What is the role of nuclear imaging in septic arthritis (SA) imaging?

Updated: May 12, 2016
  • Author: Lourdes Nunez-Atahualpa, MD; Chief Editor: Felix S Chew, MD, MBA, MEd  more...
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Answer

Early-phase (blood flow) and later (blood pool) images show increased activity at the joint and on both sides of the affected area. Delayed images obtained at 4-6 hours should demonstrate continued increased activity in the bone with associated osteomyelitis.

Decreased uptake in the femoral head can be seen with decreased perfusion related to high intra-articular pressures from the joint effusion or occlusion of blood vessels by bacteria. [38]

Scintigraphy with 99mTc-MDP is extremely sensitive, though not specific, for septic arthritis. Nevertheless, early stages of the disease may yield normal findings. [39]  Three-phase bone scanning has a reported sensitivity of 90-100% and a specificity of 73-79% for osteomyelitis. These values are likely decreased in septic arthritis without associated osteomyelitis.

Newer agents such as indium (In)-labeled autologous white blood cells, leukocytes labeled with 99mTc-hexamethyl propylamine oxime (HMPAO),99mTc-labeled antigranulocyte monoclonal antibodies, and gallium-67 citrate have also been used to evaluate septic arthritis and osteomyelitis with increased specificity. However, 99mTc-MDP remains the mainstay of scintigraphic imaging. [12, 13]

A positively labeled white cell scan is specific. A positive 3-phase bone scan is specific if no other factors that could cause increased bone turnover are present. Thus, bone scanning is most useful if radiographic results are normal. If other factors (eg, trauma, arthritis) that could cause a false-positive bone scan are present, results should be confirmed with another study such as white blood cell scanning.

Any process that results in increased bone turnover (eg, trauma, nonseptic arthritis) can result in a false-positive finding. Reflex sympathetic dystrophy could cause uptake on both sides of a joint, but it can be differentiated by assessing the clinical history and by finding involvement of all the joints in the affected extremity rather than a single joint.


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