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Year |
2005 |
|---|---|
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Question Number |
77. |
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Category |
Foot and Ankle |
Question
A 20-year-old man with type I diabetes mellitus sustained an ankle fracture tripping over a piece of wood. He was initially treated with two screws and a period of no weight bearing. An initial radiograph and one obtained 6 weeks after surgery are shown in Figures 21a and 21b, respectively. The radiograph shown in Figure 21c is obtained 2 months later when the patient reports increased ankle swelling. What is the most likely diagnosis?
1- Paget’s disease
2- Osteosarcoma
3- Rheumatoid arthritis
4- Osteomyelitis
5- Neuroarthropathy
Figures
Answer (click for answer)
PREFERRED RESPONSE: 5
Anytime you see a history of DM in the question, immediately think – vascular insufficiency, neuropathy, impaired healing. Remembering these common themes will help you answer many of these questions. This is an obvious case of an ankle fracture complicated by poor healing and impaired sensation (i.e, Charcot arthropathy). The obvious answer is #5. Radiographs of Charcot joints will show joint subluxation and bone fragmentation in the early stages and severely deformed joints with significant sclerosis, coalescence of bone fragments, and unsuccessful attempts to reform the joint in later stages. Despite the impressive appearance on x-rays, the patient will have minimal discomfort and an exam featuring a deformed foot with a significantly impaired neurovascular exam and possible warmth and erythema. It is more typical after the 5th decade of life but occurs earlier in life-long or poorly-controlled diabetics. Paget’s disease will feature x-rays demonstrating lytic lesions with accompanying thickened, sclerotic cortices and may involve any weight-bearing portion of the skeleton or the skull. Osteosarcoma will appear as a permeative destructive bone lesion with associated periosteal reaction. It has frequently been described to occur in a sunburst pattern. The most common locations are the metaphyses of the distal femur and proximal tibia followed by the proximal humerus, proximal femur, pelvis, and spine. Rheumatoid arthritis appears as a narrowed joint space with metaphyseal erosions, generalized osteoporosis, and possible joint ankylosis. Osteomyelitis is a great imitator of other processes on radiographs but typically exhibits bone destruction. Other potential radiographic findings include periosteal bone formation, sinus tracts, and sequestrum or involucrum formation.
Review from UTDOL:
PATHOGENESIS — The pathogenesis of this condition is uncertain but it is probably due to a combination of mechanical and vascular factors resulting from diabetic peripheral neuropathy. As an example, lack of proprioception secondary to peripheral neuropathy may result in ligamentous laxity, increased range of joint movement, instability, and damage by minor trauma, to which the relatively insensitive neuropathic foot is prone.
An alternative theory suggests that automatic neuropathy results in vasomotor changes and the formation of arteriovenous shunts. These in turn result in reductions in effective skin and bone blood flow, despite the good and sometimes bounding foot pulses in these patients.
Regardless of the initiating mechanism, there may be an initial resorptive phase in the development of a neuropathic joint which may then be followed by a hypertrophic repair phase.
Radiological findings are variable, depending upon the stage and site of the arthropathy.
• In early acute disease, the radiologic changes may be mild or nonspecific, showing only soft tissue swelling, loss of joint space, or osteopenia.
• In the forefoot, bone resorption may predominate, leading to osteolysis of phalanges and a variety of changes including partial or complete disappearance of the metatarsal heads or “pencil-pointing” of phalangeal and metatarsal shafts.
• In the midfoot and hindfoot, osseous fragmentation, sclerosis and new bone formation, subluxation, and dislocation are more likely to ocurr.
• Stress fractures, which may be difficult to diagnose, can complicate the neuroarthropathy. An uncomplicated stress fracture can be located by scintiscan and confirmed by MRI or serial radiography. However, both MRI and scintiscan are less specific in the diabetic neuropathic foot and delay in diagnosis may occur if one waits for the radiologic changes to become apparent.
While a second radiograph some weeks after presentation may clarify the diagnosis of acute early neuropathic arthropathy, delays in diagnosis and treatment are inevitable. Unfortunately, other radiologic tests are not more helpful. Bone scan, for example, may be nonspecific, with increased isotope uptake seen both in patients with diabetic neuroarthropathy and in those with peripheral neuropathy alone.
