Diagnosis: Felon
Based on the clinical presentation of a swollen thumb bulb following a puncture wound from tools with an intact nail bed, this is most consistent with a felon—a closed-space infection of the pulp (fingertip pad) of the distal phalanx.
Clinical Reasoning
A felon presents as a tense, painful swelling of the fingertip pulp, which matches the description of a "swollen bulb of the thumb finger" after penetrating trauma 1, 2. The key distinguishing features are:
- Location: The infection involves the pulp space (the fleshy pad) of the distal digit, not the nail fold or surrounding structures 1
- Mechanism: Puncture wounds from tools commonly introduce bacteria into the closed compartments of the fingertip, leading to abscess formation in the pulp space 3, 4
- Intact nail bed: This rules out nail bed injury and makes onychomycosis (a chronic fungal nail infection) irrelevant to this acute presentation 1
Why Not the Other Options
Paronychia (Option B): This involves infection of the nail fold (the skin around the nail edges), not the pulp of the fingertip 1. The intact nail bed and description of bulb swelling point away from this diagnosis.
Onychomycosis (Option C): This is a chronic fungal infection of the nail plate itself, not an acute bacterial infection following trauma 5. This is completely unrelated to the acute puncture wound scenario.
Cellulitis (Option D): While cellulitis can occur after puncture wounds, it presents as spreading erythema, warmth, and edema of superficial tissues without the characteristic tense, localized abscess formation in a closed space that defines a felon 5, 6
Management Approach
Immediate surgical drainage is required for a felon to prevent complications including osteomyelitis, flexor tenosynovitis, and tissue necrosis 1, 2:
- Surgical incision and drainage: The closed-space nature of the pulp compartment creates high pressure that compromises blood flow and allows rapid bacterial proliferation 4, 2
- Wound exploration: Use a sterile probe to assess depth, detect foreign bodies, and evaluate for bone involvement 5
- Culture specimens: Obtain tissue samples (not superficial swabs) before antibiotic initiation for accurate pathogen identification 5
- Empiric antibiotics: Cover Staphylococcus aureus (including MRSA in high-risk populations) and Streptococcus species, which are the most common pathogens in hand infections 5, 1
- Tetanus prophylaxis: Update if vaccination status is unknown or >5 years since last booster for contaminated wounds 6
Critical Pitfalls to Avoid
- Delayed surgical intervention: Attempting antibiotic therapy alone without drainage will fail because the closed-space infection requires decompression 1, 2
- Inadequate drainage: Incomplete incision may leave loculated pus pockets that perpetuate infection 4
- Missing osteomyelitis: Puncture wounds can seed bone infection, particularly in the distal phalanx; probe the wound to assess for bone involvement and consider imaging if there's suspicion 5, 3, 7
- Pseudomonas risk: While less common in hand felons than foot puncture wounds, consider Pseudomonas coverage if the injury involved penetration through rubber-soled footwear or contaminated materials 3