Guyon’s canal is a distinct, unyielding fibro-osseous tunnel situated at the volar wrist, bordered strictly by the pisiform medially and the hook of the hamate laterally. Which vital neurovascular structures pass directly through this specific canal and are vulnerable to compression here (e.g., from a ganglion cyst or ‘handlebar palsy’)?

Explanation:
The correct option is a. Guyon's canal contains strictly the ulnar nerve and the ulnar artery. The ulnar nerve enters the canal and divides into superficial (sensory) and deep (motor) branches. Compression in this tight space (often termed ulnar tunnel syndrome) can be caused by ganglion cysts, repetitive trauma (like cycling, hence 'handlebar palsy'), or hook of hamate fractures. It typically presents with numbness in the ring and small fingers and profound weakness of the intrinsic hand muscles, while completely sparing the median nerve territory. Reference: Campbell's Operative Orthopaedics. Fundamental Ortho mcq anatomy.