What is the management for an adult patient with sea urchin spines embedded in their foot?

Management of Sea Urchin Spines in the Foot

Immediate hot water immersion followed by complete spine extraction under physician guidance is the recommended approach to prevent long-term complications including granuloma formation, arthritis, and chronic inflammation. 1

Immediate Management (First 24 Hours)

Hot water soaks should be initiated immediately to inactivate pro-inflammatory compounds in the sea urchin venom. 1 This represents the most critical initial intervention to reduce subsequent inflammatory reactions and should be performed as soon as possible after injury.

Initial Assessment

• Examine for spine depth and proximity to joints or tendons, as spines near deep structures can induce arthritis, inflammatory tenosynovitis, and other delayed complications. 1
• Obtain imaging (radiographs or MRI) for risk stratification to determine the exact location and depth of retained spines, which guides the appropriate extraction technique. 1, 2
• MRI is superior to plain radiographs for detecting soft tissue changes and subtle bone involvement, particularly when spines are near joints. 2

Spine Extraction Strategy

All visible and embedded spines should be extracted by a physician rather than attempting self-removal or observation. 1 This is a critical departure from older approaches that suggested leaving spines in place.

Rationale for Complete Extraction

• Superficially retained spines trigger local granulomatous inflammatory responses that can persist for months to years. 1, 3, 4
• Deep spines near joints cause sea urchin arthritis and synovitis even 30 months after initial injury. 2
• The proteinaceous covering of calcium carbonate spines causes immune reactions of variable presentation. 2
• Attempts at incomplete removal can increase reaction severity, but this refers to aggressive manipulation without proper technique—not to contraindicate physician-guided extraction. 5

Extraction Technique Selection

• Superficial spines: Direct extraction with appropriate instruments under sterile conditions. 1
• Deep spines near joints or tendons: May require surgical consultation for complete removal to prevent arthritis and tenosynovitis. 1, 2
• Imaging-guided extraction should be considered when spines are not easily palpable or visible. 1

Post-Extraction Management

Following spine removal, the wound should be thoroughly cleansed and monitored for signs of infection or granuloma formation. 5, 1

Monitoring for Complications

• Granuloma formation can occur weeks to months after injury if spines are incompletely removed. 3, 4
• Joint involvement may not be apparent on initial plain radiographs and can manifest as delayed arthritis. 2
• Systemic reactions from toxins in certain species can occur, though local pain is most common. 5

Common Pitfalls to Avoid

• Do not adopt a "watch and wait" approach for retained spines, as this leads to granulomatous reactions and potential arthritis. 1, 3
• Do not rely solely on plain radiographs when spines are near joints—MRI provides superior soft tissue detail. 2
• Do not dismiss seemingly minor injuries, as consequences vary significantly based on injury location and elapsed time to treatment. 1
• Do not attempt aggressive self-extraction, which can fragment spines and worsen outcomes. 5

Special Considerations for Foot Injuries

Foot injuries carry particular risk due to weight-bearing stress and proximity to multiple joints and tendons. 1 The plantar surface and areas near the metatarsophalangeal joints are especially vulnerable to long-term complications if spines are retained near these structures. 2

• Ensure appropriate offloading during the healing period to prevent mechanical stress on affected areas. 1
• Consider more aggressive imaging for plantar foot injuries given the difficulty in clinical assessment and high risk of joint involvement. 2