Review Article

A systematic review of radiological outcomes and implant positioning in robotic-assisted functionally aligned robotic total knee arthroplasty

¹ Orthopaedics Surgery and Sports Medicine Department, Hôpital de la Croix-Rousse, Lyon, France
² Third Academic Department of Orthopaedics, Papageorgiou General Hospital, Thessaloniki 56403, Greece
³ Orthopedic Surgery Department, Lyon Ortho Clinic, Clinique de la Sauvegarde, Lyon, France
⁴ Ortopedia e Traumatologia, Fondazione Poliambulanza Istituto Ospedaliero, Via Bissolati 57, 25124 Brescia, Italy
⁵ Fondazione Policlinico Universitario Campus Bio-Medico, Roma, Italy
⁶ Second Department of Orthopaedics, Hygeia General Hospital of Athens, Greece
⁷ School of Health Rehabilitation Sciences, University of Patras, Greece
⁸ IFSTTAR, LBMC UMR_T9406, Univ Lyon, Claude Bernard Lyon 1 University, Lyon, France

^* Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it. ; This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 11 December 2025
Accepted: 22 December 2025

Abstract

Introduction: Functional alignment (FA) or functional knee positioning is a patient-specific strategy for total knee arthroplasty (TKA) that utilizes robotics to balance coronal, sagittal, and axial planes while preserving joint-line orientation and soft-tissue tension within predefined guardrails. Although early clinical outcomes are encouraging, the radiographic profile and workflow consistency of robotic FA have not been clearly synthesized. Methods: In accordance with PRISMA guidelines, English-language studies of primary robotic FA-TKA with ≥2-year follow-up were searched. Eligible designs included RCTs, prospective/retrospective cohorts, and large case series (≥50 patients). Information on pre- and postoperative coronal alignment [hip–knee–ankle angle (HKA), lateral distal femoral angle (LDFA), medial proximal tibial angle (MPTA)], component positioning (femoral valgus/rotation/flexion; tibial varus/rotation/slope), and explicit FA workflow boundaries (guardrails) was extracted. Results: Twenty-one cohorts (5,360 knees) reported at least one radiographic or workflow endpoint. Preoperatively, the predominant deformity was varus. Postoperatively, limb alignment converged near neutral: HKA clustered around 178–179.5°, with LDFA ~89–91° and MPTA ~87–89°. Component positions were tightly distributed within FA targets: femoral valgus ≈ 0.5–1.5°, tibial varus ≈ ~3°, femoral flexion ~6–9°, and tibial slope ~0–3°; tibial rotation was overwhelmingly referenced to Akagi’s line, and femoral rotation to the TEA in most series. Reported guardrails showed strong convergence: typical workflows included femoral valgus −3° to +6°, tibial varus 0–6°, tibial slope 0–3°, and femoral ER ~3–6° to TEA. Across cohorts, achieved radiographs closely tracked these limits, indicating high adherence and reproducibility. Most observational studies had a moderate risk of bias; the lone RCT was low risk. Discussion: Robotic FA-TKA delivers a radiographic profile with slight femoral valgus and modest tibial varus, while keeping components within narrow, pre-specified guardrails. Level of evidence: Level III, systematic review and meta-analysis.