DIABETIC CHARCOT ARTHROPATHY
Clinical Presentation
Patients with an acute Charcot arthropathy of the foot will often present with swelling around the midfoot or ankle. This occurs in patients with a longstanding diabetes or other conditions that lead to altered sensation in the foot. This condition can be painful, although not as painful as it would be if they had normal sensation. Patients may give a history of increased activity leading to increased repetitive loading through their foot or ankle. Alternatively, they may give a history of a mild injury.
Charcot arthropathy is essentially a stress fracturing or stress reaction through a part of the foot leading to breakdown of this area. The body responds to this by increasing the blood flow to the area and trying to heal this in the same way that it heals any type of stress fracturing. The three common locations, include the tarsal-metatarsal [Lisfranc] joints, the transverse tarsal joint, and the ankle joint. This is a particularly frustrating and debilitating condition because it takes so long for it to resolve. It is not uncommon for this condition to take 6, 12, or even more months to resolve. Furthermore, when it does settle, the foot may change shape and the resulting deformity may predispose the patient to develop an ulcer over this area.
Physical Examination
Physical exam will involve inspection of the foot. It is important to look for breaks in the skin to rule out infection. This condition can present in a similar manner to a serious infection of the foot. However, it usually is NOT associated with an infection unless there is an obvious break in the skin where bacteria can enter.
It is important to assess the sensation of the foot, which is usually altered when detailed sensation testing is performed. In addition, the blood supply to the foot should be assessed.
Finally it is important to assess the other foot. As a Charcot arthropathy on one foot greatly increases that chance that the patient will develop a similar situation on the other foot.
Imaging Studies
Plain radiographs will demonstrate a breakdown in the joints and bones involved. This usually corresponds to the area of the foot, which is subject to the bulk of the force when the patient stands and walks. This is why the midfoot joints are most commonly involved. A bone scan is not indicated unless there is an obvious break in the foot. A bone scan will be hot and typically will not differentiate from a serious infection, therefore, it is not usually indicated.
Treatment
Non-Operative Treatment
Patient education is at the heart of any effective treatment plan for Charcot arthropathy. Education is critical because charcot arthropathy is such a serious and debilitating condition that takes many months to run its course. Patients need to have a good understanding of what is actually happening.
Treatment involves a period of either nonweightbearing in a total contact cast or limited weightbearing in a diabetic Cam Walker / boot. The acuity of the condition, as well as the extent of the deformity will determine whether weightbearing can be allowed.
Activity modification is also important, as patients will need to limit the number of steps they take during the day, as well as the amount of time that they are standing on their foot. There are devices that are available such as knee walkers, which can help offload the involved foot.
There are some studies that suggest that the use of bisphosphonates may be helpful in treating Charcot arthropathy by limiting osteoclastic activity.
Operative Treatment
If a marked deformity has occurred, or there is a disassociation between the midfoot and the hindfoot, or an evidence of complete instability at the ankle level, then surgery may be recommended. Surgery in this instance is associated with significant risks. Not only are there the increased risks of infection and wound healing problems characteristic of patients with diabetes, but there is also an increased risk of nonunion due to the patient’s altered sensation and therefore, tendency to load the foot earlier than they should.
Surgery when it is performed may consist of a simple removal of the prominence [exostectomy] by shaving off the prominent bone. Alternatively, a reconstruction may be performed by repositioning the foot and fusing the area that is involved in the Charcot arthropathy. In the midfoot, this would involve fixing the front and back part of the foot together and holding in place with a series of screws and possibly plates. If the Charcot process involves the ankle, this fixation may be performed with screws and/or plates. Alternatively, a nail may be placed through the heel bone up into the lower leg to help stabilize the position and hopefully obtain a satisfactory fusion at the level of the ankle. Any surgery that involves fusion will typically require a long period of nonweightbearing off in the order of 8 or more weeks.
During the recovery time for the Charcot arthropathy, it is important to closely monitor the opposite foot as this foot is likely to be subject to more force and may also develop a Charcot arthropathy.