Neuropathic (Charcot)

 Disturbance in sensation leads to multiple microfractures o Pain sensation is intact from muscles and soft tissue  Distribution and causes o Shoulders – syrinx, spinal tumor o Hips – tertiary , o Knees – tertiary syphilis (more bone production), diabetes (less bone production) o Feet – diabetes o Other causes . Amyloidosis . Congenital indifference to pain . Polio . Alcoholism

 X-ray findings o Sclerosis o Destruction of o Fragmentation o Soft tissue swelling from synovitis o Joint effusions o Osteophytosis o Disorganized and disrupted joint o No osteoporosis

Marked sclerosis, fragmentation and joint destruction are the hallmarks of a neuropathic joint here cause by tabes

 DDX o Degenerative joint disease . Eventually neuropathic joint shows more sclerosis . More fragmentation in neuropathic . More destruction of bone in neuropathic o CPPD . Associated with which a neuropathic joint is not

Neuropathic (Charcot) Arthropathy

General Considerations  Most commonly caused by diabetes today  Bilaterally is rare in foot  Disturbance in sensation leads to multiple microfractures o Pain sensation is intact from muscles and soft tissue  Distribution and causes o Shoulders – , spinal tumor o Elbows and wrists -- syringomyelia o Hips – tertiary syphilis, diabetes o Knees – tertiary syphilis (more bone production), diabetes (less bone production) o Feet – diabetes, congenital insensitivity to pain, chronic alcoholism o Other causes . . Amyloidosis – knee and ankle . Congenital indifference to pain . Polio . Alcoholism Clinical Findings  Signs of in acute phase  Swelling is very common  Pain can occur in 75% of cases but is usually less severe than would be expected on the basis of the radiologic findings  Instability  Loss of joint function  May produce a mass at the joint because of swelling Imaging Findings  Conventional radiography is usually sufficient to make the diagnosis  Findings include: o Sclerosis from eburnation of subchondral bone o Destruction of joint o Fragmentation o Subluxation and dislocation o Soft tissue swelling from synovitis may be massive o Joint effusions o Osteophytosis o Disorganized and disrupted joint o No osteoporosis Differential Diagnosis  Degenerative joint disease o Especially in early stages o Eventually neuropathic joint shows more sclerosis o More fragmentation in neuropathic o More destruction of bone in neuropathic  Calcium Pyrophosphate Deposition Disease o Associated with chondrocalcinosis which a neuropathic joint is not o Also more fragmentation in neuropathic joint  o MRI and nuclear medicine scans, including FDG-PET scans, may help in differentiation Treatment  Usually non-operative  Surgery if unstable, nonreducible fractures or dislocations

Neuropathic arthropathy (Charcot joint) can be defined as bone and joint changes that occur secondary to loss of sensation and that accompany a variety of disorders. Charcot first described the relationship between loss of sensation and arthropathy in 1868. The radiographic changes of this condition include destruction of articular surfaces, opaque subchondral bones, joint debris, deformity, and dislocation (see the images below). Neuropathic arthropathy (Charcot joint) poses a special problem in imaging when it is associated with a soft-tissue infection.[1, 2, 3, 4, 5, 6, 7]

Neuropathic arthropathy (Charcot joint). Neuropathic arthropathy of the shoulder in a patient with syringomyelia. Note the destruction of the articular surface, dislocation, and debris, which are pathognomonic for a neuropathic joint. Neuropathic arthropathy (Charcot joint). of the distal metatarsals and phalanges with tapering results in a pencil-like appearance in the late stage of . Leprosy is one of many causes of neuropathic arthropathy (Charcot joint); joint manifestations of this disease include signs of Charcot disease, which advances despite treatment.[8] Neuropathic arthropathy related to diabetes, syphilis, leprosy, and connective tissue disorders is more common in the elderly population. Neuroarthropathy related to asymbolia, , and spinal trauma is more common in young individuals. Sensory impairment associated with spina bifida and myelomeningocele is the most frequent cause of neuropathic arthropathy (Charcot joint) in childhood.

