What are the two main mechanisms for development of osteomyelitis?
1. Direct inoculation from a wound, ulcer or superficial infection. This is the most common cause. 2. Hematogenous spread. More common in children.
What nuclear medicine scans can be recommended to confirm the diagnosis?
A radiolabeled WBC scan, gallium 67 or F-18 FDG PET study can be used to confirm the diagnosis of osteomyelitis. These are agents which are able to localise inflammation. If vertebral osteomyelitis is suspected, gallium 67 of F-18 FDG PET should be used instead of a WBC scan.
Hypothetically if there was pregnant patient with a similar presentation, what alternative modality can be used to assist with this diagnosis?
MRI can be used to assess for intraosseous oedema, periosteal reaction and cortical defects that would suggest osteomyelitis. For detection of septic arthritis, findings include subchondral oedema, pericapsular oedema and synovial enhancement with gadolinium contrast. In our case, the patient had metallic shrapnel that was a contraindication for MRI.
On the dynamic flow images, there is hyperaemia involving the medial aspect of the left foot from the distal phalange of the hallux to the mid foot. This persists on the blood pool images. Intense focal osteoblastic activity localised to the left first metatarsophalangeal joint, phalanges and metatarsal of the hallux. Less intense radiotracer accumulation in the left mid foot and medial left calf reflect hyperaemia from increased tracer delivery to the left hallux.
These findings are consistent with septic arthritis of the left first metatarsal phalangeal joint and osteomyelitis of the 1st metatarsal and phalanges.