The Ulnar Nerve And Its Cubital Tunnel
The ulnar nerve threads a tight bony groove behind the elbow.
- Elbow: Tunnel floor (medial epicondyle groove)
- Osborne's lig.: Tunnel roof (cubital tunnel retinaculum)
- 4th–5th: Nerve fibers supplied (ring and little finger)
- ~1 cm: Normal glide range (during elbow flexion)
Where the nerve travels
It runs behind the medial epicondyle, unprotected by muscle.
What it controls
It carries sensation and grip strength to the hand's ulnar side.
Why this spot is vulnerable
The tunnel is the narrowest, most exposed point along its path.
Compression Onset From Sustained Flexion
Bending the elbow stretches and squeezes the tunnel around the nerve.
- ~55%: Tunnel volume loss (at full elbow flexion)
- Leaning, sleep: Common triggers (prolonged bent-elbow posture)
- 6×: Nerve pressure rise (flexed vs extended elbow)
- Tingling: Early symptom (intermittent, position-dependent)
The flexion effect
Bending the elbow tightens the retinaculum over the nerve.
Repetitive strain
Leaning on the elbow or sleeping flexed adds daily pressure.
Reversible at this stage
Symptoms often ease once the elbow straightens again.
Tinel's Sign — Provoking The Nerve
Tapping the tunnel reproduces the patient's tingling instantly.
- Cubital tunnel: Test site (behind medial epicondyle)
- Tingling: Positive response (radiates to ring, little finger)
- ~70%: Test sensitivity (for ulnar nerve entrapment)
- Irritated axon: Result meaning (mechanically hypersensitive nerve)
How the test works
A light tap over the nerve provokes an electric-like tingle.
Where it radiates
Sensation shoots down into the ring and little fingers.
Clinical significance
A positive sign confirms active nerve irritation at the elbow.
Sensory Loss In The Ring And Little Finger
Ongoing compression starves the nerve, dulling feeling and grip.
- Ring, little: Sensation loss (ulnar-sided digits)
- Weak pinch: Motor sign (reduced grip strength)
- Muscle wasting: Advanced finding (first dorsal interosseous)
- Slowed: Nerve conduction (across the elbow segment)
Numbness sets in
Reduced blood flow impairs nerve signaling over time.
Grip weakens
Small hand muscles lose strength and coordination.
Risk of permanence
Untreated compression can cause lasting nerve damage.
Ulnar Nerve Transposition
The nerve is rerouted in front of the elbow to relieve pressure.
- Transposition: Procedure (anterior nerve relocation)
- Anterior: New position (to medial epicondyle)
- ~85%: Success rate (symptom improvement)
- 6–12 wks: Recovery time (to full activity)
The surgical goal
Moving the nerve stops it from stretching over the epicondyle.
How it is done
The nerve is freed and repositioned under nearby soft tissue.
Expected outcome
Tunnel pressure releases and sensation gradually returns.