Ulnar facet locking screw locations of volar locking plates placed without flexor pollicis longus tendon contact: A cadaver study

Abstract

BackgroundThe volar locking plate (VLP) system provides stable fixation and is widely used for distal radius fractures. Studies have shown that irritation of the implant prominence is a risk factor for flexor tendon rupture, especially of the flexor pollicis longus (FPL). Contact between VLPs and flexor tendons should be avoided. We aimed to investigate the ulnar facet locking screw locations of various VLPs placed without FPL tendon contact in cadaver wrists. HypothesisWe hypothesized that ulnar facet locking screws would be in the vicinity of the subchondral bone when the plate is placed in the most distal position without FPL tendon contact. Materials and methodsThe study assessed two variable-angles and four fixed locking plates. We placed each plate in six different cadavers, resulting in 36 different plate-cadaver combinations. Plates were placed in the most distal position without FPL tendon contact. We drilled the most ulnar hole (hole A) and the second ulnar hole (hole B) of the distal row. All drilling procedures were performed using a specific jig for each fixed locking plate. For variable-angle locking plates, we drilled with a fixed jig for each plate. We obtained lateral radiographs when the drill penetrated the dorsal cortex and measured the distance between the drill and the articular surface. ResultsWith regard to hole A, the mean distances between the drill and the center of the articular surface were 2.6–5.2mm for the four fixed locking plates and 4.9–5.6mm for the two variable-angle locking plates. With regard to hole B, the mean distances between the drill and the center of the articular surface were 3.8–5.9mm for the four fixed locking plates and 5.5–5.9mm for the two variable-angle locking plates. DiscussionWhen clinicians place a VLP without FPL tendon contact, the distance between the ulnar facet screws and the center of the articular surface is over 3mm in most cases. Surgeons should select variable-angle drilling for strong articular support when using variable-angle locking plates. Level of evidenceIII, diagnostic Level.