"The formation of an involucrum can be analogised to the process of soft tissue walling off an abscess elsewhere in the body. The involucrum involves a layer of granulation tissue, surrounded by irregular expansile cortical or cancellous bone 1. The inner layer serves to contain the infection, but further separates it from the body's immune system, and biofilm formation can occur, prolonging and complicating infection 2. The outer layer, continuous with the healthy bone away from the site of infection, provides strength to the infected bone and allows continuity of function while the body combats the infection 2."