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Cubital Tunnel Syndrome

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Overview

Exam Detail:

Key Revision Focus: The 5 Sites of Ulnar Nerve Compression at the Elbow. Osborne's Ligament. Arcade of Struthers. McGowan Classification. Froment's Sign, Wartenberg's Sign. Simple Decompression vs Anterior Transposition (Subcutaneous, Intramuscular, Submuscular). Medial Epicondylectomy. Protecting the MABC Nerve.

1. Clinical Overview

Cubital Tunnel Syndrome (CuTS) is the second most common peripheral nerve entrapment neuropathy after Carpal Tunnel Syndrome. It results from compression or traction of the Ulnar Nerve at the elbow, most commonly as it passes through the Cubital Tunnel beneath Osborne's Ligament. The condition causes numbness and tingling in the ring and little fingers, hand weakness, and, in advanced cases, visible muscle wasting and clawing.

Clinical Pearl:

The Key Question: Is it compression at the elbow (Cubital Tunnel) or at the wrist (Guyon's Canal)? Clues:

  • Elbow (CuTS): Numbness on the dorsal ulnar hand (Dorsal Cutaneous Branch of Ulnar Nerve - branches proximal to Guyon's Canal). Sensory loss in the ulnar 1.5 fingers.
  • Wrist (Guyon's): Sparing of the dorsal ulnar hand (DCB is normal). Isolated motor or sensory loss depending on the zone.

Key Concepts

  1. Anatomy of the Ulnar Nerve at the Elbow: The ulnar nerve traverses five recognized sites of potential compression around the elbow. Knowing these is critical for viva discussions and surgical planning.
    SiteStructureClinical Significance
    1. Arcade of StruthersFascial band ~8 cm proximal to medial epicondyle, from medial intermuscular septum to medial head of triceps.Can compress nerve if tight. Must be released if transposing nerve anteriorly.
    2. Medial Intermuscular Septum (MIMS)The fascial wall between anterior (flexor) and posterior (triceps) compartments.Can become a "cutting edge" compressing the nerve after anterior transposition if not released.
    3. Medial EpicondyleThe bony groove (Postcondylar Groove / Ulnar Sulcus) behind the medial epicondyle.Shallow groove = nerve more prone to subluxation. Osteophytes can compress.
    4. Osborne's Ligament / Humeroulnar Arcade (HUA)Fascial band forming the "roof" of the Cubital Tunnel. Runs between the two heads of the FCU.Most common site of compression. Tightens with elbow flexion. Release of this ligament is the core of "Simple Decompression." Also known as the Cubital Tunnel Retinaculum.
    5. Within the Flexor Carpi Ulnaris (FCU) MuscleThe deep aponeurosis of FCU.Less common, but can compress the nerve as it passes between the two heads of FCU.
  2. Cubital Tunnel:
    • Boundaries:
      • Roof: Osborne's Ligament (Humeroulnar Arcade / Cubital Tunnel Retinaculum). Also, the overlying FCU aponeurosis.
      • Floor: Medial Collateral Ligament (MCL) of the elbow and the elbow capsule.
      • Walls: The two heads of FCU (Humeral and Ulnar heads).
    • Dynamic Changes: The tunnel narrows with elbow flexion. The MCL bulges into the tunnel. Osborne's ligament tightens. Intra-tunnel pressure increases dramatically (up to 6-fold).
  3. Causes of Cubital Tunnel Syndrome:
    • Idiopathic (Most Common): No clear anatomical lesion. Presumed repetitive microtrauma.
    • Repetitive Elbow Flexion: Occupations or activities involving prolonged or repeated flexion (e.g., throwing athletes, phone use).
    • Direct Pressure: Leaning on the elbow (e.g., driving with arm resting on window sill, "Cell Phone Elbow").
    • Anatomical Variants:
      • Anconeus Epitrochlearis Muscle: A rare accessory muscle crossing the cubital tunnel (present in ~10%). Can compress the nerve.
      • Tight Osborne's Ligament.
      • Shallow Postcondylar Groove.
    • Ulnar Nerve Subluxation/Dislocation: The nerve hypermobility causes it to snap over the medial epicondyle with flexion, causing repeated trauma.
    • Post-Traumatic: Cubitus Valgus deformity (Tardy Ulnar Palsy after childhood lateral condyle fracture). Heterotopic ossification. Elbow contracture.
    • Space-Occupying Lesion: Ganglion cyst, Lipoma, Schwannoma, Osteophyte, Heterotopic Bone.
    • Inflammatory: Rheumatoid Arthritis (synovitis), Gout.
  4. Clinical Classification (McGowan - Classic):
    GradeSensoryMotor
    I (Mild)Paraesthesias, NumbnessNone
    II (Moderate)Sensory lossWeakness, No wasting
    III (Severe)Marked sensory lossWeakness AND Wasting
    A more detailed modification includes IIA (weakness without wasting) and IIB (weakness with wasting), with IIIA/IIIB for asynchrony of the first dorsal interosseous.
  5. Double Crush Syndrome:
    • Proximal compression (C8/T1 radiculopathy, Thoracic Outlet Syndrome) can make the nerve more susceptible to compression at the elbow.
    • Conversely, Cubital Tunnel Syndrome can co-exist with Carpal Tunnel Syndrome (Triple Crush).
    • Always examine the cervical spine.

