Intended for healthcare professionals

Endgames Picture Quiz

Spinal injury in ankylosing spondylitis

BMJ 2014; 348 doi: (Published 16 June 2014) Cite this as: BMJ 2014;348:g3849
  1. G Stenhouse, specialist registrar, radiology,
  2. C Ulbricht, consultant spinal neurosurgeon,
  3. M Khanna, consultant, musculoskeletal radiology
  1. 1Department of Radiology, Imperial College Healthcare NHS Trust, London W2 1NY, UK
  1. Correspondence to: G Stenhouse gregors45{at}

A 51 year old man attended the emergency department because of a painful neck after falling from standing height while climbing out of the bath. He slipped backwards in the bath and landed heavily on his back. He didn’t remember hitting his head. He lived alone and was previously independent, although his activities had become increasingly difficult in recent years owing to ankylosing spondylitis. The neck pain worsened during the day and he attended hospital. On initial clinical examination, he was alert and communicative. He had paravertebral soft tissue discomfort at the level of the mid-cervical spine but no midline bony tenderness. His range of neck movement was limited, although this was not unusual for him. No neurological deficits were noted and he was discharged with analgesia.

He came back to the hospital five days later because of ongoing neck pain. Despite the seemingly innocuous injury at the time, the attending doctor recognised the greater risk of spinal injury in patients with ankylosing spondylitis and urgently requested cervical spine imaging (fig 1).


Fig 1 Lateral radiograph of the cervical spine


  • 1. What acute abnormality does the radiograph show?

  • 2. What factors should be considered high risk for potential cervical spine injury in alert adult patients with neck pain?

  • 3. What radiological features might lead you to suspect an underlying disease?

  • 4. What further imaging could be considered and how would you manage this patient in the acute setting?


1. What acute abnormality does the radiograph show?

Short answer

Unstable fracture dislocation at the level of C5/6 with fracture extension into the posterior elements.

Long answer

When reviewing a cervical spine radiograph, the C7-T1 junction should always be analysed. Alignment on a lateral film should be assessed using four anatomical lines—the anterior and posterior spinal lines, the spinolaminar and the spinous process lines (fig 2). In this case they are all disrupted (fig 3). There is a transverse fracture extending through the C5-C6 intervertebral disc with anterior subluxation of C5 on C6. The fracture extends into the posterior elements and is therefore unstable because it affects all three columns. The three column model of Denis was used to predict soft tissue injury from bone injury, and spinal stability depends on having at least two intact columns.1 Although this classification was developed for thoracolumbar fractures, it is also often applied to cervical injuries. The anterior column comprises the anterior longitudinal ligament and anterior two thirds of the vertebral body; the middle column comprises the posterior third of the vertebral body and posterior longitudinal ligament; and the posterior column comprises the posterior elements and posterior ligaments. It is also important to assess the prevertebral soft tissues for swelling, which can be an important clue to injury. This sign on a radiograph is insensitive, however, and its absence does not provide reassurance.


Fig 2 Lateral radiograph of a normal cervical spine illustrating the anterior and posterior longitudinal lines (red), the spinolaminar line (blue), and the spinous process lines (yellow)


Fig 3 Lateral radiograph of the cervical spine in this patient. The anterior and posterior longitudinal lines and the spinolaminar line are all disrupted. There is an anterior kyphosis, with a transverse fracture extending through the C5-C6 intervertebral disc into the posterior elements. Note the “bamboo spine” with syndesmophytes, calcification of the spinal longitudinal ligaments, and ankylosis of the posterior elements

2. What factors should be considered high risk for potential cervical spine injury in alert adult patients with neck pain?

Short answer

Guidelines from the College of Emergency Medicine published in 2010 provide guidance on which patients need imaging of the cervical spine and the imaging modality of choice.2 Computed tomography of the cervical spine is the primary imaging modality recommended for patients with a pre-existing vertebral anatomical abnormality (such as ankylosing spondylitis) who have experienced blunt trauma that may have injured the neck.

Long answer

The College of Emergency Medicine provides recommendations on best practice for the initial management of alert, cooperative adult patients whose mechanism of injury has the potential to result in blunt or penetrating injury to the cervical spine.2 It also provides guidance on which patients should have imaging of the cervical spine performed (box 1) and the use of computed tomography in cervical injury (box 2).

