Four-dimensional computed tomography-derived distal radioulnar joint osteokinematics during pronosupination with unilateral triangular fibrocartilage complex injuries.

The distal radioulnar joint (DRUJ) is a load-bearing joint that permits pronosupination of the forearm. Pronosupination may provoke instability following injuries to the soft tissue stabilizers of the joint, particularly when loaded against resistance. The objective of this study was to assess osteokinematics between the radius and ulna during pronosupination in 12 participants with suspected unilateral DRUJ injury enrolled in a prospective study using four-dimensional computed tomography (4DCT) at baseline and six months after arthroscopic surgery. We hypothesized that inter-landmark distances between the ulnar styloid and three landmarks on the distal radius-the central reference point, dorsal corner, and volar corner-would be related to relative pronosupination position, wrist injury status (injured versus uninjured), application of load (unresisted versus resisted), and timepoint (preoperative versus postoperative). Generalized linear mixed effects models were created to assess the change in inter-landmark distances with different levels of the predictor variables. Inter-landmark distances at all three radius landmarks were significantly associated with pronosupination angle and application of resistance. The effects of injury and surgery were less consistent and, if present, significant at only the volar corner landmark. The random effect for participant was statistically significant in all models. 4DCT-derived osteokinematics reflect position in the pronosupination arc and the application of resistance. However, the effect of injury or intervention was not statistically significant in the majority of single-landmark models. This suggests that 4DCT detects changes in biomechanical phenomena, although more sophisticated biomarkers may be justified for injury classification.