Photo of Rachel B. Weil

We write this as we prepare to leave for an overseas trip.   We have our N95s, our face shields, and our vaccine card, along with a bit of apprehension and a large measure of giddy gratitude.  It has been a long eighteen months (and counting).  We’ll fill in some details next time, but we’ll sign off for vacation with a nice decision out of the Zimmer hip prosthesis MDL.  In In re Zimmer M/L Taper Hip Prosthesis (Tammy Nutting), 2021 WL 3475681 (S.D.N.Y. August 6, 2021), the court, in a rare decision applying Idaho law, took on a couple of our favorite issues with assurance and sense.  The plaintiff underwent a total hip replacement during which she was implanted the defendant’s femoral head along with an additional neck piece that joins the taper stem to the femoral head.  She alleged that these pieces, when joined, were prone to micromotion between the components, leading to metal release and corrosion that caused her to suffer tissue necrosis and pain and required her to undergo revision surgery.  The decision addresses the defendant’s Rule 702 motion to exclude the plaintiff’s “design defect” expert along with its motion for summary judgment on warnings causation – two pet issues of ours, both of which are the subjects of many jurisprudential misadventures.  But not here.

Motion to Exclude Design Defect Expert

Under Idaho law, a plaintiff can prevail on a design defect claim only if she proves that her injury was the result of defective or unsafe product, either with “direct evidence of an identifiable, specific defect” or with “evidence of a malfunction of the product and the absence of evidence of abnormal use” along with “absence of evidence of reasonable secondary causes which would eliminate” the liability of the defendant.  Nutting, 2021 WL 3475681 at *4-5 (citation omitted).   To prevail on this latter “malfunction” theory, “the product at issue must be of a type which permits a jury to infer that an injury would not have occurred had there not been a defect attributable to the manufacturer.”  Id. at *5 (internal punctuation and citation omitted).   (Grammar-obsessed parenthetical:  both of these improper uses of “which” instead of “that” – a pet peeve – are direct quotes.)

The plaintiff’s “design defect” expert was an impressively-credentialed biomedical engineer.  The expert offered the opinion that the plaintiff’s device was defective because the defendants designed an intentional taper angle mismatched between the two components, producing “a high likelihood of MACC (machine-assisted crevice corrosion).”  Id.  (citation omitted).  As the court explained, “the ‘mismatch’ is the difference between the angles of the components, which affects how the components will fit together at the taper junction where the head and neck trunnion join when the surgeon implants them together.”  Id.  The expert opined that the plaintiff’s device had a “five-minute mismatch,” and that mismatches greater than four minutes, 30 sections were “in a range sufficient to cause micromotion and fretting. . . .”  Id. at *7.

The problem was that that the expert, like many we encounter every day, had no reliable basis for her defect opinion.  In the words of the court, there was “too large a gap between [the expert’s proposed testimony and the data” upon which she relied.  Id.   She “assume[ed] that the amount of mismatch in [the plaintiff’s] device was sufficient to cause her injuries, without explaining how much mismatch is necessary for clinically significant corrosion and adverse local tissue reaction to occur.” Id.   The plaintiff tried to cure this in her briefing, citing to the testing of a different product – not the product at issue – that, she argued, supported her expert’s opinion.  But the court stated (we love this), “It is [the expert’s] opinions the Court must assess, not Plaintiff’s counsel’s arguments.”  Id. at *8.  The expert did not “adequately explain her basis for crediting studies that examined different products from different companies over the contrary evidence provided by [the defendant’s] testing of its own, similar products.”  Id.   Nor could the expert revert to an opinion that the defendant should have conducted additional testing, because this opinion “shift[ed] the burden to [the defendant] to disprove a defect, and did not satisfy Rule 702’s “helpfulness” standard, requiring “a valid scientific connection to the pertinent inquiry as a precondition to admissibility.” Id. at *9 (internal punctuation and citation omitted).  The opinion that the defendant should have conducted additional testing “lack[ed] that scientific connection,” because the expert did not “explain the costs and benefits so that the factfinder could determine whether additional testing would be reasonable or unreasonable.”  Id.   Finally, the expert’s “alternative design” opinions were inadmissible because they considered only the risk of corrosion and did not weigh other risks that could be associated with the proposed alternatives.

Ultimately, the court invoked Joiner, holding that there as “simply too great an analytic gap between the data and the opinion proffered,” and that the expert’s opinions were “connected to existing data only by the ipse dixit of the expert.”  Id. at *10 (citation omitted).   We love this gutsy holding, particularly in a factually-complex context in which many judges would have thrown up their figurative hands.

Motion for Summary Judgment

The exclusion of the design defect expert left the plaintiff without the expert causation testimony she needed to submit this issue to the jury. The plaintiff’s orthopedic surgery expert offered the opinion that the defendant’s device caused the plaintiff’s injuries, “[b]ut, importantly, he [did] not opine that a specific defect caused the MACC.”  Id.   (This distinction – between a product causing an injury and a defect in the product causing the injury – is one that courts and juries blur all the time.)  The expert argued only that something went wrong with the plaintiff’s device, and the plaintiff argued that the jury could infer the existence of a defect.  But this did not satisfy Idaho’s requirement that the product be “of a type which permits a jury to infer that an injury would not have occurred had there not been a defect attributable to the manufacturer.”  Id. at *11.  Taper corrosion is a known risk of metal hip implants, so a jury could not infer that such corrosion would not have occurred if the device were not defective.   And so, because the plaintiff had no expert evidence of a specific design defect and could not rely on a “malfunction” theory, the court granted summary judgment on the design defect claim.

The defendant also moved for summary judgment on the plaintiff’s failure-to-warn claim, arguing both that it had supplied adequate warnings to the plaintiff’s physician and that, in any event, the plaintiff could not prove that any alleged inadequacy of the warnings proximately caused her injuries.  The court seized upon the latter (and our favorite) point, holding that the adequacy of the warnings was irrelevant because the plaintiff could not prove “warnings causation.”  It was a classic “failure to read” situation:  the doctor testified that he never read the package insert, so no additional warning could have changed his decision to prescribe the device.   In such situations, the court emphasized, “the failure to provide an adequate warning cannot be the proximate cause of an injury, because even if [an] additional warning had been provided, the doctor, having failed to review the warning in the first place, would be unaware.”  Id. at *13 (citation omitted).   (Here is another post about failure to read, also in a hip implant case.)   And so the court granted summary judgment on the warnings claims as well.

Needless to say, we were delighted to read this opinion.   We’re headed for the airport soon.   ‘Til next time, stay safe out there.