Updated: 4/15/2018

Pronator Syndrome

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Introduction
  • compressive neuropathy of the median nerve at the level of the elbow
  • Epidemiology
    • more common in women
    • common in 5th decade
    • has been associated with well-developed forearm muscles (e.g. weight lifters)
  • Pathoanatomy
    • 5 potential sites of entrapment include 
      • supracondylar process 
        • residual osseous structure on distal humerus present in 1% of population
      • ligament of Struthers 
        • travels from tip of supracondylar process to medial epicondyle 
        • not to be confused with arcade of Struthers which is a site of ulnar compression neuropathy in cubital tunnel syndrome
      • bicipital aponeurosis (a.k.a. lacertus fibrosus) 
      • between ulnar and humeral heads of pronator teres 
      • FDS aponeurotic arch  
  • Associated conditions
    • commonly associated with medial epicondylitis
Presentation
  • Symptoms
    • paresthesias in thumb, index, middle finger and radial half of ring finger as seen in carpal tunnel syndrome
      • in pronator syndrome paresthesias often made worse with repetitive pronosupination
    • should have characteristics differentiating from carpal tunnel syndrome (CTS) 
      • aching pain over proximal volar forearm
      • sensory disturbances over the distribution of palmar cutaneous branch of the median nerve (palm of hand) which arises 4 to 5 cm proximal to carpal tunnel   
      • lack of night symptoms
  • Physical exam
    • provocative tests are specific for different sites of entrapment
      • positive Tinel sign in the proximal anterior forearm but no Tinel sign at wrist nor provocative symptoms with wrist flexion as would be seen in CTS
      • resisted elbow flexion with forearm supination (compression at bicipital aponeurosis)
      • resisted forearm pronation with elbow extended (compression at two heads of pronator teres)
      • resisted contraction of FDS to middle finger (compression at FDS fibrous arch)
    • possible coexisting medial epicondylitis
Imaging
  • Radiographs 
    • recommended views
      • elbow films are mandatory 
    • findings
      • may see supracondylar process 
Studies
  • EMG and NCV
    • may be helpful if positive but are usually inconclusive
    • may exclude other sites of nerve compression or identify double-crush syndrome
Treatment
  • Nonoperative
    • rest, splinting, and NSAIDS for 3-6 months
      • indications
        • mild to moderate symptoms
      • technique
        • splint should avoid forearm rotation
  • Operative
    • surgical decompression of median nerve 
      • indications
        •  only when nonoperative management fails for 3-6 months
      • technique
        • decompression of the median nerve at all 5 possible sites of compression
      • outcomes 
        • of surgical decompression are variable
          • 80% of patients having relief of symptoms
 

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