The Impact of Soong Grading on Long-term Functional Outcomes Following Volar Locking Plate Fixation of Distal Radius Fractures: A Cross-sectional Study

Abstract

Distal radius fractures are the most common adult Orthopaedic fracture, accounting for 17.5% of UK trauma presentations. The Soong system grades post-operative volar plate prominence relative to the volar rim (0–2). However, no studies to date have compared consultant-agreed Soong grading with long-term functional outcomes. A retrospective review was conducted of adults (≥ 18 years) who underwent volar plate fixation for distal radius fractures between 1 January 2018 and 1 December 2021. Exclusions included patients under 18, surgery outside the Trust, alternative fixation methods and polytrauma. Three upper limb consultants independently graded postoperative radiographs using the Soong system. Long term follow-up outcomes were assessed using telephone interviews, assessing 3 key patient reported outcome measures - PRWE, QuickDASH and bMHQ. 211 patients were identified; 173 met inclusion criteria. Interobserver reliability using Fleiss’ kappa was 0.31, indicating “fair” agreement. Functional outcomes at 6.2 years post-operative follow-up were compared between agreed categories of Soong Groups 0 and 1 + 2. Mean PRWE scores were 3.27 and 25.53 respectively, with a mean difference of 22.26 exceeding the MCID of 21.2, indicating clinically worse pain and function with higher Soong gradings at long-term follow-up. Mean QuickDASH scores were 2.14 and 7.64, though the difference was below the powered MCID. Mean bMHQ scores were 59.27 and 57.14; however, the study was underpowered to confirm clinical significance in this parameter. Higher Soong grades are associated with persistent loss of wrist function and increased pain at six-year follow-up, independent of patient factors, fracture configuration or complications. Interobserver agreement was only fair, suggesting a need to refine the Soong grading system to improve consistency and guide management. Level III evidence.