CUBITAL TUNNEL SYNDROME
Second Most Common Entrapment Neuropathy | Ulnar Nerve | Elbow
McGowan Grading
Critical Must-Knows
- Ulnar Nerve Territory: Small finger and ulnar half of ring finger (palmar and dorsal)
- Froment's Sign: Thumb IP flexion when pinching - indicates adductor pollicis weakness
- Wartenberg's Sign: Small finger abduction at rest - indicates weak 3rd palmar interosseous
- Claw Hand: Ring and small finger hyperextension at MCP with IP flexion (ulnar paradox)
- Surgery Options: In-situ decompression vs anterior transposition - similar outcomes
Examiner's Pearls
- "Froment's positive = motor involvement = Grade II+
- "Intrinsic atrophy = urgent surgery, incomplete recovery
- "Elbow flexion test reproduces symptoms
- "Ulnar claw is WORSE with LOW lesion (ulnar paradox)
Clinical Imaging
Imaging Gallery
Critical Cubital Tunnel Exam Points
Froment's Sign
Thumb IP flexion when pinching paper. Indicates adductor pollicis weakness (ulnar nerve). Uses FPL (median) to compensate.
Wartenberg's Sign
Small finger abducted at rest. Weak 3rd palmar interosseous cannot adduct small finger. "Catching on pocket" complaint.
Ulnar Paradox
Claw WORSE in low lesion. High lesion: FDP paralyzed so less IP flexion. Low lesion: FDP works so more clawing.
Motor Recovery
May be incomplete if atrophy. Intrinsic muscle recovery depends on duration. Sensory recovers better than motor.
Quick Decision Guide
| Presentation | McGowan Grade | Treatment | Key Pearl |
|---|---|---|---|
| Intermittent numbness only, normal exam | Grade I | Conservative: splint, activity modification | Trial for 3 months before surgery |
| Weakness on exam, positive Froment's | Grade II | Consider surgery if fails conservative | Motor involvement = surgical indication |
| Intrinsic atrophy, claw hand | Grade III | Urgent surgical decompression | Motor recovery may be incomplete |
FWCUlnar Nerve Motor Signs
Memory Hook:FWC = Froment's, Wartenberg's, Claw - the three motor signs of ulnar palsy, in order of severity!
HALF PADUlnar Nerve Hand Muscles
Memory Hook:HALF of the hand is paralyzed by ulnar nerve injury - remember HALF PAD!
FOAMCubital Tunnel Compression Sites
Memory Hook:FOAM - Four sites of potential compression from distal to proximal!
Overview and Epidemiology
Why Cubital Tunnel Matters
Cubital tunnel syndrome is the second most common peripheral nerve compression after CTS. Understanding ulnar nerve anatomy, McGowan grading, and surgical options is essential for the exam.
Cubital Tunnel Syndrome is compression of the ulnar nerve at the elbow as it passes between the medial epicondyle and olecranon.
Demographics
- Male predominance: 2:1 ratio
- Peak age: 30-50 years
- Bilateral: 30% of cases
- Occupational risk: Repetitive elbow flexion, leaning on elbows
Understanding risk factors helps identify at-risk patients.
Causes
- Idiopathic: Most common
- Repetitive flexion: Occupational, sleeping with bent elbow
- Direct pressure: Leaning on elbows
- Cubitus valgus: Tardy ulnar palsy post-fracture
- Osteophytes: Elbow arthritis
Screen for underlying causes in all patients.
Pathophysiology and Mechanisms
Cubital Tunnel Anatomy
The cubital tunnel is a fibro-osseous tunnel at the elbow. FLOOR is the MCL and elbow capsule. ROOF is Osborne's ligament (arcuate ligament connecting the two heads of FCU). The ulnar nerve becomes superficial and vulnerable here.
Anatomical Relationships:
- Proximal: Arcade of Struthers (5-10cm above epicondyle)
- At Tunnel: Between medial epicondyle and olecranon
- Distal: Between two heads of FCU (Osborne's ligament)
Dynamic Factors:
- Elbow flexion: Nerve stretches 4-8mm, tunnel narrows 55%
- Nerve excursion: 10mm with full flexion
- Pressure: Increases 6x from extension to flexion
Classification Systems
McGowan Classification (Modified)
| Grade | Symptoms | Examination | Treatment |
|---|---|---|---|
| I | Intermittent paresthesias | Normal strength and sensation | Conservative |
| IIA | Intermittent paresthesias | Weakness without atrophy | Surgery if fails conservative |
| IIB | Persistent paresthesias | Weakness without atrophy | Surgery recommended |
| III | Persistent symptoms | Intrinsic atrophy | Urgent surgery |
McGowan grading guides treatment decisions.
