Court upholds the reliance of Biomedical Engineering Expert Witness on MAUDE data but rejects his opinions on medical causation 

Court upholds the reliance of Biomedical Engineering Expert Witness on MAUDE data but rejects his opinions on medical causation 

Plaintiff Terry Jennings-Moline filed this lawsuit against Defendants DePuy Orthopaedics, Inc. and related Johnson & Johnson entities. The case stems from hip replacement surgery Jennings-Moline underwent in January 2016, when her surgeon, Dr. Douglas McInnis, implanted a Pinnacle hip implant containing an AltrX polyethene acetabular liner (AltrX liner) made by Defendants. In February 2018, McInnis performed revision surgery on Jennings-Moline after determining the AltrX liner had dissociated, meaning it had detached from the hip implant. McInnis replaced the liner but kept the existing hip implant hardware.  

In April 2019, Jennings-Moline filed a lawsuit against Defendants in state court, alleging various claims based on the dissociation of the AltrX liner and her resulting revision surgery. Defendants removed the case to federal court. In August 2019, Jennings-Moline underwent a second revision surgery in which the AltrX liner was replaced with a liner made by another manufacturer.  

In February 2020, the Judicial Panel on Multidistrict Litigation transferred Jennings-Moline’s case to the Northern District of Texas for coordinated pretrial proceedings with other lawsuits concerning Defendants’ Pinnacle hip implants. In January 2023, the case was remanded back to the District of Idaho.  

Prior to the remand, Jennings-Moline disclosed Nathaniel P. Young as an expert witness on medical device defects. In January 2022, Young provided an expert report after reviewing data on the AltrX liner from the FDA’s Manufacturer and User Facility Device Experience (MAUDE) database. Young noted 129 reports of liner dissociation with the AltrX liner prior to Jennings-Moline’s first hip surgery. Young opined the data showed the dissociation problem was specific to the AltrX liner and suggested a design defect.  

Young also conducted a literature review using Google Scholar search engine, searching for “liner dissociation.” He reviewed 18 articles on the topic. Based on the MAUDE data and literature review, Young offered opinions about what the data showed regarding the AltrX liner, the absence of alternative causes for its failure, Jennings-Moline’s resulting physical issues, Defendants’ negligence, and that the data suggested a design defect.  

Defendants moved to exclude Young’s expert opinions as unreliable under Rule 702 of the Federal Rules of Evidence. Defendants argued the MAUDE data was unreliable and Young’s literature review was incomplete.  

Biomedical Engineering Expert Witness 

Nathaniel P. Young is a biomedical and mechanical engineer with at least eighteen years of experience and expertise in medical device development, design, and testing. He did his post graduation in Mechanical Engineering from the University of Utah and holds a Bachelor of Science degree in Biomedical Engineering from the Johns Hopkins University.

Discussions by the Court  

The Court began by stating the legal standard that governs the admissibility of expert testimony under Rule 702 of the Federal Rules of Evidence. Rule 702 imposes certain limitations on the admission of expert testimony, emphasizing the need for the testimony to be based on specialized knowledge and to be relevant and reliable in helping the trier of fact understand the evidence or determine a fact in issue. The district court plays a critical role as the gatekeeper of the admissibility of expert testimony. This gatekeeping function requires the Court to assess both the relevance and reliability of the proffered evidence. Expert opinion testimony is deemed relevant if it has a valid connection to the pertinent inquiry, while reliability hinges on whether the knowledge underlying the testimony is based on reliable principles and methods with a solid foundation in the relevant discipline. The emphasis is on the basis for the expert’s opinion, not just their qualifications. This role of the district court was affirmed in Daubert v. Merrell Dow Pharms., Inc. 

Notably, as of December 1, 2023, Rule 702 has been amended to clarify that the proponent of expert testimony must establish, by a preponderance of the evidence, compliance with all of Rule 702’s substantive standards for admissibility. This change aims to rectify prior instances of courts misapplying Rule 702 and failing to apply the reliability requirements correctly, considering many courts had held that the critical questions of the sufficiency of an expert’s basis, and the application of the expert’s methodology, were questions of weight and not admissibility. The Rule’s amendment also emphasizes that each expert opinion must stay within the bounds of what can be reliably concluded from the expert’s basis and methodology, ensuring that expert opinions remain within the scope of a reliable application of principles and methods to the facts of the case. 

Turning to the specific challenges raised by the Defendants regarding the expert testimony of Young, they primarily revolved around Young’s use of the MAUDE database, his literature review, and his medical causation opinions. 

