Soft Tissue and Bone Infections

Abstract

Penetrating injuries and staphylococceal pathogens are the most frequent causes of infections at the hand, with the soft tissues involved in about 95%, and the bones and joints in 5%, only. In soft tissue infections, MRI is mostly necessary for depicting infections of the deep palmar spaces, whereas finger infections are prome to clinical examination. Typically, bone and joint infections are first visible in radiograms two weeks after clinical onset. MRI is powerful in early detection and in the assessment of spreading of both osteomyelitis and infectious arthritis, the adjacent soft tissues included. CT imaging is the modality of choice in the search of sequestra and cloaca when the superficial soft tissues and the skin are involved in chronic osteomyelitis. At the hands, rare infections are of tuberculous, syphilitic, leprous, viral, fungal, and parasitic orgin.

Key Points

• Approximately 95% of all hand infections are located within the soft tissues, with only 5% involving bone or joint.

• The majority of superficial soft-tissue infections can be managed clinically without the need of imaging. However, radiographs, CT or MRI is required in two clinical settings: First, if spread of infection from the soft tissues to the adjacent bones or joints is suspected. Second, if a deep palmar abscess is suspected.

• In acute osteomyelitis, radiographic signs typically lag behind the onset of the infection by 8–10 days. In the majority of cases, initial findings are very subtle, before marked and poorly defined bone destruction appears.

• MRI is the most powerful imaging tool in detecting and comprehensively staging soft tissue and bone infections. Intravenous gadolinium is recommended for better differentiating abscesses from diffuse infections and the surrounding edema.

• CT imaging is best suited in chronic osteomyelitis for depicting the osseous structures, particularly for detecting sequestra that should be surgically removed to reduce the risk of reactivation of the osteomyelitis.

• Tuberculosis of the flexor tendon sheaths, the bones or the joints of the hands should be considered with slowly progressive infections associated with painless swelling and/or a draining sinus.

• Full clinical information is required for correct interpretation of the destructive bone and joint changes. Identification of the causative pathogen is mandatory to indicate the appropriate antibiotic therapy. Imaging-guided aspiration can be useful for this purpose.