A Biomechanical Comparison of Screw and Plate Fixations for Scaphoid Fractures

Abstract

Headless screw fixation is the current gold standard of surgical repair for scaphoid fractures. However, maintaining reduction of certain types of scaphoid fractures is challenging with a compression screw. Plate fixation may offer superior fixation in some scaphoid fractures, particularly those with comminution, nonunion, segmental bony defects, and osteopenic or osteoporotic bone. This study questions whether method of fixation is a determinant in load to failure in segmental scaphoid fractures, and whether any fixation provides a greater mechanical advantage in simulated normal versus osteoporotic bone. Polyurethane models were fashioned to simulate scaphoids with 3-mm segmental defects. Defects were bridged by one of three constructs: a locking plate, a nonlocking plate, or a headless compression screw. Three models for each fixation construct were tested for both simulated normal and osteoporotic bone density. Load to failure was recorded as the load at which the 3-mm segmental defect was closed. Gap closure occurred in all trials. In simulated normal bone, there were no statistically significant differences in load to failure between fixation methods. In simulated osteoporotic bone, the locking plate had a 28% greater load to failure as compared with screw fixation. While biomechanical testing shows that plate and screw fixations are equivalent in normal density bone for fixation of a segmental scaphoid defect, locking plates are superior to screw fixation in simulated osteoporotic bone models. Plate fixation may provide superior fixation for complex scaphoid fractures, particularly in osteopenic bone.

Fixation Techniques for Scaphoid Nonunion

“…32 Castañeda et al used polyurethane models with defects that were bridged by a locking plate, nonlocking plate, or headless compression screw, simulating both normal bone density and osteoporosis and measuring the load to failure. 46 No mechanical advantage in normal bone density was observed, but in osteoporotic models, locking plates showed a 28% increased load to failure than screw fixation, indicating clinical relevance in surgical fixation for complex scaphoid fractures or deformities.…”

Update to Management of Acute Scaphoid Fractures

“…No differences were found in normally dense bone. 32 Arthroscopic-assisted scaphoid fracture fixation has also been popularized in an effort to minimize vascular compromise to the scaphoid. 33…”