Buttress Plating Versus Anterior-to-Posterior Lag Screws for Fixation of the Posterior Malleolus: A Biomechanical Study

Abstract

Objectives: The preferred method of fixation for posterior malleolus fractures remains controversial, and practices vary widely among surgeons. The purpose of this study was to compare anterior-to-posterior (AP) lag screws with posterior buttress plating for fixation of posterior malleolus fractures in a human cadaveric model. Methods: Posterior malleolus fractures involving 30% of the distal tibial articular surface were created in 7 pairs of fresh frozen cadaveric ankles. One specimen in each pair was randomly assigned to fixation with either 2 AP lag screws or a one-third tubular buttress plate without supplemental lag screws. Each specimen was then subjected to cyclic loading from 0% to 50% of body weight for 5000 cycles followed by loading to failure. Outcome measures included permanent axial displacement during each test cycle (axial displacement at no load), peak axial displacement during each test cycle (axial displacement at 50% body weight), load at 1-mm axial displacement, ultimate load, and axial displacement at ultimate load. Results: The buttress plate group showed significantly less peak axial displacement at all time points during cyclic loading. Permanent axial displacement was significantly less in the buttress plate group beginning at cycle 200. There were no significant differences between the 2 groups during load-to-failure testing. Conclusion: Posterior malleolus fractures treated with posterior buttress plating showed significantly less displacement during cyclical loading compared with fractures fixed with AP lag screws. Surgeons should consider these findings when selecting a fixation strategy for these common fractures. Further research is warranted to investigate the clinical implications of these biomechanical findings.

Biomechanical efficacy of AP, PA lag screws and posterior plating for fixation of posterior malleolar fractures: a three dimensional finite element study

“…But these studies compared only the two fixation methods. In one of these biomechanical studies comparison was done between AP screws and posterior buttress plate and in another study, the analysis was done for PA lag screw and posterior plate [ 20 , 29 ]. Here we have compared the three different fixation modalities.…”

“…Our computational findings are consistent with previous biomechanical and clinical studies. In a recent biomechanical study, Bennett et al [ 20 ] has compared the fixation strength of one-third tubular posterolateral plate and AP lag screws in the cadaveric models of posterior malleolar fractures. The results of this study advocated the less displacement using the posterior buttress plating than AP lag screws during cyclical loading.…”

“…3 . In this experiment, the force was applied to the fracture fragment in the direction of fracture mechanism [ 20 ]. Three different magnitudes of axial force i.e.…”

High Incidence of Implant Failure Happened Using Anterior-posterior Screws for the Fixation of Tibial Posterior Pilon Fracture.

“…The characteristics of posterior pilon fracture reported by former researches [1][2][3][4][5][6][7] include: posterior malleolus fragment displace proximally, posterior dislocation of talus, die-punch fragment, posterior malleolus fracture line extending to midial malleolus. However, the proportion of the midial malleolus involved is not fully discussed.…”

“…But the clinical outcome of A-P screws was seldom reported. However, large intact fragment is common in posterior pilon fracture, and anterior to posterior screws xation is an traditional method [6] to x the large intact fragment. Although seldom reported, A-P screws is still widely used, especially in primary hospitals in China.…”