DePuy and several other manufacturers of knee replacement systems have collectively been the subject of thousands of product liability lawsuits. Litigation results have been mixed, and DePuy has settled some cases. No doubt the outcome in most cases depends on whether the testimony of the plaintiff’s expert is admitted or excluded. Today’s case involves DePuy’s successful exclusion of the plaintiff’s expert’s opinion and, as a result, summary judgment in its favor.
The case has an ungainly caption: Sprafka v. Medical Device Business Services, Inc., an Indiana Corporation, formerly known as DePuy Orthopaedics, Inc.; DePuy Orthopaedics, Inc. (8th Cir., No. 24-1874, 6/4/2025). The opinion refers to the defendants collectively as “DePuy.”
Artificial knee replacement systems are generally comprised of a metallic femoral piece, a metallic tibial baseplate, a tibial insert, and a dome kneecap. DePuy has designed and manufactured several models of artificial knee replacement systems, including . . . the ATTUNE (introduced in 2013) . . . . Total knee replacement is considered one of the most successful surgical procedures, but every system model has some failures that often require revision surgery to reduce knee pain and improve functionality. Though rare, one of the more common failures is called tibial component loosening, where the tibial baseplate does not stay securely fixed to the tibia (“debonds”).
Sprafka’s right knee was replaced in August 2016 using the ATTUNE system. . . . On June 10, 2020, Sprafka saw a new surgeon, Dr. Breien, who conducted an examination and concluded the tibial baseplate had loosened from her tibia, causing Sprafka’s pain. Dr. Breien performed revision surgery in September 2020, replacing the ATTUNE with another implant. Dr. Breien observed that the ATTUNE’s tibial baseplate came free from the tibia with little or no force. He concluded the baseplate had debonded from the bone.
Sprafka filed this products liability action in August 2021, asserting design defect and failure to warn claims. . . . To support her design defect claim, Sprafka retained Dr. Truman, a biomedical engineer. Dr. Truman offered . . . preliminary opinions [that] the ATTUNE system was defectively designed [and] a safer alternative existed at the time it was developed . . . . DePuy moved to exclude the opinions of Dr. Truman and for summary judgment. The district court found that Dr. Truman, while qualified, rendered unreliable and speculative opinions. . . .
The standard of review on appeal is of particular interest. The Eighth Circuit emphasized the broad discretion of district courts to admit or exclude expert testimony pursuant to Federal Rule of Evidence 702 and Daubert (citations and internal quotation marks omitted):
We review the exclusion of expert opinions under the deferential abuse of discretion standard. To be admissible, expert opinions must be based upon sufficient facts or data and must be the product of reliable principles and methods that have been reliably applied to the facts of the case. Reliability can be established by showing that the expert’s theory or technique can be (or has been) tested, that the theory or technique has been subject to peer review and publication, that there is a known or potential rate of error, and that the theory or technique is generally accepted in the scientific community. A district court has great latitude in determining whether expert testimony meets the reliability requisites of Rule 702. We will not reverse a district court’s Daubert ruling unless it is manifestly erroneous.
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We agree with the district court that Dr. Truman’s opinions fail to satisfy the requirements of Rule 702 and the Daubert standards. Her opinions have not been subjected to typical scientific scrutiny through peer review and publication. Rather, they were prepared for litigation and based primarily on two published case studies with limited participants – fifteen patients in one study and three in another study – as well as Dr. Breien’s testimony that he and his partners have observed an “unacceptably” high rate of revisions following implantation of the ATTUNE knee replacement system. In both case studies, the author examined the number of ATTUNE revisions due to debonding but did not consider the total number of ATTUNE systems implanted. Similarly, Dr. Breien acknowledged that he did not know the actual rate of debonding . . . . Other data relied on by Dr. Truman included registry data, which appears to show the ATTUNE system may have a similar or lower revision rate than other systems on the market.
Evidence in the record indicates that aseptic loosening is an issue for knee replacement systems. The fact that a system loosens does not automatically demonstrate a product defect. . . . Further, Dr. Truman’s recognition that the case studies do not establish the rate of debonding for the ATTUNE system reinforces the speculative nature of her opinion that the ATTUNE system has a higher failure rate than other systems. Without a scientific or reliable basis to establish the rate of debonding for the ATTUNE knee replacement system, or data showing how the ATTUNE system compares with other devices on the market, Dr. Truman’s opinions lack reliability. The district court did not abuse its discretion in excluding Dr. Truman’s opinions.
