Optimizing Volar Lunate Facet Fracture Fixation: Finite Element Analysis and Cadaveric Testing

Volar lunate facet (VLF) fractures are prone to loss of reduction after volar plating. We used finite element analysis (FEA) and cadaveric testing to identify failure mechanisms and determine how screw configuration alters load transfer. A CT-derived radius model with a 10 × 15 × 5-mm VLF fragment was fixed with a 4-hole hook plate using locking and nonlocking (NL) screws. A 500-N radiolunate compressive load was applied, and von Mises stresses were quantified. Sensitivity analyses varied loading, bone density, fracture characteristics, and implant material. Ten distal radii underwent cyclic loading followed by load-to-failure testing; failure modes and locations were compared with FEA hotspots. FEA identified two stress concentrations: the distal plate contour/screw-hole region and the ulnar hook insertion into the VLF fragment. In the baseline 1[NL]&3[NL] construct, peak construct and radius stresses were 697.2 and 154.6 MPa. The 1[NL]&2[NL] configuration produced the lowest stresses (54.5 and 27.3 MPa), whereas locking hole 3 reduced construct stress to 587.2 MPa. Cadaver failure load was 1239.2 ± 438.5 N (range: 630.0-1990.1 N); failures were loss of reduction/fracture dislocation (4/10) or plate failure (6/10), with failure locations corresponding to FEA hotspots. Off-axis loading, reduced bone density, and fracture-line translation increased construct stress and altered hotspot location. FEA-predicted hook-fragment stress corresponded to loss of reduction, whereas distal plate stress corresponded to plate failure. Among modeled configurations, 1[NL]&2[NL] minimized construct and radius stress, although unbalanced cadaveric groups preclude claims of clinical superiority. These findings support fragment capture while minimizing distal plate stress.