Surgical approach and insert constraint are associated with small differences in patellar tilt after robotic‐assisted total knee arthroplasty: A retrospective comparative radiographic study

Abstract Purpose Patellofemoral alignment remains important after total knee arthroplasty (TKA). Robotic‐assisted functional positioning may reduce the impact of approach‐ and implant‐related factors on the patellofemoral joint. This study evaluated the association between surgical approach and insert constraint with postoperative static patellar alignment following robotic‐assisted TKA. Methods This retrospective comparative radiographic study included 320 primary nonresurfaced robotic‐assisted TKA performed with the MAKO system between March 2021 and December 2024. Patients were divided into four groups: mini‐subvastus condylar‐stabilised (MSV‐CS, n = 134), mini‐subvastus posterior‐stabilised (MSV‐PS, n = 63), medial parapatellar condylar‐stabilised (MPP‐CS, n = 75) and medial parapatellar posterior‐stabilised (MPP‐PS, n = 48). Standardised Merchant axial radiographs at 30° and lateral radiographs were obtained at 2 months and 1 year. Patellar tilt was the primary outcome. Secondary outcomes were qualitative patellar centreing, patellar thickness and the modified Blackburne–Peel index. Two‐way factorial analysis assessed surgical approach, insert constraint and their interaction. Results Baseline characteristics and final intraoperative robotic alignment parameters were comparable across groups. MSV and CS implants were associated with statistically greater patellar tilt than MPP and PS implants, respectively, but the absolute differences were small, approximately 1°. No significant interaction was observed between surgical approach and insert constraint. Patellar height did not differ between groups. Conclusion Robotic‐assisted functional positioning provided consistent static patellofemoral alignment regardless of surgical approach or insert constraint. Although statistically significant differences in patellar tilt were detected, their approximately 1° magnitude suggests a negligible radiographic effect. Their clinical significance remains unknown because clinical outcomes and dynamic patellar tracking were not assessed. Level of Evidence Level IV.