[Air Entrapment Caused by Valve Mechanisms in Chronic Wounds, a Benign Phenomenon? A Series of Three Cases]

Benign subcutaneous emphysema caused by a valve mechanism and subsequent air entrapment is rare. Less invasive treatment can be performed, but acute life-threatening infectious diseases should be ruled out before treatment; these include gas gangrene or other infections caused by gas producing bacteria.

We retrospectively report on three patients with chronic wounds who developed benign subcutaneous extremity emphysema caused by valve mechanisms with subsequent air entrapment. Patient 1 had a chronic wound at his stump after a lower leg amputation years ago. Due to weight loading and unloading of the lower leg prosthesis while walking, air was sucked in and triggered subcutaneous emphysema. Patient 2 had a persistent fistula at his lateral thigh due to a chronic osteomyelitis and Girdlestone hip. Caused by the up-and-down movements of the femur during walking air was entrapped and led to emphysema. Patient 3 had a drain in his knee for development of a chronic fistula because of a persistent infection of his knee prosthesis. In extension of the knee, the drain was clamped in and air was entrapped during knee flexion and then seeped into the surrounding subcutaneous tissue. No signs of infection in the blood samples were present in two of the patients. None of the patients had fever and no gas producing bacteria were identified in the microbiological cultures. Only multisensitive Staphylococcus aureus was present in the wounds of patients 1 and 2.

Two patients were treated surgically. One patient was treated by fasciotomy plus debridement and irrigation of the wound. A second patient was treated by debridement of the Girdlestone hip, air evacuation and insertion of a drain. No sign of infection - such as necrosis or gangreneous tissue - was seen during these operations. In patient 3, the drain was removed in flexion of the knee and air was removed from the subcutaneous tissue through a separate, sterile needle punction.

There have been few published reports on benign subcutaneous emphysema caused by a valve mechanism. No standardised treatments exist, as it is initially difficult to distinguish this condition from an acute life-threatening infection. If a patient has a chronic wound at the location of the endoprosthesis or stump prosthesis after amputation, the possibility of benign air entrapment should be routinely considered.