Neuropathic ankle fractures

Case Reports

CJEM 2012;14(2):128-132

Abstract

Résumé

According to the Canadian Diabetes Association, an estimated 246 million people worldwide suffer from diabetes mellitus, including 2 million Canadians. Diabetes is currently the fourth leading cause of death worldwide, and, sadly, the number of people affected is rising and is expected to reach 366 million globally by 2030.¹

Diabetes is a systemic disease that affects most systems in the body, including the musculoskeletal system. Diabetics are at increased risk for bone disease, including fragility fractures, vasculopathy, and neuropathy, which can sometimes lead to neuropathic fractures. Neuropathic fractures occur in areas of reduced sensation secondary to diseases such as diabetes and result from chronic destruction of the bones and joints. Early diagnosis and patient education are critical in the prevention of such complications, and it is essential that all health care team members are vigilant with their assessment and follow-up. The following case report describes a diabetic patient who suffered from such a devastating fracture and discusses the unique diagnostic process, management, and potential complications associated with this patient population.

Case Report

A 65-year-old female household ambulator presented with a 3-week history of a swollen left ankle. The swelling began after a minor ankle inversion injury. The patient did not fall but heard an audible snap, and the ankle became immediately swollen. She continued to ambulate postinjury without pain.

There was a long past medical history of poorly controlled type 2 diabetes mellitus with evidence of end-organ damage that included retinopathy, renal insufficiency, and peripheral neuropathy leading to a forefoot ulceration. On physical examination 3 weeks postinjury, she had a well-aligned but very swollen ankle. Initial radiographs revealed a minimally displaced fibular fracture (Figure 1).

She was placed in a well-padded cast and instructed to remain non–weight bearing. One week later, she returned with continued swelling and radiographs were obtained (Figure 2).

There continued to be no discomfort. Her cast was soft on the sole, and she confessed to some weight bearing. She refused to be admitted to hospital for treatment and was recasted. She returned 1 week later with more deformity and a draining ulcer over the medial malleolus (Figure 3 and Figure 4).

She finally agreed to hospital admission. Unfortunately, despite 2 weeks of intravenous antibiotics and splinting, her medial ulcer and the associated cellulitis did not improve. Therefore, it was felt that surgical intervention was required. Owing to poor bone quality, an unreconstructable tibial plafond, and probable deep infection, a hindfoot arthrodesis was deemed the best surgical approach.

A tibiotalocalcaneal arthrodesis was performed with a retrograde hindfoot nail. She was kept non–weight bearing as an inpatient for 3 months. The ulcer settled, and she began to ambulate with a walker. She has returned to her status as a household ambulator.

Discussion

Diabetics are at a high risk for bone disease owing to decreased unmineralized bone matrix, hypercalciuria, elevated collagen glycosylation, and a low rate of bone turnover with decreased bone formation and resorption. Consequently, these patients have decreased bone density, thus placing them at risk for fragility fractures.² In addition, vascular disease is common as arteriosclerosis is seen more frequently in diabetics and its manifestations are more aggressive and diffuse compared to those of nondiabetics. Macrovascular disease causes calcification of the tunica media, which leads to the “lead pipe” appearance of the arteries in the distal limbs, thereby predisposing patients to peripheral vascular insufficiency.¹

Neuropathy is a common manifestation of diabetes mellitus, causing irreversible and progressive damage to the sensory, motor, and autonomic nervous systems.^1,3,4 Up to 40% of diabetic patients will be diagnosed with peripheral neuropathy within the first 10 years of their disease, and 80% of diabetics with foot ulcers suffer from neuropathy.^5,6 Neuropathy results in decreased pain and pressure perception, leading to muscle imbalance and anatomic deformities, as well as impairment of the skin's integrity and dysfunction of the microcirculation. In the early stages, there is evidence of disruption of the articular cartilage and ligaments and eburnation and resorption of bone, in addition to the formation of osteophytes, periosteal bone, and loose bodies.⁷

Neuropathic arthropathy, which is often referred to as Charcot arthropathy, is a noninfectious, destructive process that results in eventual joint dislocation and periarticular fracture. It is a common complication of conditions that alter sensation, such as diabetes mellitus. Light touch and pain sensation are frequently affected, whereas motor function remains intact; therefore, these patients are at risk for injury owing to their inability to perceive joint overload or trauma.^3,6 Charcot arthropathy generally presents with a warm, edematous, erythematous limb that may or may not be painful. Radiologic findings range from microfractures to bone fragmentation to severe joint subluxation and deformity.^5,6,8

