RANDOMIZED CONTROLLED TRIAL COMPARING TRADITIONAL WITH ENHANCED-FIXATION DESIGNS OF A NOVEL CEMENTED TOTAL KNEE ARTHROPLASTY TIBIAL COMPONENT

The Attune S+ total knee replacement (TKR) is a recently released device featuring a novel backside surface design and surface finish on the tibial baseplate, intended to enhance cement bonding. This study aims to study the effect of the enhanced fixation surface on tibial baseplate stability by comparing the Attune S+ to the original Attune tibial baseplate using model-based radiostereometric analysis (MBRSA). Fifty-four patients requiring primary total knee arthroplasty for end-stage osteoarthritis were enrolled at two Canadian centres. Patients were randomized to receive either the Attune or Attune S+ tibial baseplate. Surgical technique was standardized between the two sites. Patients underwent supine RSA imaging at 6 weeks (baseline), 3, 6, 12, and 24 months following surgery, with an additional weight-bearing RSA image obtained at 24 months at one site. The primary study outcome was progression of tibial baseplate subsidence between 12 and 24 months which was compared against a literature threshold of 0.2mm for “acceptable” migration. Patient reported outcome measures were captured throughout the study, including Oxford-12 Knee Score (OKS), European Quality of Life (EQ-5D), Knee Replacement Expectation Survey (KRES), Pain Catastrophizing Score (PCS), Patient's Knee Implant Performance (PKIP), UCLA Activity Score (UCLA), visual analogue scales for pain and satisfaction (Pain VAS, Sat VAS). Statistical analysis utilized paired and unpaired t-tests with significance set at p≤0.05. Forty-four patients (26 females) completed the study to 24 months; 6 were withdrawn, 1 suffered a hip fracture and did not complete follow-up, and 3 were not analyzed due to RSA bead issues. Mean patient age was 66 years (SD=6.7) and body mass index was 32.3kg/m2 (SD=5.8). Tibial baseplate subsidence between 12 and 24 months was not statistically different between Attune (0.000±0.044mm) and Attune S+ (0.018±0.023mm) groups (p=0.128). No patients demonstrated ≥0.2mm of baseplate subsidence between 12 and 24 months. No significant differences in cumulative tibial baseplate subsidence or other directions of motion were found at any follow-up (p > 0.100). Weight bearing exams performed on 12 Attune and 12 Attune S+ patients revealed no difference in baseplate subsidence (p=0.935) and virtually no induced movement compared to non-weight-bearing (0.001±0.026mm). All patients reported significant functional improvement from baseline to 12 and 24 months after surgery. No statistically significant differences were found between patient groups but the PCS, EQ-5D, and Pain VAS scores trended (0.1>p>0.05) towards statistical difference at select post-operative intervals. However, this study was not powered to detect meaningful differences in such outcomes. Our study demonstrates that the Attune and Attune S+ tibial baseplate variants achieve rigid cemented fixation that is maintained to 2 years post-surgery with acceptably low-risk potential for aseptic loosening as well as similar patient-reported health and functional outcomes.