Clinical Pearls

  • Elbow Flexion is the Enemy: The nerve is most compressed when the elbow is flexed. Patients often wake at night because they sleep with elbows flexed.
  • Intrinsic Weakness before Extrinsic: The intrinsic muscles of the hand (interossei, lumbricals to 4th/5th fingers, adductor pollicis, hypothenar muscles) are affected before the extrinsic muscles (FCU, FDP to 4th/5th). This is because ulnar nerve fascicles to intrinsics are located peripherally within the nerve and are more susceptible to compression.
  • Ulnar Paradox: In a high ulnar nerve lesion (e.g., at the elbow), clawing of the ring and little fingers is less severe than in a low lesion (e.g., at the wrist). This is because in high lesions, FDP to 4th/5th is also paralyzed, so the fingers cannot flex at the DIP (which contributes to the claw posture).
  • Medial Antebrachial Cutaneous Nerve (MABC): This sensory nerve (from the medial cord) runs close to the cubital tunnel and is at risk during surgery. Its posterior branch crosses the surgical field. Injury causes painful neuroma or numbness on the medial forearm.

2. Epidemiology

  • Incidence: Second most common upper extremity entrapment neuropathy. Estimated at ~25 per 100,000 person-years.
  • Sex: Male = Female (some studies show slight Male predominance).
  • Age: Peak incidence in 4th-6th decades. Can occur at any age.
  • Risk Factors:
    Risk FactorAssociation
    Repetitive Elbow Flexion/ExtensionHigh (Occupational, Sports - especially throwing)
    Prolonged Elbow LeaningHigh
    Diabetes MellitusOR ~2.0 (Nerve vulnerable)
    Obesity (BMI > 30)OR ~1.5-2.0
    Previous Elbow Fracture / Cubitus ValgusHigh (Tardy Ulnar Palsy)
    Ulnar Nerve SubluxationHigh
    Rheumatoid ArthritisHigh (Synovitis)
    Prolonged Bedrest / ICU AdmissionHigh (Immobility, Positioning)

3. Pathophysiology

The pathophysiology of Cubital Tunnel Syndrome is similar to other entrapment neuropathies – a cascade of compression, ischemia, and structural nerve damage.

Step 1: Initiating Event (Extrinsic or Intrinsic Compression)

  • Extrinsic Compression: External pressure (leaning on elbow), tight Osborne's ligament, anatomical variant (Anconeus Epitrochlearis), SOL.
  • Intrinsic Factors: Shallow postcondylar groove, nerve subluxation, cubitus valgus deformity.
  • Repetitive Traction: The nerve is stretched during elbow flexion. The nerve must glide ~ 10mm. Adhesions or tethering prevent this glide, causing traction injury.

Step 2: Microvascular Compromise (Ischemia)

  • Compression elevates endoneurial pressure within the nerve fascicles.
  • This compresses the vasa nervorum (intrinsic blood supply).
  • Ischemia impairs oxidative metabolism of the Schwann cells and axons.
  • Venous congestion occurs first, followed by capillary flow reduction.

Step 3: Blood-Nerve Barrier Breakdown and Edema

  • Ischemia damages the endothelial tight junctions of the blood-nerve barrier.
  • Plasma proteins and fluid leak into the endoneurium → Intra-fascicular edema.
  • Edema further increases endoneurial pressure, worsening ischemia (vicious cycle).
  • The nerve may become visibly swollen proximal to the compression site (pseudoneuroma).

Step 4: Demyelination (Conduction Block / Slowing)

  • Chronic ischemia and pressure impair Schwann cell function.
  • Segmental demyelination occurs at the compression site.
  • Large, myelinated fibers (motor and proprioceptive/touch) are affected first.
  • Clinically: Numbness, tingling, clumsiness. Weakness may be subtle.
  • Nerve Conduction Studies (NCS): Slowed conduction velocity across the elbow segment, prolonged motor latency. This stage is often reversible with decompression.

Step 5: Axonal Degeneration (Wallerian Degeneration)

  • Prolonged or severe compression causes axonal death within the fascicles.
  • Wallerian degeneration occurs distal to the injury site.
  • Clinically: Motor weakness becomes pronounced. Muscle wasting begins. Sensory loss is fixed.
  • EMG: Denervation potentials (fibrillations, positive sharp waves) in ulnar-innervated muscles.
  • NCS: Reduced amplitudes of CMAP and SNAP.
  • Recovery after decompression is slower and less complete. Axonal regeneration proceeds at ~1mm/day (~1 inch/month). Full recovery may take 1-2 years, or be incomplete.

Step 6: Chronic Changes and Fibrosis (End-Stage)

  • Longstanding compression leads to intra-neural fibrosis.
  • The nerve becomes scarred, thickened, and adherent to surrounding tissues.
  • The muscle atrophy becomes irreversible (fatty replacement of muscle fibers).
  • Surgical outcomes are poor. Tendon transfers may be needed.

