NEWSLETTER 14: CHARCOT'S JOINT

Charcot's Joint is also known as neuropathic arthropathy. Charcot's joint is a chronic, progressive joint degeneration, often devastating, seen most commonly in peripheral weight-bearing joints and vertebrae, which develop as a result of the loss of normal sensory innervation of the joint. It was described by Charcot as a result of tabes dorsalis.

Charcot foot or Charcot joint is of particular note because between 1% and 2.5% of people with diabetes suffer from this condition. It is caused by abnormalities in the nerves in the feet, which can numb the feet so that the sufferer does not feel pain at first and is not aware of injury. Instead of resting an injured foot or seeking medical help, the patient often continues to walk, causing further damage. Early changes appear like an infection, with the foot becoming swollen, red, and warm. A seriously affected foot can become deformed. The bones may crack, splinter, and erode, and the joints may shift, change shape, and become unstable. Diabetic peripheral neuropathy is a risk factor for this disease.

PREVALENCE:

1. 1 case/750 patients with diabetes mellitus; 5 cases/100 of those with peripheral neuropathy (foot is most commonly involved)
2. 20% to 40% of patients with syringomyelia (shoulder most commonly involved)
3. 5% to 10% of patients with tabes dorsalis; usually >60 yr (spine, hip, and knee most commonly involved)

Progressive destruction of the insensate joint was first described by Mitchell in 1831, but it was most clearly delineated by Charcot in 1868 and hence is sometimes referred to as "Charcot's changes" (1,2). During this pre-X-ray era, the classic clinical description was the feeling of a "bag of bones" (3). Both Mitchell and Charcot postulated this condition was the result of damage to that portion of the nervous system believed to control nutrition of the bones and joints. The famous German surgeon Volkmann challenged this view almost immediately and argued that progressive microtrauma to the unfeeling joint was the cause (4). This latter view became known as the German Theory and was widely taught as recently as 10 years ago.

Increasing evidence suggests the possibility of a neurovascular etiology: that bone resorption from hypervascularity secondary to autonomic neuropathy is a likely cause (5). This theory would explain several common clinical observations:

• initial presentation of a hot, red swollen foot
• variable but often rapid destruction of the bony architecture, sometimes within a few weeks
• documented progression of bony destruction despite complete bed rest or total paralysis (3,6)

PHYSICAL FINDINGS & CLINICAL PRESENTATION

Neuropathic joint disease is relatively painless, often in spite of considerable destruction

• Often, diffusely warm, swollen, and occasionally erythematous involved joint, the latter suggesting sepsis
• Possible progression of joint instability; palpable osseous debris; crepitus common
• Often, frank dislocation, leading to bony deformity, especially in more superficial joints

Neuropathic arthropathy is often mistaken for gout, tumor, thrombophlebitis or infection since the initial clinical symptom is usually a reddened, swollen area with mild discomfort. It appears most commonly in the mid-tarsal region, leading quickly to midfoot collapse or forefoot valgus deformity. Neuropathic arthropathy also can develop in the forefoot or hindfoot, and sometimes results in pathologic fibular fracture (13). Once the active disease process fully resolves, a fixed deformity remains. The classic rigid, rockerbottom foot that results is always difficult and sometimes impossible to manage with orthoses, partly due to the characteristic denial that often accompanies painless lesions.

ETIOLOGY

The most widely accepted theory is the "neurotraumatic" theory:

• Impairment and loss of joint sensitivity decreases the protective mechanism about the joint.
• Rapid destruction occurs.
• Chronic inflammation and repetitive effusions develop, eventually contributing to joint instability and incongruity.

DIFFERENTIAL DIAGNOSIS

• Osteomyelitis, cellulitis, abscess
• Infectious arthritis
• Osteoarthritis
• Rheumatoid and other inflammatory arthritides

WORKUP

• An underlying neurologic disorder must always be present.
• Syringomyelia, tabes dorsalis, Charcot-Marie-Tooth disease, congenital indifference to pain, alcoholism, and spinal dysraphism can all lead to the disorder.

