Technique to quantify subsurface cracks in retrieved polyethylene components using micro-CT

No current method to study delamination and subsurface cracking in polyethylene joint replacement components provides accurate, nondestructive, and quantitative measurements. A technique to study damage both at and below the surface could be of great benefit. We report the development of a micro-CT technique to nondestructively examine and quantify subsurface cracking in retrieved polyethylene tibial inserts. Five severely delaminated inserts and two never-implanted inserts were obtained from our institution's implant retrieval library and scanned with micro-CT. The insert subsurface was examined for cracks, and their location and widths were measured using a digital line tool. Subsurface cracks were readily apparent only in the images of the delaminated inserts. Cracks ran horizontally, just below the articular and back-side surfaces, and vertically at the center and lateral edges of the inserts and at the tibial post. Cracks ranged from 0.12 to 6.01 mm below the surface, with widths of 0.06-0.97 mm. Micro-CT can nondestructively visualize and quantify subsurface cracks. This is an enhancement to its previously reported use to quantify surface deviations from wear. Micro-CT is well suited for longitudinal pin-on-disk and wear simulator trials, in addition to studies of retrieved components.