Pseudotumours associated with metal-on-metal hip resurfacing: 10-year Newcastle experience.

We report the incidence of pseudotumours in a single-surgeon consecutive series of 670 metal-on-metal hip resurfacings performed in the last ten years, with a minimum follow-up of one year. Two cases of pseudotumours have been found and are discussed in detail including metrology and wear analyses of the explanted components. The first was a painless, large synovial cyst in the thigh, secondary to aseptic femoral cup loosening 8 years following hip resurfacing. The second was a painful collection of wear debris in the psoas region at one year post surgery caused by impingement, resulting in eccentric edge wearing. In the first case it was decided to retain the bearing surface; in the second case, conversion to a metal-on-polyethylene hip replacement was performed. In our experience the risk of pseudotumours is low (0.15%) and can be fully explained. In selected cases the bearing surface can be retained.