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  • A compressive neuropathy of the ulnar nerve  
    • 2nd most common compression neuropathy of the upper extremity
  • Sites of entrapment
    • most common 
      • between the two heads of FCU/aponeurosis (most common site)
      • within arcade of Struthers (hiatus in medial intermuscular septum)
      • between Osborne's ligament and MCL
    • less common sites of compression include
      • medial head of triceps
      • medial intermuscular septum
      • medial epicondyle
      • fascial bands within FCU
      • anconeus epitrochlearis (anomalous muscle from the medial olecranon to the medial epicondyle)
      • aponeurosis of FDS proximal edge
    • external sources of compression
      • fractures and medial epicondyle nonunions
      • osteophytes
      • heterotopic ossification
      • tumors and ganglion cysts
  • Associated conditions
    • cubitus varus or valgus deformities
    • medial epicondylitis
    • burns
    • elbow contracture release
  • Ulnar nerve topic
    • pierces intramuscular septum at arcade of Struthers 8 cm proximal to the medial epicondyle as it passes from the anterior to posterior compartment of the arm
    • enters cubital tunnel
  • Cubital tunnel
    • roof
      • formed by FCU fascia and Osborne's ligament (travels from the medial epicondyle to the olecranon)
    • floor
      • formed by posterior and transverse bands of MCL and elbow joint capsule
    • walls
      • formed by medial epicondyle and olecranon
  • Symptoms
    • paresthesias of small finger, ulnar half of ring finger, and ulnar dorsal hand 
      • exacerbating activities include 
        • cell phone use (excessive flexion)
        • occupational or athletic activities requiring repetitive elbow flexion and valgus stress
    • night symptoms
      • caused by sleeping with arm in flexion
  • Physical exam
    • inspection and palpation
      • interosseous and first web space atrophy 
      • ring and small finger clawing
      • observe ulnar nerve subluxation over the medial epicondyle as the elbow moves through a flexion-extension arc 
    • sensory
      • decreased sensation in ulnar 1-1/2 digits
    • motor
      • loss of the ulnar nerve results in paralysis of intrinsic muscles (adductor pollicis, deep head FPB, interossei, and lumbricals 4 and 5) which leads to
        • weakened grasp
          • from loss of MP joint flexion power
        • weak pinch
          • from loss of thumb adduction (as much as 70% of pinch strength is lost)
        • Froment sign  
          • compensatory thumb IP flexion by FPL (AIN) during key pinch
            • compensates for the loss of MCP flexion by adductor pollicis (ulna n.)
              • adductor pollicis muscle normally acts as a MCP flexor, first metacarpal adductor, and IP extensor
        • Jeanne sign 
          • compensatory thumb MCP hyperextension and thumb adduction by EPL (radial n.) with key pinch
            • compensates for loss of IP extension and thumb adduction by adductor pollicis (ulna n.)
        • Wartenberg sign
          • persistent small finger abduction and extension during attempted adduction secondary to weak 3rd palmar interosseous and small finger lumbrical
        • Masse sign
          • palmar arch flattening and loss of ulnar hand elevation secondary to weak opponens digiti quinti and decreased small finger MCP flexion
    • extrinsic weakness
      • Pollock's test
        • shows weakness of two ulnar FDPs
    • provocative tests
      • Tinel sign positive over cubital tunnel
      • elbow flexion test
        • positive when flexion of the elbow for 60 seconds reproduces symptoms
      • direct cubital tunnel compression exacerbates symptoms
  • EMG / NCV
    • helpful in establishing diagnosis and prognosis
    • threshold for diagnosis
      • conduction velocity <50 m/sec across elbow
      • low amplitudes of sensory nerve action potentials and compound muscle action potentials
  • Nonoperative
    • NSAIDs, activity modification, and nighttime elbow extension splinting
      • indications
        • first line of treatment with mild symptoms
      • technique
        • night bracing in 45° extension with forearm in neutral rotation
      • outcomes
        • management is effective in ~50% of cases
  • Operative
    • in situ ulnar nerve decompression without transposition  
      • approach
        • elbow medial approach  
      • indications
        • when nonoperative management fails
        • before motor denervation occurs
      • technique
        • open release of cubital tunnel retinaculum
        • endoscopically-assisted cubital tunnel release
          • favorable early results but lacks long-term data
      • outcomes
        • meta-analyses have shown similar clinical results with significantly fewer complications compared to decompression with transposition
        • 80-90% good results when symptoms are intermittent and denervation has not yet occurred
        • poor prognosis correlates most with intrinsic muscle atrophy
    • ulnar nerve decompression and anterior transposition  
      • indications
        • failed in situ release
        • throwing athlete
        • patient with poor ulnar nerve bed from tumor, osteophyte, or heterotopic bone
      • technique
        • subcutaneous, submuscular, or intramuscular transposition
      • outcomes
        • similar outcomes to in situ release but increased risk of creating a new point of compression
    • medial epicondylectomy 
      • indications
        • visible and symptomatic subluxating ulnar nerve
      • technique
        • in situ release with medial epicondylectomy
      • outcomes
        • risk of destabilizing the medial elbow by damaging the medial ulnar collateral ligament
  • Recurrence
    • secondary to inadequate decompression, perineural scarring, or tethering at the intermuscular septum or FCU fascia
    • higher rate of recurrence than after carpal tunnel release
  • Neuroma formation
    • iatrogenic injury to a branch of the medial antebrachial cutaneous nerve may cause persistent posteromedial elbow pain

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