Ultrasound-diagnosed bone and joint destruction as a typical image in advanced Charcots arthropathy - case report.

The paper presents a case of Charcot foot in a patient with long standing type 2 diabetes and complicated by peripheral neuropathy. It was initially diagnosed by an ultrasound examination and subsequently confirmed by an X-ray and an magnetic resonance imaging. Diabetic neuropathy is nowadays the most frequent cause of Charcot arthropathy, although it can be also a result of other diseases of the nervous system. In the acute phase the patient usually presents with edema, redness and increased temperature of the foot, which can suggest many other diagnoses including bacterial infection, gout, venous thrombosis or trauma. Because of its non specific clinical presentation and unsufficient awareness of the specificity of the diabetic foot syndrome among health professionals and the patients the diagnosis of this process is in many cases delayed. In the acute phase appropriate treatment needs to be initiated (mainly off loading and immobilization of the foot in a total contact cast), otherwise a rapidly progressing destruction of the bones and joints will usually begin, leading to fractures, dislocations and a severe foot deformity. Increased awareness among doctors taking care of the diabetic patients and appropriate use of the imaging methods can definitely improve efficacy of the diagnostic process and help to optimize the treatment of Charcot arthropathy. The standard approach usually includes use of radiography, magnetic resonance imaging and scintigraphy. In some cases a sonographer may be the first one to notice typical signs of bony destruction in a patient with Charcot arthropathy and suggest immediate further imaging in order to confirm the diagnosis and to minimize the risk of mutilating complications.

Introduction

Diabetic foot syndrome is one of the most common complications of diabetes. Alongside neuropathy and ischemia this syndrome includes infections within the soft tissues and bony structures of the foot (as a consequence of neurogenic and vascular abnormalities) and a less frequent complication – neuropathic osteoarthropathy known as Charcot arthropathy. In the differential diagnosis of Charcot arthropathy clinical data, laboratory results and radiological images should be taken into account. Patients who present a swollen foot or ankle may be referred for an ultrasound scan as an initial imaging method and in these cases an inquisitive sonographer has a chance to play a vital role in providing a quick diagnosis, resulting in appropriate treatment.

Case report

Forty-one-year-old man with 10 years history of type 2 diabetes (HbA1c 8.2%) visited a rheumatologist with pronounced swelling of his left foot, associated with moderate erythema and mild pain. There was no history of a foot ulcer and the skin was intact (fig. 1).

Fig. 1

Photograph of the patient's feet at the time of the ultrasound scan

The patient associated the onset of these symptoms with a minor left foot injury which occurred nearly a year before. The radiograph performed at that time was reported normal and an orthopedic surgeon diagnosed an ankle distortion. Over the course of one year there was a significant regression of foot edema and erythema, and the skin temperature, which had initially been increased, returned to normal. In January 2011 the patient decided to repeat the radiograph of his left foot. The radiological report described significant bony changes, suggested gout as their cause and the patient was referred for further rheumatological consultation.

The consulting rheumatologist requested an ultrasound scan which showed irregularity and dislocation of the midfoot bones. Joint effusion and features of moderately increased vascularity in the PD option were observed, but no other abnormalities were noted (figs. 2, 3). As the patient did not provide any earlier radiographs of his foot nor any other diagnostic imaging results, the sonographer decided that further diagnostic procedures were necessary and referred the patient for a plain radiograph of the foot (fig. 4). The radiograph revealed fragmentation of the midfoot bones, subluxations and luxations in the tarsal and tarsometatarsal joints. These findings combined with the clinical data were consistent with the diagnosis of Charcot arthropathy.

Fig. 2

Ultrasound scan reveals irregularity of the midfoot bones – panoramic imaging option

Fig. 3

Ultrasound scan reveals effusion and moderately increased synovial vascularity in PD option

Fig. 4

Frontal radiograph of the feet depicts bony debris within the left foot structures: fragmentation, subluxations and luxations within the tarsal and tarsometatarsal joints. Right foot appears to be normal

The patient was referred to the Diabetic Foot Clinic, where the diagnosis of neuropathic arthropathy was confirmed. He underwent a subsequent MRI of his left foot, which revealed severe destruction in the bony structures and joints of his left foot, dislocations in the midfoot joints and bone marrow edema (figs. 5 A, B).

Fig. 5

MRI of the left foot: sagittal T1-weighted (A) and T2-weighted fat saturated images (B) depict destructive changes: fragmentation, subluxations and luxations within the tarsal and tarsometatarsal joints, bone marrow edema of midfoot bones accompanied by soft tissue edema

Two months after the diagnosis of Charcot arthropathy of the left foot was confirmed the patient contacted the Diabetic Foot Clinic due to increasing edema of his contralateral foot and the subsequent appearance of an extensive but superficial ulceration on its plantar aspect (fig. 6). In laboratory results mildly increased inflammatory markers were noted (CRP at 10.4 mg/L and ESR 34 mm/h – non-fasting results). The right foot was significantly warmer and the difference of the temperature between both his feet was 4.5°C.