4. Clinical Presentation

Symptoms

  1. Numbness and Paraesthesias:
    • Location: Ulnar 1.5 fingers (little finger and ulnar half of ring finger) and the ulnar border of the hand.
    • Dorsal ulnar hand numbness (supplied by the Dorsal Cutaneous Branch) is a key differentiator from Guyon's Canal Syndrome.
    • Character: Tingling, "pins and needles," burning.
    • Timing: Often worse at night (sleeping with elbows flexed). Worse with prolonged elbow flexion (reading, phone use, driving).
  2. Weakness and Clumsiness:
    • Difficulty with fine motor tasks: Buttons, keys, writing, picking up small objects.
    • Weak grip (key pinch is particularly affected).
    • Dropping things.
  3. Pain:
    • Often dull, aching pain at the medial elbow.
    • May radiate down the forearm to the hand.
    • Not always present.
  4. Wasting (Late):
    • Visible wasting of the First Dorsal Interosseous (FDI) muscle (gutter between thumb and index metacarpals).
    • Wasting of the Hypothenar eminence.
    • Sunken appearance of the interosseous spaces on the dorsum of the hand.

Red Flags

Red FlagConsider
Neck Pain, Bilateral SymptomsC8/T1 Radiculopathy, Cervical Myelopathy
Arm Pain + Hand Symptoms worse with overhead activityThoracic Outlet Syndrome (TOS)
Rapid Progression, Mass at ElbowTumor (Schwannoma, Neurofibroma)
Systemic Symptoms (Weight Loss, Fever)Malignancy, Infection, Vasculitis
History of Elbow Fracture in ChildhoodTardy Ulnar Palsy (Cubitus Valgus)
Painless, Purely Motor WeaknessConsider Motor Neuron Disease (ALS)

Differential Diagnosis

ConditionKey Differentiating Features
Guyon's Canal SyndromeUlnar nerve compression at wrist. Dorsal ulnar hand sensation is PRESERVED (DCB branches before the wrist). Weakness in ulnar intrinsics only (FDP, FCU may be normal).
C8/T1 RadiculopathyNeck pain. Full dermatomal sensory loss (C8 = Medial forearm; T1 = Medial arm). Weakness in all C8/T1 myotomes (not just ulnar). Abnormal reflexes. MRI Spine abnormal.
Thoracic Outlet Syndrome (TOS)Pain often in shoulder, axilla, and radiates down arm. Symptoms often postural (worse with arm overhead). Adson's/Roos test. Sensory loss may be patchy.
Medial EpicondylitisPain at medial epicondyle with resisted wrist flexion/pronation. No neurological deficit. Tenderness at flexor-pronator origin.
Motor Neuron Disease (ALS)Painless, progressive weakness. Upper AND Lower Motor Neuron signs. No sensory loss. Widespread fasciculations.
Pancoast TumorLung apex tumor invading brachial plexus (C8/T1). Horner's Syndrome. Shoulder pain. Chest X-ray abnormal.

5. Clinical Examination

1. Look (Inspection)

  • Carrying Angle: Cubitus Valgus (increased angle between arm and forearm in extension). Associated with Tardy Ulnar Palsy.
  • Elbow Posture: Contracture? Effusion?
  • Hand Muscle Wasting:
    • First Dorsal Interosseous (FDI): Gutter between thumb and index finger metacarpals. Most visible and earliest wasting.
    • Hypothenar Eminence: Flattening of the little finger side of the palm.
    • All Interossei: Sunken "guttering" between metacarpals on dorsum of hand.
  • Clawing (Ulnar Claw Hand / "Benediction Sign" in Ulnar Palsy):
    • Ring and little fingers: Hyperextension at MCP joint and flexion at IP joints.
    • Occurs due to loss of Lumbrical/Interosseous function (MCP flexion, IP extension) with unopposed FDP/EDC action.
    • Ulnar Paradox: Clawing is less prominent in high lesions (e.g., elbow) because FDP to ring/little is also weak.

2. Feel (Palpation)

  • Tinel's Sign at Elbow:
    • Percuss over the ulnar nerve at the postcondylar groove (between medial epicondyle and olecranon).
    • Positive: Tingling or electric shock sensation radiating to the ulnar hand.
  • Ulnar Nerve Subluxation:
    • Palpate the nerve in the groove while passively flexing and extending the elbow.
    • Positive: Nerve "snaps" over the medial epicondyle during flexion.
  • Tenderness: At the medial epicondyle or along the nerve.

3. Move (Range of Motion)

  • Elbow ROM: Check for contracture or stiffness.
  • Elbow Flexion Test:
    • Technique: Maximally flex both elbows, with wrists in neutral. Hold for 60 seconds.
    • Positive: Reproduction of symptoms (numbness, tingling, pain in ulnar distribution).
    • Sensitivity ~75%, Specificity ~98% (but bilateral positive is common).
  • Pressure Provocation Test:
    • Apply direct pressure over the cubital tunnel with the elbow in flexion for 30-60 seconds.
    • Positive: Reproduction of symptoms.
  • Combined Flexion-Pressure Test: Flex elbow maximally AND apply pressure over the nerve. Highly sensitive.

4. Neurological Assessment

  • Sensation:
    • Test Light Touch and Pinprick in the:
      • Ulnar 1.5 digits (Palmar and Dorsal).
      • Ulnar border of the hand.
      • Dorsal ulnar hand (Dorsal Cutaneous Branch territory). KEY to differentiate from Guyon's.
    • Compare side-to-side.
    • Two-Point Discrimination (2PD): Normal <6mm on digital pulp. Elevated 2PD is an early sign of sensory loss.
  • Motor (Ulnar Nerve Innervated Muscles):
    MuscleTest ActionClinical Note
    First Dorsal Interosseous (FDI)Index finger abduction (against resistance)Often the first muscle to weaken and waste.
    Palmar Interossei (PI)Finger adduction ("Hold paper between fingers")Weakness causes finger "escape" (Wartenberg's Sign).
    Abductor Digiti Minimi (ADM)Little finger abductionWasting visible on ulnar border of hand.
    Adductor Pollicis (AP)Thumb adduction ("Hold paper between thumb and palm")Weakness causes compensatory FPL activation (Froment's Sign).
    Lumbricals to Ring & Little (3rd & 4th)Finger flexion at MCP with IP extensionWeakness contributes to clawing.
    Flexor Carpi Ulnaris (FCU)Wrist flexion with ulnar deviationOften spared or mildly affected. Branches high.
    Flexor Digitorum Profundus (FDP) to Ring & LittleDIP flexion against resistanceOften spared or mildly affected. Branches high.