Neuropathic arthropathy can be classified into hypertrophic and atrophic types. Hypertrophic changes predominate in the upper motor neuron lesions, and atrophic changes occur in peripheral nerve injuries. The early stage ofosteoarthritis simulates neuropathic arthropathy (Charcot joint), both radiologically and pathologically.

Progressive joint effusion, fracture, fragmentation, and subluxation should raise the suspicion of neuroarthropathy. In the advanced stage, abnormal findings on radiographs include subchondral sclerosis, osteophytosis, subluxation, and soft-tissue swelling. Long-standing neuroarthropathy is characterized by disorganization of . The finding of considerable amounts of cartilaginous and osseous debris within the synovial membrane (termed detritic synovitis) should alert the pathologist that the changes may represent a neuropathic joint. Other causes of detritic synovitis include osteonecrosis, calcium pyrophosphate dihydrate crystal deposition disease, psoriatic , , and osteolysis with detritic synovitis. Preferred examination Radiography may be the only imaging required for the diagnosis of neuropathic arthropathy (Charcot joint). In the appropriate clinical setting, a fairly accurate diagnosis can be achieved. The roles of ultrasonography and computed tomography (CT) scanning are limited; however, these 2 modalities can be helpful in identifying any local collection, and they can be used to guide aspiration cytology. The role of magnetic resonance imaging (MRI) and radionuclide scanning is to differentiate soft-tissue infection from osteomyelitis.[9, 10] Limitation of techniques Radiographic findings in the early stages of neuropathic arthropathy (Charcot joint) may simulate osteoarthritis. Radiographs may not demonstrate findings that help in diagnosing osteomyelitis in neuropathic joints, which is a common problem.

The roles of ultrasonography and CT scanning are limited. Ultrasonography can be used to identify any local collection when infection occurs and to guide aspiration for cytologic analysis; however, it provides no further information regarding the integrity of underlying bone. Although CT scanning may be helpful in evaluating cortical destruction, sequestra, and intraosseous gas, these changes are not specific for neuropathic arthropathy.

The role of MRI and radionuclide scanning is to differentiate soft-tissue infection from osteomyelitis. Bone marrow is nonspecific and has several causes; therefore, differentiating bone marrow edema from neuropathic arthropathy (Charcot joint) may not be possible on the basis of MRI findings alone. Similarly, enhanced bone activity on radionuclide scans is a nonspecific finding and may occur with several neoplastic, inflammatory, and degenerative processes. Differential diagnosis and other problems to be considered Calcium pyrophosphate deposition disease and primary osteoarthritis are in the differential diagnosis. In addition, in the early stage, neuropathic arthropathy (Charcot joint) can simulate osteoarthritis, and bone fragmentation and collapse are seen in osteonecrosis, posttraumatic osteoarthritis, intra- articular steroid injection, infection, and alkaptonuria.

Baker et al reviewed neuropathic arthropathy in diabetics.[11] Neuropathic diabetic arthropathy, particularly in the feet, is the leading cause of morbidity in diabetic patients. It has many mimics. Ulcers, sinus tracts, or an abscess with an adjacent region of abnormal signal intensity in bone marrow suggests osteomyelitis. Contrast-enhanced MRI allows differentiation of viable tissue from necrotic regions in infections, which require surgical debridement in addition to antibiotic therapy. Subtraction images are particularly useful for visualizing nonviable tissue.

Dialysis-associated occurs in diabetic patients with a long history of hemodialysis. Intervertebral disk space narrowing without T2 signal hyperintensity, extensive endplate erosions without endplate remodelling, and facet joint involvement are suggestive of spondyloarthropathy instead of infectious diskitis or degenerative disk disease. The clinical features of infective diskitis and spondyloarthropathy overlap, but knowledge of the patient's medical history, and recognition of imaging characteristics described above allows the radiologist to make a prompt and accurate diagnosis, leading to prompt appropriate treatment.[11] Special concerns The incidence of osteomyelitis is increased in patients with neuropathic joints, particularly in the foot. Hence, careful follow-up imaging is essential.

