Pronated Oblique View in Assessing Proximal Scaphoid Articular Cannulated Screw Penetration

Abstract

Volar and percutaneous techniques of screw fixation for scaphoid fractures usually do not involve direct visualization of the dorsoproximal scaphoid articular surface. Intra-articular screw penetration may be overlooked if the proper fluoroscopic views are not obtained. The hypothesis of this study is that the pronated oblique fluoroscopic view of the scaphoid is the most sensitive in detecting dorsal articular screw penetration of the scaphoid when compared with other views. A 3.6-mm Steinmann pin was inserted along the central axis of the scaphoid using an open dorsal technique in 10 embalmed cadaver wrists. The pin was then withdrawn from the palmar side until it was flush with the dorsal articular surface of the scaphoid. Five fluoroscopic views of the wrist were then obtained by rotating the forearm, keeping the image beam parallel to the floor: (1) anteroposterior, (2) supinated lateral, (3) pronated lateral, (4) 60 degrees supinated oblique (60 degrees supinated from wrist neutral), and (5) 60 degrees pronated oblique (60 degrees pronated from wrist neutral). The Steinmann pin was then allowed to visually protrude proximally from the articular surface in 0.5-mm increments, and all views were repeated. The view in which articular violation was first observed was recorded, as was the corresponding amount of pin protrusion. The pronated oblique was the fluoroscopic view in which articular penetration was first observed in all 10 specimens before it was evident on the other views. The amount of pin penetrating the articular surface before it was detected on the other views was 1 mm in 6 wrists and 2 mm in 4 wrists. Statistical analysis using Fischer's exact test was performed to determine whether the radiographic projection had an effect on the determination of articular penetration. The pronated oblique view was the first view to demonstrate articular penetration, with an average radiographically measured articular penetration of 1.4 mm +/- 0.5. This study confirms our hypothesis that the pronated oblique view is the most important fluoroscopic image to obtain when evaluating penetration of the proximal scaphoid articular surface.