Patients usually present for evaluation of finger or hand injuries that were sustained while using a high-pressure tool for painting, lubrication or doing maintenance on diesel fuel injectors. Injury usually occurs when the operator wipes a blocked nozzle or tries to steady the gun with his or her free (nondominant) hand. The pain may be mild if it has been a short time since the injury. Initial local symptoms include pain, swelling, and numbness. Often, the pain is severe after a few hours and usually tracks along the line of injection (Fig. 1). Ask the patient what material was used in the device at the time of injection. The four most common substances injected are grease, paint, pain solvent, and diesel fuel. Injection injuries have been reported with water, air, hydraulic fuel, and cement. Patients should be asked about hand dominance and the last time of tetanus immunization.

Only a small site of the injection may be seen early in the course of this condition. A careful assessment should be made of the location of the injection and the route of the injected material. Over time, a significant increase in edema is common. The increase in edema may be associated with impaired arterial inflow and venous drainage (compartment syndrome) (Chapter 22, Compartment Syndrome, Fig. 1).
The early appearance of these wounds is seemingly innocuous. The material can be injected from the fingertip to the elbow if a synovial space has been opened. If the material is injected into the subcutaneous space, it can be expected to spread locally, often down the path of the digital nerves and arteries. The entire arm should be examined for local tenderness along a musculotendinous unit that indicates the path of injection.