Soft Tissue Infections

Septic Bursitis

The human body contains more than 150 bursae, which are sacs or potential spaces lined with a synovial membrane and containing synovial fluid. Bursae, located in the subcutaneous tissue over bony prominences, permit virtually friction-free movement of the skin over these prominences, minimizing irritation. With excessive irritation or use of a joint, a bursa can become inflamed and swollen as more synovial fluid is produced to lubricate the movement of adjacent tissues (see Plate 8-1 ). Excessive irritation can come from the outside of the bursa (knee rubbing on the floor) or from inside the bursa (bone spur). The bursal swelling becomes chronic and persistent, leading to conditions such as housemaid knee.

Direct trauma to the skin overlying the bursa can seed the fluid in an inflamed, swollen bursa with bacteria. The fluid is an excellent medium for bacterial growth, and the infection leads to extensive cellulitis (skin) or septic bursitis, characterized by heat, swelling, marked local tenderness, and loss of range of motion of the adjacent joint.

Treatment of septic bursitis consists of needle aspiration of the bursa to obtain fluid for culture, administration of appropriate antibiotics, and continuous application of warm, moist compresses to the area of inflammation. If the infected bursa does not respond quickly to such local treatment, it should be incised and drained.

Septic Arthritis

Septic arthritis occurs when a joint is seeded with an infective organism, either by direct contamination through traumatic or operative penetration of the joint, by contiguous spread of infection from osteomyelitis in an adjacent bone, or by hematogenous spread from bacteremia resulting from a distant focus of infection in the body. Hematogenous septic arthritis is particularly common in children, especially in the hip. Because of the unique blood supply to the femoral head, the accumulation of pus under pressure within the hip joint can compress the nutrient vessels to the femoral head. If the pressure persists for more than a few hours, osteonecrosis can develop. Therefore, in a child's hip, the development of pus under pressure as a consequence of septic arthritis must be treated as an emergency. Immediate drainage of the fluid and pus is essential not only to treat the infection but also to avoid the devastating complication of osteonecrosis of the femoral head.

The general principles of the treatment of septic arthritis are similar to those of the treatment of septic bursitis. Aspirated joint fluid is cultured to determine appropriate antibiotics. Aspirations should be repeated as needed to remove the infected and necrotic material from the joint. In most cases, the most effective way to remove the pus is by incision and drainage of the joint, followed by thorough irrigation. Aggressive early treatment usually results in complete resolution of the infection without residual joint problems. Persistent smoldering infections, however, will destroy the articular cartilage, leading to postinfection arthritis and sometimes complete destruction of the joint.