Acute Charcot arthropathy as a first presentation of type 2 diabetes mellitus

Abstract

Charcot arthropathy in people with diabetes is generally seen when diabetes has been well established, and therefore it is not routinely considered as a differential diagnosis in people presenting with erythematous and oedematous joints in primary care. We present two cases of acute Charcot arthropathy as a first presentation of type 2 diabetes mellitus. The first case describes a man in his 70s, who presented with a 5-week history of right foot pain, treated initially in the community as cellulitis. A diagnosis of acute Charcot arthropathy was made in the emergency department following review by the orthopaedic and podiatry department. The second case describes a woman in her 40s who presented with a 2-week history of ankle pain. Charcot arthropathy is associated with significant morbidity and mortality, and these cases highlight the importance of including Charcot arthropathy in the differential diagnosis when people present with atypical joint swelling.

Background

Charcot neuroarthropathy was first described in 1868 by Jean-Marie Charcot in a patient with syphilis.¹ In 1936, the first case of Charcot arthropathy in diabetes was reported.² Today, Charcot neuroarthropathy is typically seen as a late complication of diabetes, presenting when the patient has established peripheral neuropathy.³

The pathogenesis of the development of a Charcot arthropathy has been long debated and likely comprises both neurovascular and neurotraumatic components. Charcot arthropathy is usually preceded by a minor injury or stumble, which can stimulate increased blood flow to the area of microtrauma or stress causing excessive bone resorption, weakening of the surrounding structures, subluxation, instability and dislocation of the bones within the foot. Neurotrauma proposes that if there is presence of distal symmetrical polyneuropathy in a patient with type 2 diabetes mellitus (T2DM), this can lead to repetitive trauma, abnormal plantar pressures and repetitive stress on the bones within the foot, which may fracture and become unstable.⁴ In 2004, Jeffcoate first described the receptor activator of nuclear factor kappa B (RANK)/RANK–ligand (RANK-L) signalling pathway in the pathogenesis of Charcot arthropathy.⁵ The neurobone inflammatory theory is based on the idea that microtrauma leads to release of proinflammatory cytokines such as interleukin-1b and tumour necrosis factor alpha, which are mediators of bone resorption via osteoclasts.⁶ These proinflammatory cytokines lead to increased expression of RANK-L which is located on the cell membranes of osteoblasts.⁶ RANK-L stimulates the expression of a transcription factor, nuclear factor kappa B (NF-kB), which causes the maturation and activation of osteoclasts and osteolysis.⁶ Osteoprotegerin, a glycoprotein that is also upregulated by NF-kB, is an antagonist of RANK-L and acts to limit osteolysis.⁶ The actual aetiology of Charcot arthropathy seems to incorporate a combination of these three described mechanisms⁷ but peripheral neuropathy is considered essential in all.⁸

In people with diabetes, the foot is the most common joint affected by Charcot neuroarthropathy. The acute form typically presents as Eichenholtz stage 0 or 1,⁹ with warmth and erythema as well as an oedematous foot or ankle. It tends to be painful in 75% of cases.^{10 11} An acute Charcot joint may be triggered by minor trauma or can occur spontaneously. It is associated with a number of medical conditions including leprosy, syphilis and rheumatoid arthritis, but by far the most common cause is diabetes. The prevalence of Charcot arthropathy in people with diabetes ranges from 0.1% to 7.5% with much higher rates (up to 35%) reported in those with peripheral neuropathy.¹² The incidence of Charcot arthropathy from the Danish national patient register was 7.4 per 10 000 person-years; most patients who present with Charcot arthropathy will be in their fifth or sixth decade and will have had diabetes for at least 10 years.^{13 14} Rarely has an acute Charcot joint been described as the first presentation of diabetes,^{15 16} but here we describe two cases of an acute Charcot foot at time of presentation in Irish patients with undiagnosed T2DM.