5. Special Motor Signs

  • Froment's Sign:
    • Ask patient to hold a piece of paper between their thumb and radial side of their index finger (key pinch / lateral pinch).
    • Positive: The thumb Interphalangeal (IP) joint flexes (FPL activation, innervated by Median/AIN) to compensate for weak Adductor Pollicis.
    • Indicates Adductor Pollicis weakness.
  • Wartenberg's Sign:
    • Ask patient to adduct all fingers together (press them all against each other).
    • Positive: The little finger remains abducted (cannot be fully adducted) because the 3rd Palmar Interosseous (adductor of little finger) is weak, and the abducting forces (EDM, ADM) are unopposed.
  • Jeanne's Sign:
    • Hyperextension of the thumb MCP joint during pinch (to compensate for weak AP).
  • Egawa's Sign:
    • Inability to abduct the middle finger. Tests the 2nd dorsal interosseous.
  • Pollock's Sign:
    • Inability to flex the DIP joint of the little and ring fingers (testing FDP to 4th/5th). Indicates a high lesion.

6. Additional Assessments

  • Cervical Spine Examination: Rule out C8/T1 radiculopathy. Spurling's test, ROM, dermatomes, myotomes.
  • Thoracic Outlet Tests (if suspected): Adson's, Wright's, Roos stress test.
  • Contralateral Limb: Compare findings.

6. Investigations

First-Line: Nerve Conduction Studies (NCS) and Electromyography (EMG)

  • Considered the Gold Standard for confirming diagnosis and assessing severity.
  • Nerve Conduction Studies (NCS):
    • Motor Conduction Velocity (MCV): Measured across the elbow segment (above and below the epicondyle).
      • Normal: >50 m/s.
      • Abnormal: Slowing of MCV across the elbow by >10 m/s compared to the forearm segment suggests localized compression.
    • Compound Muscle Action Potential (CMAP) Amplitude: Measured at ADM or FDI.
      • Reduced amplitude indicates axonal loss.
    • Sensory Nerve Action Potential (SNAP): Measuring the dorsal cutaneous branch.
      • Reduced or absent SNAP indicates sensory fiber involvement.
  • Electromyography (EMG):
    • Needle examination of ulnar-innervated muscles (FDI, ADM, FCU, FDP 4/5).
    • Denervation findings: Fibrillation potentials, Positive Sharp Waves. Indicate axonal loss.
    • Chronic changes: Reduced recruitment, large polyphasic motor unit potentials (MUPs), indicating reinnervation.
    • Also examine C8/T1 myotome muscles not innervated by the ulnar nerve (e.g., Abductor Pollicis Brevis - median, Extensor Indicis Proprius - radial) to rule out radiculopathy.
  • Limitations: ~10-20% of clinically evident CuTS may have normal or equivocal NCS/EMG. A normal study does NOT definitively rule out the diagnosis.

Second-Line: Plain Radiographs (X-ray)

  • Views: AP and Lateral of the elbow.
  • Findings:
    • Cubitus Valgus: Increased carrying angle (after lateral condyle malunion).
    • Arthritis: Osteophytes, joint space narrowing.
    • Heterotopic Ossification: Post-traumatic.
    • Old Fracture: Evidence of previous injury.

Third-Line: Advanced Imaging

  • MRI of Elbow:
    • Useful if a mass lesion (ganglion, tumor) is suspected.
    • Can visualize the ulnar nerve directly. May show nerve enlargement, T2 hyperintensity (edema), or displacement.
    • Can identify Anconeus Epitrochlearis muscle.
  • Ultrasound:
    • Dynamic imaging. Can visualize nerve thickening, subluxation during elbow flexion, and masses.
    • Can assess cross-sectional area (CSA) of the nerve. Increased CSA (>8-10 mm²) at the elbow suggests compression.
    • Operator-dependent.
  • MRI Cervical Spine:
    • If C8/T1 radiculopathy or cervical myelopathy is suspected (neck pain, arm symptoms, bilateral findings, dermatomal loss).

7. Management

Management follows a stepwise approach: conservative first for mild cases, surgical for moderate-to-severe or refractory cases.

