The prevalence of diabetic Charot neuro-osteoarthropathy (CNO) of the foot is difficult to determine due to the lack of clear clinical and radiological diagnostic criteria, as well as lack of awareness, which leads to many cases being misdiagnosed.1 The acute phase of diabetic CNO often goes unnoticed, resulting in delayed management and progression to the chronic phase and subsequent irreversible foot deformity.
In the early phase of acute CNO, patients may present with foot swelling, erythema and elevated foot temperature, but have normal radiological findings. This is classified as Eichenholtz stage 0. This is a pre-fragmentation stage, and it is critical to identify this early to prevent the long term sequelae that may lead to foot deformity and ulceration.2 General practitioners should have a high index of suspicion for CNO when soft tissue, bone or joint deformity is present in the foot of a diabetic patient, along with loss of protective sensation, absent deep tendon reflexes and diminished vibratory sense.1
A presentation of CNO at Eichenholtz stage 0 may mimic or be misdiagnosed as sprain, acute gouty arthritis, cellulitis or osteomyelitis. Most cases of infection will usually involve a direct source of inoculation through an opening in the skin with neuropathic ulcer.3 Clinical examination and investigations, erythrocyte sedimentation rate, c-reactive protein and white blood cell count can exclude infective causes. Indium-111 leucocyte scanning or magnetic resonance imaging (MRI) may be warranted, especially in evaluating patients with apparent soft tissue infection or plantar ulcer.4
However, differentiating between acute infection and CNO remains difficult. MRI and indium-III scanning may show bone marrow oedema and localisation of leucocytes to infected areas, respectively. These findings are highly sensitive to detect acute infection but may give false positive results in the presence of osteoarthropathy.4,5 Definitive diagnosis of acute CNO can be established through bone marrow biopsy. However, this procedure is invasive and involves risks to the patient.6
The high index of suspicion for acute CNO in the case study was based on history, clinical examination and basic investigations, which did not support the diagnosis of infection or acute gouty arthritis. Several predictors that heightened the risk for acute CNO were diabetes mellitus for more than 10 years, macrovascular (nephropathy) and microvascular (retinopathy and neuropathy) diabetic complications, and poor glycaemic control with HbA1c of 8.1%.7
Further investigations, such as an MRI or leucocyte scan, were not performed in this case due to availability and cost. Hence, further management with total contact casting was commenced to arrest the progression of acute CNO.
The aim of management in the acute phase of CNO is to halt the inflammatory process, relieve pain and minimise potential foot deformity.8 Total contact casting of the affected limb is one of the most effective pressure offloading and immobilisation devices to bring about bone healing and reduce inflammation.9
In acute CNO, especially with normal radiological findings, the period of casting and the decision to cease offloading is based on the disappearance of inflammation by clinical evidence such as a reduction in oedema, skin erythema and local skin temperature.10 In view of the difficulty in establishing the resolution of acute inflammation and the lack of sensitivity in objective imaging (particularly MRI), several authors have advocated a protocol for a period of casting for 3–6 months to ensure total healing.11,12 However, prolonged casting can lead to negative sequelae including restriction of mobility, which can lead to an increased risk of falling, reduced quality of life, reduced bone mineral density and increased body mass index.10 Therefore, the duration of casting needs to be closely monitored and decisions around ceasing casting and offloading must be balanced between the risks and benefits of offloading and reloading.
We have reported an unusual case of bilateral acute diabetic CNO of the foot, which presented with sequential involvement of each foot within a very short time interval. It was diagnosed early based on clinical presentation and with normal radiograph findings (Eichenholtz stage 0). The duration of casting was based primarily on the disappearance of oedema and skin erythema, as well as skin temperature. The patient’s feet were monitored closely with biweekly reviews and casts were removed as early possible (after 8 weeks). This meant the degree of deformity was minimised and the patient was then able to ambulate and return to work after 3 months with accommodative custom-made shoes and custom-moulded total contact insoles.
Competing interests: None.
Provenance and peer review: Commissioned; externally peer reviewed.