Distal Radius Volar Plate Design and Volar Prominence to the Watershed Line in Clinical Practice: Comparison of Soong Grading of 2 Common Plates in 400 Patients.

PURPOSE:To compare plate positioning in clinical practice of 2 commonly used volar locking plate designs with respect to the watershed line as classified by the Soong grading system. METHODS:For this retrospective study, we included a total of 400 patients who underwent open reduction and internal fixation between May 2013 and February 2018. Cohort 1 was defined as patients treated with distal volar radius (DVR) plates during this period. Cohort 2 comprised 200 patients who had volar plate fixation with variable angle locking compression plates (LCP) during the same period. Standardized lateral wrist radiographs were categorized into Soong grade 0, 1, or 2. RESULTS:In cohort 1, 87 plates (43.5%) were not prominent volar to the watershed line, grade 0; 95 plates (47.5%) demonstrated grade 1 prominence; and 18 plates (9.0%) demonstrated grade 2 prominence. In cohort 2, 63 plates (31.5%) were grade 0; 103 plates (51.5%) were grade 1; and 34 plates (17%) had grade 2 prominence on, and volar to, the watershed line. These radiographic results show a greater incidence of volar plate prominence with respect to the watershed line, as defined as Soong grading, in cohort 2. CONCLUSION:This study shows that the use of the variable angle LCP plate is associated with more prominent volar positioning with respect to the watershed line compared with the DVR plate. TYPE OF STUDY/LEVEL OF EVIDENCE:Therapeutic II.