Table 18.1 Nomenclature of bone tumors
Neuropathic joint disease (Charcot’s joint) is a progressive destructive arthritis associated with loss of pain sensation, proprioception, or both. In addition, normal muscular reflexes that modulate joint movement are decreased. Without these protective mechanisms, joints are subjected to repeated trauma, resulting in progressive cartilage and bone damage. Neuropathic arthropathy was first described by Jean Martin Charcot in 1868 in patients with tabes dorsalis. The term Charcot joint is commonly used interchangeably with neuropathic joint. Today, diabetes mellitus is the most frequent cause of neuropathic joint disease (Fig. 33-1). A variety of other disorders are associated with neuropathic arthritis including leprosy, yaws, syringomyelia, meningomyelocele, congenital indifference to pain, peroneal muscular atrophy (Charcot-Marie-Tooth disease), and amyloidosis. An arthritis resembling neuropathic joint disease is seen in patients who have received frequent intraarticular glucocorticoid injections into a weightbearing joint and in patients with CPPD. The distribution of joint involvement depends on the underlying neurologic disorder. In tabes dorsalis, knees, hips, and ankles are most commonly affected; in syringomyelia, the glenohumeral joint, elbow, and wrist; and in diabetes mellitus, the tarsal and tarsometatarsal joints.
EPIDEMIOLOGY & DEMOGRAPHICS
• 1 case/750 patients with diabetes mellitus; 5 cases/100 of those with peripheral neuropathy (foot is most commonly involved)
• 20% to 40% of patients with syringomyelia (shoulder most commonly involved)
• 5% to 10% of patients with tabes dorsalis; usually >60 years (spine, hip, and knee most commonly involved)
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 joint disease usually begins in a single joint and then progresses to involve other joints, depending on the underlying neurologic disorder. The involved joint progressively becomes enlarged from bony overgrowth and synovial effusion.
FIGURE 33-1 Charcot arthropathy associated with diabetes mellitus. Lateral foot radiograph demonstrating complete loss of the arch due to bony fragmentation and dislocation in the midfoot.
Loose bodies may be palpated in the joint cavity. Joint instability, subluxation, and crepitus occur as the disease progresses. Neuropathic joints may develop rapidly, and a totally disorganized joint with multiple bony fragments may evolve in a patient within weeks or months. The amount of pain experienced by the patient is less than would be anticipated based on the degree of joint involvement. Patients may experience sudden joint pain from intraarticular fractures of osteophytes or condyles.
Neuropathic arthritis is encountered most often in patients with diabetes mellitus, with the incidence estimated in the range of 0.5%. The usual age of onset is ≥50 years following several years of diabetes, but exceptions occur. The tarsal and tarsometatarsal joints are most often affected, followed by the metatarsophalangeal and talotibial joints. The knees and spine are occasionally involved. In about 20%, neuropathic arthritis may be present in both feet. Patients often attribute the onset of foot pain to antecedent trauma such as twisting their foot. Neuropathic changes may develop rapidly following a foot fracture or dislocation. Swelling of the foot and ankle are often present. Downward collapse of the tarsal bones leads to convexity of the sole, referred to as a “rocker foot.” Large osteophytes may protrude from the top of the foot. Calluses frequently form over the metatarsal heads and may lead to infected ulcers and osteomyelitis. Radiographs may show resorption and tapering of the distal metatarsal bones. The term Lisfranc fracture-dislocation is sometimes used to describe the destructive changes at the tarsometatarsal joints.
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.
• Osteomyelitis, cellulitis, abscess
• Infectious arthritis
• Rheumatoid and other inflammatory arthritides
• An underlying neurologic disorder must always be present.
• Diabetes mellitus with peripheral neuropathy is the most common cause.
• Syringomyelia, tabes dorsalis, Charcot-Marie-Tooth disease, congenital indifference to pain, alcoholism, and spinal dysraphism can all lead to the disorder.
In questionable cases, aspiration, sometimes including biopsy, to rule out sepsis
• Sufficient to establish diagnosis in most cases, especially if etiology is known
• Findings: variable degrees of destruction and dislocation
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
Once the full-blown neuropathic joint has developed, treatment is difficult.