LABORATORY TESTS

In questionable cases, aspiration, sometimes including biopsy, to rule out sepsis.

It is currently impossible to halt progression of the disease, but it is quite feasible to prevent the devastating secondary deformities with optimal management. The key factor is a high index of suspicion that patients with peripheral neuropathy will develop spontaneous, rapid progression of bony destruction. The clinical symptoms of swelling, redness or excess warmth are not always present but should be considered warning signals.

IMAGING STUDIES

Plain roentgenography

• Sufficient to establish diagnosis in most cases, especially if etiology is known
• Findings: variable degrees of destruction and dislocation

TREATMENT

ACUTE GENERAL Rx

• Protection of effusions, sprains, and fractures until all hyperemic response has resolved
• Braces, special shoes with molded inserts, and elevation of the extremity
• Patient education with avoidance of weight bearing when lower extremity joints are involved
• Surgery: only limited value

DISPOSITION

Once the full-blown neuropathic joint has developed, treatment is difficult. Risk for Amputation is ever present. Extensive surgery may be required, and, in extreme cases, amputation may be necessary. Diabetes is responsible for more than half of all the lower limb amputations performed in the US each year and every year there are more than 86,000 foot amputations due to this disease. According to a 2002 study, 25% of these amputations are performed on the toe, 6% mid-foot, 38% below the knee, and 21% above the knee. The remaining 10% of amputations are performed on the hip, pelvis, knee, and other sites.

PREVENTION

Preventive foot care could reduce the risk of amputation in people with diabetes by 44% to 85%. Some tips for preventing problems include the following:

• Patients should inspect their feet daily and watch for changes in color or texture, odor, and firm or hardened areas, which may indicate infection and potential ulcers.
• When patients wash their feet, the water should be warm (not hot) and the feet and areas between the toes should be thoroughly dried afterward. Check water temperature with the hand or a thermometer before stepping in.
• Moisturizers should be applied, but not between the toes.
• Corns and calluses should be gently pumiced and toenails trimmed short and the edges filed to avoid cutting adjacent toes.
• Patients should not use medicated pads or try to shave the corns or calluses themselves.
• Well-fitting footwear is very important. In a 2001 study, 30% of diabetes patients wore shoes that were too narrow. Patients should also avoid high heels, sandals, thongs, and going barefoot. Specific therapeutic shoes, boots, and insoles do not appear to add advantage over careful attention and monitoring of the feet. However, people who are not attentive might do better with such footwear. For example, custom-molded boots (e.g., Conformer Diabetic Boot) are designed to increase the surface area over which foot pressure is distributed. This reduces stress on the ulcers and allows them to heal. Special insoles (e.g., the Rocker insole) have also been designed to reduce pressure on the front of the foot.
• Shoes should be changed often during the day.
• Wear socks, particularly with extra padding (which can be purchased).
• Patients should avoid tight stockings or any clothing that constricts the legs and feet.
• Foot pain, numbness, or tingling is worse at night; diphenhydramine (Benadryl) may help.

A specialist in foot care should be consulted for any problems.

Treating Foot Disorders in Diabetes

About one-third of foot ulcers will heal within 20 weeks with good wound care treatments. Some treatments are as follows:

• In virtually all cases, wound care requires debridement, which is the removal of injured tissue until only healthy tissue remains. Debridement may be accomplished using chemical (enzymes), surgical, or mechanical (e.g. irrigation) means. Hospitalization and intravenous antibiotics for up to 28 days may be needed for severe foot ulcers.
• Hydrogels (Nu-Gel, Intrasite Gel, Scherisorb, Clearsite, Duoderm, Geliperm) are proving to be effective in healing ulcers and are noninvasive and soothing. They should be applied and covered with a dressing.
• Charcot foot is initially treated with strict immobilization of the foot and ankle; some centers use a cast that allows the patient to move and still protects the foot. A 2001 study in the UK concluded that a single dose of pamidronate, a bisphosphonate, reduces bone turnover, symptoms, and disease activity. When the acute phase has passed, patients usually need lifelong protection of the foot using a brace initially and custom footwear.

