In Redd v. DePuy Orthopaedics, Inc., the Eighth Circuit Court of Appeals has reminded litigators of the importance of ensuring expert witnesses perform a thorough review of a matter, including apparent alternative causal explanations, prior to issuing their opinions.

In 2008, plaintiff Redd underwent a total hip replacement, receiving an implant supplied by hip manufacturer DePuy Orthopaedics, Inc. At the time of her surgery, Redd suffered from a number of risk factors that placed her at a higher risk for failure of the implant as she took immunosuppressant drugs and was considered morbidly obese. Four years after her initial surgery, the implanted hip stem fractured. During the revision surgery to replace the hip stem, the doctors determined that the stem had not properly grown into the bone at the top of Redd’s hip, which was a known possibility given her risk factors. Two years after her revision, Redd again experienced a hip stem fracture. Plaintiff brought a federal diversity action against DePuy Orthopaedics, alleging negligence and strict liability claims based on product defect and failure to warn. DePuy moved for summary judgment and for exclusion of plaintiff’s expert testimony under Federal Rule of Evidence 702 and the analysis set forth in Daubert v. Merrell Dow Pharmaceuticals, Inc., 509 U.S. 579 (1993).

Plaintiff retained a professor of metallurgy and materials science, Dr. Shankar Sastry, to testify as to the cause of the fracture. In preparing his expert report, Dr. Sastry failed to review records related to the manufacturing process of the hip implant and disregarded consideration of biomechanical factors that could have resulted in failure of the prosthesis. Dr. Sastry concluded that it was the physical state of the implant’s metal that caused the fracture. He further concluded that any individual environmental or biomechanical factors would have been a secondary cause of the fracture.

In granting DePuy’s motion to exclude Dr. Sastry’s testimony, the US District Court for the Eastern District of Missouri concluded that Dr. Sastry lacked a scientific or factual basis to conclude that there was a manufacturing defect or to opine on causation, and that he failed to consider the necessary issues of the forces that were exerted on the implant as it was placed in Redd’s hip. Following exclusion of Dr. Sastry’s testimony, Redd lacked expert testimony on defect or causation and DePuy’s motion for summary judgment was granted.

On appeal, the Eighth Circuit reviewed the district court’s exclusion of Dr. Sastry’s testimony, the propriety of which is governed by Rule 702 and the Daubert standard. Plaintiff argued that the district court erred by requiring Dr. Sastry to exclude other potential causes of the fracture. The Eighth Circuit concluded that, while an expert is not required to rule out all possible causes of an injury, he or she nonetheless should adequately account for obvious alternative explanations. Dr. Sastry did not consider the obvious alternative explanation for the fracture—failure of the hip stem to grow into the patient’s upper hip bone and subsequent failure to properly distribute her weight—which was a known possibility at the time of Redd’s surgery given her risk factors. Because Dr. Sastry failed to consider the individual biomechanical forces placed on the prosthesis in issuing his report, the district court’s decision to exclude the causation testimony was affirmed.

The opinion may be found here.