Tooth-knuckle injuries are sustained when the clenched fist of a patient strikes the teeth of an opponent.
Tooth-knuckle injuries are also referred to as clenched fist injuries, closed fist injuries and fight bite injuries.
These injuries are most commonly found in young adult male patients, with studies placing the average age around 30 years old. Alcohol is also frequently involved 1.
The injury most commonly involves the dominant hand (~65%) and the region over the metacarpophalangeal joint (~80%) 1. Patients who present initially are more likely to have fractures and dislocations. Patients who delay presentation are more likely to present with the infective complications of this injury such as cellulitis, septic arthritis, septic tenosynovitis or osteomyelitis 2. The average time delay from injury to presentation is 3 to 6 days 1. Pain, swelling, erythema, an open discharging wound and reduced range of motion are common findings. Other trauma such as craniofacial and dental should be considered due to the nature of how the injury is sustained.
Skin laceration sustained during the impact of the knuckle on the tooth permits the entrance of pathogens into the subcutaneous tissues 2. Damage to deeper structures is also common such as the extensor tendon, joint capsule, cartilage and bone occurring in up to 75% of cases 1. Damage to these structures and infection tracking into a deep cavity is a major concern. When the hand is relaxed, the proximal movement of the skin and the extensor tendon relative to the deeper tissues creates the possibility of sealing pathogens in a potential space with an anaerobic environment 2.
The pathogens most commonly associated with the injury include: Staphylococcus aureus, Streptococcus viridans, Eikenella corrodens and Escherichia coli 1.
The injury may produce findings visible on plain radiograph such as dislocations, fractures (e.g. Boxer fracture), swelling of the subcutaneous tissues and the presence of foreign bodies (teeth or teeth fragments).
Septic arthritis may produce joint space narrowing and osteomyelitis may produce bone erosion and periostitis 3.
Treatment and prognosis
Treatment usually consists of broad-spectrum antibiotics active against Gram-negative and positive bacteria and anaerobes, debridement and washout of the wound, post-surgical hand elevation and ongoing hand therapy 4. Poor functional outcomes are common (in up to 65%) and chronic osteomyelitis is also possible making amputation necessary (reportedly in as many as 18% of patients) 5,6. However, in one Australian study, the rate of amputation was found to be reassuringly low at 0% 7.
Delays in presentation, injuries over the proximal interphalangeal joint and deeply penetrating wounds are associated with more serious complications like septic arthritis, osteomyelitis and amputation 1.
- 1. Smith HR, Hartman H, Loveridge J, Gunnarsson R. Predicting serious complications and high cost of treatment of tooth-knuckle injuries: a systematic literature review. (2016) European journal of trauma and emergency surgery : official publication of the European Trauma Society. 42 (6): 701-710. doi:10.1007/s00068-016-0701-6 - Pubmed
- 2. Patrick KY Goon, Matti Mahmoud, Vaikunthan Rajaratnam. Hand Trauma Pitfalls: A Retrospective Study of Fight Bites. (2008) European Journal of Trauma and Emergency Surgery. 34 (2): 135. doi:10.1007/s00068-007-6183-9 - Pubmed
- 3. Donald Resnick, Carlos J. Pineda, Michael H. Weisman, Roger Kerr. Osteomyelitis and septic arthritis of the hand following human bites. (2016) Skeletal Radiology. 14 (4): 263. doi:10.1007/BF00352616 - Pubmed
- 4. Patzakis MJ, Wilkins J, Bassett RL. Surgical findings in clenched-fist injuries. (1987) Clinical orthopaedics and related research. Pubmed
- 5. Shewring DJ, Trickett RW, Subramanian KN, Hnyda R. The management of clenched fist 'fight bite' injuries of the hand. (2015) The Journal of hand surgery, European volume. 40 (8): 819-24. doi:10.1177/1753193415576249 - Pubmed
- 6. Mennen U, Howells CJ. Human fight-bite injuries of the hand. A study of 100 cases within 18 months. (1991) Journal of hand surgery (Edinburgh, Scotland). 16 (4): 431-5. Pubmed
- 7. Tonta K, Kimble FW. Human bites of the hand: the Tasmanian experience. (2001) ANZ journal of surgery. 71 (8): 467-71. Pubmed