PMCF (Post Market Clinical Followup) Enrollment Sizes (Spinal Implants)

[Chrisx]

Our notified body is asking for PMCF studies with sufficient enrollment to evaluate all product variants. I don't think they have considered what that entails for a spinal implant. Has anyone had a similar question. It makes sense on the surface, until you do the math. For example, our anterior cervical plate has 41 different sizes, times 15 different screw sizes times enrollment of say 20 patients, comes to 12,300 patients. I guess you could do a DOE, but I never heard of a DOE PMCF study. This is actually one of our simpler systems. For one of our stand-alone interbodies, enrollment could be in the 100,000 or more. I just find it hard to believe this same question is being posed to other manufacturers of spinal implants.

 

[Julie O]

What is a DOE?

 

[Chrisx]

DOE stands for design of experiments. It is statistical tool used to reduce the number of experiments in a study that has multiple variables. I think it would be highly unusual to use it for PMCF.

 

[Marcelo]

Does the clinical performance (including clinical benefits) and clinical safety of the devices change between variants?Did you CER identified, fully disclosed, and evaluated the differences between variants and give explanations explanations as to why the differences are not expected to significantly affect the clinical performance and clinical safety of the device under evaluation? (I adapted this fro m the text of the MEDDEV about equivalent devices, but the idea is the same).

I've had some questions asked related to variants in the past and the answer to these questions was enough to fulfill the expectations of NBs.

 

[Julie O]

Ah, of course. Yes, unusual, but then it's an unusual situation. Otherwise I had the same thought as Marcelo. Plan C - get a new NB.

 

[Chrisx]

They backed off a bit from their initial stance. They accepted that if equivalence could be demonstrated across a product family, then the sample size could be smaller. However, this was not stated in their nonconformity. We will see if they accept our equivalence rationale.

Thanks
ChrisX