Purpose: The goal was to determine whether locking screws (LS) or smooth locking pegs (SP), optimize fixation of 4-part intraarticular distal radius fractures. The secondary goal was to determine which combinations of LS and SP influence construct stability.

Method: In anatomic radius models, 4-part intraarticular distal radius fractures were fixed using volar locking plates. For the first part, 16 specimens were randomized to receive either 2 LS or 2 SP in each of the 3 pairs of holes in the plate. For the second part, 30 specimens were randomized to receive any 4 combinations of LS and SP in each of the 3 pairs of holes. Axial loading to failure was applied.

Results: Constructs consisting of 4 SP within the lunate fragment were significantly weaker than constructs with 4 LS (mean 626.18 N vs. mean 980.76 N, p=0.01283). Constructs with SP in the ulnar positions of the lunate fragment were weaker than with LS in these positions (mean 736.73 N vs. 977.37 N respectively, p=0.00866). LS in the subchondral position of the lunate fragment were stronger than SP in these positions (mean 1226.99 N vs. 933.64 N, p= 0.00468) and any other combination (mean 1226.99 N vs. 941.97 N, p=0.0027).

Conclusion: The use of LS as opposed to SP for 4-part intraarticular distal radius fractures, particularly subchondral and in ulnar side of the lunate fragment, optimizes construct stability. This may have implications on postoperative rehabilitation protocols and may limit costs related to the use of volar locking plates.