Diabetes-related foot ulcers and infections are most common cause of non-traumatic amputations, resulting in high morbidity and high healthcare costs. lifetime prevalence of foot ulceration is approximately 25 %. Imaging findings, especially MRI, play a crucial role in the diagnosis and evaluation of diabetic foot complications. Moreover, surgical treatment is widely used and postoperative evaluation of diabetic foot is challenging, accordingly. 

1. Pathogenesis of diabetic foot

Skin ulcers, foreign bodies or bites could be entry portal for soft tissue and bone infections. Skin ulcers are commonly at pressure points of foot, including 1^st and 5^th metatarsal head. Combination of neuropathy, decreased blood supply and impaired immune system make eradication of diabetic pedal disease difficult.

• Diabetes-related foot ulcers and infections à high morbidity and high healthcare costs
• 25% of DM patient ; lifetime prevalence of foot ulceration
• Greatest risk factor for osteomyelitis and amputation
• Most common cause of nontraumatic amputations 

  A. The risk factors for the development of a foot ulcer

• microvascular disease with resultant neuropathy
• redistribution of fat away from the sole of the foot

  B. Nervous system damage

• aproximately 70% of patients with diabetes
• directly contributes to foot disorders
• motor and sensory neuropathies → change biomechanics and proprioception →  skin breakdown

  C. Infection

• ulcers, foreign body, bites
• skin ulceration ; entry portal for soft-tissue and bone infections
• anhidrosis due to autonomic neuropathy → produces dry skin  ; vulnerable to callus formation and cracking

  D. Loss of sympathetic neuroregulation

• result in limb hyperemia and increased bone resorption
• weakened subchondral bone à neuropathic destruction

 E. Combination of neuropathy, decreased blood supply and impaired immune system → Difficult eradication of diabetic pedal disease

Fig. 1: Schematic image of pathogenesis of DM foot. Combination of neuropathy, decreased blood supply and impaired immune system make eradication of diabetic pedal disease difficult.

  F. Propagation of infection

• centripetal pattern ; from soft tissu to adjacent bone and joint
• from distal to proximal, along tendon
• contiguous spread through the skin
• hematogenous spread

Fig. 2: Schematic image of pathogenesis of DM foot and progressing to gangrene.

2. Skin ulceration ; commonly at pressure point

•  1^st  and 5^th metatarsal head
• calcaneal tuberosity
• distal phalanges
• Malleoli

Fig. 3: Pressure points of foot. ① Distal phalanges, ② 1st metatarsal head, ③ 5th metatarsal head, ④ Calcaneal tuberosity