                    CUBITAL TUNNEL SYNDROME
                              ↓
┌─────────────────────────────────────────────────────────────┐
│                        DIAGNOSIS                            │
│  - Clinical (Tinel's, Elbow Flexion Test, Motor/Sensory)    │
│  - NCS/EMG (Confirm, Localize, Assess Severity)             │
│  - X-ray +/- MRI (Rule out bony/soft tissue cause)          │
└─────────────────────────────────────────────────────────────┘
                              ↓
┌─────────────────────────────────────────────────────────────┐
│               ASSESS SEVERITY (McGowan Grade)               │
│  Grade I (Mild): Paraesthesias, No weakness                 │
│  Grade II (Moderate): Weakness, No/Minimal wasting          │
│  Grade III (Severe): Weakness AND Wasting                   │
└─────────────────────────────────────────────────────────────┘
                              ↓
          ┌───────────────────┴───────────────────┐
          ↓                                       ↓
┌──────────────────────────┐           ┌──────────────────────────┐
│    GRADE I (MILD)        │           │  GRADE II/III (MOD-SEV)  │
│    OR MILD GRADE II      │           │  OR FAILED CONSERVATIVE  │
└───────────┬──────────────┘           └───────────┬──────────────┘
            ↓                                       ↓
┌────────────────────────────┐         ┌────────────────────────────┐
│   CONSERVATIVE MANAGEMENT  │         │   SURGICAL MANAGEMENT      │
│  (3-6 Months Trial)        │         │                            │
├────────────────────────────┤         ├────────────────────────────┤
│ 1. Activity Modification   │         │ OPTIONS:                   │
│ 2. Night Splinting (Ext)   │         │ 1. Simple Decompression    │
│ 3. Elbow Padding           │         │ 2. Anterior Transposition  │
│ 4. Nerve Gliding Exercises │         │    (SubCu, IM, SubMu)      │
│ 5. NSAIDs                  │         │ 3. Medial Epicondylectomy  │
└────────────────────────────┘         └────────────────────────────┘
            ↓                                       ↓
     ┌──────┴──────┐                         (See Algorithm Below)
     ↓             ↓
┌─────────┐   ┌────────────┐
│ IMPROVED│   │ NO IMPROVE │
└────┬────┘   └─────┬──────┘
     ↓              ↓
  Continue     Proceed to
  Conserv.        Surgery

Surgical Algorithm (Procedure Selection - IMPORTANT FOR EXAM)

Clinical ScenarioRecommended Procedure
Mild-Moderate CuTS, No Subluxation, No Anatomical CauseSimple (In Situ) Decompression
Subluxating Ulnar NerveAnterior Transposition (Nerve will sublux over released tunnel edge)
Severe CuTS with WastingAnterior Transposition (Submuscular often preferred for best vascularized bed)
Post-Traumatic / Cubitus Valgus / Significant DeformityAnterior Transposition
Revision Surgery (Failed Prior Decompression)Anterior Transposition (Nerve is likely in scar)
Large Osteophytes / Shallow Groove / Medial Epicondyle ImpingementMedial Epicondylectomy (Alternative to transposition)
Athletes (Throwing)Consider Submuscular Transposition (Protects nerve better)

1. Conservative Management

  • Indications: McGowan Grade I. Mild Grade II. Initial management for most.
  • Success Rate: ~50% of mild cases improve with conservative measures.
  • Modalities:
    1. Activity Modification:
      • Avoid prolonged elbow flexion.
      • Avoid leaning on elbow.
      • Take breaks from repetitive tasks.
      • Ergonomic workstation adjustments.
    2. Night Splinting:
      • Elbow extension splint. Keeps elbow at 30-45° flexion (not full extension, which can stretch nerve) during sleep.
      • A rolled towel wrapped around the elbow can suffice.
    3. Elbow Padding:
      • Protects nerve from direct pressure.
    4. Nerve Gliding Exercises:
      • Gentle stretches to promote nerve excursion and prevent adhesions.
    5. NSAIDs:
      • For symptom relief. Limited efficacy.
  • Duration: Trial for 3-6 months before considering surgery.

2. Surgical Management

  • Indications:
    1. Failure of conservative management for 3-6 months.
    2. McGowan Grade II (Moderate) with objective weakness.
    3. McGowan Grade III (Severe) – Surgery should NOT be delayed as outcomes worsen with prolonged axonal loss.
    4. Presence of a compressive lesion (ganglion, tumor).
    5. Ulnar nerve subluxation (contraindication to simple decompression alone).

A. Simple (In Situ) Decompression

  • The most common and first-line surgical option for most primary cases.
  • Technique:
    1. Incision: ~6-8 cm curvilinear posterior to medial epicondyle.
    2. Identify and protect the Posterior Branch of the Medial Antebrachial Cutaneous (MABC) Nerve (crosses the incision).
    3. Identify the Ulnar Nerve proximal to the epicondyle.
    4. Release Osborne's Ligament (Cubital Tunnel Retinaculum) – this is the "roof."
    5. Follow the nerve distally, releasing the deep fascia of FCU.
    6. Follow the nerve proximally, releasing any tight Arcade of Struthers or fascia at the MIMS (if transposition not planned, be conservative here).
    7. Ensure free excursion of the nerve. Check for subluxation.
  • Advantages: Simpler, Shorter operation, Less dissection = Preserved blood supply, Faster recovery, Comparable outcomes to transposition in most studies.
  • Disadvantages: Cannot be used if nerve subluxates (will sublux over the released edge and become irritated). Does not address proximal compressors.
  • Outcome: Good-Excellent results in 70-90% of patients.
  • Evidence: Multiple RCTs comparing Simple Decompression to Anterior Transposition for primary CuTS have shown equivalent or superior outcomes for Simple Decompression, with fewer complications. [PMID: 27419811, 25415280] (See Landmark Trials).

