Wilkes v Depuy International Ltd

Factual and Procedural Background

In January 2007, the Plaintiff underwent a surgical procedure at The Hospital to insert an artificial left hip, including a metal femoral shaft component known as the "C-Stem," manufactured by the Defendant. In January 2010, the C-Stem fractured, and during replacement surgery, metal debris was found around the joint. The Plaintiff brought claims alleging negligence by the Defendant and a claim under the Consumer Protection Act 1987 ("the Act"), asserting the C-Stem had a defect as defined by the Act because its safety did not meet the expectations of persons generally.

A preliminary issue was ordered for trial, focusing solely on whether, considering the fracture but excluding metallosis and negligence, the Defendant was liable under section 3 of the Act. The trial involved lay and expert evidence, including testimony from the Plaintiff and employees of the Defendant, and expert engineers with experience in medical devices and materials engineering. The evidence also included statements from the surgeon who performed the procedure, although he was not cross-examined due to unavailability.

The case involved detailed examination of the regulatory framework governing medical devices, the design and testing of the C-Stem, and the factual circumstances surrounding the Plaintiff’s hip replacement and subsequent fracture of the device.

Legal Issues Presented

1. Whether the Defendant is liable to the Plaintiff under section 3 of the Consumer Protection Act 1987 for the fracture of the C-Stem component, considering the product's safety relative to persons generally entitled to expect.
2. Whether the C-Stem contained a "defect" within the meaning of the Act at the time it was put into circulation.
3. The relevance and application of risk-benefit analysis, product standards, regulatory compliance, warnings, and the role of intermediaries in assessing defect and liability.

Arguments of the Parties

Appellant's Arguments

• The C-Stem was defective in design because it suffered early fracture due to a known stress concentration caused by the neck thread, which could have been eliminated or mitigated by simple design changes.
• The product's safety was below what persons generally were entitled to expect, particularly as the margin of safety in the design was too low.
• The risk of stem neck fracture should have been designed out or substantially reduced, and the failure to do so constituted a defect.
• The warnings and instructions for use (IFU) were inadequate to inform the Plaintiff properly about the risk of fracture.
• The defect was avoidable and the product was "non-standard" as it possibly fell outside design specifications.
• Causation should be established on the basis of material contribution rather than requiring proof of doubling the risk.

Appellee's Arguments

• The C-Stem complied with all relevant mandatory standards and regulatory requirements, including fatigue testing to levels exceeding those required by British Standards.
• The product was "standard," performing as intended and meeting safety expectations at the time it was marketed.
• The risk of stem fracture is small, inherent in design compromises, and was appropriately balanced against benefits in the risk-benefit analysis conducted by regulators.
• The warnings in the IFU were clear and unambiguous, sufficiently informing professional intermediaries (orthopaedic surgeons) who then advised patients accordingly.
• Design changes suggested by the Plaintiff’s expert might have adverse effects, such as requiring more bone removal or increasing discomfort or risk in other ways.
• The presence of a learned intermediary (the surgeon) is a relevant circumstance and the Defendant had no direct duty to warn the Plaintiff.
• Causation was not established, and the fracture was unpredictable due to many biomechanical variables.

Table of Precedents Cited

Precedent	Rule or Principle Cited For	Application by the Court
A v National Blood Authority [2001] 3 All ER 289	Framework for proving defect under the Consumer Protection Act; distinction between standard and non-standard products; role of causation.	The court discussed and critiqued Burton J’s approach, finding parts of it problematic but broadly useful; ultimately declined to adopt rigid categorization of defects.
Tesco Stores v Pollard [2006] EWCA Civ 393	Clarification that liability under the Act is without fault, not absolute liability or warranty of performance.	Cited for the principle that defect does not equate to fault or negligence.
Ide v ATB Sales Limited [2008] EWCA Civ 424	Claimant need not prove cause of defect with specificity; defect defined by lack of safety.	Applied to confirm that defect can exist without precise knowledge of cause of failure.
XYZ v Schering Health Care Limited [2002] EWHC 1420	Principle that claim based on increased risk requires proof that risk more than doubled.	Referenced by Defendant’s counsel as relevant to causation in risk-based claims.
Fairchild v Glenhaven Funeral Services Limited [2002] UKHL 22	Causation principles in circumstances of multiple potential causes and increased risk.	Referenced by Plaintiff’s counsel arguing for material contribution standard rather than doubling risk.
Bogle v McDonald's Restaurants Limited [2002] EWHC 490	Consideration of avoidability of risk and risk-benefit balance in product safety assessment.	Used to support the view that avoidability is a soft-edged concept relevant to risk-benefit analysis.
Worsley v Tambrands [1999] EWHC 273	Impact of warnings on the assessment of defect under the Act.	Supported the conclusion that warnings qualify public expectations and affect defect analysis.
Richardson v LRC Products Limited [2000] PIQR P163	Discussion on the degree of specificity required to prove defect.	Referenced to note academic debate but not determinative in this case.

Court's Reasoning and Analysis

The court began by examining the statutory definition of defect under the Consumer Protection Act 1987, emphasizing that defect relates solely to the safety of the product as objectively assessed against what persons generally are entitled to expect at the time the product was put on the market. The court rejected the approach that places causation before defect, holding that defect must be established first.

The court acknowledged the inherent relativity of safety in medicinal products, requiring a balancing of risks and benefits (risk-benefit analysis). It noted that no product is entirely risk-free and that the regulatory regime, including CE marking and compliance with British and European standards, provides powerful evidence of acceptable safety levels.

The court considered the relevance of various factors, including compliance with standards and regulations, warnings and instructions for use (IFU), the role of learned intermediaries (orthopaedic surgeons), and the avoidability of risks. It found that the presence of a learned intermediary is a relevant circumstance and that warnings given in the IFU, aimed at professional users, were clear and sufficient.

Turning to the fracture itself, the court accepted the expert consensus that the fracture was a fatigue failure initiated at the thread grooves on the neck of the stem, which concentrate stress. However, the court preferred the evidence of the Defendant’s expert over the Plaintiff’s expert, finding that the biomechanical variables affecting load and failure were complex and unpredictable, and that the fatigue testing and post-market surveillance showed a very low failure rate consistent with acceptable safety.

The court rejected the Plaintiff’s argument that the product was "non-standard" or outside specification, finding no credible evidence of manufacturing defect or design failure. It also rejected the argument that the design should have eliminated the thread or altered it, considering the holistic nature of design and the benefits the thread provides, especially for compatibility with ceramic heads.

Regarding warnings, the court found the IFU adequately disclosed the risk of fatigue failure and identified relevant risk factors such as obesity and high activity levels. The surgeon, as a learned intermediary, was sufficiently informed to advise the Plaintiff.

Ultimately, the court concluded that the C-Stem’s safety was not below the level persons are generally entitled to expect and that the fracture was a rare, unpredictable event within the accepted risk profile of the product. Therefore, the product was not defective under the Act.

The court did not address causation in detail, as liability was contingent on defect, which was not established.

Holding and Implications

The court held that the Defendant is not liable to the Plaintiff under section 3 of the Consumer Protection Act 1987 for the fracture of the C-Stem femoral stem.

The direct consequence of this decision is that the Plaintiff’s claim based on the alleged defect in the C-Stem fails. The court’s ruling confirms that compliance with rigorous regulatory standards, appropriate warnings, and a balanced risk-benefit assessment are significant factors in determining defect under the Act. No new precedent was established; the decision applies existing principles to the facts of this case, emphasizing the objective and holistic nature of the safety assessment for medical devices.