Metallurgy Expert Hip ReplacementThe Eighth Circuit Court of Appeals, in a per curiam opinion, recently held that the district court didn’t abuse its discretion by excluding parts of a metallurgy expert’s testimony.

At the time of her total hip replacement, Plaintiff was a little over five feet tall, weighed 302 pounds, and took immunosuppressant drugs—factors that placed her at a higher risk for failure of the hip replacement. Her implanted hip stem fractured. When the hip stem was removed, doctors learned that it had not properly grown into the bone at the top of Plaintiff’s hip (a possibility they had been aware of given her risk factors). She received a second hip stem implant which also fractured less than two years after it was inserted.

After that, she filed suit against the hip manufacturer, alleging product defect and failure to warn under Missouri law. She hired a metallurgist as an expert witness to testify about the allegedly defective product. The district court excluded the expert’s testimony on defect and causation and granted Manufacturer summary judgment on all Plaintiff’s claims.

The district court noted that the metallurgy expert had conducted research in fatigue fracture initiation in metal objects, but not in metal objects implanted in the human body. His analysis considered metallurgical factors, but not any biomechanical factors (such as a hip stem’s failure to grow into the hip bone like Plaintiff’s). He also didn’t review any records related to the manufacturing process of Plaintiff’s replacement hip before issuing his expert report.

The expert’s report concluded that the metal in Plaintiff’s hip stem was predominantly in a hexagonal close-packed (“HCP” or “non austenitic”) phase, rather than in a face-centered cubic (“FCC” or “austenitic”) phase which, along with the coarse grain size of the metal alloy, had caused a premature and sudden fatigue fracture. He acknowledged that environmental factors could have also contributed to the failure of the hip implant, but said that “any small variation in the biomechanical forces” would have been “secondary in nature” to the hip stem’s non-austenitic state “in terms for the failure.”

After the close of discovery, Manufacturer moved for summary judgment and the exclusion of the expert’s testimony. Plaintiff then submitted an affidavit from the expert testifying that Manufacturer’s own specifications required the material in the hip stem implant to be austenitic and that environmental factors would be “secondary in the cause of the fracture when the material is inherently defective to begin with.” Manufacturer responded with a motion to strike the metallurgy expert’s affidavit as impermissibly supplementing or changing his expert opinion after the close of discovery.

The district court granted Manufacturer’s motion to exclude parts of the metallurgy expert’s testimony after concluding that he lacked “a scientific or factual basis to conclude that there was a manufacturing defect or to opine on causation,” although he was qualified to testify about metallurgy (i.e., that the material was in an HCP or non austenitic phase). The district court found that the expert failed to “consider the necessary issues of the forces that were exerted on [the] implant as it was placed in Plaintiff’s hip.” The district court also granted Manufacturer’s motion to strike the expert’s affidavit since “many of [his] statements directly contradicted things he said in his deposition” and a party cannot “change testimony just to avoid summary judgment or a Daubert motion.”

As a result, Plaintiff lacked expert testimony on defect or causation, and Manufacturer’s motion for summary judgment on her manufacturing defect claim was granted, along with her remaining claims. Plaintiff appealed.

The Eighth Circuit held that a party may not avoid summary judgment by submitting an affidavit that contradicts rather than clarifies previous sworn testimony. In this case, the metallurgy expert’s affidavit “arguably crossed the line between clarifying prior testimony and changing prior testimony.” Given the differences between the testimony the metallurgy expert provided during discovery and his affidavit, the Court concluded that the district court didn’t abuse its discretion by excluding the affidavit from consideration at summary judgment.

Plaintiff also argued that the district court erred by excluding the metallurgy expert’s testimony that her hip stem implant had a manufacturing defect and that defect caused the hip stem to fracture.

The Court first considered the metallurgy expert’s testimony that the non austenitic phase of the metal caused Plaintiff’s hip stem to fracture. The district court excluded this testimony because the metallurgy expert hadn’t considered “the forces that were applied to the hip stem” or “any biomechanical forces.” Plaintiff argued that the district court erred by requiring the metallurgy expert to exclude other potential causes of the fracture. The Eighth Circuit noted that although Plaintiff was correct that an expert need not rule out all possible causes of an injury, an expert nonetheless should “adequately account[] for obvious alternative explanations,” quoting the Advisory Committee notes to 2000 amendment to the Federal Rules of Evidence.

Here, the metallurgy expert didn’t consider the obvious alternative explanation for the fracture recognized by Plaintiff’s own doctors: the failure of the hip stem to grow into Plaintiff’s upper hip bone and properly distribute her weight. Although the metallurgy expert testified during his deposition that environmental factors would have been secondary causes of the fracture to the defective material if there had been “small variations in biomechanical forces,” he nonetheless didn’t consider whether the biomechanical forces applied to Plaintiff’s hip stem had amounted to such small variations (indeed, he did not at all consider the biomechanical forces applied to the hip stem). Therefore, the Eighth Circuit held that the district court acted within its discretion by excluding the metallurgy expert’s opinion on causation under Rule 702.

The Court didn’t need to determine whether the district court abused its discretion by excluding the metallurgy expert’s testimony on manufacturing defect because the exclusion of his causation testimony alone supported the summary judgment order. Under Missouri law, a “plaintiff in a strict products liability . . . claim must show,” among other things, “that the alleged defect caused the claimed damages,” the Court noted, quoting one of its earlier decisions.

Since the fracture of Plaintiff’s hip stem implant was a sophisticated injury, and Plaintiff lacked any admissible expert testimony on the cause of that fracture, the district court did not err by granting Manufacturer summary judgment on her defect claim.

The Eighth Circuit affirmed the judgment of the district court.