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Predicting valgus malalignment after mobile-bearing UKA using a new method: the arithmetic HKA of the arthritic knee

  • Knee Arthroplasty
  • Published:
Archives of Orthopaedic and Trauma Surgery Aims and scope Submit manuscript

Abstract

Background

Valgus malalignment is one of the most common reasons for the progression of osteoarthritis in the lateral compartment of the knee after mobile-bearing unicompartmental knee arthroplasty (UKA). The arithmetic hip-knee-ankle angle (aHKA) of the Coronal Plane Alignment of the Knee (CPAK) classification could reflect the constitutional alignment of the arthritic knee. The purpose of this study was to observe the relationship between the aHKA and valgus malalignment after mobile-bearing UKA.

Methods

This retrospective study was conducted using 200 knees undergoing UKA from January 1, 2019, to August 1, 2022. These radiographic signs, including preoperative hip–knee–ankle angle (HKA), mechanical proximal tibial angle (MPTA), mechanical lateral distal femoral angle (LDFA), and postoperative HKA, were measured using standardized weight-bearing long-leg radiographs. Patients with postoperative HKA > 180° and postoperative HKA ≤ 180° were classified as the valgus group and non-valgus group, respectively. The aHKA was calculated as 180° + MPTA − LDFA in this study, which had the same meaning as that (aHKA = MPTA − LDFA) in the CPAK classification. The Spearman correlation analysis, the Mann–Whitney U test, the chi-square test, the Fisher’s exact test, and multiple logistic regression were used in the study.

Results

Of the 200 knees included in our study, 28 knees were classified as the valgus group, while 172 knees were in the non-valgus group. The mean ± standard deviation (SD) of aHKA (all groups) was 177.04 ± 2.58°. In the valgus group, 11 knees (39.3%) had a value of aHKA > 180°, while 17 knees (60.7%) had a value of aHKA ≤ 180°. In the non-valgus group, 12 knees (7.0%) had a value of aHKA > 180°, while 160 knees (93.0%) had a value of aHKA ≤ 180°. In Spearman correlation analysis, aHKA was positively correlated with postoperative HKA (r = 0.693, p < 0.001). In univariate analysis, preoperative HKA (p < 0.001), LDFA (p = 0.02), MPTA (p < 0.001), and aHKA (p < 0.001) showed significant differences between the valgus and non-valgus groups. Variables with p < 0.1 in univariate analysis were further analyzed using multiple logistic regression analysis, and the variable-aHKA (> 180° vs ≤ 180°, odds ratio (OR) = 5.899, 95% confidence interval (CI) = 1.213 to 28.686, and p = 0.028) was expressed as the risk factor of postoperative valgus malalignment.

Conclusion

The aHKA is correlated with the postoperative alignment of mobile-bearing UKA and a high aHKA (> 180°) will increase the risk of postoperative valgus malalignment. Therefore, mobile-bearing UKA should be performed with caution in patients with preoperative aHKA > 180°.

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All of the data are available in contact with the correspondence author.

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Funding

This study was funded by the Capital Health Research and Development of Special (Grant number 2020-2-4067), National Natural Science Foundation of China (Grant number 82072494, 81972130), and Elite Medical Professionals project of China-Japan Friendship Hospital (Grant number ZRJY2021-GG08).

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Author notes

  1. Changquan Liu and Handong Chen contributed equally to this work.

Authors and Affiliations

  1. China-Japan Friendship Hospital (Institute of Clinical Medical Sciences), Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China

    Changquan Liu, Qidong Zhang & Wanshou Guo

  2. Department of Orthopaedic Surgery, China-Japan Friendship Hospital, Beijing, China

    Changquan Liu, Handong Chen, Cheng Huang, Qidong Zhang & Wanshou Guo

  3. Beijing University of Chinese Medicine, Beijing, China

    Handong Chen

  4. Department of Orthopaedic Surgery, Peking University China-Japan Friendship School of Clinical Medicine, Beijing, China

    Juncheng Ge

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  1. Changquan Liu
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Contributions

CL, QZ and WG designed the study. CL and JG did the data collection. CL, HC and CH did the data analysis. CL and HC wrote the article. QZ and WG revised the article. All authors read and approved the final manuscript.

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Correspondence to Qidong Zhang or Wanshou Guo.

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All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The study was approved by the institutional review board of China-Japan Friendship Hospital (approval number 2020–50-k28).

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Liu, C., Chen, H., Ge, J. et al. Predicting valgus malalignment after mobile-bearing UKA using a new method: the arithmetic HKA of the arthritic knee. Arch Orthop Trauma Surg 143, 6381–6391 (2023). https://doi.org/10.1007/s00402-023-04921-y

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