Harris Orthopaedics Laboratory:
Device Lifecycle Testing (Wear, Fatigue, Creep), Case Studies

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Patellae wear testing: In the absence of any standard patellae wear testing protocols, we modified one of our knee simulators to investigate the wear behavior of a specific patellae design using both conventional and highly-crosslinked UHMWPE. We demonstrated the important role of patellar component oxidative stability in preventing failure during high-stress activities, such as stair climbing.

Wear testing of kinematically advanced TKR: We evaluated the long-term wear performance of a kinematically advanced TKR design. However, standard ISO/ASTM displacement profiles were not appropriate for this particular device. We conducted dynamic computer simulations to predict the kinematic waveforms, which we used to conduct extended wear testing of the device on the knee simulator.

Aggressive hip wear testing: We designed an aggressive Mode 3 hip wear testing to address a question posed by the FDA for the clearance of a highly crosslinked, vitamin-E stabilized UHMWPE acetabular liner. We developed a method to reproducibly roughen femoral heads and completed a 5 million cycle aggressive testing. The testing results contributed toward achieving FDA clearance for the product.

Assessment of hip wear after in vivo damage: Component damage can occur during implantation. Damage can come from either surgical instruments or third-body particles. Some novel femoral head designs use a relatively thin surface coating that can get damaged during the implantation process. We investigated the change in wear response of acetabular liners etween fresh, undamaged femoral heads and surgically retrieved damaged femoral heads. The results suggested that the head damage described previously would not lead to catastrophic runaway wear of highly-crosslinked UHMWPE.

Spine wear testing: We helped assess a new lumbar intervertebral spacer's wear behavior. We leveraged our expertise in joint simulators and knowledge of the unique kinematics of the spine to design test fixtures that allowed use of our existing simulator as a lumbar spine simulator in accordance with ISO 18192.

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