The effect of contouring on fatigue resistance of three types of fracture fixation plates

• Authors: Angela S.P. Lin, Georgia Institute of Technology; Chelsea M. Fechter, Georgia Institute of Technology; Mark Magill, Emory University; Felix Wipf, Stryker Trauma AG; Thomas Moore, Emory University; Robert Guldberg, Emory University
• Journal Title: Journal of Orthopaedic Surgery and Research
• Volume: Volume 11, Number 1
• Publisher: BioMed Central | 2016-09-26, Pages 107-107
• Type of Work: Article | Final Publisher PDF
• Publisher DOI: http://doi.org/10.1186/s13018-016-0439-1
• Subjects: Engineering, Biomedical; Health Sciences, Medicine and Surgery
• Keywords: Science & Technology; Life Sciences & Biomedicine; Orthopedics; Bone plates; Bone fractures; Fracture fixation; MM LOCKING; GAP MODEL; STIFFNESS; SURGERY; DESIGN

Abstract

Background: Metallic reconstruction plates used for fracture stabilization typically require intraoperative contouring for patient-specific anatomical fit. Despite this, characterization of plate mechanical properties after contouring has previously been limited. The objective of this study was to assess whether contouring affects fatigue resistance for three types of Stryker seven-hole stainless steel (SS) 316LVM fracture fixation plates. The hypothesis was that for each plate type, more contouring repetitions would result in lower fatigue resistance. Methods: Plates were contoured using a bench-top plate bender to ±20° either 0×, 3×, 6×, or 9× (n = 5 per group) and tested in the straight configuration. Cyclic four-point bending was applied in an incremental stepwise staircase approach (one step = 100,000 cycles, 10 Hz) until failure (defined as brittle fracture or plastic deformation of 10° permanent bend). Moment-cycle product (MCP) was computed as the summation of maximum moment × number of cycles and used as the primary measure of fatigue resistance. Results: No significant differences in fatigue resistance were detected between contouring groups for Basic Fragment Set (BFS) Reconstruction Plates. Significantly lower fatigue resistance was measured for 9× contoured Matta Pelvic System (MPS) Straight Plates compared to 0× contoured plates (p = 0.023). MPS Flex Plates contoured 3× had greater fatigue resistance than 0× contoured (p = 0.031) and 9× contoured plates (p = 0.032). Conclusions: This work provides fatigue resistance-based evidence that clinicians should avoid high repetitions of contouring for MPS Straight Plates. Meanwhile, BFS Reconstruction Plates and MPS Flex Plates are not negatively affected by contouring. These results allow for improved intraoperative decisions about using or discarding plates after multiple contouring repetitions.