Case presentation

Case 1

A man in his 70s was referred by his general practitioner (GP) with a 5-week history of right plantar foot pain with no preceding history of trauma and a small necrotic ulcer on the tip of his right third toe (figure 1A, B). He had been treated with flucloxacillin and phenoxymethylpenicillin for a week prior to presentation. On examination, there was discolouration of his right third toe and tenderness on palpation of the right foot. Sensation to 10 g monofilament and tuning fork was absent but he had normal foot pulses. His right foot was 4°C warmer than his left foot. He described ongoing bilateral paraesthesia in both feet for the preceding months but he put the symptoms down to his occupation as a butcher and being on his feet for 8 hours a day. Body weight was 72.5 kg with a body mass index (BMI) of 25.1 kg/m². He had no medical history and was taking no medications. He was an ex-smoker and consumed 70 units of alcohol per week. He had a family history of T2DM. At presentation, his glucose was 25 mmol/L with a glycated haemoglobin (HbA1c) of 99 mmol/mol (11.2%). He was initially started on metformin and insulin glargine. Plain film X-ray of the right foot showed a Lisfranc dislocation of the tarsometatarsal joints with possible fractures of the base of the second and third metatarsals and bony destruction of the third distal phalanx, in keeping with osteomyelitis in the latter. He underwent debridement and removal of the necrotic third distal phalanx. Subsequent MRI of the right foot showed marked bone oedema across the mid-tarsal bones, base of all five metatarsals and head of the talus with cartilage loss across the midfoot joints and almost complete dorsal dislocation of the base of the metatarsals relative to the mid-tarsal bones in keeping with chronic Charcot midfoot. He was linked in with the podiatry service and offloaded with a total contact cast which he wore for 4 months prior to being transitioned to VACOped boot. His postoperative recovery was uneventful initially and he continued to attend the specialist diabetes multidisciplinary team foot clinic every month. Unfortunately, he subsequently developed an ulcer on the medial aspect of his midfoot. He was initially managed in the community with oral antibiotics but the ulcer continued to deteriorate and he recently required an admission to hospital for treatment of osteomyelitis, which is ongoing.

Figure 1.

(A) Ulcer on tip of right third toe. (B) Evidence of Charcot arthropathy of the right midfoot.

Case 2

A woman in her 40s presented to the emergency department with a 2-week history of right ankle swelling following twisting her ankle. There was evidence of erythema to the medial surface of the right foot extending proximally to the right calf. She had been treated with flucloxacillin by the GP with no improvement. On plain X-ray, there was evidence of a Lisfranc midfoot fracture-dislocation, with surrounding degenerative changes and new bone formation (figure 2). She was given a repeat course of flucloxacillin and referred to the orthopaedic outpatient clinic. The foot was not offloaded and she was allowed to continue to walk. Her medical history was significant for obesity with a body weight of 114 kg and a BMI of 41 kg/m², but she had no known history of diabetes. Three weeks later, she attended the orthopaedic outpatient clinic and had a CT scan of the right foot, which showed complete disarticulation of the midfoot and medial cuneiform with widespread destruction of the articular surfaces, with bone fragments at all surfaces, as well as MRI (figure 3). She was admitted electively for a surgical fusion of her right midfoot.

Figure 2.

Lisfranc dislocation of the tarsometatarsal joints.

Figure 3.

MRI of the right foot showing bony oedema and extensive bone changes consistent with midfoot Charcot foot disease. The classic ‘rocker bottom’ deformity is seen as a result of midfoot involvement.

