Introduction Cemented fixation of the tibial component is the standard treatment for patients older than 65 with long-standing excellent results. Whether cemented fixation is best even for younger patients is still debated, and if uncemented fixation is chosen, the question remains as to whether screws are necessary as an adjunct. We present the results of a prospective randomized study comparing cemented and two modes of uncemented fixation.
Methods Thirty-five patients (mean age 56 years, range 29 to 64) were operated with the Profix (Smith&
Nephew) TKA for gonarthrosis grade III to V. At the operation, the patients were randomly allocated to fixation of the tibial component with cement (Group C, n=6), uncemented fixation with hydroxyapatite (HA) coating without screws (Group HA, n=14), or uncemented fixation with HA coating and with screws (Group HA+, n=15). The implants and tibiae were prepared for RSA with tantalum markers. RSA was performed post-operatively, three, 12 and 24 months post-op.
Results There were no complications or revisions during the follow-up. For all three types of fixation the migration was larger during the initial three months, after which the migration leveled off. At three months, subsidence and tilting of the implant was significantly larger for group HA- compared to group C (P = 0.009 − 0.036), with the migration for group HA+ in between. This difference between the groups persisted up to 24 months. When examining the migration from three to 24 months, the implants in all three groups displayed very small migration, magnitudes well below the detection limit of RSA. There were no differences in magnitude of migration between the three groups between three and 24 months.
Conclusions The uncemented tibial component displays relatively large migration within the first three months compared to the cemented implant, and uncemented fixation without screws has larger migration than when screws are used. This larger initial migration for the uncemented fixation probably is due to “setting-in” of the prostheses. However, if the uncemented implant “survives” this early period, the results of the present study indicate a good long term prognosis, even when no screws are used for additional stability. This is important, since osteolysis frequently has been observed in relation to screws in the proximal tibia. One reason for the stable fixation of the uncemented implants may be the use of HA-coating.
In relation to the conduct of this study, one or more of the authors is in receipt of a research grant from a non-commercial source.
