Sensitivity and Specificity of Skyline and Carpal Shoot-Through Fluoroscopic Views of Volar Plate Fixation of the Distal Radius: A Cadaveric Investigation of Dorsal Cortex Screw Penetration

Abstract

Background: Volar plate fixation of distal radius fractures can result in soft tissue injuries. Abnormal contour of the dorsal cortex of the distal radius provides difficulties in discerning screw penetration on standard radiographs. The skyline and carpal shoot-through views are additional views to improve dorsal cortex visibility. We report on the sensitivity and specificity of determining screw protrusion with these views. Methods: Seven fresh frozen cadavers were instrumented with a distal radius volar locking plate. Initial screw length was determined by depth gauge measurement. A dorsal dissection of the wrist was performed to detect screw penetration. Protruding screws were documented and replaced with screws of the appropriate length and deemed as baseline. Screws were then sequentially lengthened by 2 and 4 mm. Skyline and carpal shoot-through views were obtained at baseline, 2 mm, and 4 mm. The images were randomized and compiled into an untimed survey asking orthopedic surgeons to determine whether screws were penetrating through the dorsal cortex. Results: Based on depth gauge measurements, 4 out of 44 (9.1%) volar plate locking screws penetrated the dorsal cortex, as confirmed with dorsal dissection. Sensitivities for the skyline and carpal shoot-through views were 75% and 86% (P ≤ .001), respectively, for 2-mm protrusions, and 76% and 89% (P ≤ .001), respectively, for 4-mm screw protrusions. Specificities were 85% and 84% for the skyline and shoot-through views, respectively. Conclusions: We believe that the carpal shoot-through view has utility and can be implemented to augment standard intraoperative views, and may decrease the incidence of screw protrusion resulting in soft tissue injuries.