EndoLab® employs an adapted hip simulator platform for the wear testing of carpometacarpal (CMC) joint prostheses. Due to the lack of standardized motion profiles for this joint, the simulator is programmed to reproduce a combination of conical “low-load” motion patterns and linear “pinch grip” movements, simulating functional activities such as key pinching.
Testing is typically performed under loads below 100 N at a frequency of 1 Hz, guided by established wear testing standards for hip and knee prostheses. The articulation is lubricated with calf serum to mimic synovial fluid, with the test medium maintained at 37°C. A standard test duration comprises 5 000 000 cycles. While a sample size of three specimens plus one loaded soak control is commonly applied, the system allows testing of up to six specimens alongside two loaded soak controls.
The small size of CMC prostheses presents specific challenges, particularly with respect to component fixation and wear measurement. EndoLab® has developed dedicated embedding procedures that ensure precise alignment while allowing non-destructive removal of components for gravimetric analysis. Given the very low wear rates typical for these implants, high measurement sensitivity is essential. This requirement is addressed by a proprietary high-precision weighing robot developed in-house.
In addition to gravimetric wear determination, further analyses are frequently performed upon request. These include characterization of wear particles and quantification of metal ions in the test fluid, providing valuable information on corrosion behaviour and biocompatibility. The assessment is complemented by high-resolution microscopy of the articulating surfaces and detailed photographic documentation of CMC wear patterns.