B. Anterior Transposition

  • Technique: After decompression, the ulnar nerve is moved from behind the medial epicondyle to the front of it. This:
    • Removes the nerve from the site of compression.
    • Reduces tension on the nerve during elbow flexion.
    • Shortens the path of the nerve (reduces traction injury).
  • Three Main Types:
    TypeTechniqueProsCons
    SubcutaneousNerve placed in subcutaneous fat anterior to epicondyle. A fascial sling may hold it.Simpler, Good blood supply.Nerve superficial = vulnerable to trauma. Risk of subluxation anteriorly.
    IntramuscularNerve placed within the belly of the Flexor-Pronator muscle mass.Muscular bed.Technically harder. Risk of scarring within muscle.
    SubmuscularFlexor-Pronator mass is elevated from medial epicondyle. Nerve placed beneath the muscle. Muscle is then reattached.Best protection (nerve deep). Vascularized muscle bed.Most extensive surgery. Longest recovery. Potential for Flexor-Pronator weakness.
  • Indications:
    • Ulnar nerve subluxation.
    • Revision surgery (failed prior decompression).
    • Significant post-traumatic deformity or scarring.
    • Severe CuTS with wasting (some prefer submuscular for these).
    • Throwing athletes (some prefer submuscular for better protection).
  • Key Surgical Steps (Common to all types):
    1. Fully decompress the nerve (as above).
    2. Release the Arcade of Struthers (if present).
    3. Excise the Medial Intermuscular Septum (MIMS): This is CRITICAL. If the nerve is moved anterior but the septum is left, the nerve can sublux back and forth over the sharp edge of the septum, or be compressed against it. Excise ~1-2 cm.
    4. Carefully dissect the nerve free, preserving its vascular pedicle.
    5. Transpose the nerve anteriorly into the chosen plane.
    6. Create a fasciodermal sling or reattach muscle origin (submuscular) to prevent nerve from falling back.

C. Medial Epicondylectomy

  • Technique: Remove the medial epicondyle (the bony bump). This deepens the groove and removes the surface over which the nerve subluxates.
  • Indications:
    • Alternative to transposition.
    • Useful when large osteophytes or a shallow groove contributes to compression.
    • Avoids the extensive dissection of transposition.
  • Pros: Less dissection than transposition to nerve = better blood supply preservation. Removes bony impingement.
  • Cons: Potential for medial elbow instability if too aggressive (must preserve MCL origin). Post-operative medial elbow pain.
  • Outcome: Good results reported, comparable to decompression or transposition in some series.

Post-Operative Rehabilitation

  • Simple Decompression / Subcutaneous Transposition:
    • Early ROM encouraged.
    • Bulky dressing for 1-2 weeks.
    • Full activity by 4-6 weeks.
  • Submuscular Transposition:
    • Posterior splint for 1-2 weeks.
    • Protected ROM for 2-4 weeks (avoid resisted flexion/pronation to protect muscle reattachment).
    • Gradual progression. Full strength by 3 months.

8. Complications

Surgical Complications

ComplicationIncidenceNotes
Medial Antebrachial Cutaneous (MABC) Nerve Injury5-15%Numbness or painful neuroma on the medial forearm. The posterior branch crosses the surgical field. Meticulous identification and protection is essential.
Persistent or Worsening Symptoms5-20%Incomplete release, Wrong diagnosis (TOS, C8/T1), Irreversible nerve damage pre-operatively.
Recurrent Symptoms5-10%Scar tissue formation around the nerve. More common after transposition (more dissection).
Elbow Stiffness5-10%Especially after submuscular transposition.
Wound Complications3-5%Hematoma, Seroma, Infection, Dehiscence.
Ulnar Nerve Injury / Devascularization<3%Over-aggressive dissection, traction. Can worsen symptoms.
Flexor-Pronator WeaknessVariableAfter submuscular transposition if muscle origin not well reattached.
Medial Elbow InstabilityRareAfter excessive Medial Epicondylectomy (MCL origin damaged).
Subluxation of Transposed Nerve<5%Nerve slips back posteriorly (subcutaneous especially). May need fascial sling.

9. Prognosis & Outcomes

  • Conservative Management: ~50% of mild cases improve. Best for early, mild disease.
  • Surgical Management:
    • Overall success rates are 70-90% (Good-Excellent outcomes).
    • Predictors of Good Outcome:
      • Shorter duration of symptoms (<6 months).
      • McGowan Grade I or II (before significant wasting).
      • Positive pre-operative NCS localized to the elbow.
      • Absence of significant muscle wasting.
    • Predictors of Poor Outcome:
      • Longstanding symptoms (>1 year).
      • Severe muscle wasting (McGowan III). Axonal loss is often irreversible.
      • Diabetes Mellitus.
      • Worker's compensation claim.
      • Revision surgery.
  • Time to Recovery:
    • Sensory symptoms often improve first (weeks to months).
    • Motor recovery is slower. Strength may take 6-12 months to improve, and may be incomplete if axonal loss was severe.
    • Muscle atrophy may be permanent if the muscle has undergone fatty replacement.

10. Evidence & Guidelines

Guidelines

  • AAOS: No formal Clinical Practice Guideline for Cubital Tunnel Syndrome.
  • General Consensus:
    • Conservative management for mild cases.
    • Surgery for moderate-to-severe cases or failure of conservative treatment.
    • Simple Decompression is recommended as the primary surgical option for most non-subluxating, primary CuTS.
    • Transposition is reserved for subluxating nerves, revision cases, and severe deformity.

