Ulnar Impaction Syndrome is a degenerative wrist condition caused by the ulnar head impacting upon the ulnar-sided carpus and triangular fibrocartilage complex resulting in degeneration of these structures.
It is also called ulnar abutment, ulnocarpal loading and impingement syndrome
Causes of Ulnar Impaction Syndrome
The syndrome occurs in people with a positive ulnar variance which may occur because of
- Distal radius fractures with radial shortening
- Radial head excision
- Essex Lopresti fracture
- Galeazzi fracture
- Excessive repeated loading of the ulnar-carpus in daily activities
- Madelung deformity
Clinical presentation of Ulnar Impaction Syndrome
Ulnar impaction syndrome mostly affects middle-aged patients. Patients present with chronic or sub-acute ulnar-sided wrist pain especially on the dorsal side of triangular fibrocartilage.
Pain is exacerbated by activity especially firm grip, pronation and ulnar deviation of the wrist. [These movements cause an increase in ulnar variance.]
WIth wrist positioned in ulnar deviation, dorsal and palmar displacement of the ulna is attempted. The test is considered positive if the pain is produced.
Nakamura’s Ulnar Stress Test
With wrist in ulnar deviation and pronation, the wrist is axially loaded, flexed and extended. The test is considered positive if the pain is produced.
This test is done to evaluate for TFCC tear or ulnotriquetral ligament tear. The test is performed by palpation of the ulnar wrist between the styloid and flexor carpi ulnaris tendon.
Imaging in Ulnar Impaction Syndrome
Xrays are normal in early disease. A positive ulnar variance may be noted. Degenerative changes in ulnar side of the carpal bones may be noted when the condition advances.
MRI shows signal changes in ulnar side of proximal part of lunate, radial side of proximal part of triquetrum. the changes noted may be
- Subchondral sclerosis
- Bone edema
- Subchondral cyst
- Chondromalacia of distal ulnar cartilage
- Increase in central TFCC signal
- Lunotriquetral ligament tear
Treatment of Ulnar Impaction Syndrome
Treatment of ulnar impaction syndrome varies depending on the amount of ulnar variance, and the severity of pathological changes, the contour of the distal ulnar and the presence of lunotriquetral instability.
Mild cases may be treated with analgesics and local therapy including heat and analgesic gel
Surgical treatment options include
Open Wafer Procedure
Surgical resection of the distal 2–3 mm of the dome of the ulnar head
Excision of a 2-3mm slice of the ulnar shaft followed by fixation
Arthroscopic Wafer Procedure
Minimally invasive and allows rapid return to normal activities.
Complete or partial ulnar head resection. Done in advanced lesions
Arthrodesis of the distal radioulnar joint with distal ulnar pseudoarthrosis
When ulnocarpal impaction occurs following fractures of radius, the procedure can restore normal joint anatomy