A 65-year-old man comes to the office due to a week of low-grade fever and dull pain in his right foot. He developed a small ulcer on his right foot 2 months ago that slowly worsened and never healed. He does not recall any precipitating trauma. The patient has a history of type 2 diabetes mellitus, hypertension, hyperlipidemia, coronary artery disease, and peripheral artery disease. He smoked a pack of cigarettes daily for 35 years but quit 5 years ago. Temperature is 38.3 C (101 F), blood pressure is 130/80 mm Hg, and pulse is 88/min. Physical examination shows a 2x2 cm ulcer on the plantar surface of the right forefoot surrounded by a halo of erythema and edema. There is no visible bone at the base of the ulcer, and metal probing does not contact bone. Pedal pulses are decreased bilaterally. Right foot x-ray reveals cortical erosion of the first metatarsal. Which of the following is the most likely mechanism for bone infection in this patient?

Question

A 65-year-old man comes to the office due to a week of low-grade fever and dull pain in his right foot.  He developed a small ulcer on his right foot 2 months ago that slowly worsened and never healed.  He does not recall any precipitating trauma.  The patient has a history of type 2 diabetes mellitus, hypertension, hyperlipidemia, coronary artery disease, and peripheral artery disease.  He smoked a pack of cigarettes daily for 35 years but quit 5 years ago.  Temperature is 38.3 C (101 F), blood pressure is 130/80 mm Hg, and pulse is 88/min.  Physical examination shows a 2x2 cm ulcer on the plantar surface of the right forefoot surrounded by a halo of erythema and edema.  There is no visible bone at the base of the ulcer, and metal probing does not contact bone.  Pedal pulses are decreased bilaterally.  Right foot x-ray reveals cortical erosion of the first metatarsal.  Which of the following is the most likely mechanism for bone infection in this patient?

Quizplus · Accepted Answer

Foot infections are common in patients with diabetes mellitus. Risk is increased in those with poor glycemic control (impaired immunity), neuropathy (impaired recognition), and/or peripheral artery disease (impaired healing). Infections typically develop in areas of skin trauma or defect; less noticeable portals of entry such as skin cracks/fissures, fungal infections, or hangnails may make early recognition particularly problematic. Symptoms usually start with localized skin erythema, warmth, tenderness, and edema. Deeper infections should be suspected in those with long-standing wounds (>1-2 weeks), systemic symptoms (fever, chills), large ulcer size (>2 cm), elevated erythrocyte sedimentation rate, and the presence or palpation of bone in the ulcer base. Patients with any of these features almost always have polymicrobial infections with a mixture of gram-positive (eg, Staphylococcus aureus, Streptococcus pyogenes), gram-negative (eg, Pseudomonas aeruginosa), and anaerobic organisms. This patient with a long-standing ulcer, fever, and x-ray evidence of osteomyelitis likely has a polymicrobial bone infection due to contiguous spread from the overlying ulcer. He requires wound debridement, evaluation of his arterial insufficiency, and empiric, intravenous antibiotics (eg, piperacillin-tazobactam plus vancomycin). Bone biopsy with microbial culture is sometimes performed prior to antibiotic therapy, but many patients are treated empirically. (Choices A, B, C, and E) Superficial diabetic foot infections may be monomicrobial, but deeper infections are almost always polymicrobial. This patient has many signs (eg, size, chronicity, osteomyelitis) of deeper infection. In adults, underlying osteomyelitis with an overlying wound is almost always the result of contiguous spread. Hematogenous osteomyelitis accounts for 20% of osteomyelitis cases in adults (it is much more common in children) and primarily affects the vertebrae, pelvis, and hips. Lymphatic spread is not a common route for the development of osteomyelitis. Educational objective: Diabetic foot infections are common in patients with poor glycemic control, neuropathy, and peripheral vascular disease. Most deep, long-standing diabetic wounds are polymicrobial with a mixture of gram-positive, gram-negative, and anaerobic organisms. Underlying osteomyelitis is common due to contiguous spread from the wound.

A 65-Year-Old Man Comes to the Office Due to a Week