Summary Ulnar Styloid Impaction Syndrome is a common cause of ulnar-sided wrist pain secondary to impaction between the ulnar styloid tip and the triquetrum. Diagnosis is made by PA wrist radiographs which reveal positive ulnar variance with subchondral sclerosis of the ulnar styloid and/or triquetrum. Treatment is a course of rest, NSAIDs and splinting. In refractory cases, operative ulnar shortening osteotomy is indicated. Epidemiology Incidence common cause of ulnar-sided wrist pain Demographics more prevalent in Asians than Whites more positive ulnar variance Etiology 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 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 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) Differential TFCC injury Ulnocarpal abutment syndrome DRUJ injury Pisotriquetral arthritis ECU tendonitis LT tear 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 Prognosis Little known about natural history