Objective: To examine the stability of plate (locking and non-) versus screw constructs in the fixation of these fractures.
Methods: An anteromedial coronoid facet fracture (OTA/AO type 21-B1, O'Driscoll type 2, subtype 3) was simulated in 24 synthetic ulna bones that were then assigned to 3 fracture fixation groups: non-locking plate, locking plate (LP), or screw fixation. Each construct was first cycled in tension (through a simulated medial collateral ligament) and then in compression. They were then loaded to failure (displacement >2 mm). Fracture fragment displacement was recorded with an optical tracking system.
Results: During tension testing, a mean maximum fragment displacement of 12 ± 13 and 14 ± 9 μm was seen in the locking and non-locking constructs, respectively. There was no difference in fragment motion between the plated constructs. All screw-only fixed constructs failed during the tension protocol. During compression testing, the mean maximum fragment displacement for the screw-only construct (64 ± 79 μm) was significantly greater than locking (9 ± 5 μm) and non-locking constructs (10 ± 9 μm). During load to failure testing, the maximum load to failure in the screw-only group (316 ± 83 N) was significantly lower than locking (650.4 ± 107 N) and non-locking constructs (550 ± 76 N). There was no difference in load to failure between the plated groups.
Conclusion: Fixation of anteromedial coronoid fractures (type 2, subtype 3) is best achieved with a plating technique. Although LPs had greater stiffness, they did not offer any advantage over conventional non-LPs with respect to fracture fragment displacement in this study.
Clinical relevance: Isolated screw fixation showed inferior stability when compared with plate constructs for these fractures. This could result in loss of fracture reduction leading to instability and posttraumatic arthrosis.