Final answer:
Considerable neck extension is not recommended in animals with atlantoaxial instability due to the risk of damaging the ligament that maintains the alignment of the dens and the atlas, potentially causing serious complications.
Step-by-step explanation:
When dealing with animals who have atlantoaxial instability, certain views or positions should be avoided to prevent further injury or exacerbation of symptoms. One such view that is not recommended is considerable extension of the neck. This is because the atlantoaxial joint, consisting of the atlas (C1 vertebra) and the axis (C2 vertebra), plays a crucial role in the rotational movements of the head. The joint allows the head to move to the right or left, similar to shaking the head 'no'. However, in cases of instability, there is a risk of damaging the strong ligament that holds the dens in place against the anterior arch, thus causing serious complications. Extension of the neck could disturb this alignment and exacerbate the condition.