CHARCOT’S FOOT

Figure 1: X-ray of the feet showing Figure 2: Annotated x-ray of the feet Charcot's joint deformity. showing Charcot's joint deformity. (Click on image to enlarge) (Click on image to enlarge)

A Charcot joint (neuropathic joint) is due to a progressive destructive joint disorder in patients with impaired pain sensation and proprioception. In contemporary medicine, particularly when involving the foot/ankle, this is due to longstanding diabetes. The 2 theories for the pathophysiology of this condition are the neuro-traumatic theory in which repeated trauma with no sensory feedback occurs and the neurovascular theory in which the absence of neural stimuli results in vasodilatation and hyperemia which promotes . Other less common causes aside from diabetes include the D S’s: Syphilis Steriods Syringomyelia Spina Bifida Scleroderma On plain film radiography it is characterised by multiple findings, remembered as the 6 D’s: Dense bones (sub-chondral sclerosis) Degeneration Destruction Deformity Debris (loose bodies) Dislocation

Charcot neuro- osteoarthrop athy

Charcot neuro-osteoarthropathy is a degenerative disease with progressive destruction of the bones and joints. It is seen in patients with neurological disorders with sensory loss of the feet, including tabes dorsalis, leprosy, diabetic neuropathy, and other conditions involving injury to the spinal cord. In 1868 Jean-Martin Charcot gave the first detailed description of the neuropathic aspect of this condition in a patient with syphilis. Today, diabetes mellitus is the most common etiology associated with Charcot osteoarthropathy, with the joints of the foot and ankle being most commonly affected.

Here an illustration with the key MR-features of acute Charcot neuro-osteoarthropathy:

 Subarticular marrow edema in the midfoot  Subcutaneous soft tissues are relatively uninvolved. 

The exact nature of Charcot arthropathy is unknown.

The neurotraumatic theory states that Charcot arthropathy is caused by an unperceived trauma to an insensate foot. The sensory neuropathy renders the patient unaware of the osseous destruction that occurs with continuous ambulation.

The neurovascular theory suggests that the underlying condition leads to the development of autonomic neuropathy, causing the extremity to receive an increased blood flow, which in turn results in a mismatch in bone destruction by increased osteoclastic activity and bone synthesis (1).

The image shows a progressive neuro-osteoarthropathy of the tarsometatarsal joints (Lisfranc dislocation) with subchondral cysts, erosions, joint distention and dislocation. 

Acute Charcot

Acute active Charcot neuro-osteoarthropathy is defined by clinical signs. There should be neuropathy and a warm and swollen foot. The skin temperature should be 2?C or more at the site of maximum deformity of the affected foot compared with a similar site on the contralateral foot. Osteomyelitis should be excluded and fever is not present. Serum C-reactive protein level is normal or only a slightly elevated. The differential diagnosis is infection (osteomyelitis, cellulitis, ), inflammation (, ) and deep vein thrombosis.

 In this early stage, radiographic abnormalities are not present. The acute stage of Charcot neuro-osteoarthropathy shows rapid and progressive bone and joint destruction within days or weeks. Immobility by total contact casting can prevent further bone and joint destruction.

Here a radiograph of a patient with diabetic neuropathy and a red hot foot. In the acute stage, the radiographs are normal and may not exclude the diagnosis of acute Charcot neuro-osteoarthropathy.

Within 4 months there is progressive decrease of calcaneal inclination with equinus deformity at the ankle. There is destruction of the tarsometatarsal joint with the typical rocker-bottom deformity.

Bony debris is seen on the dorsal aspect of the foot.

In the acute stage, MRI shows only subchondral bone marrow edema.

