Findings

1. Sequestrum - YES
   • Within the circled area, there is an elongated, dense (hypersclerotic) fragment of bone, clearly demarcated from the surrounding tissue. This is the sequestrum - devitalized, avascular dead bone that has separated from the living cortex.
2. Involucrum
   • Surrounding the sequestrum is a thick, irregular shell of new periosteal bone (involucrum) - the body's attempt to wall off the infection.
3. Radiolucent zone (cloaca gap)
   • A radiolucent halo between the sequestrum and the involucrum, representing pus and granulation tissue.
4. Medullary sclerosis + cortical thickening
   • Extensive sclerosis and widening of the tibial shaft, consistent with long-standing chronic osteomyelitis.
5. Right tibia/fibula - appears normal.

Clinical implications

• A sequestrum acts as a nidus for persistent infection - antibiotics cannot penetrate avascular dead bone.
• Definitive treatment requires surgical sequestrectomy + debridement (Cierny-Mader classification likely Stage III or IV).
• Pre-op CT or MRI is advisable to map the full extent of sequestrum, identify any cloacae, and assess soft tissue involvement.
• Microbiology (deep tissue culture intraoperatively) is important - S. aureus is the most common organism in chronic osteomyelitis.