The acute injury is due to the introduction of a foreign material, under high pressure between 2,000-10,000 psi, into the poorly distensible digital or palmar tissues. The pathophysiology involves acute and chronic inflammation and foreign body granulomatous formation. Damage results from the impact, ischemia resulting from vascular compression, chemical inflammation, and secondary infection. Fuel and paint injections lead to the most severe inflammatory response with a high incidence of amputation. Grease and oil-based compounds may lead to oleogranulomas with chronic fistula formation, scarring, and eventual loss of digit function.
Morbidity is dependent to a large degree upon the material injected.
Grease, the more common injectant, causes a less severe inflammatory response. 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 most common site of injury is the index finger. The palm and long finger are the next most frequently injured. With time, edema and intense pain develop and the digit may appear erythematous or cold.