Perilunate fracture-dislocations: characteristics of ulnar sided instability

Perilunate dislocation (PLD) and perilunate fracture-dislocations (PLFD) are complex carpal derangements involve both bone and ligaments due to high-energy trauma. Mayfield defined four stages of injury based on a cadaver model. This stages is limited to the most common pattern of acute perilunate instability, which is radial-sided perilunate injury. Occasionally the opposite direction from ulnar to radial can occur, as described by Viegas as an axial load applied to ulnar palm side of the wrist. The purpose of this study is to investigate the distribution of the different forms of chip fracture and radiographic characteristics of uncommon ulnar-sided perilunate injury.

 A monocenter retrospective study with ninety-six patients (98 wrists) were reviewed. The injuries were categorized according to Herzberg classification. We examined small chip avulsion fractures using the radiographs. Based on these data, we investigated the correlation between specific fracture and radial translation for ulnar-sided perilunate instability of the wrist. Carpal-ulnar distance ratio (CUDR) was used for measuring radial translation of the carpus.

The distribution in our study was similar to Hezberg. There were 41 PLD (Perilunate dislocation) and 57 PLFD (Perilunate fracture-dislocation). In PLFD, the TS (trans-scaphoid) type was observed in 41(72%) patients, TRS (trans-radial styloid) type in 18(31%) and TT (trans-triquetrum) in 10. Sixty percent of the 98 PLD and PLFD had associated chip avulsion fractures. The most frequent associated chip fractures involved the ulnar styloid, the volar triquetrum, radial dorsal rim and dorsal triquetrum. The average CUDR of PLD and PLFD  was within normal range(normally 0.30.03). The CUDR of the patients with TRS was 0.39, 0.335 for ulnar styloid fracture, and 0.325 for volar avulsion of triquetrum. Among them, only TRS’s median CUDR was significantly correlated with radial translation (P = 0.029).

We recommend considering the broad and transverse-oblique radial styloid body fracture is associated with radial translation of the carpus, ulnar-sided perilunate injury.

Keywords: Perilunate dislocation, Perilunate fracture dislocation, radial translation, ulnar-sided injury