Experimental Investigation on Fatigue Evaluation of Orthopaedic Locking Compression Plate

Locking compression plate (LCP) is a common orthopedic instrument for internal fixation and healing of bone trauma. It is important to study on mechanical behavior and failure investigation of LCP because its failure leads to lots of cost and pain to the patient. In this paper, fatigue life of an eight-hole tibia LCP is evaluated under flexural loading. A four-point bending jig is manufactured and fatigue tests are performed for different compression loads. Fatigue life cycles are investigated for compression loads of ۵۰۰, ۶۰۰, ۷۰۰, ۸۰۰, ۹۰۰ and ۱۰۰۰ N and relation between compression load and life cycles is estimated. ۱۲۵ walking days is estimated for the patient during treatment period according to life cycle results. Post failure analysis results on fracture surface revealed that the crack initiated from the edge of compression hole and propagated from lower to the upper surface of LCP according to beach marks.  Finally, Scanning electron microscopy (SEM) on the fracture surface revealed striations as a proof of fatigue crack growth. The striation spacing near the crack initiation site is found to be smaller than this spacing far from the initiation zone. The fatigue crack propagation life is estimated as ۱۶۰۰ cycles according to the number of striation spacings.

Keywords:

Failure Analysis , Fatigue Life , Four-Point Bending , Locking Compression Plate , Striation Spacing