Sprafka v. DePuy Orthopaedics, Inc.

Background

Julie Sprafka had osteoarthritis in her right knee. After conservative treatments failed, she underwent a right total knee replacement on August 18, 2016. Dr. Andrea Saterbak implanted an Attune device with a fixed-bearing tibial baseplate cemented to the tibia.

Sprafka continued to experience knee pain. In 2020, Dr. Kristoffer Breien concluded that the device was loose and performed revision surgery. During that surgery, the tibial baseplate came loose after one tap from a mallet. Based on the effort needed to remove it, Dr. Breien concluded that the baseplate had separated from the cement and caused the device to loosen.

Sprafka sued Medical Device Business Services, Inc. and DePuy Orthopaedics, Inc. She initially asserted strict liability, negligent products liability, breach of implied warranty, and breach of express warranty. During the summary-judgment briefing, she withdrew both warranty claims. Her remaining theories were that the Attune was defectively designed and that the defendants failed to provide adequate warnings or instructions about debonding risks.

Sprafka relied on expert testimony from Mari Truman, a biomedical engineer with more than forty years of experience in biomechanics and orthopedics. The defendants moved to exclude Truman’s testimony and separately moved for summary judgment.

Expert-testimony ruling

Under Federal Rule of Evidence 702, expert testimony may be admitted when it will help the jury, is based on sufficient facts or data, uses reliable principles and methods, and reliably applies those methods to the case. The court acts as a gatekeeper by deciding whether the testimony is relevant and reliable.

The parties did not dispute Truman’s qualifications or that expert testimony would help the jury understand the medical device. The dispute concerned reliability. Truman offered three main opinions: that the Attune was defectively designed, that a safer alternative design existed when the Attune was developed, and that the defendants’ testing was inadequate.

The court excluded Truman’s design-defect opinion. It found that she relied heavily on case reports, device-report data, and observations by Dr. Breien, but that this evidence did not establish either the rate or the cause of debonding. The court also noted that debonding was not unique to the Attune and that registry data showed the Attune performed the same as or better than comparable devices in revision rates. Truman could not identify the precise pocket depth or surface roughness that would have prevented debonding without further testing.

The court also excluded Truman’s safer-alternative opinion. Truman proposed deeper cement pockets, more pocket surface area, undercuts or dovetails, and greater surface texture. But she could not identify the precise specifications that would have prevented debonding, had not adequately considered possible tradeoffs such as bone loss during revision surgery, and lacked testing or other reliable data showing that the proposed changes would produce better clinical results. The court also noted that the Attune S+ did not exist when Sprafka received her device and that Truman did not know whether it had a lower debonding rate.

Finally, the court excluded Truman’s opinion that the defendants should have performed additional testing under operating-room and physiological loading conditions. Truman could not specify the test’s parameters, identify another manufacturer that had performed comparable testing, cite a peer-reviewed article establishing the need for such testing, or explain the test’s costs and benefits.

The court emphasized that it was not deciding that Truman’s opinions were wrong. Rather, it concluded that the opinions were unsupported by enough reliable information and amounted, at most, to an educated guess. The court therefore granted the defendants’ motion to exclude Truman’s testimony in its entirety.

Summary-judgment ruling

Summary judgment is entered when the evidence shows no genuine dispute about a fact that could affect the result and the moving party is entitled to judgment under the law. Under Minnesota law, the court explained, expert testimony is required in complex medical-device products-liability cases when the alleged defect and its operation are beyond ordinary jurors’ knowledge.

The court concluded that Sprafka needed Truman’s testimony to prove that the Attune was defective and that its design caused her device to debond. Without that testimony, Sprafka could not prove her remaining strict-liability and negligent-products-liability claims. The court therefore granted the defendants’ motion for summary judgment.

Disposition

The court granted the defendants’ motion to exclude Mari Truman’s expert testimony. It also granted the defendants’ motion for summary judgment. The court dismissed Sprafka’s claims against the defendants with prejudice and directed that judgment be entered.