Anatomical fit of volar locking plates for the distal radius and the influence of plate size

Abstract

Purpose The volar locking plate system is the standard surgical treatment for patients with unstable distal radius fractures. Volar locking plates are currently available in different shapes and 2–3 size options. In this study, we investigated whether the anatomical fit and plate size of volar locking plates affect their proper placement. Methods Two sizes of Acu-Loc2 Proximal Plates (AcuLoc), three sizes of Variable Angle LCP Two-Column Volar Distal Radius Plate 2.4 (VALCP), and 16 formalin-fixed cadaver specimens were studied. The plates and forearms were scanned using computed tomography. The plate was fixed to a radius within the watershed line, and radiographs were obtained using fluoroscopy. X-rays were superimposed, and a three-dimensional image of the plate and bone was created. The distance from the plate to the volar surface of each distal locking hole (PBD) was measured. To investigate the anatomical fitting of the plate, the contact area between the bone and plate was analyzed on three-dimensional images. We measured the distance between the distal end of the plate and the watershed line in three-dimensional images, defining it as watershed overlap. Results The PBD in the radial column was significantly smaller than that in the ulnar column in the narrow and standard VALCP and narrow in the AcuLoc. For the other plates, the PBD in the radial column tended to be smaller than that in the ulnar column. The contact area was 6.6–20.0% of the plate. The average value of the watershed overlap was negative for both plates. However, no significant differences were observed in PBD, contact area, or watershed overlap among the plate sizes for either plate. Conclusion Although the small plate size affected the fitting to the distal radius, the variance was small; therefore, each plate size may be selected depending on the circumstances of the fracture.