Landmark Papers & Evidence (Simple Decompression vs Transposition Debate)

  1. Biggs M, Curtis JA. Randomized, prospective study comparing ulnar neurolysis in situ with submuscular transposition. Neurosurgery. 2006 Feb;58(2):296-304. [PMID: 16462483]
    • RCT. No significant difference in outcome between simple decompression and submuscular transposition at 1 year.
  2. Gervasio O, Gambardella G, Zaccone C, Branca D. Simple decompression versus anterior submuscular transposition of the ulnar nerve in severe cubital tunnel syndrome: a prospective randomized study. Neurosurgery. 2005;56(1):108-17. [PMID: 15617593]
    • RCT for severe CuTS. Both methods effective. Submuscular transposition had higher complication rate.
  3. Bartels RH, Verhagen WI, van der Wilt GJ, Meulstee J, van Rossum LG, Grotenhuis JA. Prospective randomized controlled study comparing simple decompression versus anterior subcutaneous transposition for idiopathic neuropathy of the ulnar nerve at the elbow: Part 1. Neurosurgery. 2005 Mar;56(3):522-30. [PMID: 15730578]
    • RCT. Simple decompression equivalent to subcutaneous transposition. Transposition had more complications.
  4. Caliandro P, et al. Treatment for ulnar neuropathy at the elbow. Cochrane Database Syst Rev. 2016 Nov 15;11(11):CD006839. [PMID: 27845499]
    • Systematic Review. Found no significant difference between simple decompression and transposition. Recommended simple decompression as first-line due to lower complication rate.
  5. Zlowodzki M, et al. Anterior transposition compared with simple decompression for treatment of cubital tunnel syndrome. A meta-analysis of randomized, controlled trials. J Bone Joint Surg Am. 2007 Dec;89(12):2591-8. [PMID: 18056488]
    • Meta-analysis. No difference in motor or sensory outcomes. Transposition had higher rate of wound complications.

Summary of Evidence: Simple Decompression is the preferred first-line surgical treatment for primary, non-subluxating Cubital Tunnel Syndrome. Anterior Transposition is reserved for subluxation, revision, or severe deformity. The choice between transposition types (SubCu, IM, SubMu) is less clearly defined by evidence and often surgeon preference.

11. Patient Explanation

What is Cubital Tunnel Syndrome?

You have a nerve called the Ulnar Nerve that runs from your neck, down your arm, past your elbow, and into your hand. It's the nerve that gives you that "funny bone" sensation when you hit your elbow. At the elbow, this nerve passes through a tight tunnel behind the bony bump on the inner side (the medial epicondyle).

In Cubital Tunnel Syndrome, this nerve gets pinched or irritated in that tunnel. This causes numbness and tingling in your little finger and the side of your ring finger, and can lead to weakness in your hand.

Why does it happen?

  • Often, there's no obvious cause. It's just how your anatomy is.
  • Bending your elbow for long periods (sleeping with a bent elbow, holding a phone, leaning on your elbow) makes it worse.
  • Sometimes it's related to a previous elbow injury.

How is it treated?

  1. Non-surgical options (for mild cases):
    • Avoid leaning on your elbow.
    • Keep your elbow straight at night – we might give you a splint to wear while you sleep.
    • Padding for the elbow.
    • Most mild cases get better with these simple measures over a few months.
  2. Surgery (if non-surgical treatment doesn't work, or the nerve damage is more severe):
    • The simplest operation is called a "Simple Decompression." We make a small cut near your elbow and release the tight band of tissue pressing on the nerve. This gives the nerve more room.
    • If your nerve tends to slip over the bony bump (subluxation), or if you've had surgery before, we might need to move the nerve to a new position in front of the elbow (Anterior Transposition). This keeps it out of harm's way.
    • Surgery usually takes about an hour and is often done as a day case.

What are the risks of surgery?

  • Numbness on the inner forearm: There's a small sensory nerve that crosses the incision. It can be damaged, causing numbness or tingling (happens in about 5-10% of cases).
  • Persistent symptoms: Sometimes the nerve damage is too severe for the nerve to fully recover, and some numbness or weakness may persist.
  • Infection, bleeding, stiffness (uncommon).

What is the recovery like?

  • You can usually move your elbow straight away.
  • The wound takes 2 weeks to heal.
  • Numbness and tingling often improve first, over weeks to months.
  • Strength recovery is slower. If you had significant weakness before surgery, it can take 6-12 months for strength to return, and it may not fully return if the nerve was badly damaged.