Although not thoroughly understood, neuropathic arthropathy is expected to increase in frequency due to the continuing increase in the lifespan of the diabetic. Careful orthotic management by a podiatrist when provided as part of a comprehensive multidisciplinary treatment plan can significantly improve the ambulatory potential and quality of life for patients who would otherwise experience rapid bony destruction, recurrent ulceration and eventual infection leading to amputation of their feet.

References:

1. Mitchell JK. On a new practice in acute and chronic rheumatism. American Journal of Medical Science 1831;8:55.
2. Charcot JM. Lectures sur les maladies du system nerveux. Archives de Physiologie 1868.
3. Delano PJ. The pathogenesis of Charcot's joint. American Journal of Roentgenology 1946;56: 189-200.
4. Brower AC. The acute neuropathic joint. Arthritis and Rheumatism 1988;31 :12.
5. Edmonds ME. The diabetic foot: pathophysiology and treatment. Clinics in Endicrinology and Metabolism 1986; 15(4) :889-9 16.
6. Brower AC, Allman RM. Pathogenesis of the neurotrophic joint; neurotraumatic vs. neurovascular. Radiology 1981 ; 139:349-354.
7. Close ME, Gramm HF, Legg M, et al. Diabetic osteoarthropathy: clinical and roentgenographic observations in 90 cases. American Journal of Roentgenology 1974;121:22-34.
8. Jordan WR. Neuritic manifestations in diabetes mellitus. Archives of Internal Medicine 1936;57:307-366.
9. Bailey CC, Root HF. Neuropathic foot lesions in diabetes mellitus. New England Journal of Medicine 1982;72:439-450.
10. Sinha S. Neuro-arthropathy (Charcot joints) in diabetes mellitus. Medicine 1972; 51(3): 191-210.
11. Frykberg RG. Diabetic osteopathy. In: Brenner MA (ed). Management of the Diabetic Foot. Williams & Wilkins, Baltimore 1987;75-86.
12. Jacobs B. Malpractice considerations in treatment of the diabetic foot. In: Brenner MA (ed). Management of the Diabetic Foot. Williams & Wilkins, Baltimore 1987;212-216.
13. Harrelson JM. Management of the diabetic foot. Orthopedic Clinics of North America 1989 ;2t)(4) :605-619.
14. Lorber D. Neuropathy and the diabetic foot. In: Brenner MA (ed). Management of the Diabetic Foot. Williams & Wilkins, Baltimore 1987:18-47.
15. Rubin G, Dixon MA. The use of the AFO and PTB orthoses for severe pes planus. Clinical Prosthetics and Orthotics 1986; 10(l) :24-26.
16. Lehmann JG, Warken CG, Pemberton DR. et al. Load-bearing function of patellar-tendon-bearing braces of various designs. Archives of Physical Medicine and Rehabilitation 1971 ;52:366-370.
17. Coleman WC. Footwear in a management program of injury prevention. In: Levin ME. O'Neal LW (ed). The Diabetic Foot, Fourth Edition. CV Mosby, St. Louis 1988293-309.
18. Titus BR. A patellar-tendon-bearing orthosis. Orthotics and Prosthetics 1975:29(1) :35-40.
19. Demopoulos IT, Eschen JE. Experience with plastic patellar-tendon-bearing orthoses. Orthotics and Prosthetics 1974;28(4) :5-21.
20. Madden G. Orthotic management for osteochondritis dissecans of the talar dome. Journal of Prosthetics and Orthotics 1989;1:72-75.

Sincerely:

Joseph Saponaro, MD, DABIM, FACP, CPI, CCI, CCTI, CCRC, CCRP
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