First, the Defendants argued that Young’s reliance on the MAUDE database was flawed and unreliable. They cited cases where courts have excluded expert testimony based on adverse event report data, like the MAUDE database, deeming it an unreliable source of information for proving causation. However, it’s important to note that these cases do not universally reject the use of MAUDE data for all purposes. Some courts have allowed experts to rely on the data for issues other than causation. In the case at hand, Young acknowledged the limitations of the MAUDE data and did not solely rely on it for causation opinions. Many of his opinions such as were observations of what the data showed, which could be considered a reliable application of his methodology. For instance, Young had observed from the MAUDE data that the AltrX liner had a documented history of liner dissociation; liner dissociation was rarely seen in other products; a significant number of failures occurred before Jennings-Moline’s surgery; and the failure occurred throughout the product’s history. From these observations of the MAUDE data, Young opined, for example, that the dissociation problem was specific to the AltrX liner; Defendants had significant time to address the issue; a manufacturing defect was unlikely; and the AltrX liner’s design caused its dissociation. Therefore, the Court found Young’s methodology regarding the MAUDE data to be reliable and within the bounds of a permissible application of Rule 702. 

Additionally, the Defendants challenged Young’s literature review, criticizing the extent of his review and his reliance on abstracts and case reports. The Court noted that such challenges went to the weight, not the admissibility of the testimony. The Court found that Young’s review was likely sufficient to support his design defect opinion, and therefore, it did not render his opinions unreliable. 

However, the Court identified two instances where Young ventured into the realm of medical causation opinions, which he was not qualified to make. The first opinion that the absence of failures with other companies’ products strongly suggested that the failure of the AltrX liner was not due to physician placement or technique or due to patient movement or misuse was Young’s statement about the absence of alternative causes for the AltrX liner’s failure, which was specific to the surgeries of Jennings-Moline and not reliably based on Young’s review of the MAUDE data or a literature review. The second consisted of Young’s assertion that Jennings-Moline’s additional procedures have resulted in physical issues associated with multiple orthopedic procedures, is a medical opinion that Young is not qualified to make. The Court concurred with these objections and ruled that Young may not testify about the absence of alternative causes or Jennings-Moline’s physical issues. 

At oral argument, Defendants had characterized Young’s statement that the design of the AltrX liner in the Pinnacle cup resulted in the disassembly of Jennings-Moline’s two hip replacements necessitating revision surgeries as an improper medical causation opinion. However, the Court found that the liners’ disassembly and Jennings-Moline’s resulting surgeries were undisputed facts testified to by her surgeon, McInnis. Because McInnis had testified that the liner failed and Jennings-Moline underwent surgeries as a result, and Defendants did not dispute those facts, the Court found Young’s statement about the liner’s disassembly and resulting surgeries was not an improper medical causation opinion. Young could rely on those undisputed facts.

Furthermore, the Defendants argued that Young failed to account for the number of liner sales when calculating and comparing ‘failure rates’. Young countered that he did not have an opinion on failure rates, a fact that the Defendants acknowledge. As a result, the Court determined that Young’s failure to consider the number of liner sales did not render his opinions unreliable, as he is not making claims related to failure rates.  

Finally, Defendants argued that Young should not be allowed to express his opinion that Defendants were negligent. In Young’s expert report, he asserted, “Due to DePuy Orthopaedics’ negligence and their failure to rectify the faulty liner design, Ms. Jennings-Moline had to endure two corrective surgeries within a two-year span to address liner dissociation.” Jennings-Moline concurred with the request to remove this statement from Young’s report and testimony. The Court excluded Young’s negligence opinion, since Jennings-Moline agreed it should be struck. 


The Court ruled that Young was barred from testifying about Defendants’ negligence, the absence of alternative causes for the AltrX liner’s dissociation in Jennings-Moline’s hip replacement, or her physical issues associated with multiple orthopedic procedures. However, Young could testify about what the MAUDE data and literature showed and opine on whether or not the data suggested a design defect. The Court has not arrived on an outcome for this case since the remaining issues involved in this case still await resolution. 

Key Takeaways 

This case illustrates the importance of ensuring expert witness opinions are relevant and reliable under Rule 702 of the Federal Rules of Evidence. The Court excluded portions of the Plaintiff’s expert’s opinions after finding they were unsupported medical causation opinions beyond his expertise. This demonstrates experts should not testify on matters outside their specialized knowledge.

However, the Court found that Young could reliably use the FDA’s MAUDE database for its adverse events reports, despite its limitations, as long as Young’s methodology in searching the MAUDE’s database was reliable.