Locking compression plate breakage and fracture non-union: a finite element study of three patient-specific cases

The locking compression plate (LCP) system offers a number of advantages in fracture fixation combining angular stability through the use of locking screws with traditional fixation techniques. However, the system is complex, requiring careful attention to biomechanical principles and good surgical technique. From a series of clinical cases, where locking plate fixation was used in fractures of long bones, three were selected. Patient-specific geometric information was obtained from AP and lateral plain radiographs, and the Finite Element (FE) models were generated manually. The first case study highlighted the importance of the working length on the construct stability. By increasing the working length, the construct became more flexible. The resulting increase in interfragmentary motion promoted indirect healing with the formation of callus. In the second case study, plate breakage occurred as a result of an inappropriate fixation technique. The fixation involved the use of locked screws at the level of the fracture passing the fracture line. This reduced the flexibility of the implant which hindered the micro-motion needed for callus formation. Fatigue failure eventually occurred due to cyclic loading past the yield stress of the LCP. In the third case study, the long working length of the construct made it relatively flexible. The larger area of stress distribution on the plate reduced the local strain, resulting in a protective effect against fatigue failure of the implant. In Conclusion, successful application of the LCP demands a good understanding of the biomechanics and careful preoperative planning.