Although neuropathy is common in diabetic patients, neuropathic fractures occur surprisingly less often, with an incidence of only 1 to 2.5%. However, they can be devastating when they occur owing to the high incidence of complications such as impaired wound healing, infection, and malunion or nonunion.^7,9 Neuropathic fractures occur as a result of decreased sensation combined with normal motor function and active use; thus, they can occur in the acute setting or as a consequence of overuse.⁷

Assessment of the diabetic foot involves a comprehensive history and physical examination that includes both neurologic and vascular assessments. A 129 Hz tuning fork and the 10 g Semmes-Weinstein monofilament are two noninvasive, inexpensive, and relatively reliable methods for screening patients for neuropathy.⁷ Although the use of these tools is encouraged, it may not be realistic for many emergency physicians; therefore, palpation of peripheral pulses remains the foundation of the vascular evaluation. It should be noted that the ankle/brachial pressure is frequently unreliable in patients with diabetes.⁶ Light touch, vibration sense, temperature distinction, and two-point discrimination tests can be used as quick methods for assessing a patient for sensory deficits.^7,10 Radiographs should be obtained with the patient weight bearing if possible because these films provide a more accurate anatomic assessment of the functional stability of the ankle joint that may not be as evident on non–weight-bearing films.⁶ Findings often demonstrate either an atrophic process with bone resorption or a hypertrophic process with periarticular bone and osteophyte formation.⁷

The treatment of neuropathic ankle fractures remains controversial because complication rates remain high with both conservative and surgical treatment regimens. Open reduction and internal fixation (ORIF) continues to be the treatment of choice when closed reduction attempts fail, despite the increased risk of postoperative complications. These complications are especially high in patients whose treatment has been delayed, who have other comorbid conditions, or who abuse drugs or alcohol.³ The most recent literature advocates surgical intervention with increased immobilization periods for medically stable diabetic patients who have displaced fractures because these patients are at risk for developing Charcot arthropathy and ulcerations.¹¹ The mainstay in treatment for Charcot arthropathy remains extended immobilization and non–weight bearing in a cast or brace.¹⁰ This conservative, nonoperative treatment places the patient at a significant risk for developing wound complications, which are difficult to treat and may further compromise the healing potential and the integrity of the joint in diabetics.^10,11 However, because complication rates for surgical procedures can be as high as 47%, it may be advantageous to forgo operative intervention for noninvasive treatments such as extended immobilization and elevation. These conservative options may be especially beneficial for certain populations such as low-demand and elderly patients, whose malunions may be an acceptable result.⁸

Complications from both conservative and operative treatment of ankle fractures are consistently higher in diabetic patients, especially those who have long-standing disease and are insulin dependent.^11,12 Significant risk factors for complications also include peripheral vascular disease, which may be indicated by absent pedal pulses, as well as peripheral neuropathy. These factors may predispose the patient to developing Charcot arthropathy.^11,12 Complications include both superficial and deep infections, hardware failures, reflex sympathetic dystrophy, wound dehiscence, ulcerations, delayed fracture healing, malunions, nonunions, and Charcot arthropathy.^7–9,13,14 These potential complications must be taken into consideration when determining a treatment plan for the diabetic patient with a neuropathic ankle fracture.⁶

Conclusion

Peripheral neuropathy is a serious complication of diabetes that places patients at an increased risk for neuropathic fractures and complications from these fractures secondary to decreased pain and pressure perception. Although the treatment of neuropathic ankle fractures remains controversial, it is evident that early diagnosis and intervention, whether conservative or surgical, remain the key. It is imperative to prevent progressive complications from continued weight bearing, as was demonstrated in this case. Prevention of the initial neuropathy and later neuropathic fractures should remain the goal of patient care. This can be accomplished through education about the importance of tight glucose control and thorough foot care. Use of the tools, techniques, and appropriate imaging discussed above can aid the emergency physician in making an accurate, initial diagnosis, which may help prevent the devastating complications that were seen in this patient.