Mechanical testing and statistics
Understanding Structural Integrity and Statistical Justification
Mechanical testing is a core component of pre-clinical evaluation in medical device development. It provides quantifiable evidence of a product’s structural performance under physiological loads, which is critical in the feasibility and verification phases. However, the value of testing depends heavily on the number and type of samples tested.
Early Feasibility Testing
During the early stages of development, mechanical tests help identify design weaknesses, validate working principles, and refine component geometry. At this stage, small sample sets, or even a single unit, can provide actionable insights. Although statistical rigor is not yet required, documenting the rationale for sample selection is important, especially when tests are destructive or when evaluating specific subcomponents.
Feasibility testing also helps assess process-related variation. For example, the mechanical properties of 3D-printed components can vary across different locations on the build plate or between batches. Testing across multiple positions or print runs helps quantify variability early on, which supports better design decisions and manufacturing consistency.
Verification Testing and Sample Size Planning
Verification testing is intended to provide formal evidence that design inputs have been met. Regulatory authorities expect a documented rationale for the sample size, ideally based on recognized standards (e.g., ISO, ASTM). Where no standard applies, statistical methods are used to determine an appropriate sample size based on expected performance, variability, confidence levels, and clinical relevance.
Accurate input data, often obtained from feasibility testing, are essential to avoid underestimating or overestimating the sample size. Inadequate planning can lead to re-testing, delayed timelines, and additional costs.
At GBA Group, we support medical device developers by providing structured, pragmatic testing strategies that align with technical requirements and regulatory expectations. Through early-stage prototyping, in-house laboratory capabilities, and extensive industry knowledge, we define meaningful test methods and sample size rationales. Our goal is to ensure that verification activities are efficient, scientifically sound, and withstand scrutiny from notified bodies and regulatory authorities.
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