Diabetic foot and osteomyelitis

60 year old male patient, long standing diabetic with grade II nephropathy presented with a non healing left foot ulcer. As an initial investigation a radiograph of the foot was ordered.

AP plain

Oblique and frontal radiograph of left foot

AP

Findings

  • 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.

A detailed evaluation with MRI was suggested to assess extent of soft tissue involvement.

short-axis-t1

Short axis T1 FSE

Untitled1

Long axis IDEAL water

Findings

  • 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.

Correlation CT was done to assess extent of bone destruction

axial-bone

CT long axis bone window

Findings

  • 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.
3d-vrt

3D VRT

Key learning points

  • 6 D’s of neuropathic joint disease
    1. destruction
    2. dense bones (sclerosis)
    3. debris
    4. dislocation
    5. distension
    6. disorganisation
  • Mid foot disease – most common site of affliction in neuropathic joint disease being the pressure points of the foot combined with the decreased sensation making them more prone for injury.
  • Hind foot disease – points towards osteomyelitis.
  • Periarticular distribution – neuropathic rather than infective.
  • Osteitis vs osteomyelitis
    • osteitis: T1 isointense T2 hyperintense marrow seen as a response to the neuropathic destruction
    • osteomyelitis: T1 hypointense T2 hyperintense marrow.
    • Ghost sign: Non visualization of bone in T1, appearance in T2 suggestive of osteomyelitis.

Read more

  1. Yochum and Rowe, suppurative osteomyelitis, chapter 12, Essentials of Skeletal Radiology. 
  2. Donovan, Andrea, and Mark E. Schweitzer. “Use of MR Imaging in Diagnosing Diabetes-related Pedal Osteomyelitis 1.” Radiographics 30.3 (2010): 723-736.
  3. Baker, Jonathan C., et al. “Diabetic musculoskeletal complications and their imaging mimics.” Radiographics 32.7 (2012): 1959-1974.