Intraoperative Fluoroscopy Versus Postoperative Radiographs in Assessing Distal Radius Volar Plate Position: Reliability of the Soong Classification

PURPOSE: Fluoroscopic imaging remains the standard intraoperative imaging modality for volar locking plate fixation of distal radius fractures, and correlation with postoperative radiographs remains unclear. The purpose of this study was to assess the reliability of the Soong classification system between intraoperative fluoroscopy and postoperative radiographs for distal radius volar plate position. METHODS: Eleven hand surgery resident physicians (3 in postgraduate year 2, 2 in postgraduate year 3, 3 in postgraduate year 4, and 3 in postgraduate year 5) and 4 attending physicians classified images using the Soong classification system. Fluoroscopic and radiographic lateral images from 30 patients were randomized and deidentified. Thirty percent of the images were duplicated for intraobserver reliability. Seventy-eight images were randomized and presented to each observer in 1 consecutive session. Cohen kappa values were calculated for intraobserver reliability, and Fleiss kappa values were calculated for interobserver reliability. RESULTS: Intraobserver reliability demonstrated moderate reliability overall. The intraobserver reliability was highest among postgraduate year 4 residents and attending physicians demonstrating substantial reliability. Lateral intraoperative fluoroscopic and postoperative radiographic imaging demonstrated no difference in intraobserver reliability overall. Interobserver reliability was highest among postgraduate year 5 residents demonstrating moderate reliability and attending physicians demonstrating substantial reliability. CONCLUSIONS: There was no difference in the intraobserver reliability of the Soong classification system between the lateral images of intraoperative fluoroscopy and postoperative radiographs. Fluoroscopic analysis using the Soong classification system is a reliable method to determine plate prominence and has demonstrated increasing reliability based on year of training. Fluoroscopic analysis using the Soong classification system and direct visualization during surgery for the assessment of plate prominence is recommended, with the understanding that higher Soong grades are associated with increased rates of complications. TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic III.