Presentation
Diabetic with grade II nephropathy and non healing mid foot ulcer.
Patient Data
destruction of the base of 5th metatarsal with moth eaten appearance and loose debris
non visualization of the 3rd and 4th tarsometatarsal joint space
loss of normal tarsometatarsal joint planes
the intermediate and lateral cuneiform, and the cuboid intertarsal planes are lost
CT documents the suspected destructive process primarily epicentered in the mid foot involving the tarsals and tarsometatarsal joints (a periarticular distribution) with increasing severity towards the lateral aspect
significant erosion of the cuboid and base of 5th metatarsal
extensive mid foot soft tissue edema
extensive bone marrow signal changes (T1 hypointense, IDEAL hyperintense) is seen involving the tarsals and base of metatarsals
a sinus track is seen from cuboid tracking into the lateral mid foot skin as well as posteriorly
fluid signal is seen along the fibularis longus tendon and tendon sheath tracking cranially
altered marrow signals also seen in the lateral malleolus and lateral aspect of calcaneum and talus
extensive edema and fluid signal intensity is seen within the intrinsic muscles of the foot
Case Discussion
Long standing diabetic patients tend to develop diabetic neuropathy. The weight bearing portion of the foot is commonly affected. It tends to have a periarticular bony involvement which during the early stages are difficult to distinguish from osteomyelitis. However as more progressive destruction occurs, the periarticular distribution becomes more evident and is confined to the mid foot.
Altered marrow signals in bone may be seen in neuropathy alone due to reactive osteitis. However extension of marrow signal changes to hind foot should always raise the possibility of osteomyelitis.
Of course, a neuropathic joint is more prone to osteomyelitis than a healthy one.
The development of a sinus track along the cuboid is a way for the infection to decompress itself, what we call empyema necessitans. (an innate mechanism to drain infection from the body).
More and more bones of the foot will be prone for spread for infection and urgent intervention is necessary.
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