Here MRI images of a patient with acute Charcot neuro-osteoarthropathy. The bone marrow edema typically is not restricted to one or two bones, but is seen in the entire midfoot. Bone marrow edema and its enhancement are typically centered in the subchondral bone, suggesting articular disease. The subcutaneous tissues are relatively normal and there is no or other signs of infection.

 Chronic Charcot

The chronic inactive stage no longer shows a warm and red foot. The edema usually persists. Crepitus, palpable loose bodies and large are the result of extensive bone and cartilage destruction. Joint deformity, subluxation and dislocation of the metatarsals lead to a rocker-bottom type deformity in which the cuboid becomes a weight-bearing structure. This results in excessive skin callus formation, blisters and foot ulceration. At the stage of chronic inactive Charcot osteoarthropathy, bone healing and change of active periosteal reaction will proceed into inactive periosteal reaction and sclerotic borders.

The classic radiographic description of neuro-osteoarthropathy is that of the five D' s. Debris may be present and effusions may decompress along fascial planes, carrying bony debris far from the joint. Dislocation is the result of ligamentous laxity.

 On the far left, a normal radiograph in the acute stage of Charcot. Subsequently progressive Charcot neuro-osteoarthropathy is seen with dislocation of the Lisfranc joint.

CLASSIFICATION, EPIDEMIOLOGY, AND CLINICAL PRESENTATION

Psoriatic arthritis (PsA) is a form of arthritis that occurs in patients with psoriasis. It has the hallmarks of an "inflammatory" arthritis, including joint pain, , and swelling, often with prominent stiffness, not unlike the most well-characterized form of inflammatory arthritis, rheumatoid arthritis (RA).[1-8] However, in terms of clinical, genetic, histologic, and immunohistochemical patterns, PsA best fits with the ,[1-5,7,9-13] which include , , the arthritis associated with inflammatory bowel disease, and undifferentiated spondyloarthropathy. Distinct features of PsA, shared with other spondyloarthropathies, include enthesopathy (inflammation of insertion sites of tendon, ligament, and joint capsule), dactylitis (swelling of a digit), a tendency toward asymmetric, sometimes oligoarticular joint involvement, iritis, and a greater chance for male involvement than what is seen in RA.[1,3-6,8,12,14]

Although sporadic case reports of an association between psoriasis and a unique form of arthritis had appeared in the medical literature beginning in the late 1800s, it was not until John Moll and Verna Wright,[1] in 1973, published a review of a large case series of patients that PsA was definitively acknowledged in its own right. In their original case series, 5 subtypes of PsA were characterized (Table 1). The oligoarticular form is the most common. Subsequent case series, including patients with long duration of disease, identify polyarticular presentation as most common, often with progressive joint destruction and disability.[3,7,15,16]

