Differential Diagnosis for Thumb Injury

The patient presents with a smashed thumb, minimal bruising, and disproportionate pain. Here's a categorized differential diagnosis:

• Single most likely diagnosis
  • Fracture (e.g., Boxer's fracture or non-displaced fracture): The patient's complaint of constant throbbing pain and tenderness, despite minimal visible bruising, suggests an underlying fracture. The pain being out of proportion to the visible injury supports this diagnosis, as fractures can be painful even without significant external trauma signs.
• Other Likely diagnoses
  • Ligament sprain or strain: The mechanism of injury (smashing the thumb) could result in ligament damage, leading to pain and tenderness. However, the severity of pain might be less than what is typically seen with fractures.
  • Contusion or soft tissue injury: Although there's minimal bruising, a contusion or soft tissue injury could still cause significant pain, especially if the injury involves deeper tissues.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Compartment syndrome: Although less common in the thumb compared to other parts of the body, compartment syndrome is a medical emergency that requires prompt diagnosis and treatment. Severe pain out of proportion to the injury, especially if accompanied by pallor, poikilothermia, paresthesia, or pulselessness, should raise suspicion.
  • Infection (e.g., cellulitis or abscess): While the timeline might be short for a significant infection, any open wound or break in the skin could potentially introduce bacteria, leading to an infection. The presence of increasing redness, swelling, warmth, or pus would support this diagnosis.
• Rare diagnoses
  • Raynaud's phenomenon: This condition involves vasospasm of the arteries to the fingers and toes and can be triggered by trauma. It might present with pain, but typically, there would be more prominent signs of vasospasm, such as color changes.
  • Reflex sympathetic dystrophy (RSD) or complex regional pain syndrome (CRPS): These conditions are characterized by chronic pain, swelling, and changes in skin temperature and color that are disproportionate to the injury. They are rare and typically develop over a longer period than 5 days.