Scaphoid Fractures and Carpal Instability – Radiographic Measures

Objective: Scaphoid fractures with signs of associated carpal instability have been considered unstable fractures with elevated risk of nonunion. The mode of fracture displacement includes extension and supination of the proximal fragment with no significant motion of the distal fragment, differing from the rotatory instability of the scapholunate ligament (SLIL) injury.

We aimed to examine the prevalence of radiographic signs of carpal instability, comparing fractures with ligament injuries. Our hypothesis was that there is a correlation between wrist position and the presence of these signs.

Methods: Wrist radiographs of the patients with scaphoid fractures and SLIL injuries were compared with a control group with no pathology. Measures of carpal instability included –scapholunate (SL), radioscaphoid (RS) and radiolunate (RL) angles on lateral radiographs and the cortical ring sign (CRS). An association was examined with measures of wrist position – radiocapitate (RC) and radius-3^rd metacarpal (R3M) angles on PA views and radiocapitate (RC) angle on lateral views.

Results: We examined radiographs of 57 patients with fractures, 23 with SLIL injuries and 43 with no pathology. Measures of wrist instability differed between the three groups although the mere presence of a ring on the scaphoid PA view did not differ. The SL angle differed between the healthy and the displaced body fracture and static SLIL injury groups (p<0.001). The RS angle differed between the healthy and SLIL injury groups (p<0.001).

In the study groups, wrist position was found to be in flexion (lateral view RC angle) and radial deviation (PA view R3M angle) in comparison with the healthy group (p<0.001 and p=0.18, respectively). A CRS could be seen with wrist radial deviation (PA view RC and R3M angles)(p=0.003 and p=0.003, respectively) and wrist flexion (lateral view RC)(p=0.024). A complete CRS was specifically associated with wrist radial deviation (measured with the PA view RC angle) in comparison with absent or incomplete CRS (p=0.004). The RS angle was correlated with the lateral RC and PA R3M angles (R=0.5).

Conclusions: Differentiating complete and incomplete CRS was found to be the more significant measure, then examining the mere presence of a ring on the scaphoid PA view.

Wrist position was found to be a significant factor when examining measures of wrist instability and pathology. Wrists with pathology were found to be flexed and radially deviated, possibly a position that will alleviate pain. When utilizing different measures of carpal instability, the effect of wrist position should be considered.