Sea Urchin Spine Injury to the Hand
A 25-year-old right-hand dominant male student presented to an urgent care clinic with a sea urchin (Kina) spike injury to his right hand. Two days earlier, while scuba diving, he sustained multiple puncture wounds to the right palm, ring finger, and little finger. He was reviewed by his GP the following day, who attempted removal of the spikes without success. A plain X-ray was obtained, which did not reveal any retained radiopaque foreign bodies. He was commenced on oral flucloxacillin and referred to hand therapy. The hand therapist who saw him advised an ultrasound and directed him to urgent care as his right hand, particularly the ring finger, had worsened.
On examination, there were multiple puncture wounds on the right hand: three on the medial palm, two on the medial aspect of the distal phalanx and DIP joint of the ring finger, and three on the little finger. The ring finger, especially around the DIP joint, was erythematous, swollen, and tender, with painful limitation of movement. The distal finger was also red and swollen. There was no evidence of proximal tracking.
The impression was of infected sea urchin wounds with possible septic arthritis of the right ring finger DIP joint. The patient was given a tetanus booster and referred to the local plastics team.
He proceeded to OT for removal of Kina spines under general anaesthesia. Eight spikes were removed from the right little and ring fingers. There was no penetration into the DIP joint capsule and no evidence of septic arthritis. He was admitted overnight for intravenous antibiotics and discharged the following day on oral trimethoprim/sulfamethoxazole for one week, with a plan for review in plastics clinic in seven days.
Learning Nuggets
New Zealand coastal waters host approximately 70 sea urchin species, with 11 found on reefs. The most well-known is Kina (Evechinus chloroticus).1 However, medical literature on Kina-related injuries is limited. Sea urchin injuries (SUI) are uncommon in New Zealand urgent care, and primary care doctors may lack familiarity with their management. In this case the GP referred the patient to hand therapy and prescribed antibiotics, which might not have covered a marine infection.
*This case illustrates the importance of complete removal of sea urchin spines.
*Kina have sharp external spines and grasping organs covered with venom producing tissue.2 Acute symptoms primarily include severe local pain, which can radiate to the entire limb. Mild systemic effects, such as nausea, diaphoresis, and hypotension, may occur due to circulating venom.2
*Temporary blue-black discolouration is also possible.3
*Delayed complications from retained spines near deep structures include granulomas (40–50%), sea urchin arthritis (SUA) (30%), and acute inflammatory synovitis/tenosynovitis (10%).3 Less common issues include delayed hypersensitivity reactions, infectious synovitis, skin infections, neurological involvement, and osteomyelitis.3 These reactions typically emerge two or more weeks post-injury.3 SUA resembles acute synovitis, lasting from two months to a year 3, and is characterized by a symptom-free period before synovitis develops. Laboratory tests are normal, but joint swelling and restricted motion occur.4
*SUI are among the most common marine injuries worldwide, yet no consensus guidelines exist for their management.3 An algorithm may help reduce long-term morbidity.3
*First aid: This involves removal of toxin-secreting pincers and easily extractable spines, irrigation of the wound, and immersion in 45°C hot water for 30–90 minutes to inactivate toxins. Adding vinegar (1:1 ratio) may be beneficial.3 Wound cleaning, tetanus prophylaxis, and antibiotics should follow.3,5,6
*Antibiotics: A 7–14 day course of oral ciprofloxacin (500 mg BD), co-trimoxazole (800 mg BD), or doxycycline (100 mg BD) is recommended.3,7
*No anti-venom exists for SUI.7 No significant Kina envenomation cases have been reported in the literature.
*Imaging and surgical intervention: If spines are embedded near deep structures, X-ray and ultrasound are advised, with early surgical consultation.3 Superficial spines can be removed with forceps under local anaesthetic.3 Other techniques include punch biopsy, laser, and liquid nitrogen.3
*Infectious tenosynovitis: Urgent surgical management is required if signs are present.3
*Delayed onset cases: X-ray, ultrasound, and potentially MRI are necessary.3
*Surgical consultation is recommended, and deeply embedded spines should be fully removed.3 SUA cases benefit from debridement and synovectomy/tenosynovectomy.3,4
*Although systemic and intralesional steroids have shown positive effects, data is insufficient for recommendations.3
*Antibiotics and NSAIDs have proven ineffective for SUA.4
References
- Wassilieff M. Starfish, sea urchins and other echinoderms. In: Te Ara – The Encyclopedia of New Zealand. 2006. Available from: teara.govt.nz/en/starfish-sea-urchins-and-other-echinoderms/print
- Slaughter R. New Zealand’s venomous creatures. N Z Med J. 2009;122(1290):83–97. Available from: pubmed.ncbi.nlm.nih.gov/19319171/
- Schwartz Z, Cohen M, Lipner SR. Sea urchin injuries: a review and clinical approach algorithm. J Dermatol Treat. 2021;32(2):150-6. doi: 10.1080/09546634.2019.1638884
- Wada T, Soma T, Gaman K, Usui M, Yamashita T. Sea urchin spine arthritis of the hand. J Hand Surg Am. 2008;33(3):398-401. doi: 10.1016/j.jhsa.2007.10.038
- DermNet NZ. Marine wounds and stings. 2023. Available from: dermnetnz.org/topics/marine-wounds-and-stings
- Isbister GK. Managing injuries by venomous sea creatures in Australia. Aust Prescr. 2007;30(5):117-21. Available from: australianprescriber.tg.org.au/articles/managing-injuries-by-venomous-sea-creatures-in-australia.html
- The Royal Australian College of General Practitioners. Marine envenomations. Aust Fam Physician. Available from: racgp.org.au/afp/2015/january-february/marine-envenomations
- Gelman Y, Kong EL, Murphy-Lavoie HM. Sea urchin toxicity. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2025. Available from: ncbi.nlm.nih.gov/books/NBK541116/
