Assessment of the position of the distal portion of the ulna in lateral projection radiographs of the wrist - Analysis of the influence of pronation-supination and flexion-extension on the pisoscaphoid and the ulnotriquetraldistances: A cadaver study

RATIONALE AND OBJECTIVES. Accurate assessment of the distal radioulnar join t is of paramount importance for the detection of possible dislocation or s ubluxation. Using a cadaveric model, the authors attempted to establish a q uantitative method that would allow identification of normal and abnormal d istal radioulnar joint anatomy on well-positioned and rotated conventional radiographs. METHODS. Four cadaveric wrists, in which subsequent sectioning confirmed th e absence of disease, and one cadaveric wrist with a circumscribed lesion o f the triangular fibrocartilaginous complex were studied. Defined movements in flexion and extension (+/- 10 degrees, 20 degrees, 30 degrees) and in p ronation and supination (+/- 10 degrees, 20 degrees, 30 degrees) as well as combined flexion/extension and pronation/supination were performed. The ul notriquetral and the pisoscaphoid distances were assessed in each position. Correlation with cryosections was achieved. RESULTS. A strong linear correlation between the degree of pronation or sup ination and the pisoscaphoid and ulnotriquetral distances was noted. Flexio n and extension produced no significant effect on the pisoscaphoid distance , but a defined shift of the ulnotriquetral distance occurred with increasi ng flexion and extension. CONCLUSIONS. If all parameters are taken into account, this correlation aid s in estimating the degree of possible malpositioning of the wrist during r adiography and the degree of subluxation of the distal radioulnar joint. Ta bular data with parameters to correct for instances of malrotated images an d to estimate the extent of dislocation or malrotation of the distal radiou lnar joint are provided.