Box 1: Indications for imaging of the cervical spine

  • Glasgow coma score <15 on assessment in the emergency department

  • Paralysis, focal neurological deficit, or paraesthesia in extremities

  • Abnormal vital signs (systolic blood pressure <90 mm Hg, respiratory rate <10 or >24 breaths/min)

  • Urgent need to identify a cervical fracture (for example, before surgery)

  • Severe neck pain (>7/10) or neck pain and dangerous mechanism of injury (fall >1 m or at least five stairs, axial load to head, high speed or rollover motor vehicle crash, ejection from a vehicle, collision between motorised recreational vehicles, bicycle collision)

  • >65 years of age

  • Injured >48 hours earlier or re-attendance with the same injury

  • Pre-existing vertebral anatomical abnormalities (such as ankylosing spondylitis, rheumatoid arthritis, spinal stenosis, or previous cervical surgery)

Box 2: Criteria for the use of computed tomography in cervical injury

  • Glasgow coma score <13 on initial assessment

  • Intubated patients

  • Inadequate plain radiography series

  • Suspicion or certainty of abnormality on plain radiography series

  • Patients being scanned for head injury or multi-region trauma

  • Known vertebral disease (such as ankylosing spondylitis, rheumatoid arthritis, spinal stenosis, or previous cervical surgery)

  • Dementia (or a chronic disability that precludes accurate assessment)

  • Neurological signs and symptoms referable to the cervical spine

  • Severe neck pain (>7/10)

  • Patient has significantly reduced range of neck movement (cannot actively rotate the neck 45° in both directions)

Recently revised National Institute for Health and Care Excellence guidelines for computed tomography in head trauma also recommend urgent computed tomography imaging of the cervical spine in adults with head injury who are over 65 years, have sustained a dangerous mechanism of injury (as in box 1), or have a focal peripheral neurological deficit or paraesthesia in the upper or lower limbs.3

3. What radiological features might lead you to suspect an underlying disease?

Short answer

The radiograph shows vertebral body fusion, with marginal syndesmophytes in keeping with a “bamboo spine” and ankylosis of the posterior elements. These features are typical of ankylosing spondylitis.

Long answer

Ankylosing spondylitis is a seronegative arthropathy that mainly affects the spine and sacroiliac joints. Inflammation in the spine leads to new bone formation in the form of enthesophytes (bone outgrowths at the ligament attachments) and syndesmophytes (osseous bridges between vertebrae). In bamboo spine, the outer fibres of the annulus fibrosus of the intervertebral discs ossify, which results in the formation of marginal syndesmophytes between adjoining vertebrae. The spinal longitudinal ligaments also calcify, giving the appearances of a bamboo stem. The typical age of onset is between the second and fifth decades.4

Spinal fractures are up to four times more common in patients with ankylosing spondylitis, and the lifetime incidence in these patients is 14%.5 Doctors must therefore have a much lower threshold for imaging of the spine in patients with ankylosing spondylitis, even with seemingly innocuous injury. Unstable cervical fractures are also associated with nearly twice the mortality in patients with ankylosing spondylitis as in the general population (35%).6

More than three quarters of spinal fractures occur in the cervical spine—this region is particularly susceptible because it is located at the junction of a fused thoracic area with a more mobile head and neck.7 Neck hyperextension is often the mechanism of injury. Patients with ankylosing spondylitis do not always hit their head when falling backwards because of the pre-existing kyphotic spinal deformity, and when attempting to get up, the head often recoils forwards owing to the kyphosis. Because the bone is osteoporotic, the fracture pattern can look like a flexion injury as part of the vertebral body collapses. This is a good example of how a flexion or kyphotic deformity can be caused by a hyperextension injury.

