What nerve injury is associated with a sacral fracture?

• A. Sciatic nerve
• B. Cauda equina
• C. Femoral nerve
• D. Pudendal nerve

Answer: (B)

When a sacral fracture disrupts the sacral canal, it can compress multiple nerve roots that comprise the cauda equina. This collection of roots (including those supplying the perineum and lower limbs) is vulnerable to injury from a fracture that extends into the canal, making cauda equina syndrome the typical associated nerve injury. The resulting deficits are often bilateral and include saddle anesthesia, bladder and bowel dysfunction, reduced anal sphincter tone, and weakness or numbness in the legs—an emergency that requires prompt surgical assessment.

Other nerves listed’re not the usual pattern for a sacral fracture. The sciatic nerve is a large peripheral nerve that can be affected by hip or leg trauma but is not the classic injury from a sacral fracture itself. The femoral nerve lies higher in the pelvis and primarily carries motor and sensory input from the anterior thigh, which is not the typical consequence of a sacral canal injury. The pudendal nerve comes from S2–S4 and can be affected in pelvic injuries, but the hallmark and most consistent association with sacral fractures are the widespread root injuries characteristic of cauda equina syndrome.