INVESTIGATING THE RELATIONSHIP BETWEEN PREOPERATIVE ANATOMY, IMPLANT POSITIONING, AND PATIENT-REPORTED OUTCOMES IN ROBOTIC ARM-ASSISTED TOTAL KNEE ARTHROPLASTY

Despite growing utilisation of Robotic arm-assisted total knee arthroplasty (RA-TKA), there remains a limited understanding of how individual patient anatomy and the resulting intraoperative decisions influence patient-reported outcome measures (PROMs). A retrospective cohort study was undertaken with relevant perioperative data collected from patients undergoing RA-TKA at a large University teaching hospital between 2022-2024. Outcomes were 6 week and 1-year Oxford Knee Scores (OKS) Minimum Clinically Important Difference (MCID) attainment. Multivariable logistic regression (adjusting for age, sex, baseline OKS, and pre-operative Coronal Plane Alignment of the Knee (CPAK) classification) was performed to assess the relationship between OKS MCID attainment and: (1) Change in CPAK classification (2) Implant positioning outside industry defined radiological parameters, and (3) Degree of coronal deformity correction. Statistical significance was set at p≤0.05. A total of 374 patients (mean age 72, 56% female) were included, of which 229 and 142 had 6 week and 1-year OKS available respectively. 82% patients changed CPAK classification post-op, with no significant association with 6 week / 1-year MCID attainment. Femoral or tibial coronal alignment outside the recommended parameters was however associated with significantly greater 1-year MCID attainment (OR 4.57 (1.09-24.35, p = 0.05). Every 1 degree of alignment correction towards neutral was also associated with 3% greater chance of 1-year PROMs MCID attainment (Coefficient 0.03 0.01 to 0.06, p = 0.012). Patient anatomy and implant positioning do appear to influence PROMs following RA-TKA. Further work is required to understand optimal implant placement for specific anatomical knee phenotypes at an individual patient level.