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Gender-specific distribution of knee morphology according to CPAK and functional phenotype classification: analysis of 8739 osteoarthritic knees prior to total knee arthroplasty using artificial intelligence

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Knee Surgery, Sports Traumatology, Arthroscopy Aims and scope

A Correction to this article was published on 07 October 2023

This article has been updated

Abstract

Purpose

Osteoarthritis of the knee is commonly associated with malalignment of the lower limb. Recent classifications, as the Coronal Plane Alignment of the Knee (CPAK) and Functional Phenotype classification, describe the bony knee morphology in addition to the overall limb alignment. Data on distribution of these classifications is not sufficient in large populations. The aim of this study was to analyse the preoperative knee morphology with regard to the aforementioned classifications in long leg radiographs prior to total knee arthroplasty surgery using Artificial Intelligence.

Methods

The cohort comprised 8739 preoperative long leg radiographs of 7456 patients of all total knee arthroplasty surgeries between 2009 and 2021 from our institutional database. The automated measurements were performed with the validated Artificial Intelligence software LAMA (ImageBiopsy Lab, Vienna) and included standardized axes and angles [hip-knee-ankle angle (HKA), mechanical lateral distal femur angle (mLDFA), mechanical medial proximal tibia angle (mMPTA), mechanical axis deviation (MAD), anatomic mechanic axis deviation (AMA) and joint line convergence angle (JLCA)]. CPAK and functional phenotype classifications were performed and all measurements were analysed for gender, age, and body mass index (BMI) within these subgroups.

Results

Varus alignment was more common in men (m: 2008, 68.5%; f: 2953, 50.8%) while neutral (m: 578, 19.7%; f: 1357, 23.4%) and valgus (m: 345, 11.8%; f: 1498, 25.8%) alignment was more common in women. The most common morphotypes according to CPAK classification were CPAK Type I (2454; 28.1%), Type II (2383; 27.3%), and Type III (1830; 20.9%). An apex proximal joint line (CPAK Type VII, VIII and IX) was only found in 1.3% of all cases (n = 121). In men, CPAK Type I (1136; 38.8%) and CPAK Type II (799; 27.3%) were the most common types and women were spread more equally between CPAK Type I (1318; 22.7%), Type II (1584; 27.3%) and Type III (1494; 25.7%) (p < 0.001). The most common combination of femur and tibia types was NEUmLDFA0°,NEUmMPTA0° (m: 514, 17.5%; f: 1004, 17.3%), but men showed femoral varus more often. Patients with a higher BMI showed a significantly lower age at surgery (R2 = 0.09, p < 0.001). There were significant differences between men and women for all radiographic parameters (p < 0.001).

Conclusion

Distribution in knee morphology with gender-specific differences highlights the wide range in osteoarthritic knees, characterized by CPAK and phenotype classification and may influence future surgical planning.

Level of evidence

Level III.

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Acknowledgements

The authors would like to acknowledge Christina Schober for maintaining the databases and Bernd Otzelberger for the statistical support.

Author information

Authors and Affiliations

  1. Michael Ogon Laboratory for Orthopedic Research, Orthopedic Hospital Vienna Speising, Speisinger Straße 109, 1130, Vienna, Austria

    Stephanie Huber, Jennyfer A. Mitterer, Sascha M. Vallant, Sebastian Simon, Florian Hanak-Hammerl, Gilbert M. Schwarz & Jochen G. Hofstaetter

  2. Center for Anatomy and Cell Biology, Medical University Vienna Speising, Währinger Straße 13, 1090, Vienna, Austria

    Stephanie Huber & Gilbert M. Schwarz

  3. 2nd Department, Orthopedic Hospital Vienna Speising, Speisinger Straße 109, 1130, Vienna, Austria

    Sebastian Simon & Jochen G. Hofstaetter

  4. Department of Orthopedics and Trauma-Surgery, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria

    Gilbert M. Schwarz

  5. Department of Orthopedics and Trauma-Surgery, AUVA Trauma Hospital Graz, Göstinger Straße 26, 8020, Graz, Austria

    Antonio Klasan

  6. Johannes Kepler University Linz, Altenberger Strasse 69, 4040, Linz, Austria

    Antonio Klasan

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Contributions

All listed authors contributed substantially to this work (SH, JAM and JGH for study conception and design; SH, JAM and FH for the data collection, SH, JAM, SMV, SS and JGH for the data analysis; SH, GMS, AK, and JGH for the data interpretation; SH, JAM, AK and JGH for the drafting of the manuscript, the figures, and the literature search) and approved the submission to KSSTA.

Corresponding author

Correspondence to Jochen G. Hofstaetter.

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Conflict of interest

There is no agreement with commercial interest related to this study, which would limit or delay the publication in any way or would limit all data generated for the study.

Funding

The “Michael Ogon Laboratory for Orthopaedic Research” received a research grant from “Image Biopsy Lab GmbH”. The collection, analysis, and interpretation of data, writing of the report, and the decision to submit the paper for publication were performed by the authors and not influenced by Image Biopsy Lab.

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EK: 46/2020.

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Huber, S., Mitterer, J.A., Vallant, S.M. et al. Gender-specific distribution of knee morphology according to CPAK and functional phenotype classification: analysis of 8739 osteoarthritic knees prior to total knee arthroplasty using artificial intelligence. Knee Surg Sports Traumatol Arthrosc 31, 4220–4230 (2023). https://doi.org/10.1007/s00167-023-07459-z

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