Introduction

On 21 May 2018 Mrs Justice Andrews delivered a landmark judgment in the largest products group litigation before the Courts in England and Wales, the DePuy Pinnacle Metal-on-Metal Hips Group Litigation[1]. The Court found in favour of the Defendant, DePuy. This case is a very important decision in product liability law and particularly regarding the definition of “defect” under the Consumer Protection Act 1987 (“the CPA”).

The Pinnacle Litigation was one of a number of group actions under the CPA against manufacturers of Metal-on Metal (“MoM”) total hip replacements and resurfacing products introduced in the 2000s. It was ordered to proceed as a trial of a preliminary issue to determine whether DePuy was liable to the Claimants in relation to its Pinnacle Ultamet total hip replacement, subject to any development risk defence. All the other claims were stayed pending the outcome. It was hoped that the resolution of these claims at preliminary issue trial would provide guidance for claims against the other manufacturers. Representatives of other manufactures made written closing submissions however the actual evidence heard at trial concerned only the Pinnacle Ultamet.

Background to the case

In the late 1990s/early 2000s, MoM hip prostheses were developed with the aim of overcoming some of the limitations caused by traditional Metal-on-Polyethylene (“MoP”) designs, namely combatting the problem of polyethylene wear osteolysis; providing a greater range of motion; and reducing the incidence of dislocation. These issues were particularly problematic for younger and active patients, and the DePuy’s Pinnacle Ultamet (a large head MoM) was developed specifically with these patients in mind and with a view to improving survivorship of the prosthetic beyond 10 years.  The use of large head MoM prostheses such as the Pinnacle Ultamet increased rapidly in the early part of the 2000s, peaked in 2007, before declining and sharply dropping off in 2010. The primary reason for this was the high failure rates of MoM implants, largely due to patients suffering from a soft tissue reaction around the hip known as an Adverse Reaction to Metal Debris (“ARMD”).

The claims in this litigation were brought against DePuy by 312 individuals who were implanted with one or more Pinnacle MoM prostheses. All the claimants claimed to have suffered an ARMD generated by their prostheses, necessitating revision surgery.

The Claimants’ case, brought under Part 1 of the CPA, was that the prostheses supplied to them were defective within the meaning of section 3 – that “the safety of the product [was] not such as persons generally are entitled to expect” – and that this caused them personal injury for which DePuy was liable. The offence has strict liability, so there was no need to show negligence on the part of DePuy. As stated above, the preliminary issue at trial was namely “whether or not the defendant is liable to the claimant, subject to any development risk defence“, and encompassed any issues of causation.

In their primary case, the Claimants alleged that the Pinnacle Ultamet had a “tendency or propensity” to cause ARMD, which constituted a defect when considered by reference to all the relevant circumstances. In the alternative they pleaded that it had an “abnormal potential for damage” compared to other comparable products.

The meaning of “defect”

A “defect” was determined by the level of safety that the public was entitled to expect at the time the product was first introduced to market. The Court could have regard to everything now known about the product, irrespective of whether that information was available at the time it was put on the market. The Court adopted the flexible approach in Wilkes v DePuy[2] when deciding what circumstances are relevant and the weight to be given to each when establishing whether a product was defective under the CPA. Following Wilkes, the Court held that it was entitled to have regard to all circumstances which may have a bearing on the assessment of the safety of the product, and that those circumstances might differ depending on the product and the nature of the complaint. Furthermore, proof of a causal connection between defect and damage should not be attempted without first ascertaining there is a defect.  It was stated that the Court could consider the product’s cost, its risk-benefit profile, the avoidability of the safety risk, the existence of a learned intermediary and the information and warnings passed on to such intermediary. Compliance with regulatory requirements could also have considerable weight for determining safety.

The Claimants’ Primary Case

The Claimants argued that the products’ “tendency” to cause ARMD was itself a defect under the CPA when considered by reference to all the relevant circumstances. They relied on A v NBA[3] which had equated what the public was “entitled to expect” to “the legitimate expectation” of persons generally. The Court fundamentally rejected this argument. Following Wilkes, which had criticised the NBA approach, it stated that safety is inherently and necessarily a relative concept because no product, and particularly a medicinal product, can be absolutely safe. The development of ARMD was one of the normal risks inherent in the use of the product, and no hip prosthesis would last forever. The Claimants’ were characterising a potentially harmful characteristic of the product, arising during normal use, and without there being anything wrong with the product, as a “defect”. By this logic all MoM hip prostheses would be defective. The Court held that the Claimant’s primary approach to defect was “untenable” and “directly contrary to the spirit and objectives” of the legislation.

The Claimants’ Alternative Case

As for the Claimant’s alternative case – that the Pinnacle Ultamet prosthesis had “an abnormal potential for damage” compared to other comparable products – Mrs Justice Andrews stated that the case would turn on whether it could be established on the evidence that the Pinnacle Ultamet prostheses had a materially greater risk of early failure and revision, when compared with appropriate comparator prostheses. Mrs Justice Andrews confirmed that this alternative case was consistent with the approach in Wilkes.

The Claimants relied heavily on statistics from various sources, notably the data from the National Joint Registry (“NJR”), to argue that the revision rate of Ultamet was materially higher than comparable prostheses.  They relied on comparative cumulative risks of revision (“CRR”) to demonstrate that a materially increased risk of early failure existed at the time when the product was introduced to the UK market in 2002.

DePuy argued that the statistics relied upon by the Claimant were unreliable and the Court agreed. In particular, the Court held that the NJR data was subject to a number of limitations and confounding issues including factors such as patients’ activity and BMI, outlier surgeons with significantly higher revision rates, incomplete data, unsuitable comparators and a panic engendered by the media reports in wake of MHRA guidance and the withdrawal of a different product.

The best available data on CRR for hip prostheses during that time period, the Court said, was from the National Swedish Hip Arthroplasty Registry (“SHAR”) which Mrs Justice Andrews concluded after substantial analysis, did not show a material difference (when compared with the NJR data) between the CRRs at 10 years of the Pinnacle Ultamet and the most suitable comparator – a metal on conventional polyethylene prosthesis.  The 2000 NICE guidance “benchmark” for revision rates for primary hip replacement was broadly consistent with the SHAR revision rates at the time.

The Court was very unimpressed by the expert evidence put forward by the Claimants to contend that there were various aspects of the design and manufacture of the product that increased the potential for metal wear, and Mrs Justice Andrews concluded that the Pinnacle system was overall a well-designed product.

The Court therefore stated that the Claimants’ alternative claim must fail.

Causation

In light of the Court’s findings that the product was not defective, a conclusion on causation was not reached.

Conclusion

The decision in this case will be welcome news for manufacturers and their insurers. Wilkes and NBA had produced very different methods for approaching CPA claims. This case reinforces the approach taken in Wilkes,and suggests a shift away from the NBA approach. However, since all these cases were in the High Court, neither approach has overruled the other. The more flexible and holistic approach being proposed by Wilkes and this case suggests that claims under the CPA should be easier to defend.  The Court’s considerable care and caution in its approach to statistics also illustrates the importance of reliable data, and the way in which such data is put to use as evidence.

[1] Gee and others v DePuy International Limited [2018] EWHC 1208 (QB).
[2] Wilkes v DePuy International Limited [2016] EWHC 3096 (QB) [2017] 3 All ER 589.
[3] A v National Blood Authority [2001] 3 All ER 289.