Biomechanical Analysis of Standard Locking Compression Plate versus Dual Minifragment Locking Plates in Ulna Shaft...

The main postoperative complications after fixation of ulna shaft fractures are nonunion and soft tissue irritation. Current standards recommend 3.5 mm locking compression plates, which are prone to cause soft tissue irritation, necessitating secondary implant removal in approximately 25% of cases. Therefore, an alternative approach considering a combination of two minifragment locking plates has been proposed. The aim of this study was to biomechanically compare a single 3.5 mm locking compression plate fixation versus dual minifragment locked plating of ulna shaft fractures in a human cadaveric model.

Sixteen paired human cadaveric ulnae with a standardized 10-mm simulated fracture gap were fixed either via dual minifragment locked plating using a 2.5 and a 2.0 mm plates placed orthogonally onto the medial and posterolateral surface of the ulna, or with a single 3.5 mm locking compression plate placed medially. Biomechanical testing included nondestructive quasistatic axial, torsional, and bending loading, followed by cyclic torsional loading to failure in external rotation simulating supination, with monitoring of the interfragmentary movements via motion tracking.

No significant differences between the two plating techniques were detected for axial stiffness, torsional stiffness in supination and pronation, bending stiffness in varus and valgus, as well as posterior and anterior bending stiffness, P ≥ .094. Under cyclic loading over 2,000 cycles, dual minifragment locked plating demonstrated overall significantly bigger angular displacement versus single locked plating, P ≤ .018. However, no significant differences were registered between the two fixation techniques for overall shear displacement across the fracture gap over 2,000 cycles, P ≥ .312. Number of cycles until catastrophic failure was not significantly different between the techniques, P = .203. All constructs treated with both plating methods failed because of bone breakage at the most distal screw.

From a biomechanical perspective, a dual minifragment construct implementing a 2.5 mm and a 2.0 mm locking plates offers comparable stability for fixation of ulna shaft fractures versus 3.5 mm single locked plating, featuring similar stiffness and shear displacement at the fracture site under torsional loading.

Dual minifragment locked plating offers biomechanical stability comparable to to that of a standard 3.5 mm plate fixation of ulna shaft fractures, making it a potential alternative to the latter that may minimize soft tissue irritation; however, clinical research is necessary to confirm its efficacy and safety in vivo.