Fig. 6

Photograph of the patient's feet 2 months later depicts deformity of both feet and ulceration on the plantar aspect of the right foot

The radiograph of the patient's right foot revealed dislocations and fragmentation of the midfoot bones consistent with Charcot arthropathy (fig. 7). The diagnosis was confirmed by an MRI, which showed similar changes to those, previously observed in his left foot – destruction in the bony structures of the foot, dislocations in the midfoot joints, and bone marrow edema. The images confirmed the diagnosis of bilateral Charcot arthropathy, but combined with the clinical data (slightly increased inflammatory markers and presence of an ulcer) did not allow for the exclusion of a secondary soft tissue and/or bony infection within the right foot.

Fig. 7

Frontal radiograph of the right foot 2 months later – destructive changes within the right foot bony structures: fragmentation, subluxations and luxations within the tarsal and tarsometatarsal joints

Discussion

Acute Charcot arthropathy is a frequently overlooked complication of diabetes and according to the literature reports up to 25% of cases are misdiagnosed(. It clinically presents as a red, hot, swollen foot or ankle with usually mild or absent pain (due to sensory neuropathy). The differential diagnosis includes mainly cellulitis and osteomyelitis, post-traumatic changes, deep vein thrombosis, gout, tendovaginitis and joint inflammation.

In the initial stage plain radiographs, which, in spite of the recent progress in diagnostic imaging techniques, still remain a mainstay in bony structures imaging, do not show any changes. The laboratory findings are also nonspecific. Early changes can be seen in bone scintigraphy as areas of increased radiopharmaceutical uptake and in MRI, which reveals features of bone marrow edema, soft tissue swelling and joint effusion(. If at this point proper treatment is not administered, a dynamic, progressive (from day to day – as per literature descriptions) destruction of bony structures may occur( – subluxations, luxations, fractures, cartilage and bone fragmentation, leading to the appearance of bony debris, which happened in our patient's case.

In cases with an unfortunate outcome, mainly affecting those who do not avoid weight bearing, irreversible deformity takes place, including convexity on the medial aspect of the foot (medial convexity) or rocker bottom deformity. MR imaging in the acute phase reveals enhancement after CM administration, however the enhancement is nonspecific. Therefore CM administration is not considered to be necessary although it allows for a better soft tissue evaluation for the presence of an abscess or sinus tract in case of infection(.

Ultrasound evaluation enables soft tissue assessment in terms of joint, tendon sheath and bursa effusion or abscesses. It is also possible to visualize increased vascularity typical of the active phase of Charcot arthropathy. Ultrasound evaluation of bony structures is limited to visualization of their external contours and possible dislocations.

An essential part of the treatment is immobilization of the affected foot, preferably in a total contact cast and avoiding weight bearing. A total contact cast is applied on average for 8–12 weeks until the process stabilizes (clinically stabilization of the process is defined by the difference of skin temperature between the feet being less than 2°C). At this stage the radiopharmaceutical uptake in bone scintigraphy decreases and the signal intensity in MRI scans gradually becomes normal or decreased in all the sequences which correlates with osteosclerosis seen on radiographs.

However, if in the acute phase of the disease (due to weight-bearing and lack of casting) deformity and dislocations of bony structures occur, the image of the bones and joints of the foot will be irreversibly changed. Thus it is vital to make both diabetic patients and healthcare professionals, including radiologists/ sonographers, aware of the possibility of this complication, in order to diagnose all cases of Charcot arthropathy as early as possible and to minimize the risk of irreversible deformity.

Although the process is usually unilateral, some cases of bilateral foot involvement have been described. It happens more frequently in those cases of Charcot arthropathy, when no weight is borne on the affected foot as per doctor's advice and the contralateral foot becomes overloaded, as in our patient's case.

Conclusions

Diabetes is the most common cause of Charcot's arthropathy and the disease is most likely to affect the foot. Changes characteristic of neuropathic osteoarthropathy may also be caused by other diseases, both congenital and acquired, injuries of the central and peripheral nervous system and they may involve joints of upper and lower extremities and the spine(. Quick diagnosis is essential to prevent irreversible deformities within the musculoskeletal system. Diagnostic procedures include plain radiographs, bone scintigraphy and/or MRI and in some cases an ultrasound scan may be of benefit. The most recent data suggest that elastography may be useful in evaluation of plantar fascia, which alters in the course of Charcot arthropathy(.

An ultrasound scan is not a basic diagnostic method in diabetic foot syndrome. However, the knowledge of possible clinical complications of diabetes and their radiological symptomatology enables the sonographer, when taking into account the patient's medical history, to suspect Charcot arthropathy and make an urgent referral for further investigations, contributing to quick diagnosis and initiating appropriate treatment in order to minimize the risk of significant deformity and amputation.