Which of the following is a sign of a Dens fracture?

A Dens fracture, which typically involves the odontoid process of the second cervical vertebra (C2), can manifest with various clinical signs. Among those listed, neck stiffness is a notable sign because it reflects the disruption of normal cervical spine mechanics and the surrounding musculature in response to injury.

When a Dens fracture occurs, there is often a resultant inflammatory response and potential injury to nearby structures such as ligaments and muscles, contributing to a restriction in range of motion and stiffness in the neck. This stiffness may be accompanied by pain, but the essence of neck stiffness as a sign emphasizes the mechanical disruption and the body's protective response to minimize movement in the vicinity of the injury.

In contrast, while pain with extension may be observed (as it is potentially related to injury), it is not as definitive a sign as neck stiffness. Severe back spasms could be attributed to multiple causes and are not specific to Dens fractures. Loss of bladder control typically indicates spinal cord involvement or neurological compromise, which is less directly associated with a Dens fracture unless there are additional complications or injuries. Therefore, neck stiffness stands out as a primary clinical manifestation indicating the presence of a Dens fracture.