Clinical Assessment
History
- Numbness: Small and ulnar ring finger
- Timing: Worse at night, with elbow flexion
- Dropping objects: Weakness of grip
- Phone sign: Numbness holding phone to ear
- Red flags: Rapid progression, severe weakness
Ask about occupation and sleeping position.
Examination
- Tinel's: Over cubital tunnel
- Elbow flexion test: 60 seconds sustained flexion
- Froment's sign: IP flexion when pinching
- Wartenberg's sign: Small finger abduction
- Two-point discrimination: Greater than 6mm abnormal
Always compare to contralateral side.
Key Clinical Signs
| Sign | Technique | Positive Finding | Indicates |
|---|---|---|---|
| Froment's | Pinch paper between thumb and index | IP flexion of thumb | Adductor pollicis weakness |
| Wartenberg's | Observe hand at rest | Small finger abducted | 3rd palmar interosseous weakness |
| Elbow Flexion | Sustained elbow flexion 60 seconds | Paresthesias reproduced | Ulnar nerve compression |
| Scratch Collapse | Resist shoulder external rotation while scratching nerve | Momentary weakness | Nerve irritability |
Differential Diagnosis
Consider: C8/T1 radiculopathy, thoracic outlet syndrome, Guyon's canal compression (ulnar tunnel), pancoast tumor. Check for double crush syndrome.
Investigations
Investigation Protocol
Clinical diagnosis in typical presentations with positive Tinel's, elbow flexion test, and motor signs.
Gold standard. Slowing of motor conduction velocity across elbow (less than 50 m/s). Compare to segment above and below.
For severity grading. Denervation potentials in intrinsics (FDI, ADM). Fibrillations indicate axonal loss.
X-ray: Cubitus valgus, osteophytes, prior fracture. MRI: Subluxation, mass lesion, nerve changes.
Multimodal Assessment Example
Management Algorithm
Conservative Management
Conservative Treatment Steps
Avoid prolonged elbow flexion. Ergonomic workplace assessment. Avoid leaning on elbows.
Keep elbow extended at night. Towel wrap or commercial splint. Prevents nocturnal flexion.
Protect nerve from direct pressure. Wear during day if occupational exposure.
Conservative treatment is appropriate for McGowan Grade I with intermittent symptoms only.
Surgical Technique
In-Situ Decompression
Surgical Steps
Supine, arm on table. Elbow flexed 20-30 degrees. Tourniquet optional.
Curved incision between medial epicondyle and olecranon. 6-8cm. Protect medial antebrachial cutaneous nerve.
Identify and protect nerve. Release Osborne's ligament (FCU aponeurosis). Release distally between FCU heads.
Release arcade of Struthers if tight. Release medial intermuscular septum.
Layered closure. Check nerve excursion. No drain required.
In-situ decompression is technically simpler with lower complication rate.
Complications
Complications of Cubital Tunnel Surgery
| Complication | Incidence | Management |
|---|---|---|
| MABC neuroma | 5-10% | Careful dissection, neurolysis if symptomatic |
| Recurrence | 5-15% | Revision with transposition |
| Elbow instability | Rare | Avoid MCL injury, repair if damaged |
| Wound complications | 2-5% | Standard wound care |
| Incomplete recovery | 10-20% | Counsel pre-operatively especially if atrophy |
MABC nerve injury causing painful neuroma is the most common complication. Careful handling and protection during dissection is essential.
Postoperative Care
Postoperative Protocol
Soft dressing, sling optional. Elevate arm. Finger ROM immediately. Wound check at 1 week.
Remove sutures. Begin gentle elbow ROM. Avoid resisted flexion.
Progressive strengthening. Full ROM by 4 weeks. Grip strengthening from week 6.
Assess nerve recovery. Sensory improvement first. Motor recovery may take 6-12 months.
Return to work: Desk work 1-2 weeks. Manual work 6-8 weeks.
Outcomes and Prognosis
Success Rates:
- In-situ decompression: 80-90% good/excellent
- Anterior transposition: 80-90% good/excellent
- Comparison: No significant difference in outcomes
Prognostic Factors:
| Factor | Better Outcome | Worse Outcome |
|---|---|---|
| McGowan Grade | I-II | III with atrophy |
| Duration | Short (under 6 months) | Long (over 1 year) |
| Age | Younger | Elderly |
| Atrophy | Absent | Present |
Motor recovery is often incomplete if intrinsic atrophy is present pre-operatively.
