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Microseparation test PI-78 (ISO 14242-4)

Normative References  

PI-78: (ISO 14242-4) Implants for surgery - wear of total hip-joint prostheses - Part 4: Testing total hip joint prostheses under variations in surgical positioning

Hard-on-hard bearings in Total Hip Replacements (THR) have shown very low wear rates when tested according to ISO 14242-1 under standard gait conditions. In order to simulate a more severe load scenario, microseparation can be included. Clinically microseparation is assumed to occur during swing phase when the load is minimal and is associated with joint laxity, medialized cups or femoral head offset deficiency.

For in-vitro testing, microspearation is generated by a spring, which produces a medial-superior translation of the cup relative to the femoral head resulting in localized contact between the head and the superior rim of the cup. The distraction of the head from the cup is measured by a custom made measuring device being placed directly at the implant. Note: Controlling the distraction of the cup from the head rather than measuring the horizontal displacement of the spring ensures that the adjustment of the horizontal translation is not affected by the stiffness of the test set-up.  

Implant Testing - Microseparation test PI-78 (ISO 14242-4) Microseparation test PI-78 (ISO 14242-4)