Description of device
Femoral stem medical devices are implanted into a patient’s thigh bone. They are classified as a type 3 medical device in the EU and are typically made from metal or metal alloys that may be surface treated. They can remain in place for a patient’s lifetime. A patient may have two implants at any given time. Over 90,000 were sold in the UK in 2017.
Specific Sample Related Considerations for Chemical Characterisation
- Material of Construction: metal material – less extractable and no chance of solvent penetration to the material (extraction is a surface phenomenon)
- Analytical Limits: very low due to large surface area, therefore a large amount of sample concentration is required
- Extraction Type: exhaustive extraction which can further affect analytical limits and requires additional time and testing
- Overall chemical characterisation complexity rating = 7

Key Factors for Chemical Characterisation
- Related Guideline – 10993-18
- Extraction Type – Exhaustive (due to long term, >30 days contact)
- Solvents – 3 (polar, semi-polar, non-polar)
- Typical Sample Size – Very Large (200cm2)
- Extraction volume 200 mL
- Analytical Limits (without concentration) = 0.00075 ug/mL