base can be indicative of either an apophysis or an avulsion fracture 2, 3.
• Apophyseal injuries, including avulsion fractures, are common in young athletes and can be difficult to diagnose using X-ray examination alone, especially when an ossification center of the apophysis does not exist 2.
• Ultrasonography is considered a suitable diagnostic tool for apophyseal injuries, offering advantages such as no radiation exposure, early detection, and dynamic examination 2.
• The differentiation between an apophysis and an avulsion fracture is crucial for establishing the appropriate treatment and rehabilitation program 2, 4.

Diagnostic Considerations

• Radiography is the first imaging modality used to diagnose avulsion injuries, but advanced imaging modalities like ultrasonography, computed tomography, or magnetic resonance imaging may be required to identify subtle lesions or fully delineate the extent of the injury 5, 3.
• Ultrasonography has a high spatial resolution and allows for dynamic assessment, making it useful for comparing a bone avulsion with the opposite side 3.
• Computed tomography is more sensitive for depicting tiny osseous fragments located adjacent to the expected attachment site of a ligament, tendon, or capsule 3.
• Magnetic resonance imaging is the best imaging modality for evaluating soft tissue abnormalities, including affected muscles, tendons, and ligaments 3.

Clinical Implications

• Accurate diagnosis of apophyseal injuries or avulsion fractures is essential to prevent misdiagnosis, which can lead to disability, chronic pain, and decreased performance 4, 6.
• Treatment guidelines for apophyseal avulsion fractures of the pelvis, including the fifth metatarsal base, do not exist, but surgical treatment may be preferred for major dislocations and fragment sizes, providing a faster return to pre-injury level of activity 6.