The patient with an acute CN presents with either a painful or painless foot and ankle marked with erythema, calor, edema, and deformity (7,8,9 and 10). The presence of pain experienced during the acute CN event is not clearly understood. The authors have found that pain in the acute phase is rarely encountered but may be present in two clinical case scenarios: the patient who is continuing to ambulate (subsequent trauma) on an unprotected extremity while the acute Charcot inflammatory cascade has begun and when acute CN is complicated with infection. In many instances, the diagnosis of acute CN is not being considered in these two scenarios because the examiner excludes the diagnosis given the presence of pain. The presence of pain should not exclude the possibility of developing neuropathic fractures and dislocations. In addition, initial pedal radiographs that are unremarkable may also not exclude the diagnosis of acute CN.

Often, the acute phase of CN represents a time frame in which the patient is being misdiagnosed or being treated for infection alone or acute gout and/or examined for venous obstruction. The authors’ recommendation is to educate the health care provider in these clinical case scenarios as they are usually involved with the initial patient visit. While it may be necessary to treat or rule out other differential diagnoses, the importance of offloading and immobilizing the acute Charcot neuropathic extremity cannot be overlooked as it may lead to gross deformities that ulcerate and further progress to an amputation. The problem commonly arises when the patient is being treated with antibiotics for cellulitis of the lower extremity and is permitted to walk on the affected extremity during an acute Charcot event, allowing further progression of fractures and dislocations.

In the acute phase of CN, if the diagnosis of infection is equivocal, then the patient may be hospitalized and placed on bed rest without antibiotics and evaluated frequently during the admission period. The acute inflammatory process in CN tends to clinically subside, whereas an infectious process worsens. In addition, magnetic resonance imaging (MRI) can exclude infection when it is negative or determine the presence of soft tissue infection and abscess formation when suspected; however, it is limited in determining if a Charcot deformity is complicated with osteomyelitis because bone marrow edema is present in both. Nuclear medicine imaging that includes simultaneous indium-labeled white cell and technetium-labeled polyphosphate scans may be more helpful in determining if a Charcot deformity is complicated with osteomyelitis (11). The surgeon should realize that at times false-positive results are present, and these studies should be considered in conjunction with the clinical examination (11). Charcot deformities that present with chronic ulcers whether infected or contaminated should be surgically excised prior to staged surgical reconstruction. Deep soft tissue and bone biopsy cultures during this process are obtained to determine the presence of osteomyelitis (12,13).

Furthermore, the examiner needs to be aware of detecting and treating the patient in the subacute phase of CN (9,10). In this case, initial radiographs are usually unremarkable and early osseous changes can only be detected through advanced MRI techniques. The subacute phase also includes the “pre-Charcot” patient, which describes a patient with loss of protective sensation, acute inflammation, and recent trauma (9,10). Trauma in this setting predisposes the patient at risk for developing neuropathic fractures and dislocations. A common example that is frequently encountered is a diabetic patient with peripheral neuropathy that had an open reduction internal fixation (ORIF) of an acute ankle fracture and develops CN at 6 weeks postoperatively once weight-bearing was initiated.

The clinician should always inquire about a history of trauma to determine the possible inciting event. Although cumulative microstress as a result of gait abnormalities, weight gain, or activities of daily living is generally necessary to precipitate a Charcot event, the process may also be provoked by an acute single episode of trauma like a patient with a foot or ankle fracture (10). In the early stages of CN, often small areas of periarticular osseous fragmentation are appreciated along with mild joint subluxations on plain pedal radiographs. Clinically, the foot and ankle should be assessed for minor instability and/or dislocation on the suspected joints and by using the contralateral extremity as a control if feasible. If early radiographic findings are not apparent and strong clinical suspicion is still present, then the patient should be immobilized and serial radiographs are to be repeated every 2 to 3 weeks. MRI is useful in detecting microfractures and bone marrow edema in the early stages of subacute neuroarthropathy (11). Although uncommon, the authors have seen the progression of deformities despite immobilization and non-weight-bearing, as this is probably attributed to the initial traumatic episode that started the cascade of events leading to the development of CN. Finally, the clinician needs to be aware of the prolonged periods of immobilization and protected weight-bearing required for patients with an acute CN event.

