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Ankle pain in the diabetic patient – Is it just a sprain?
Columnist presents radiographs to determine whether the patient has Charcot, chronic osteomyelitis, gout or septic arthritis.
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Upon initial consultation, a 42-year-old man presented to the emergency room with complaint of left ankle pain following a sprain roughly one week prior. He related gradual onset of a “dull ache” over the ensuing week without any recollection of true injury or episodes of swelling.
During more in-depth questioning, he admitted to history of chronic ulceration, greater than six months in duration, about his lateral left ankle, which presently was healed. His past medical history included diabetes, neuropathy and osteomyelitis. His past surgical history was unremarkable. His medication included insulin and was otherwise unremarkable.
 Patris Toney |
The patient was afebrile. Physical examination demonstrated palpable pedal pulses and unremarkable left lower extremity edema with regard to discernible differences to his contralateral leg and foot. No apparent cellulitis or increased warmth was noted to the involved ankle. Radiographs of the left foot showed erosive changes about the metatarsophalangeal joints (Figures 1 and 2) as well aggressive destruction about the ankle joint with proximal extension along the tibia and fibula (Figures 3 and 4). Labs revealed a white blood cell count within normal limits, no left shift and inflammatory markers were normal as well.
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 |  Photos courtesy of P. Toney |
Based on the radiographs, what would your diagnosis be?
- Charcot
- Chronic Osteomyelitis
- Gout
- Septic Arthritis
CASE DISCUSSION
The correct answer is B.
The patient was diagnosed with chronic osteomyelitis. Due to the extensiveness and location(s) of the osteomyelitis, a below-knee amputation was recommended along with hospitalization and intravenous antibiosis in addition to obtaining bone scans and MRIs. However, and somewhat understandably, the patient was reluctant to undergo a below-knee amputation. He refused the bone scan as well as the MRI and opted for an immobilizing cam walker. The seriousness of his infection and the potential for conversion to an even more devastating acute osteomyelitis was explained to him. The patient continued to refuse medical or surgical intervention.
Osteomyelitis, whether acute or chronic, is a destructive infectious disease, which affects the cortex, periosteum, cancellous, and marrow composition of the bone. Acute osteomyelitis manifests as a red, hot, swollen foot with or without constitutional signs of infection. Chronic osteomyelitis, on the other hand, takes on a more subtle appearance with the foot appearing healthy upon physical examination. In the diabetic population, osteomyelitis is especially devastating because the patients have decreased ability to perceive true pain and fail to exhibit early clinical signs and symptoms, thereby allowing dissemination of the infective process. Often, systemic manifestations lag due to alterations or derangements of the immune system.
This disease process is commonly associated with history of or present ulceration(s). The greater the duration of the ulceration, the deeper the ulceration and the more severe the infective process, the greater the risk for the development of osteomyelitis. The risk of osteomyelitis is considered to be even greater in the presence of exposed bone or the ability to probe to bone with a sterile instrument or the end of a cotton tip applicator. Aside from ulcerations, other causes of bone infection are through hematogenous spread or via direct bone penetration by foreign body such as puncture wounds. Most commonly caused by Staphylococcus aureus, this devastating osseous disease process also has been associated with pseudomonas along with other non-staphylococcal organisms. Even more complex is polymicrobial osteomyelitis as seen in diabetics due to the increased prevalence of polymicrobial skin and soft tissue infections.
Due to the immunologic derangements found among the diabetic population, physical examination may be unremarkable for signs of infection such as redness, increased warmth or edema. In such cases, diagnostic labs may aid in finding or diagnosing osteomyelitis. However, it is important to keep in mind that indicators for infection or inflammation such as leukocytosis may very well be absent in addition to a normal or unimpressively elevated ESR or CRP.
Other diagnostic modalities available include radiographs, MRI, CT scan and bone scans. Radiographs serve as good baseline diagnostic films when suspecting osteomyelitis. It is imperative for physicians to remember that 30% to 50% of the bone’s integrity must be compromised before destruction is evident. Additionally, there is a 10- to 14-day lag between the occurrence of destruction and its showing up on radiographs. Thus, radiographs may appear normal even in the presence of bone infection. More advanced tests include MRI, CT or bone scans. Bone scans, especially, white blood cell, gallium or indium labeled, are helpful in identifying infected bone, but have limitations. MRI and CT scans are helpful to overcome the limitation of bone scans by helping with delineating and assessing the extent of marrow damage and underlying periosteal /cortical disruption. Ultimately, bone biopsy remains the best for diagnosing osteomyelitis.
Treatment involves oral or intravenous antibiotic therapy over the duration of six weeks or more depending on multiple factors. After a period of antibiotic treatment, imaging diagnostic tests are repeated to assess the efficacy of the treatment. In cases where the infection is extensive, fails to respond to antibiotic therapy or is more agreeable to surgical intervention, then surgery can be performed via amputation or resection of infected bone with a short course of antibiotic therapy postoperatively.
Osteomyelitis is a serious disease process in which early detection affords patients, particularly diabetics, the best chances of minimized limb loss from amputation, whether it be a toe, the foot or leg.
To successfully reduce the number of lower extremity amputations, it is important that family practice physicians, internal medicine physicians, endocrinologists and other treating physicians be able to identify and diagnose osteomyelitis, which may be unintentionally overlooked or misdiagnosed due to the lack of suspicion secondary to patients demonstrating lack of cardinal signs of infections.
Early recognition and referral to a specialist for respective treatment, which can include oral or intravenous antibiosis with or without surgical intervention, help to ensure the best future for our patients. A team approach centered around the patient may give patients the best chances at a good quality of life.
Patris Toney, DPM, MPH, is a Fellow at the Center for Lower Extremity Ambulatory Research, and a Fellow at the National Center for Limb Preservation, IL.