Table 1. Unique Clinical Features of PsA DIP joint involvement

Nail changes Dactylitis

Enthesitis

Spondylitis

Lytic and periarticular new bone formation x-ray features

Iritis

What Is the Relationship Between the Skin Lesions of Psoriasis and an Inflammatory Arthritis? Psoriasis occurs in approximately 2% of the population of North America and Europe, varying somewhat in other parts of the world, depending on genetic patterns.[17- 19] Studies report an occurrence rate of PsA of 6% to 39% in patients with psoriasis.[20,21] The 6% figure is derived from a population-based case report series from Olmstead County, Minnesota (the Mayo Clinic catchment).[21] The 39% figure is derived from another Mayo Clinic study,[20] in which patients hospitalized with severe psoriasis were carefully studied for manifestations of PsA. Recent large telephone surveys of psoriasis patients have been conducted in Europe and the United States.[22] In the EuroPSO survey, 30% were diagnosed with PsA, compared with 11% in the United States.[23] A number of factors may contribute to this discrepancy, including inaccuracies or lack of diagnosis; general lack of awareness about PsA; the possibility of misdiagnosis with the more common form of arthritis, osteoarthritis; and lack of reporting of joint symptoms to physicians and possibly the degree of psoriasis involvement. Indeed, one study has suggested that patients with PsA experience less tenderness of joints than do patients with RA, which may contribute to underreporting.[24] One bone scan study of patients hospitalized for psoriasis showed evidence of periarticular light-up despite absence of polyarticular symptoms.[25] The skin lesions of psoriasis usually appear before the arthritis in up to 80% and typically by 5-10 years.[4,6,8,26] In approximately 10% to 15%, the skin and joint symptoms arise simultaneously, and in another 10% to 15%, the joint symptoms precede the development of psoriasis and might be labeled undifferentiated spondyloarthropathy until the skin lesions develop. To date, no specific marker, either clinical, immunohistochemical, or genetic, has been identified which can definitively tell us which psoriasis patients are going to develop an inflammatory arthritis. The only associated patterns identified are possibly a correlation with psoriasis severity, as previously stated, and nail involvement noted in up to 80% of PsA patients.[26]

In addition to unique clinical features, see Table 1. Some characteristic x-ray changes may aid in diagnosis. These include pencil-in-cup changes of digital joints, periostitis, joint ankylosis, tuft osteolysis, asymmetric syndesmophytes, and sacroiliac changes.[1,6,8,25,27,28] (Figure) Laboratory features are otherwise not predictable, as acute- phase reactants such as sedimentation rate and C-reactive protein may be variably elevated, and rheumatoid factor and anti-CCP antibody are usually (but not always) negative.[3,16,26]

Figure. Examples of unique radiographic features of PsA.

Challenges of Assessing Disease Severity Part of the difficulty in accurately assessing the prevalence of PsA prevalence stems from not having an adequate set of criteria for disease classification. Most clinical studies have relied on the original simple classification schema outlined by Moll and Wright, ie, in a patient with psoriasis and inflammatory arthritis, presenting with 1 of the 5 subtypes identified in their original study.[1] (Table 2) Various other criteria sets have been proposed, as reviewed by Taylor and Helliwell, but none have become significantly established.[3,11,29-32] Recently, a group of investigators led by Philip Helliwell have conducted a patient-based exercise in which 588 patients diagnosed with PsA had extensive history, physical examination, laboratory and x-ray evaluation, and were compared with 536 "control" patients with other inflammatory arthritides. Using such methodologic techniques as classification and regression tree (CART) and logistic regression analysis, a new criteria set is being developed which uses both clinical and x- ray features.[11]

Table 2. Subtypes of PsA Oligoarticular (< 5 joints), asymmetric

Polyarticular, often symmetric

Distal Interphalangeal (DIP) joint predominant

Spondylitis spine predominant

Arthritis mutilans (highly destructive/lytic)

The Spectrum of Disease Severity The spectrum of severity of PsA is broad. Some patients will experience a mild degree of pain and stiffness in a few joints with mild skin lesions, and at most will require therapy with nonsteroidal anti-inflammatory drugs (NSAIDs), occasional intra-articular or enthesial corticosteroid injections, and topical steroid creams.[26,33,34] Others will have more severe joint and/or skin symptoms, with significant pain and stiffness and embarrassing and uncomfortable skin lesions typically requiring more immunomodulatory therapy.[26,33,35,36] It is the latter group that is at risk for progressive joint destruction and disability related to both physical as well as social/work-related dysfunction, and that is also at higher risk for early mortality.[37,38] By observing a large cohort of PsA patients over time, Gladman from Toronto found that in those patients affected, PsA can result in joint deformity in 55%, lead to chronic disability in 20%, and may result in early mortality.[7,38].Using data from the SF-36 measure of quality of life, it has been noted that among the chronic diseases, psoriasis ranks second worst in physical function and third worst in relation to mental function[39] as compared with multiple other chronic disease states, including heart disease and cancer