In the anaesthetic room preoperatively, she was noted to be hyperglycaemic with a plasma glucose of 15 mmol/L and an HbA1c of 104 mmol/mol (11.7%) confirming a new diagnosis of T2DM. She was managed with a variable rate intravenous insulin infusion regime during the perioperative period with no delay to her surgery. Her postoperative recovery was unremarkable and she was discharged home on metformin 500 mg twice per day and to remain non-weight-bearing in a total contact cast for 3 months. She was seen in the orthopaedic clinic monthly thereafter, but 1 year later, she developed an ulcer as a consequence of the Charcot arthropathy on the plantar surface of her right foot (figure 4). Five years after her initial presentation, despite appropriate offloading footwear, she continued to attend the multidisciplinary foot clinic with a chronic non-healing foot ulcer, recurrent episodes of foot ulcer infection and cellulitis requiring antibiotic therapy with occasional episodes of osteomyelitis requiring hospital admission. Lower limb amputation was recommended but she declined this option and continued to have a chronic foot ulcer despite optimal therapy and offloading. Unfortunately, she was recently admitted with septic shock secondary to an acute infection of the chronic foot wound and died.

Figure 4.

Neuropathic foot ulcer in the setting of a Charcot foot.

Discussion

Today, Charcot arthropathy is a potential complication of long duration diabetes in association with peripheral neuropathy and is typically associated with a history of poor glycaemic control. This case report highlights two cases of patients, unaware of their underlying diagnosis of diabetes, who both presented with an acute Charcot arthropathy.

The presence of a Charcot joint increases the risk of diabetic foot ulcer development and subsequent lower limb amputation.¹⁷ A diagnosis of Charcot arthropathy in patients with diabetes may reduce life expectancy by on average 14 years, and almost 20% of patients will die within 2 years of diagnosis.¹⁸ Early detection of a Charcot foot is therefore essential to reduce the risk of deformity, reduce the risk of foot ulceration and the risk of lower limb amputation. Furthermore, early detection of T2DM is crucial to avoid development of Charcot arthropathy. Early diagnosis of diabetes and pre-diabetes in primary care with routine foot examination will help to detect the presence of peripheral neuropathy and those at higher risk of developing Charcot arthropathy.

Charcot arthropathy is a diagnosis of exclusion; therefore, the diagnosis can only be made after other, and often more common, causes of the swollen joint are ruled out. History and physical examination are crucial in determining the aetiology of a swollen joint. In particular with the history, any trauma or risks factors for peripheral neuropathy should be identified. Examination and investigations should be performed to exclude other differentials of a hot swollen foot including cellulitis, septic arthritis, acute gout, deep venous thrombosis, ruptured Achilles tendon or Baker’s cyst and acute tenosynovitis. Examination should include a full neurological assessment of the lower limbs as well as a focused peripheral neuropathy examination including monofilament testing, vibration, proprioception and ankle reflexes. Investigations should initially include imaging, weight-bearing radiographs of both anterior–posterior and lateral views of the affected foot and/or ankle joint. MRI is the preferred imaging choice if the initial radiographs are reported as normal and a high clinical suspicion for a Charcot joint remains. Plain radiographs can be reported as normal for up to 6 weeks after onset of the arthropathy.¹⁹

It is important that physicians working in emergency medicine and general practice have an awareness of the diagnosis of Charcot arthropathy in patients with and without diabetes who may present with a hot swollen foot in the setting of peripheral neuropathy. Key distinguishing features of a Charcot foot include the absence of a clear preceding trauma, unilateral swelling with a measurable temperature difference, erythema, pain and bounding foot pulses. A Charcot joint should also be considered when people present with ulceration in atypical sites on the foot.

Learning points.

• In patients who present with an acute hot and swollen joint, without any evidence of preceding trauma, ulceration or an open wound, diabetes should be considered.

• Charcot arthropathy is a diagnosis of exclusion. The diagnosis can only be made after careful and detailed history and examination followed by appropriate imaging studies and laboratory tests.

• Screening people with diabetes and pre-diabetes for distal symmetrical polyneuropathy is essential, as 50% of patients may be asymptomatic and Charcot foot disease can affect patients with newly diagnosed diabetes.

• Once a Charcot foot is suspected, offloading the foot is the key first step in management, and referral to a multidisciplinary diabetes foot team is recommended to improve outcomes for diabetes-related foot disease.

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