Designing tibial components for total knee arthroplasty (TKA) aims to maximise anatomic coverage while minimising implant overhang and malrotation, because poor fit or rotational mismatch can impair kinematics, increase pain, and worsen outcomes. The amount of cortical bone supporting a tibial baseplate also influences the risk of subsidence and loosening. Ethnic differences in tibial anatomy (for example, AP and ML dimensions) have been described and raise the need for implant shapes that accommodate population variation.
This study evaluated the virtual anatomical fit of a newly developed tibial implant design, oneKNEE® (B. Braun Aesculap), compared with three established tibial systems—PFC Sigma®, Attune®, and Columbus®—using population-specific statistical shape models (SSM). The primary endpoints were tibial bony coverage and a cortical support score; secondary assessments included AP/ML dimensional relationships.
SSMs representing Caucasian and Asian populations were generated from CT scans of osteoarthritic patients who were candidates for standard TKA (Kellgren–Lawrence grades 1–3). The Caucasian model used 120 anatomies (65 female, 55 male; mean age 68 ± 10 years), and the Asian model used 112 anatomies (75 female, 37 male; mean age 65 ± 12 years). The cohort intentionally excluded patients with severe deformities or anatomies requiring complex reconstruction or bespoke implants, thereby reflecting routine primary TKA candidates.
From each SSM multiple bone models of different sizes were derived (seven sizes from the Caucasian SSM and five from the Asian SSM). In addition, the analysis included individual borderline anatomies to represent anatomical extremes (14 Caucasian and 12 Asian individuals). Three-dimensional bone models were reconstructed from CT images using established segmentation software.
A consistent reference system was applied across all models: the proximo-distal (PD) axis connected the midpoint of the malleoli to the midpoint of the tibial spines; the antero-posterior (AP) axis used the Akagi Line (medial third of the tibial tuberosity to the PCL attachment) projected onto the axial plane; and the medio-lateral (ML) axis was orthogonal to AP and PD.
Virtual tibial resections were performed perpendicular to the mechanical axis at 6 mm below the deepest point of the healthy plateau, assuming 2 mm cartilage thickness. Tibial components were positioned by senior knee surgeons following strict protocols; the source reports that these protocols guided alignment and sizing consistently, but additional procedural details and stepwise placement parameters beyond these descriptions were not fully reported in the source.
The anatomical fit assessment compared implants on:
The study also analysed average anatomies separately from less average (borderline) anatomies to assess performance across typical and extreme morphologies.
Reported bony coverage for the evaluated implants varied by population and design era. Established designs had coverage in the range of 82.9% to 88.4%, whereas more recently introduced designs achieved 85.0% to 91.2% coverage. Across all tested models, the oneKNEE® design demonstrated the highest bony coverage and cortical support score, followed in rank by Attune®, Columbus®, and PFC Sigma®.
For average SSM anatomies, oneKNEE® achieved statistically significant improvements in both percent bony coverage and cortical support compared with Columbus® and PFC Sigma® (P < 0.01). In the analyses of less average anatomies, oneKNEE® showed statistically superior bony coverage relative to PFC Sigma®, while differences in cortical support were not significant for those anatomies.
The analysis applied global tests for homogeneity and Dunnett’s tests for multiple comparisons as described in the source. Reported P-values identified significant advantages for oneKNEE® over specific comparator implants in predefined comparisons (notably P < 0.01 versus Columbus® and PFC Sigma® for average anatomies). Full statistical tables, numeric values for coverage and cortical scores per implant, and detailed subgroup statistics are presented in the original article figures and tables referenced by the authors.
The computational SSM-based comparison indicates a design-level improvement in virtual anatomical fit for the oneKNEE® tibial component across Caucasian and Asian population models. The authors emphasise that these findings are theoretical and derived from virtual placement and modelling: they do not substitute for biomechanical testing or clinical outcome data. The cohort excluded extreme deformities and complex arthritic presentations, so results apply to routine primary TKA anatomy rather than all possible clinical scenarios.
Limitations reported or implied by the source include the virtual nature of the evaluation, the absence of in vitro biomechanical validation or in vivo clinical outcome correlation within this study, and that some procedural placement details were not fully described in the summary provided. The authors state that biomechanical and clinical validation are required to confirm whether the observed modelled advantages translate into clinical benefits.
All raw data files used in the study are available on Zenodo under the DOIs cited in the article. The authors declared no specific funding for the work. Several authors are employees of B. Braun Aesculap and others serve as consultants for the company; these competing interests are disclosed in the source document.