Volar RIM Plate Rarely Causes Flexor Tendon Complications in a Short Period Despite Its Plate Prominence over the Watershed Line: A Descriptive Study

Background: The DePuy Synthes variable angle LCP® Volar RIM Plate has been designed with its contour to overhang volar rim fragments of the distal radius to prevent secondary displacement after fracture fixation. Therefore, RIM potentially contributes to a risk of flexor tendon rupture due to its plate prominence over the watershed line. This is a retrospective cross-sectional study that aims at describing the occurrence of complications by utilizing RIM as well as three standards VLPs to evaluate the impact of plate design on flexor tendons. Methods: A total of 84 patients with a volar locking plate fixation were analyzed retrospectively (Far-distal; RIM: 14 cases, Juxta-articular; AcuLoc2 (ACUMED): 20 cases, Dual-Loc V7 (MEIRA): 25 cases, Extra-articular; VA-TCP (DePuy Synthes): 25 cases). Tendinous problems were evaluated with a reported adverse event and flexor tendon appearance examined by utilizing ultrasonography and direct observation during hardware removal. Plate prominence was graded according to Soong's classification and the distance to flexor tendons was measured to describe the risk that each plate damage the flexor tendons. Results: The mean follow-up period was 13.0 months. All RIM plates were placed in grade 2 (85.7%) and grade 1 (14.3%). Symptomatic and asymptomatic tendinous problems were barely reported in RIM. The examination of ultrasonography and direct observation during hardware removal showed that tendons smoothly slid without attrition on the curved plate surface of RIM despite their adjacent appositions came from its high and distal plate prominence. Conclusions: Smooth profile of RIM showed an ability to decrease the potential risk of flexor tendon damage regardless of its prominence over the watershed line. RIM can be applied more to challenging far distal fractures when used judiciously and surgeons need to be even more vigilant for symptoms of tendon irritation as usually recommended without being coward more than necessary.