https://upload.orthobullets.com/topic/6018/images/thenar atrophy..jpg
  • Most common compressive neuropathy  
    • pathologic (inflamed) synovium most common cause of idiopathic CTS
  • Epidemiology
    • affects 0.1-10% of general population
    • risk factors
      • female sex
      • obesity
      • pregnancy
      • hypothyroidism
      • rheumatoid arthritis
      • advanced age
      • chronic renal failure
      • smoking
      • alcoholism
      • repetitive motion activities
      • mucopolysaccharidosis
      • mucolipidosis
  • Pathophysiology
    • mechanism
      • precipitated by
        • exposure to repetitive motions and vibrations
        • certain athletic activities
          • cycling
          • tennis
          • throwing
    • pathoantomy
      • compression may be due to
        • repetitive motions in a patient with normal anatomy
        • space occupying lesions (e.g., gout)  
  • Associated conditions
    • diabetes mellitus
    • hypothyroidism
    • rheumatoid arthritis
    • pregnancy
    • amyloidosis
  • Prognosis
    • good prognostic indicators include
      • night symptoms
      • short incisions
      • relief of symptoms with steroid injections
      • not improved when incomplete release of transverse carpal ligament is discovered
  • Carpal tunnel defined by  
    • scaphoid tubercle and trapezium radially
    • hook of hamate and pisiform ulnarly
    • transverse carpal ligament palmarly (roof)
    • proximal carpal row dorsally (floor)
  • Carpal tunnel consists of 
    • nine flexor tendons
    • one nerve (median nerve)
    • FPL is the most radial structure
  • Branches of median nerve
    • palmar cutaneous branch of median nerve
      • lies between PL and FCR at level of the wrist flexion crease
    • recurrent motor branch of median nerve
      • 50% are extraligamentous with recurrent innervation
      • 30% are subligamentous with recurrent innervation
      • 20% are transligamentous with recurrent innervation
        • cut transverse ligament far ulnar to avoid cutting if nerve is transligamentous
  • Carpal tunnel is narrowest at the level of the hook of the hamate
  • Symptoms   
    • numbness and tingling in radial 3-1/2 digits
    • clumsiness
    • pain and paresthesias that awaken patient at night
    • self administered hand diagram
      • the most specific test (76%) for carpal tunnel syndrome
  • Physical exam 
    • inspection may show thenar atrophy  
    • carpal tunnel compression test (Durkan's test) 
      • is the most sensitive test to diagnose carpal tunnels syndrome
      • performed by pressing thumbs over the carpal tunnel and holding pressure for 30 seconds. 
        • onset of pain or paresthesia in the median nerve distribution within 30 seconds is a positive result.
    • Phalen test 
      • wrist volar flexion for ~60 sec produces symptoms
      • less sensitive than Durkin compression test
    • Tinel's test
      • provocative tests performed by tapping the median nerve over the volar carpal tunnel
    • Semmes-Weinstein testing
      • most sensitive sensory test for detecting early carpal tunnel syndrome 
      • measures a single nerve fiber innervating a receptor or group of receptors
    • innervation density test
      • static and moving two-point discrimination
      • measures multiple overlapping of different sensory units and complex cortical integration
      • the test is a good measure for assessing functional nerve regeneration after nerve repair
  • Radiographs
    • not necessary for diagnosis
  • Diagnostic criteria
    • numbness and tingling in the median nerve distribution
    • nocturnal numbness
    • weakness and/or atrophy of the thenar musculature
    • positive Tinel sign
    • positive Phalen test
    • loss of two point discrimination
  • EMG and NCV
    • overview
      • often the only objective evidence of a compressive neuropathy (valuable in work comp patients with secondary gain issues)
      • not needed to establish diagnosis (diagnosis is clinical) 
    • demyelination leads to
      • NCV
        • increase latencies (slowing) of NCV   
          • distal sensory latency of > 3.2 ms 
          • motor latencies > 4.3 ms 
        • decreased conduction velocities less specific than latencies
          • velocity of < 52 m/sec is abnormal
      • EMG
        • test the electrical activity of individual muscle fibers and motor units
        • detail insertional and spontaneous activity
        • potential pathologic findings
          • increased insertional activity
          • sharp waves
          • fibrillations
          • fasciculations
          • complex repetitive discharges  
    • Electrodiagnostic study (EDS) results are associated with outcomes after carpal tunnel surgery
      • Patients with severe findings on EDS or minimal to no findings tend to improve less than patients with middle-range findings.  
  • Histology
    • nerve histology characterized by
      • edema, fibrosis, and vascular sclerosis are most common findings 
      • scattered lymphocytes
      • amyloid deposits shown with special stains in some cases
  • Nonoperative
    • NSAIDS, night splints, activity modifications
      • indications
        • first line of treatment
      • modalities
        • night splints (good for patients with nocturnal symptoms only)  
        • activity modification (avoid aggravating activity)
    • steroid injections
      • indications
        • adjunctive conservative treatment
        • diagnostic utility in clinically and electromyographically equivocal cases 
      • outcomes
        • 80% have transient improvement of symptoms (of these 22% remain symptoms free at one year) 
        • failure to improve after injection is poor prognostic factor 
          • surgery is less effective in these patients
  • Operative
    • carpal tunnel release 
      • indications
        • failure of nonoperative treatment (including steroid injections)
          • temporary improvement with steroid injections is a good prognostic factor that the patient will have a good result with surgery) 
        • acute CTS following ORIF of a distal radius fx 
      • outcomes
        • pinch strength return in 6 week
        • grip strength is expected to return to 100% preoperative levels by 12 weeks postop 
        • rate of continued symptoms at 1+ year is 2% in moderate and 20% in severe CTS 
    • revision CTR for incomplete release
      • indications
        • failure to improve following primary surgery
          • incomplete release most common reason
      • outcomes
        • only 25% will have complete relief after revision CTR
        • 50% some relief
        • 25% will have no relief
  • Open carpal tunnel release
    • antibiotics
      • prophylactic antibiotics, systemic or local, are not indicated for patients undergoing a clean, elective carpal tunnel release 
    • technique
      • internal neurolysis, tenosynovectomy, and antebrachial fascia release do not improve outcomes
      • Guyon's canal does not need to be released as it is decompressed by carpal tunnel release
      • lengthened repair of transverse carpal ligament only required if flexor tendon repair performed (allows wrist immobilization in flexion postoperatively)
    • complications
      • correlate most closely with experience of surgeon
      • incomplete release
      • progressive thenar atrophy due to injury to an unrecognized transligamentous motor branch of the median nerve 
  • Endoscopic carpal tunnel release
    • advantage is accelerated rehabilitation
    • long term results same as open CTR
    • most common complication is incomplete division of transverse carpal ligament

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