Abstract
Background and purpose — Thresholds of implant migration for predicting long-term successful fixation of tibial components in total knee arthroplasty have not separated cemented and uncemented fixation. We compared implant migration of cemented and uncemented components at 1 year and as the change in migration from 1 to 2 years.Patients and methods — Implant migration of 360 tibial components measured using radiostereometric analysis was compared at 1 year and as the change in migration from 1 to 2 years in 222 cemented components (3 implant designs) and 138 uncemented components (5 implant designs).Results — 1-year maximum total point motion was lower for the cemented tibial components compared with the uncemented components (median = 0.31 mm [0.03–2.98] versus 0.63 mm [0.11–5.19] respectively, p < 0.001, mixed model). The change in migration from 1 to 2 years, however, was equivalent for cemented and uncemented components (mean [SD] 0.06 mm [0.19] and 0.07 mm [0.27] mm respectively, p = 0.6, mixed model).Interpretation — These findings suggest that current thresholds of acceptable migration at 1 year may be better optimized by considering cemented and uncemented tibial components separately as higher early migration of uncemented components was not associated with decreased stability from 1 to 2 years.
Highlights
Elise K LAENDE 1,2, Janie L ASTEPHEN WILSON 1,3, Joanna MILLS FLEMMING 4, Edward R VALSTAR 5, C Glen RICHARDSON 2, and Michael J DUNBAR 1,2
Subjects 518 primary total knee arthroplasty (TKA) with radiostereometric analysis (RSA) markers inserted were available from the Halifax RSA Database
The application of equivalent thresholds of acceptable RSA migration at 1 year for cemented and uncemented TKA appears to be suboptimal, as higher initial migration seen in the first postoperative year for uncemented components was not associated with greater migration between 1 and 2 years, which is an established criterion for predicting longer-term fixation (Ryd et al, 1995)
Summary
Elise K LAENDE 1,2, Janie L ASTEPHEN WILSON 1,3, Joanna MILLS FLEMMING 4, Edward R VALSTAR 5, C Glen RICHARDSON 2, and Michael J DUNBAR 1,2. 2 studies have demonstrated the predictive value of migration 1-year post-operation (Pijls et al 2012b), and the change in migration between 1 and 2 years postoperatively (Ryd et al 1995) in determining long-term survivorship Both of these studies pooled cemented and uncemented tibial components in their analyses. While cemented fixation depends on an immediate mechanical interlock provided by cured bone cement, uncemented fixation requires bone in-growth into the implant surface, which occurs in the early postoperative period (Freeman and Tennant 1992, Dalury 2016) Because of these fundamental differences in the mechanisms of early fixation for cemented and uncemented components, it is unclear if it is appropriate to evaluate cemented and uncemented tibial components under the same thresholds of early migration for prediction of successful fixation
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