The diagnosis of chronic CN is straightforward, as it is usually marked with gross clinical deformities. The dilemma usually occurs when bone destruction is evident on radiographs and is usually mistaken for osteomyelitis. The clinical case scenario of a deformed foot with no ulceration or clinical signs of infection usually rules out the possibility of osteomyelitis. The Charcot deformity should be characterized by which bones are fractured and which joints are subluxed or dislocated along with assessing for the presence of instability. Radiographs are obtained, but often, further evaluation through computed tomography (CT) with 3-D reconstruction views is required to appreciate the subtle detail of each deformity. Fractures and dislocations should be evaluated for osseous healing and bone bridging and their absence should raise suspicion of structural instability. Weight-bearing radiographs when feasible in chronic deformities consisting of anteroposterior, lateral, and hindfoot alignment views of the foot and ankle are initially performed. The examiner should note the affected joints, joint malalignment, plane of dislocations, apex of rigid deformities, relationship of midfoot deformities to the rearfoot and ankle, and the bone quality. Templates of the radiographs can be made to assist in planning out the necessary osteotomies or joint resections to achieve maximum deformity correction. CT scans can be utilized to better visualize the level of deformity that is present, particularly when radiographs are distorted secondary to overlap of the bony architecture.

Often, the chronic stage of CN about the foot and ankle is associated with the presence of complex wounds that are either contaminated or infected. Deep soft tissue infection resulting in osteomyelitis complicates the clinical case scenario further. Many publications and scientific articles have focused on differentiating CN from osteomyelitis. The clinical concern is not differentiating between the two but whether the Charcot deformity and dystrophic bone is further complicated with osteomyelitis when an ulcer is present. Charcot deformities with ulcerations that display clinical evidence of infection marked by purulent or malodorous drainage can be assumed to be complicated with a deep infection. Ulcerations that clinically present with bone exposure are also treated for osteomyelitis.

Brodsky proposed a classification system based on the anatomic location of the neuroarthropathy and also emphasized the duration of treatment and attempted prognosis (14). Type 1 neuroarthropathy involved the Lisfranc joint (tarsometatarsal joint) and the naviculocuneiform joint. Initially, it was proposed as being rarely associated with chronic instability, plantar prominences, rocker bottom deformity, and possible ulcer formation. Type 2 involved the rearfoot complex (the subtalar, talonavicular, and calcaneocuboid joints). These deformities typically resulted in longer periods of immobilization with gross deformities. Type 3A involved the ankle joint. Often, the talus is grossly dislocated, leading to severe frontal plane instability and ulceration around the medial or lateral malleoli. Type 3B is a pathologic fracture of the calcaneus that leads to tendo Achilles dysfunction. This classification system represents the most common joints to be involved. However, as CN is becoming more prevalent, the deformities more commonly encountered involve multiple joints from the ankle to the midfoot and even the forefoot.

The authors suggest that each Charcot deformity is unique and different on each patient and that certain clinical and functional parameters are needed to facilitate the development of a rational treatment plan. The deformities are usually too broad and distinct and in most cases classification is not feasible or clinically beneficial. Eichenholtz (9,10 and 11) described a staging system as opposed to a classification system that was initially based
on radiographic findings, but then clinical parameters were added to the common utilization of staging Charcot deformities as acute, coalescence, and remodeling. The first (acute) stage as we previously mentioned is when the foot is inflamed with the presence of erythema and edema and radiographs may demonstrate acute fractures, dislocations, and bone fragmentations. The second (coalescence) stage marks that early healing and reparative process as the foot is less inflamed, the edema decreases, and warmth begins to subside and radiographs may display resorption of bone fragmentation. The third (remodeling) stage involves resolution of the inflammatory process and consolidation of bone fragments and fractures. This staging system is useful in distinguishing acute from chronic Charcot deformities. The authors suggest evaluating any Charcot deformity for its presence in an acute or chronic stage, determining which joints are subluxed or dislocated, evaluating the presence of a heel cord contracture and plane of instability, and also diagnosing the presence of soft tissue compromise, ulceration, or associated infection along with possible vascular compromise. Each deformity needs to be evaluated closely, and all of the above findings need to be well understood before the patient is treated either conservatively or with surgical intervention.