Procedure 81 Ulnar Shortening Osteotomy
See Video 59: Ulnar Shortening Osteotomy
Examination/Imaging
Clinical Examination
Patients with ulnar impaction syndrome present with ulnar-sided wrist pain, swelling, and limitation of motion. This may coexist with other causes of ulnar-sided wrist pain, including triangular fibrocartilage complex (TFCC) injuries, distal radioulnar (DRU) joint instability, and lunotriquetral ligament injuries, among others. It is important to consider these conditions before attributing the symptoms to ulnar impaction syndrome, particularly among patients with negative ulnar variance.
Imaging
A neutral rotation posteroanterior view will help determine ulnar variance. Ulnar variance describes the relative positions of the distal articular surface of the radius and ulna. When both the distal radius and the distal ulna are at the same level, it is called neutral variance (12%). If the distal ulna is distal to the radius, it is called positive ulnar variance (55%), and if the distal ulna is proximal to the radius, it is called negative ulnar variance (33%). A variance of −2 mm to +2 mm is considered normal (Fig. 81-3). Ulnar variance increases with pronation (up to 1 mm) and with forceful grip (up to 2 mm) (Fig. 81-4).
A positive ulnar variance is associated with ulnar impaction syndrome. Other radiological features include cystic changes and sclerosis in the ulnar corner of the lunate, triquetrum, and radial portion of the distal ulnar head (Fig. 81-5).
Magnetic resonance imaging can identify degenerative changes related to ulnar impaction syndrome earlier than plain radiographs because it can reveal subchondral bone marrow edema and early chondromalacia on fat-suppressed, T2-weighted and short T1-weighted inversion recovery images (Fig. 81-6).
Wrist arthroscopy is the most accurate modality for diagnosis of ulnar impaction syndrome. Any other associated pathology of the wrist can also be evaluated and the condition of the TFCC noted. Palmer has proposed a classification of degenerative TFCC tears (Table 81-1).
| Type 1 | Traumatic Lesions |
| 1a | Isolated central disk perforation |
| 1b | Peripheral ulnar-sided tear of TFCC (with or without ulnar styloid fracture) |
| 1c | Distal TFCC disruption from distal ulnocarpal ligaments |
| 1d | Radial TFCC disruption ± sigmoid notch fracture |
| Type 2 | Degenerative Lesions |
| 2a | TFCC wear |
| 2b | 2a with lunate and/or ulnar chondromalacia |
| 2c | TFCC perforation with lunate and/or ulnar chondromalacia |
| 2d | 2c + lunotriquetral ligament perforation |
| 2e | 2d + ulnocarpal arthritis |
Surgical Anatomy
The radiocarpal joint transmits 82% of the load across the wrist, whereas the ulnocarpal joint transmits the remaining 18% in a neutral ulnar wrist. In subjects with a 2.5-mm positive ulnar variance, the load transmission across the ulna increases to 42%. This substantial increase in load in a positive ulnar wrist puts it at a high risk for ligamentous and articular degeneration. Increased dorsal tilt of the radius can further exacerbate loading onto the ulnar wrist. On the contrary, in a 2.5-mm negative ulnar variance wrist, the load transmission decreases to 4.3%. This is the basis for the ulnar shortening osteotomy.
