Septic Arthritis of Hip Joint Causing Avascular Necrosis of Femoral Head in a 4-year-old Girl: A Case Report with Findings of Tc-99m MDP Three Phase Bone Scan

Abstract

Septic (infectious) arthritis refers to invasion of synovial space by microbes and is a clinical emergency. Due to hyperemia of synovial vessels, the characteristic finding of three phase bone scan is increased tracer activity around the involved joint in all three phases. However, when there is prominent effusion (pus) inside the synovial cavity, tamponade of subsynovial vessels occurs, followed by avascular necrosis of intra-capsular bony structures if without urgent decompression. In this situation, the scintigraphic findings of three phase bone scan may turn to be intra-capsular photopenia in all three phases. We report a 4-year-old girl with fever, left hip pain, elevated CRP and ESR. The three phase bone scan showed intra-capsular photopenia of left hip in all three phases. Septic arthritis of left hip joint with prominent joint effusion (pus) and high intracapsular pressure were confirmed by arthrotomy. Avascular necrosis of left femoral head developed despite of the operation and antibiotic treatment. For early identification and proper treatment, it is important for nuclear medicine physicians and clinical doctors to be familiar with these important scintigraphic findings in septic arthritis.