High-pressure injection injuries should be considered a potential limb threatening surgical emergency. Immediate decompression and thorough cleansing of the offending material is required.
Most injuries result from grease guns, paint sprayers, or diesel fuel injectors.
The injection typically occurs to the fingertip when the operator is trying to wipe clear a blocked nozzle or to the palm when the operator is attempting to steady the gun with a free hand during the testing or operation of equipment.
The nondominant is involved in about 75% of cases.
The most common site of injury is the index finger. The palm and long finger are the next most frequently injured.
The mechanism of injury is the introduction of a foreign material, under high pressure (between 2,000 and 10,000 psi) into the poorly distensible digital or palmar tissues. This causes acute and chronic inflammation and foreign body granuloma formation. Damage results from the impact, ischemia due to vascular compression, chemical inflammation, and secondary infection.
The offending substances are typically grease, paints or solvents.
Fuel and paint injections lead to the most severe inflammatory response with a high incidence of subsequent amputation. Grease- and oil-based compounds may lead to oleogranulomas with chronic fistula formation, scarring, and eventual loss of digit function.
Overall, amputation rates as high as 48%.
Paint solvents appear to cause the greatest damage and result in amputation in 60-80% of the cases. That is, it largely causes necrosis.
Grease, the more common injectant, causes a less severe inflammatory response and usually causes fibrosis. Amputation rates are up to 25%.
The innocuous appearance of the wound may hide the severity of the injury.
With time, edema and intense pain develop and the digit may appear erythematous or cold.
Preoperative radiographs are important to facilitate the surgical strategy by localising subcutaneous air, debris, or unanticipated fractures.
Initial management includes obtaining xrays, administering broad-spectrum antibiotics, updating tetanus status and giving analgesics. Additionally, immobilizing and elevating the hand is important.
However, it is a surgical emergency and immediate referral to a specialist hand surgeon for prompt surgical debridement optimizes tissue salvage.
Surgery involves decompression, removal of all injected material and directed debridement of the nonviable tissue.
With paint gun injuries, it is essential that all paint be immediately removed from the wound and especially around the digital arteries.
Overall, surgery can require a number of incisions:
Opening the finger along its length
Midpalmar incision
Incisions often need to be extended proximally to include the carpal tunnel
In general, wounds are left open for serial debridement.
Amputation – is more likely if debridement is delayed more than 10 hours, especially with low viscosity substances.
Fibrosis – tissue fibrosis with resultant finger stiffness
Oleogranulomas – tissues that survive the initial injection injury but still contain grease, paint, or oil heal slowly and may develop multiple oleogranulomas of varying sizes.
Sinuses – in time, the oleomas drain through sinuses or open directly through the skin.
Factors that determine the severity of the injury:
Type and viscosity of the material injected. Paints worse the grease.
Time interval between injury and treatment. Prompt debridement required
Amount of material injected and velocity of the injectant.
Pressure of the appliance. Greater than 7,000 psi results in 100% amputation
Anatomy and distensibility of the site of injection.
Digits: tendon sheath – poor prognosis
Palm: not governed by fascial planes – better prognosis
Development of secondary infection
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