Teaching Case

We present the case of a 19 year-old patient, who was a restrained front-seat passenger in a high-velocity road traffic accident. The patient complained of abdominal pain and had pinpoint posterior mid-line tenderness on palpation of the lumbar spine, without any focal lower limb neurology.

A non-contrast CT Brain and C-spine, arterial phase CT thorax, abdomen and pelvis, followed by a delayed phase CT abdomen and pelvis was performed. This demonstrated a Chance wedge compression fracture of the fourth lumbar vertebra (Fig. 1-3) with 10% loss of vertebral body height (Fig. 5-8), extending to the left pedicle and crossing the left facet. There were non-displaced fractures of the transverse processes of L3 & L4 (Fig. 1-2). Circumferential mural thickening of jejunal loops was noted (Fig. 10-11). Perihepatic and pelvic fluid was visualised, which was felt to be haemorrhagic based on fluid density (Fig. 11). No contrast was noted in the free fluid. The patient subsequently had an MRI, which confirmed an acute L4 Chance fracture. There were non-displaced fractures of the left L3 and L4 transverse processes. There was 25% loss of vertebral body height, bone marrow oedema & surrounding soft tissue oedema (Fig. 4, 9).

A Chance, or seat belt, fracture is a flexion-distraction injury of the thoracolumbar spine, which involves all three spinal columns. The injury was first described by Chance in 1948 [1], but its association with seatbelts was not noted until the 1960s [2].

The association with intra-abdominal injury was not described until 1970 [3]. 40% of patients with Chance fractures have associated intra-abdominal injuries [4]. Smaller case series, however, report the incidence to be as high as 60 – 80% [3, 5]. Spinal surgery is often required for Chance fractures, given their degree of instability.

Radiologic features suggestive of a Chance fracture are outlined below [4].
(i) AP View
a. The empty vertebral body sign: This is well described, and may be visualised on an AP radiograph. This sign is seen due to displacement of either the spinous processes or their fracture fragments off the vertebral body
b. Horizontal fracture through either one or both of the pedicles
c. Widened interpedicular distance (May point to burst Chance fracture)
d. Transverse fractures across the articular processes, laminae and transverse processes
e. Widening of the facet joints
f. Increased intercostal spacing

(ii) Lateral View
a. Fracture line extends posteroanteriorly involving the spinous processes with fanning of the fracture fragments, then propagating into the pedicles (The vertebral body can be variably involved)
b. Fanned appearance of the spinous processes and facet joints
c. Increased vertical distance across the posterior intervertebral disk

CT & MRI can be used for more detailed evaluation of the above patterns. MRI also provides the added advantage of imaging the spinal cord, which is important given the instability of these injuries.

A high index of suspicion for Chance fractures is required in the appropriate clinical context, with particular attention paid to the clinical history and mechanism of injury sustained, as their findings can be subtle on both plain X-rays and CT. Patients often do not have overt objective neurological findings on examination. Furthermore, delayed recognition of associated intra-abdominal injuries in these patients may contribute to significant morbidity and mortality. Patients with Chance fractures should have early senior review from a general surgery and orthopaedic spinal surgery team in the first instance and should have appropriate imaging of their abdomen and pelvis if not already imaged.

This patient subsequently went on to have a diagnostic laparoscopy and was found to have a jejunal blowout perforation and mesenteric tear. The patient had successful surgical repair of these injuries (Fig. 12-13).