POLYETHYLENE WEAR OF CHARITÉ ARTIFICIAL DISCS. MACROSCOPIC AND MICROSCOPIC WEAR AND INFLAMMATORY REACTION IN PERI-PROSTHETIC TISSUE OF 23 RETRIEVALS IN 19 PATIENTS.

Abstract

We removed 23 Charité artificial discs in 19 patients due to severe back-and legpain and performed an anterior as well posterior fusion. Mean interval between insertion and retrieval is 8,4 years (3,0–16,0 years). The mean age at retrieval is 49,4 years (40–72 years). The cause of persistent or recurrent pain was one or more of several problems thought to be related to the pain: subsidence, migration, wear with or without breakage of the metal marker ring, facetjoint or adjacent degeneration. In all cases wear of the polyethylene core was seen in major or minor degree. The wear was related to posterior impingement possibly due to hyperlordosis and extension instability and was subsequently more pronounced in the peripheral rim than in the central dome. Also a relationship was noted to in vivo oxidation of the polyethylene, especially in the rim. In the periprosthetic tissue an inflammatory reaction was found, more in the severe wear cases. Polyethylene loaded macrophages were seen, also polyethylene particles lying freely in the tissue. The macrophages proved positive for Interleukin 6. The wear pattern and the inflammatory reaction resembles the pattern seen in total hips and knees. Probably a substantial number of patients will exhibit these wear changes some years after insertion. It is questionable whether changes in sterilization and packaging and better insertion and sizing techniques will prevent wear development in the future.