CASE 13641 Published on 02.05.2016

Unstable L1 fracture in ankylosing spondylitis

Section

Musculoskeletal system

Case Type

Clinical Cases

Authors

Samir Jawad, Yousef Wirenfeldt Nielsen

Department of Radiology,
University Hospital Herlev-Gentofte
Copenhagen, Denmark.

Email:samir.jawad88@gmail.com
Patient

77 years, female

Categories
Area of Interest Spine ; Imaging Technique CT
Clinical History
The patient was admitted to the emergency department due to lumbar back pain after a fall from standing height. The physical examination found that the abdomen was distended. No neurological defects were present. A contrast-enhanced CT of the chest and abdomen was performed.
Imaging Findings
The thoracic and lumbar spine showed severe changes associated with ankylosing spondylitis (AS). These changes included ankylosis between vertebrae resulting in a “bamboo spine” (Figures 1-2). Furthermore an unstable transverse fracture (extension type fracture) through the L1 vertebrae was seen (Figures 1-2). All three columns through the L1 vertebrae were fractured with an outcome angulation of 15 degrees (Figure 1). No other acute findings were present in the chest or abdomen. An acute MRI was suggested to further evaluate the spinal cords relation to the fracture. However, the patient was unable to cooperate in this procedure.
Discussion
AS is a progressive and chronic inflammatory condition, predominantly affecting the spine and the sacroiliac joints. In the later stages of the disease it is characterized by osteoporosis and syndesmophyte formation. Subsequent bridging of these syndesmophytes leads to ankylosis and the radiographic feature “bamboo spine”. These pathological transformations predispose AS patients to spinal fractures even after low energy trauma [1], such as a fall from standing height. The prevalence of spinal fractures in AS patients has been estimated to range from 4-18 % [2] with a four-fold lifetime risk compared to the background population [3]. Cervical fractures (81%) are the most common spinal fractures in patients with AS followed by fractures at the thoracic (11%) and lumbar spine (8%) [4]. Spinal fractures in AS patients are often unstable and can result in neurological injury.

AS patients using conventional X-ray can be challenging. This is due to the distorted anatomy caused by AS at the affected site of the fracture, and in the worst-case scenario a spinal fracture can go unnoticed [5]. A report showed that 42 % of AS patients with a spinal fracture did not initially receive the correct diagnosis of the fracture, which led to secondary neurological complications in 17 % these patients [6]. Cross-sectional imaging with CT or MRI should therefore be prioritized when suspecting a spinal fracture in a patient with AS. A study examining 20 AS patients with suspected spinal fractures showed that CT was able to detect six spinal fractures not seen on MRI, and vice versa MRI detected two spinal fractures not seen on CT [7]. On the other hand, MRI is more sensitive at detecting spinal cord compression, paravertebral haemorrhages and soft tissue abnormalities.

The present case illustrates a severe lumbar spine fracture in an AS patient. It underlines the fact that low energy trauma may result in disproportionate damage in this patient group with altered biodynamic strength of the vertebral column. Following imaging, internal fixation across the fracture was performed. No neurological deficits occurred.

In conclusion, patients with known AS admitted after low energy trauma should be imaged to rule out a spinal fracture. Cross-sectional imaging with either CT or MRI should be performed [8].
Differential Diagnosis List
Unstable L1 fracture in a patient with ankylosing spondylitis
Osteoporotic compression fracture
Malignant fracture
Osteomyelitis fracture
Fracture of other degenerative spinal diseases
Final Diagnosis
Unstable L1 fracture in a patient with ankylosing spondylitis
Case information
URL: https://www.eurorad.org/case/13641
DOI: 10.1594/EURORAD/CASE.13641
ISSN: 1563-4086
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