The association between tibial slope and posterior tibial tilting, not wear, in uncemented total knee arthroplasty : a secondary analysis of a five-year radiostereometry study

The primary objective of this study was to evaluate the influence of postoperative slope on the five-year tibial component migration and wear following uncemented cruciate-retaining condylar-stabilized total knee arthroplasty (TKA). Secondary objectives included the association between postoperative slope and clinical and functional outcomes. This observational study was a secondary analysis of a randomized controlled trial of 93 TKAs on insert materials. Tibial component migration and insert wear were measured across three postoperative slope groups (small (≤ 5°), intermediate (6° to 9°), and large (≥ 10°)) using radiostereometric analysis at three, six, 12, 24, and 60 months postoperatively. Patient-reported outcome measures were collected preoperatively and at all follow-up timepoints. There was an association between tibial component migration and postoperative tibial slope: the group with the largest postoperative tibial slope showed the largest posterior tilting. At five years, there was no difference in insert wear between the small, intermediate, and large slope groups. There was also no association between postoperative slope and functional or patient-reported outcomes. TKA implanted with more than 10° of slope showed increased tibial component migration and posterior tilting, independent of the native slope. At five years, there was no influence of slope on wear or functional outcomes.