12. References

  1. Biggs M, Curtis JA. Randomized, prospective study comparing ulnar neurolysis in situ with submuscular transposition. Neurosurgery. 2006;58(2):296-304. [PMID: 16462483]
  2. Bartels RH, et al. Prospective randomized controlled study comparing simple decompression versus anterior subcutaneous transposition. Neurosurgery. 2005;56(3):522-30. [PMID: 15730578]
  3. Gervasio O, et al. Simple decompression versus anterior submuscular transposition in severe cubital tunnel syndrome. Neurosurgery. 2005;56(1):108-17. [PMID: 15617593]
  4. Caliandro P, et al. Treatment for ulnar neuropathy at the elbow. Cochrane Database Syst Rev. 2016;11:CD006839. [PMID: 27845499]
  5. Zlowodzki M, et al. Anterior transposition compared with simple decompression: A meta-analysis. J Bone Joint Surg Am. 2007;89(12):2591-8. [PMID: 18056488]
  6. O'Driscoll SW, Horii E, Carmichael SW, Morrey BF. The cubital tunnel and ulnar neuropathy. J Bone Joint Surg Br. 1991;73(4):613-7. [PMID: 2071646]
  7. Osborne G. Compression neuritis of the ulnar nerve at the elbow. Hand. 1970;2(1):10-3.
  8. McGowan AJ. The results of transposition of the ulnar nerve for traumatic ulnar neuritis. J Bone Joint Surg Br. 1950;32-B(3):293-301. [PMID: 14778847]
  9. Patel VV, Heidenreich FP Jr, Bindra RR, Goldner RD, Urbaniak JR. Morphologic changes in the ulnar nerve at the elbow with flexion and extension. J Hand Surg Am. 1998;23(4):641-6. [PMID: 9708378]
  10. Dellon AL. Review of treatment results for ulnar nerve entrapment at the elbow. J Hand Surg Am. 1989;14(4):688-700. [PMID: 2754208]
  11. Geutjens GG, Langstaff RJ, Smith NJ, Jefferson D, Howell CJ, Barton NJ. Medial epicondylectomy or ulnar-nerve transposition for ulnar neuropathy at the elbow? J Bone Joint Surg Br. 1996;78(5):777-9. [PMID: 8836068]
  12. Heithoff SJ, Millender LH, Nalebuff EA, Petruska AJ Jr. Medial epicondylectomy for the treatment of ulnar nerve compression at the elbow. J Hand Surg Am. 1990;15(1):22-9. [PMID: 2299162]
  13. Svernlöv B, Larsson M, Rehn K, Adolfsson L. Conservative treatment of the cubital tunnel syndrome. J Hand Surg Eur Vol. 2009;34(2):201-7. [PMID: 19282408]
  14. Osei DA, Groves AP, Bomber K, Calfee RP. Cubital Tunnel Syndrome: Incidence and Demographics in a National Administrative Database. Neurosurgery. 2017;80(3):417-20. [PMID: 28362894]
  15. Eberlin KR, Ducic I. Surgical Algorithm for Neuroma Management: A Changing Treatment Paradigm. Plast Reconstr Surg Glob Open. 2018;6(10):e1952. [PMID: 30534492]

13. Examination Focus

Common Exam Questions (FRCS/Boards)

  1. What are the 5 sites of ulnar nerve compression at the elbow? (Answer: Arcade of Struthers, MIMS, Postcondylar Groove, Osborne's Ligament/HUA, within FCU).
  2. What is Osborne's Ligament? (Answer: The Humeroulnar Arcade / Cubital Tunnel Retinaculum. The fascial band forming the roof of the cubital tunnel between the two heads of FCU. The most common site of compression).
  3. How do you differentiate Cubital Tunnel from Guyon's Canal Syndrome? (Answer: Dorsal ulnar hand sensation. Cubital = Abnormal. Guyon's = Normal, because the Dorsal Cutaneous Branch of the ulnar nerve branches proximal to the wrist).
  4. What are Froment's and Wartenberg's signs? (Answer: Froment's = FPL compensation (thumb IP flexion) during key pinch due to weak Adductor Pollicis. Wartenberg's = Persistent abduction of the little finger due to weak 3rd Palmar Interosseous).
  5. Why must you release the Medial Intermuscular Septum during Anterior Transposition? (Answer: If left intact, it becomes a sharp edge that can compress or kink the transposed nerve as it passes anteriorly).
  6. What nerve is at risk during cubital tunnel surgery? (Answer: Medial Antebrachial Cutaneous Nerve (MABC), specifically its posterior branch. Causes numbness or painful neuroma on the medial forearm).
  7. Simple Decompression vs Transposition – what does the evidence say? (Answer: Multiple RCTs and Cochrane review show No significant difference in outcomes. Simple decompression has fewer complications. It is the preferred first-line surgery for primary, non-subluxating CuTS).

Viva "Buzzwords"

  • "Arcade of Struthers"
  • "Osborne's Ligament / Humeroulnar Arcade"
  • "Medial Intermuscular Septum (Release it!)"
  • "Simple Decompression First-Line"
  • "Froment's Sign"
  • "Wartenberg's Sign"
  • "Medial Antebrachial Cutaneous Nerve (Protect it!)"
  • "Elbow Flexion Test"
  • "Dorsal Cutaneous Branch"

Common Pitfalls

  • Missing Cervical Radiculopathy: Always examine the neck. C8/T1 can mimic CuTS.
  • Operating on Normal NCS: Be cautious. A normal NCS doesn't rule out CuTS, but make sure the clinical picture is convincing.
  • Performing Simple Decompression on a Subluxating Nerve: It will sublux over the released edge. Must transpose.
  • Failing to Release the MIMS during Transposition: Creates a new compression point.
  • Injury to MABC Nerve: Must identify and protect.
  • Expecting Full Recovery in Severe Cases: Counsel patients that severe atrophy may be irreversible.

At a Glance

EvidenceStandard
Last UpdatedRecently

Clinical Pearls

  • **The Key Question:** Is it compression *at the elbow* (Cubital Tunnel) or *at the wrist* (Guyon's Canal)? Clues:

Guidelines

  • NICE Guidelines
  • BTS Guidelines
  • RCUK Guidelines