Updated: 7/7/2020

Ulnar Styloid Impaction Syndrome

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Introduction
  • Epidemiology
    • incidence
      • common cause of ulnar-sided wrist pain
    • demographics
      • more prevalent in Asians than Whites
        • more positive ulnar variance
  • Pathophysiology
    • pathoanatomy
      • impaction between ulnar styloid tip and triquetrum that is seen in patients with excessively long ulnar styloids or ulna positive wrists
  • Associated conditions
    • radial malunion
    • congenitally short radius
    • premature radial physeal closure
  • Prognosis
    • little known about natural history
Anatomy
  • Ulnocarpal joint
    • transmits about 20% of the load through the wrist
      • increasing ulnar length by 2.5mm relative to the radius increases this load up to 50%
      • pronation and hand grasp both increase elative ulnar variance and transmission forces across the wrist
Classification
 
 Ulnar Variance
Ulnar Variance Length Difference (ulnar - radial length) Load Passing Through Radius Load Passing Through Ulna Images
Neutral  0 (<1mm)
80% 20%
Positive +2.5mm 60% 40%
Negative  -2.5mm 95% 5%
 
Presentation
  • Symptoms
    • ulnar side wrist pain
    • pain with pronation or grip
  • Physical exam
    • inspection
      • pain and swelling
      • tenderness along ulnar styloid and/or triangular fibrocartilage complex (TFCC)
    • motion
      • limited range of motion due to pain
    • ulnar stress test
      • maximum ulnar deviation, axial loading, rotation from supination to pronation to reproduce symptoms
Imaging
  • Radiographs
    • posteroanterior (PA) view to determine ulnar variance
      • excessive length determined by subtracting ulnar variance from ulnar styloid length and dividing this by the width of the ulnar head (<.22 is normal)
      • may exhibit subchondral sclerosis, cyst formation on ulnar side
    • pronated grip PA view
      • evaluate for any dynamic ulnar variance
    • contralateral comparison views
  • MRI
    • can help evaluate TFCC and the lunotriquetral interossesous ligament (LTIL)
Treatment
  • Nonoperative
    • activity modifications, NSAIDS, steroid injections
      • indications
        • first line of treatment 
      • technique
        • rest should be tried for a minimum of 6-12 weeks
  • Operative
    • ulnar shortening osteotomy 
      • currently, the gold standard
    • partial ulnar styloidectomy (Wafer procedure)
      • can be done open or arthroscopically
        • encouraging early results, but no superiority established
Complications
  • Non-union
  • Tendon rupture
  • Persistent pain/hardware irritation
  • Infection
 

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