Evidence Base
- Simple decompression vs transposition
- No significant difference in outcomes
- Transposition may have more complications
- Simple decompression preferred as first-line
- Anterior transposition vs simple decompression
- Similar efficacy
- Transposition has higher complication rate
- Simple decompression recommended initially
- Submuscular transposition outcomes
- 85% good/excellent results
- Longer recovery than subcutaneous
- Consider for high-demand patients
- Simple decompression vs transposition
- 152 patients randomized
- Similar outcomes at 1 year
- Simpler procedure preferred
- Endoscopic vs open decompression
- Similar outcomes
- Faster recovery with endoscopic
- Learning curve required
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Classic Presentation
"A 35-year-old office worker presents with 6 months of numbness in the small finger. He leans on his elbows at his desk. Tinel's is positive over the elbow. Froment's is negative."
Scenario 2: Motor Involvement
"A 45-year-old man has 12 months of small finger numbness and now notices weakness holding a key. On examination, Froment's sign is positive and there is early wasting of the first dorsal interosseous."
Scenario 3: Failed Surgery
"A patient returns 6 months after in-situ decompression with persistent symptoms and now has subluxation of the ulnar nerve with elbow flexion. What is your approach?"
MCQ Practice Points
Ulnar Nerve Territory
Q: Which fingers are affected in ulnar nerve compression? A: Small finger and ulnar half of ring finger - both palmar AND dorsal surfaces (unlike CTS which is palmar only).
Froment's Sign Muscle
Q: Which muscle is tested by Froment's sign? A: Adductor pollicis - the only muscle that adducts the thumb (except for first interosseous to lesser extent). Innervated by ulnar nerve.
Ulnar Paradox
Q: Why is clawing worse in a LOW ulnar nerve lesion? A: FDP function preserved. In high lesion, FDP to ring/small is paralyzed so IP flexion is weak. In low lesion, FDP works normally, causing pronounced IP flexion with MCP hyperextension.
Decompression vs Transposition
Q: What does the evidence show regarding in-situ decompression vs anterior transposition? A: Similar outcomes. Cochrane review (Caliandro 2016) shows no significant difference. Simple decompression has lower complication rate. Reserve transposition for subluxation or revision.
Arcade of Struthers
Q: What is the Arcade of Struthers and why is it important? A: Musculofascial band 5-10cm proximal to medial epicondyle. Potential compression site that must be released during decompression to prevent recurrence.
Osborne's Ligament
Q: What is Osborne's ligament? A: The arcuate ligament connecting the two heads of FCU. Forms the roof of the cubital tunnel. Release is essential during decompression.
Australian Context
Australian Guidelines:
- RANZCR recommends NCS for confirmation before surgical intervention
- Medicare rebates available for NCS and surgical decompression/transposition
- Most cubital tunnel surgery performed as day surgery
Medicolegal Considerations:
- Document motor examination (Froment's, Wartenberg's) at each visit
- Obtain informed consent including risk of incomplete motor recovery
- Document pre-operative intrinsic wasting - patients must understand this may not fully recover
- Warn of MABC nerve injury, wound complications, recurrence
Workcover/Insurance:
- May be work-related (occupational pressure, repetitive flexion)
- Document occupational history thoroughly
- Workplace ergonomic assessment may be required
Australian surgeons should follow RACS guidelines and document consent thoroughly.
CUBITAL TUNNEL SYNDROME
High-Yield Exam Summary
Key Anatomy
- •Ulnar nerve between medial epicondyle and olecranon
- •Osborne's ligament = FCU aponeurosis (roof)
- •Arcade of Struthers 5-10cm proximal
- •MABC nerve at risk superficially
Clinical Signs
- •Froment's = thumb IP flexion when pinching
- •Wartenberg's = small finger abducted
- •Claw hand = MCP hyperextension + IP flexion
- •Ulnar paradox = worse claw in LOW lesion
Classification
- •McGowan I = sensory only = conservative
- •McGowan II = weakness = consider surgery
- •McGowan III = atrophy = urgent surgery
- •Modified IIA/IIB distinguishes intermittent vs persistent
Surgery Options
- •In-situ decompression = first line
- •Anterior transposition = subluxation/revision
- •Submuscular = high demand/revision
- •All have 80-90% success
Complications
- •MABC neuroma = most common
- •Recurrence 5-15%
- •Incomplete motor recovery if atrophy
- •Elbow instability if MCL injured