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Knees with anteromedial osteoarthritis show a substantial phenotypic variation prior and following medial unicompartmental knee arthroplasty

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Knee Surgery, Sports Traumatology, Arthroscopy Aims and scope

Abstract

Purpose

The primary aim of this study was to evaluate the phenotypic variation using the Coronal Plane Alignment of the Knee (CPAK) classification among 1000 knees with anteromedial osteoarthritis (OA) both prior to and following medial unicompartmental knee arthroplasty (UKA). The secondary aim of this study was to investigate whether knees maintained their preoperative CPAK phenotype and to evaluate the phenotypic alterations following medial UKA.

Methods

The CPAK classification was used to analyze 1000 knees that underwent medial UKA as treatment for anteromedial OA. Knees were categorized into nine distinct CPAK phenotypes based on their arithmetic hip–knee–ankle angle (aHKA), which estimates the pre-arthritic alignment, and joint line obliquity (JLO), both pre- and postoperatively. Phenotypic variation was analyzed by sex and age, and the phenotypic alterations following medial UKA were evaluated by phenotype.

Results

Preoperatively, CPAK phenotype I had the highest prevalence (45.0%). Among males, the preoperative prevalence of CPAK phenotype I was significantly higher compared to females (53.2% vs. 35.0%, respectively; p ≤ .001), whereas females exhibited a significantly higher occurrence of CPAK phenotype V compared to males (9.8% vs. 4.4%, respectively; p ≤ .015). Following medial UKA, CPAK phenotype II had the highest prevalence (53.3%). Overall, 45.1% of knees maintained their preoperative CPAK phenotype following medial UKA, which was most frequently observed among CPAK phenotype II (67.7%) and III (65.8%).

Conclusion

There is a substantial variation in CPAK phenotypes among knees with anteromedial OA, as well as following treatment with medial UKA. This variability challenges the assumption of uniform characteristics among knees with an identical wear pattern associated with anteromedial OA and emphasizes the complexity and variability of this specific form of OA.

Level of evidence

III, Retrospective cohort study.

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Funding

This study received no funding.

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Authors and Affiliations

  1. Hospital for Special Surgery, Department of Orthopaedic Surgery, Computer Assisted Surgery Center and Sports Medicine, Weill Medical College of Cornell University, 535 East 70th Street, New York, NY, 10021, USA

    G. V. ten Noever de Brauw, T. Bayoumi, L. V. Ruderman & A. D. Pearle

  2. Department of Orthopaedic Surgery, Amsterdam UMC Location University of Amsterdam, Meibergdreef 9, Amsterdam, The Netherlands

    G. V. ten Noever de Brauw, T. Bayoumi & G. M. M. J. Kerkhoffs

  3. Amsterdam Movement Sciences, Sports, Amsterdam, The Netherlands

    G. M. M. J. Kerkhoffs

  4. Department of Orthopaedic Surgery, Medische Kliniek Velsen, Velsen-Noord, The Netherlands

    H. A. Zuiderbaan

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  1. G. V. ten Noever de Brauw
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  2. T. Bayoumi
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  3. L. V. Ruderman
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Contributions

All authors made substantial contributions and approved the final manuscript for submission to KSSTA. GVtNdB: Conceptualization; Data collection; Data analysis; Methodology; Writing—original draft; Writing—review and editing. TB, GMMJK, ADP, HAZ: Conceptualization; Writing review and editing. LVR: Conceptualization; Data collection; Writing—review and editing.

Corresponding author

Correspondence to G. V. ten Noever de Brauw.

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Conflict of interest

Dr. Andrew D. Pearle is a consultant of Smith & Nephew and DePuy Synthes. Dr. Hendrik A. Zuiderbaan is a consultant for Smith & Nephew. The other authors declare to have no potential conflict of interest.

Ethical approval

Internal Review Board approval of Hospital for Special Surgery was obtained prior to the start of the study (IRB #2022-1401).

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Informed consent was not applicable for this study.

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ten Noever de Brauw, G.V., Bayoumi, T., Ruderman, L.V. et al. Knees with anteromedial osteoarthritis show a substantial phenotypic variation prior and following medial unicompartmental knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 31, 5579–5590 (2023). https://doi.org/10.1007/s00167-023-07603-9

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