Mycobacterium doricum<unk>  and soft tissue infection. Computed tomography scan of the right lower extremity of a 21-year-old patient, showing abscess formation adjacent to nonunion of a right femur fracture. Extensive<unk>  of the forefoot<unk>  in both feet as seen on bone scan The diagnosis of<unk>  is complex and relies on a combination of clinical suspicion and indirect laboratory markers such as a high white blood cell count and fever, although confirmation of clinical and laboratory suspicion with imaging is usually necessary. Radiographs and CT are the initial method of diagnosis, but are not sensitive and only moderately specific for the diagnosis. They can show the cortical destruction of advanced<unk> , but can miss nascent or indolent diagnoses. Confirmation is most often by MRI. The presence of edema, diagnosed as increased signal on T2 sequences, is sensitive, but not specific, as edema can occur in reaction to adjacent cellulitis. Confirmation of bony marrow and cortical destruction by viewing the T1 sequences significantly increases specificity. The administration of intravenous gadolinium-based contrast enhances specificity further. In certain situations, such as severe Charcot arthropathy, diagnosis with MRI is still difficult. Similarly, it is limited in distinguishing avascular necrosis from<unk>  in sickle cell anemia. Nuclear medicine scans can be a helpful adjunct to MRI in patients who have metallic hardware that limits or prevents effective magnetic resonance. Generally a triple phase technetium 99 based scan will show increased uptake on all three phases. Gallium scans are 100% sensitive for<unk>  but not specific, and may be helpful in patients with metallic prostheses. Combined WBC imaging with marrow studies has 90% accuracy in diagnosing<unk> . Diagnosis of<unk>  is often based on radiologic results showing a lytic center with a ring of sclerosis. Culture of material taken from a bone biopsy is needed to identify the specific pathogen; alternative sampling methods such as needle puncture or surface swabs are easier to perform, but cannot be trusted to produce reliable results. Factors that may commonly complicate<unk>  are fractures of the bone, amyloidosis, endocarditis, or sepsis. Classification The definition of<unk>  is broad, and encompasses a wide variety of conditions. Traditionally, the length of time the infection has been present and whether there is suppuration (pus formation) or osteosclerosis (pathological increased density of bone) are used to arbitrarily classify<unk> . Chronic<unk>  is often defined as<unk>  that has been present for more than one month. In reality, there are no distinct subtypes; instead, there is a spectrum of pathologic features that reflects a balance between the type and severity of the cause of the inflammation, the immune system and local and systemic predisposing factors. * Suppurative<unk>  * Acute suppurative<unk>  * Chronic suppurative<unk>  * Primary (no preceding phase) * Secondary (follows an acute phase) * Non-suppurative<unk>  * Diffuse sclerosing * Focal sclerosing (condensing osteitis) * Proliferative periostitis (periostitis ossificans, Garré's sclerosing<unk>  * Osteoradionecrosis<unk>  can also be typed according to the area of the skeleton in which it is present. For example,<unk>  of the jaws is different in several respects from<unk>  present in a long bone. Vertebral<unk>  is another possible presentation.
Osteomyelitis
Cellulitis
Osteoradionecrosis
Septic arthritis
Osteitis
Rheumatoid arthritis
Osteochondropathy
Neuropathic arthropathy