The metal fatigue problems are virtually ubiquitous, and failure of artificially implanted bone material is one of them. Failure analysis of artificially implanted bone material largely determines the reliability of artificially implanted bone products and is an important issue that must be faced in the development of artificially implanted bone products.

Failure analysis of artificially implanted bone materials is an important part of accident investigation, which can help determine the nature of failure, whether it is overload fracture, fatigue failure, wear or mixed failure mode. In addition, it also helps to find out the main causes of failure, such as improper operation, excessive actual load, flaws in the material itself, defects in the weld, unreasonable geometric design resulting in stress concentration, or other unreasonable design. Knowing the nature and the cause of the failure will be of great help to prevent and improve similar failure accidents, and improve the quality and reliability of the product.

Here, metal fatigue analysis methods for artificial implanted bone plate material are introduced.

Fracture Analysis

The fracture of the metal plate actually records the information about the whole process of crack initiation, expansion and instability. SEM, EDX and other characterization methods are used to qualitatively and quantitatively analyze the structural features of the fracture surface and can provide strong evidence for the determination of fracture failure mode.

Azevedo C R F et al. qualitatively analyzed the structural characteristics of the fracture surface of the metal plate and its surrounding tissues by using SEM and EDX methods. They found that the service environment of the bone plate affects the fracture failure of the bone plate. The fracture and corrosion of the joint between the bone plate and the screw often occur. Under the action of the fretting corrosion mechanism, the plate fails due to the lower nominal stress and the uniaxial bending load.

In Vitro Simulation Analysis

In vitro simulation studies are widely used in medical implants, which can effectively avoid the disadvantages of studying objects as organisms and being difficult to deploy. Using an in vitro test to simulate a fracture plate fixation model, or to simulate a similar working environment and stress state with a bone plate in human service is an important means to study the failure process of bone plate. Kanchanomai et al. used artificial synthetic bone and locking compression plate to simulate the bearing and stress state of the femur under human gait, and achieved fatigue test under the same stress state and four-point bending state, simulating the fracture process caused by the fatigue of the bone plate during the walking of the patient.

References

Proverbio E, Bonaccorsi L M. (2002) ‘Microstructural analysis of failure of a stainless steel bone plate implant’ J Fail Anal Prev, 1(4): 33-38.

Azevedo C R F, Jr E H. (2002) ‘Failure analysis of surgical implants in Brazil’. Eng Fail Anal, 9(6): 621-633.

Azevedo C R F. (2003) ‘Failure analysis of a commercially pure titanium plate for osteosynthesis’. Eng Fail Anal, 10(2): 153-164.

Micic I D, Kim K C, Shin D J, et al. (2009) ‘Analysis of early failure of the locking compression plate in osteoporotic proximal humerus fractures’. J Orthop Sci. 14(5): 596-601.