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Publications

Journal Article Ahead of print

PubMed: 42360171 DOI: 10.1002/ksa.70506

Coronal alignment behaviour across the knee range of motion is associated with constitutional alignment and soft-tissue balance: The REAL HKA classification.

Knee Surg Sports Traumatol Arthrosc

Authors: Nikolaos Mylonakis, Eustathios Kenanidis, Alexander Maslaris, Peter Keyes Sculco, Eleftherios Tsiridis

Affiliations

  • Academic Orthopaedic Department, Papageorgiou General Hospital, School of Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece. International Center for Arthroplasty & Robotic Orthopaedic Surgery Orthopaedic Centre, Thessaloniki, Greece.
  • Academic Orthopaedic Department, Papageorgiou General Hospital, School of Medicine, Faculty of Health Sciences, Aristotle University of Thessaloniki, Thessaloniki, Greece.
  • International Center for Arthroplasty & Robotic Orthopaedic Surgery Orthopaedic Centre, Thessaloniki, Greece.
  • Department of Orthopaedics, Traumatology and Rehabilitative Medicine, University Hospitals Greifswald, Greifswald, Germany.
  • Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences (NDORMS), University of Oxford, Oxford, UK.
  • Department of Orthopedic Surgery, Hospital for Special Surgery, New York, New York, USA.

Abstract

PURPOSE

To evaluate intraoperative, pre-resection coronal alignment throughout the range of motion (ROM) in knees undergoing robotic-assisted total knee arthroplasty (ra-TKA), and to assess its relationship with the Coronal Plane Alignment of the Knee (CPAK) and the Robotic Evaluation of Articular Laxity (REAL) classifications.

METHODS

Three hundred fifty-two consecutive knees undergoing primary ra-TKA using functional alignment were included in this single-surgeon, platform and implant retrospective cohort study. Intraoperative coronal laxity was assessed before bone resections at 0°, 45° and 90° of flexion, under surgeon-applied manual varus and valgus stress without a tensioning device. Laxity was recorded as the maximum angular deviation from the neutral coronal axis and shown as an excursion bar. At each flexion angle, a coronal phenotype was defined: neutral if the bar crossed the neutral axis, varus if entirely within negative hip-knee-ankle (HKA) values and valgus if entirely within positive. By combining the phenotypes at 0°, 45° and 90°, a composite 'REAL HKA phenotype' was derived. Associations between phenotype stability and the CPAK and REAL classifications were evaluated.

RESULTS

Fourteen phenotypes were identified. Overall, 73.6% of knees demonstrated a stable phenotype. Phenotype stability varied significantly across CPAK groups (χ 2 = 60.12, p < 0.001) and was lowest in valgus knees. Within each alignment group, apex direction influenced phenotype stability; Class IV had lower odds than I (odds ratio [OR] 0.28, 95% confidence interval [CI] 0.11-0.72) and Class V had lower odds than II (OR 0.23, 95% CI 0.09-0.60). REAL flexion grouping was also associated with stability (χ 2 = 9.94, p = 0.007). Multivariable analysis confirmed independent associations of CPAK and REAL flexion grouping with phenotype stability (χ 2 = 63.26, p < 0.001, Nagelkerke R 2 = 0.24).

CONCLUSIONS

Coronal behaviour across the ROM varies in knees undergoing ra-TKA. Both constitutional alignment and soft-tissue balance are associated with dynamic coronal phenotype stability.

LEVEL OF EVIDENCE

Level IV, retrospective case series.

MeSH

Range Of Motion, Articular, Phenotype, Classification, Arthroscopy, Tissues, Arthroplasty, Replacement, Knee, Surgeons