Comparison of scapholunate distance measurements on plain radiography and computed tomography for the diagnosis of scapholunate instability associated with distal radius fracture

Purpose

To investigate radiographic criteria for scapholunate instability (SLI) in the setting of distal radius fracture (DRF) confirmed by arthroscopy.

Methods

Eighty-eight wrists with DRF treated by open reduction and internal fixation and assessed for SLI arthroscopically were evaluated. The scapholunate distance (SLD) was measured by preoperative posteroanterior wrist radiography and computed tomography (CT). SLD on radiographs was measured as the distance between the scaphoid cortex and the lunate cortex at the center of the scapholunate joint. SLDs were measured at the volar end (A1), center (A2), and dorsal end (A3) of the scapholunate joint on the central CT axial slice; and at the proximal end (C1), center (C2), and distal end (C3) of the scapholunate joint on the central CT coronal slice. Wrists were divided into three groups by arthroscopic assessments: stable (normal, Geissler grade 1 or 2), G3 (Geissler grade 3), and G4 (Geissler grade 4). SLD measurements on radiographs and CTs (A1–C3) were compared among the three groups. Receiver-operating characteristic (ROC) curve analyses were performed to evaluate the abilities of SLD measurements on radiographs and CTs to identify SLI in wrists with DRF. Interobserver and intraobserver reliabilities of SLD measurements on radiographs and CTs were analyzed by intraclass correlation coefficients (ICCs).

Results

SLDs of C3 differed significantly among the G3 and G4 groups, and among the stable and G4 groups. The area under the curve on ROC curve analysis was 0.855 for the SLD of C3, which was larger than that for SLD on radiographs. For C3, the intraobserver ICC was 0.832 and interobserver ICC was 0.73.

Conclusions

SLD at the distal end of the scapholunate joint on the central coronal CT slice was the most appropriate measurement for discrimination of Geissler grade 4 SLI in wrists with DRF.

Level of evidence

Level 2