Total disc replacement (TDR) has the potential to replace fusion as the gold standard for treatment of painful degenerative disc disease. However, complications after TDR have been associated with wear and tear, including accelerated polyethylene wear.
Image courtesy of Blausen staff (2014) under Creative Commons license 3.0.
Retrieval data published in 2012 revealed that the wear and tear, called impingement issues, have occurred in many designs, which can lead to accelerated wear and fatigue. This is particularly true for mobile bearing ball-in-socket type, fixed bearing ball-in-socket prostheses and elastomeric or compliant type prostheses. That is why ASTM has proposed a new international standard to help manufacturers improve design elements.
ASTM WK33006, “Guide for Impingement Testing of Total Disc Prostheses” is being developed to allow users to evaluate devices and determine the issues that lead to impingement.
ASTM committee F04 on Medical and Surgical Materials and Devices is responsible for the guidance, and the group welcomes members of the spinal community working on total disc replacement to join in the development of the proposed standard.
The aim is to develop preclinical fatigue and wear cycle tests for TDR parts made from polymeric, metallic or ceramic materials. These tests could inform regulatory assessments, as well as improve longevity and clinical performance of the devices. It could also unveil the next-generation design concepts and materials. Presently, there are no standards for total disc impingement.
The guidance committee acknowledges that there are many possible in vivo conditions that can influence TDR devices and that a laboratory simulation will not have universal applications. It is not their intent to address potential failures related to fixation of the implant to bony surfaces, for example. Nor does the scope of the guide enable comparisons of intervertebral disc prostheses with regard to kinematic, functional, and wear characteristics when tested under the specified conditions.
ASTM says it welcomes participation in the development of its standards. Here’s where you can go to become a member: www.astm.org/JOIN.
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