1. What abnormalities are shown on the X-Ray?
There is widening of the gap between the C1 and C2 spinous processes. There is widening of the soft tissues anterior to C1. There is a fracture of the C2 pedicle.

2. What is this clinical entity commonly called?
A Hangman's fracture.

3. What further investigations would you perform?
After C-spine stabilisation! A neuro exam, a CT of the region will also be helpful to further define the fracture.

4. How would you manage this?
Perhaps surprisingly, considering the eponymous name, this patient can be treated in a hard collar (eg Philadelphia collar) with advice about movement. Obviously such decisions would be taken in conjunction with neurosurgical/spinal colleagues after further imaging.

Further reading:
http://www.wheelessonline.com/ortho/hangmans_frx_traumatic_spondylolisthesis_of_the_axis

http://www.emedicine.com/orthoped/topic597.htm