Magnetic resonance imaging may be helpful in the diagnosis of stress fracture and in visualizing torn ligaments and intraarticular fragmentation. However, the changes of acute neuropathic arthropathy may be indistinguishable from osteomyelitis.
Acute therapy — In neuropathic arthropathy of acute onset, avoidance of weight-bearing on the affected joint should be recommended until resolution of edema and erythema occurs, with improvement of radiologic signs (eg, resolving resorptive changes, resorption of osseous debris, and evidence of repair). A minimum of eight weeks without weight-bearing has been recommended for disease of the midfoot, progressing through partial weight bearing in a cast brace to full weight bearing in about four to five months. Good chiropody and well-fitting shoes are essential at this stage.
Graves M Conclusions – Patients with diabetic neuropathy are at a higher risk of developing complications, especially Charcot arthropathy. Early diagnosis and intervention is the key to optimizing outcome. Therefore, diabetic patients with a lower extremity injury should be screened with sensory testing using a 5.07 monofilament.
Holmes conclusions – This study was undertaken to evaluate the occurrence of Charcot joint changes in diabetic patients after fractures and/or dislocations of the foot and ankle. There were 20 fracture/dislocations of the foot and ankle in 18 patients, with an average follow-up of 27 months (range 14-70 months). There were eight fractures of the midfoot, six fractures of the ankle, four fractures of the hindfoot, and two fractures of the forefoot. Eight fractures were followed by the development of Charcot changes: five in the midfoot and one each in the forefoot, hindfoot, and ankle. Of nine fractures recognized early and initially treated by early immobilization or ORIF, seven healed uneventfully. Two fractures, both open injuries, developed soft tissue infection and osteomyelitis, respectively. Of the 11 fractures in which there was a delay in diagnosis and treatment, eight developed Charcot changes. The early recognition and appropriate treatment of fractures in diabetic patients appears to be important in the prevention of Charcot joint changes.
Seminars of musculoskeletal radiology 2005
Almost all diabetic foot infections originate from a foot ulcer. Decreased pain perception and structural deformities such as previous partial foot amputation, Charcot joints, and toe deformity in combination with chronic ischemia lead to a propensity for skin breakdown and subsequent infection. Magnetic resonance (MR) imaging is increasingly performed to evaluate for potential bone infection, but diagnosis of osteomyelitis can be complicated because signal changes from acute Charcot arthropathy, fractures, and postoperative residues may be mistaken for infection. Signal alterations of bone infection may be atypical in sclerosing osteomyelitis and gangrene. Differentiation between osteomyelitis and acute or subacute neuroarthropathy requires careful analysis of the location of bone signal alterations, their distribution, and pattern because qualitative changes are often identical. Presence of secondary signs such as adjacent ulcer, cellulitis, and sinus tract is indicative of osteomyelitis. Differentiation of noninfected neuroarthropathy from infected neuroarthropathy based on MR examinations is difficult. Presence of a sinus tract, disappearance of subchondral cysts, diffuse bone marrow abnormality, and bone erosions are in favor of infection.
Reference: RECOMMENDED READINGS: Coughlim MJ, Mann RA: The diabetic foot, in Coughlin MJ, Mann RA (eds): Surgery of the Foot and Ankle, ed 7. St Louis, MO, Mosby, 1999, pp 895-969.
Graves M, Tarquinio TA: Diabetic neuroarthropathy (Charcot joints): The importance of recognizing chronic sensory deficits in the treatment of acute foot and ankle fractures in diabetic patients. Orthopedics 2003;26:415-418.
Holmes GB Jr, Hill N: Fractures and dislocations of the foot and ankle in diabetics associated with Charcot joint changes. Foot Ankle Int 1994;15:182-185.
Attachments:
OITE 2005 figure 21b.jpg (image/jpeg)
OITE 2005 figure 21a.jpg (image/jpeg)
OITE 2005 figure 21c.jpg (image/jpeg)
