No difference in early outcomes between cementless and cemented primary total knee arthroplasties

Aims There has recently been renewed interest in cementless primary total knee arthroplasty (TKA). Some authors have suggested that micromotion of cementless components before osseointegration may result in early postoperative pain. However, the existing studies have not used extensive, robust methodologies including the reporting of the minimal clinically important difference (MCID), substantial clinical benefit (SCB), patient-acceptable symptom state (PASS), and ‘time to achieve MCID’ analyses. Intuitively, MCID reflects ‘feeling better’, SCB reflects ‘feeling much better’, PASS reflects ‘feeling good’, and time to achieve MCID reflects ‘how long it took to feel better’. The aim of this study was to compare the MCID, SCB, PASS, and time to achieve MCID between cementless and cemented primary TKAs. Methods A group of 420 cementless primary TKAs were identified from a prospectively maintained multi-institutional arthroplasty registry. A 1:3 propensity score match identified 1,260 cemented primary TKAs with similar characteristics. The Knee Injury and Osteoarthritis Outcome Score-Physical Function Short-form (KOOS-PS) score was collected preoperatively and at many postoperative times. Literature-derived MCID, SCB, and PASS thresholds were used. Time to achieve MCID was assessed using survival curves with interval censoring. This is a statistical technique in survival analysis which accounts for variations in the times that scores are collected, enabling robust inferences of when the achievement of MCID is most likely to have occurred, even if it was at an unknown time between two assessments. Results Cementless and cemented primary TKAs did not significantly differ in the proportion of patients achieving MCID (72% (302/420) vs 73% (920/1,260); p = 0.658), SCB (57% (240/420) vs 61% (769/1,260); p = 0.159), or PASS (68% (286/420) vs 71% (895/1,260); p = 0.254). In the interval-censored analysis, there was no significant difference in time to achieve MCID (2.97 to 3.03 months vs 3.27 to 3.33 months; p = 0.079). Conclusion Cementless and cemented primary TKAs had similar rates of MCID, SCB, and PASS achievement and comparable time to achieve MCID. As the use of cementless TKA increases, patients can be assured that the likelihood and timelines for clinically meaningful early improvement are similar to those of cemented TKA. Cite this article: Bone Joint J 2025;107-B(12):1263–1271.