Comparison of a mobile with a fixed tibial bearing unicompartimental knee prosthesis: a prospective randomized trial using a dedicated outcome score.

Between February 1996 and December 1997, forty consecutive patients with medial compartment knee arthritis were assigned randomly into two groups. All underwent a unicompartimental knee replacement. The tibial prosthesis in group A (20 knees) had a fixed bearing and in group B (20 knees) a mobile bearing. The average age was 69. Five in group A and 71 in group B. Pre-operatively, and at an average follow-up of 5.7 years, all the knees were assessed using both a dedicated UKR score specifically developed and adopted by the Italian Orthopaedic Unicompartimental Knee Replacement Users Group (GIUM) and the Knee Society Score. During surgery in group B we experienced a medial tibial plateau fracture fixed intra-operatively. One prosthesis in group A required an early revision to a TKR because of a continuous pain without any evident sign of loosening. There were no meniscal dislocations in group B. No statistically significant difference in outcome was observed between the two groups at the latest follow-up.