Ulnar nerve injury in the upper arm

1. What is the Arcade of Struthers (AOS) and what symptoms result from injury of the ulnar nerve at this site?
2. What is Froment's sign?
3. What is Wartenberg's sign?
4. What is tardy ulnar palsy?
5. Where is the cubital tunnel and what is cubital tunnel syndrome?
6. What does the NCS show in cubital tunnel syndrome?

Answers:
1. The AOS is a fascial band that connects the brachialis to the triceps. The patient has involvement of all ulnar nerve innervated muscles, resulting in wrist flexion with radial deviation, abnormal sensation in an ulnar distribution, ulnar "claw hand" (partial finger flexion of 4th and 5th PIP and DIP due to unopposed EDC). SNAP shows abnormal dorsal ulnar cutaneous nerve and ulnar nerve findings, CMAP is also abnormal.
2. Froment's sign is the inability to hold a piece of paper by thumb and index finger using thumb adduction, instead substituting in the FPL, resulting in flexion of interphalangeal jt.
3. Wartenberg's sign is the inability to adduct to the 5th digit.
4. This is an ulnar neuropathy traditionally occurring long after a distal humerus fracture, injured secondary to bone overgrowth, scar formation, or strain from valgus deformity. Symptoms are dependent on the site of the injury.
5. The cubital tunnel is the most common site of elbow entrapment and it is located between the medial epicondyle and the olecranon with an overlying aponeurotic band. Cubital tunnel syndrome involves all ulnar nerve innervated muscles with the possible exception of the FCU.
6. SNAP shows abnormal dorsal ulnar cutaneous nerve and ulnar nerve findings. CMAP shows at least a 10m/s drop of CV across the elbow.