Interestingly, most fractures (as in this case) traverse the intervertebral disc rather than going through the vertebral body because the disc has reduced elasticity and the annulus fibrosus is calcified.8 The annulus fibrosus is a fibrous ring that surrounds the central portion of the intervertebral disc known as the nucleus pulposus. Ossification of the spinal ligaments and calcification of the annulus fibrosus result in a rigid spine with a limited ability to absorb even minimal impact.9 10 This risk is further increased by disuse osteoporosis as a result of immobility.10 11

4. What further imaging could be considered and how would you manage this patient in the acute setting?

Short answer

Computed tomography or magnetic resonance imaging of the cervical spine. The patient should be urgently referred for spinal surgery before cervical immobilisation because a cervical collar may worsen the unstable deformity by causing hyperextension.

Long answer

Patients with ankylosing spondylitis who present even with trivial trauma should be evaluated for acute spinal fractures using advanced imaging modalities because these injuries are often missed. Patients commonly find it difficult to differentiate acute fracture-type pain from their usual inflammatory pain. Furthermore, radiographs often have distorted anatomy, with a kyphosis and high riding shoulders that obscure the cervicothoracic junction. Indeed, one retrospective review showed that 60% of cervical fracture dislocations were undetectable on initial radiographs.8

Computed tomography is more sensitive than plain radiography in identifying fractures, with a reported sensitivity of 100% and specificity of 99%.12 Although plain radiography can identify a fracture, computed tomography and magnetic resonance imaging can better define the character of the fracture. They can assess fracture extension into the posterior elements and neural foramina while excluding radiographically occult fractures at other cervical levels.

Magnetic resonance imaging is the gold standard imaging modality and better at assessing the spinal cord and paraspinal soft tissues than computed tomography, although it is sometimes contraindicated and not always readily available out of hours.

In this case, computed tomography (fig 4) identified a transverse fracture through the C5-C6 intervertebral disc and posterior elements and showed around a 50% narrowing of the spinal canal. Management of the fracture depends on both the fracture pattern and the patient’s comorbidities. Patients with pre-existing vertebral anatomical abnormalities (such as those with ankylosing spondylitis) should have their necks immobilised in a comfortable position.2 In such cases, the use of a collar is not compulsory and may worsen the deformity owing to hyperextension through the fracture site.13 Urgent contact with a spinal surgeon is essential.


Fig 4 Sagittal computed tomogram of the cervical spine showing a fracture-dislocation at C5-C6, with a transverse fracture extending through the intervertebral disc into the posterior elements. Unlike plain radiography, the degree of spinal canal encroachment is easily seen on computed tomography. Note the ankylosis of the facet joints

Treatment options vary and include traction orthoses, halo vests, and surgery. Despite the tendency for these fractures to fuse, the bone quality is often poor and conservative treatment often leads to a pseudarthrosis (or false joint—the unhealed area of bone has motion like a joint). Most surgeons have a low threshold for surgery in these patients because cervical spine collars and halo bracing are often difficult to fit given the spinal deformity. Evidence is also increasing that these patients have a higher complication rate when treated non-surgically compared with surgically. A large retrospective review found a mortality rate of 51% in the non-operative group versus 23% in the operative group, with age greater than 70 years being a major risk factor.9 Before surgery, the fracture-dislocation can be managed with low weight traction (to restore preinjury alignment). Depending on the neurological deficit and any neurological deterioration, the patient may need immediate or subacute surgery (as in this case). These are often challenging surgical cases and also require anaesthetic expertise because extension during intubation can easily cause spinal cord compromise.

Patient outcome

The day after hospital admission, the patient underwent surgery with open reduction and internal fixation of the fracture-dislocation using both anterior and posterior stabilisation (fig 5). Because of the substantial fracture gap in the anterior weight bearing column, anterior (and posterior) stabilisation was undertaken; this combined procedure enables the deformity to be corrected while providing immediate stability.14 15 His operative recovery was uneventful and he was discharged six days after surgery in a Miami J cervical collar, which he wore for four weeks. He made an excellent functional recovery and was able to return to independent living.


Fig 5 Postoperative lateral radiograph of the cervical spine showing reduction of the C5-C6 fracture-dislocation with anterior and posterior spinal rods and screw fixation


Cite this as: BMJ 2014;348:g3849


  • Competing interests: We have read and understood BMJ policy on declaration of interests and declare the following interests: None.

  • Provenance and peer review: Not commissioned; externally peer reviewed.

  • Patient consent obtained.


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