The high molecular weight polyethylene remains the gold standard for a number of prostheses and indications. Its controlled wear resistance and its lack of complication under reasonable conditions of use, insure a high rate of satisfaction and survival up to 15 years after implantation. For these reasons, the surgeons in accordance with the health institutions, recommend its systematic use for all patients of more than 70 years candidates to a joint replacement of the hip, the knee and the shoulder.

Conventional UHMWPE (Ultra High Molecular Weight Polyethylene) is a very tough material, with the highest impact strength of any thermoplastic presently available. It is highly resistant to corrosive chemicals with exception of oxidizing acids; has extremely low moisture absorption and a very low coefficient of friction; is self-lubricating; and is highly resistant to abrasion.

Since the early 2000s, crosslinked variants of the conventional UHMWPE have been used and validated both in vitro and in vivo. The crosslinking process is generally made by irradiating the material (or by exposing it to electrons) at a level in-between 25 and 100 kGy. The crosslinking modifies deeply the mechanical characteristics of the material and provides an increase in hardness and wear resistance. But this improvement is counterbalanced by a reduction of the tensile strength compared with the natural state of the material and a reduction of the elongation percentage under load.




The development of an orthopaedic joint polyethylene is a compromise between the wear resistance and the mechanical characteristics. Also, other manufacturing steps will come over the crosslinking process to maintain the characteristics of the material over time and to limit the oxidation of the material.

Evolutis has developed a proprietary technology of crosslinked polyethylene: the polyethylene PEXEL.


The PEXEL technology includes:

  • A systematic control of the raw material and of the implants at different steps of the process in order to detect any defect of consolidation or homogeneity in the material
  • a method of high precision and low-temperature machining
  • a crosslinking of the molecular chains by moderate gamma irradiation
  • a resistant and opaque air-vacuum packaging

The shelf-aged polyethylene PEXEL demonstrated a wear reduction of more than 50% in comparison wit a conventional polyethylene (CERAH test according to ISO standards 14242-1 and 14242-2 on shelf aged implants at 5 millions cycles).



  • Initial molecular weight of more than 7 million gr/mole (2 to 4 million for a conventional UHMWPE)
  • 40 kGy gamma irradiation minimum
  • VacUpac air-vacuum packaging