Risk factors of postoperative valgus malalignment in mobile-bearing medial unicompartmental knee arthroplasty
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The aim of this observational study was to investigate the risk factors of postoperative valgus malalignment after mobile-bearing medial unicompartmental knee arthroplasty (UKA).
We retrospectively evaluated radiographic and surgical characteristics in 122 consecutive Oxford phase 3 UKAs. According to postoperative hip–knee–ankle angle (HKAA), 24 knees were sorted into group valgus with HKAA > 180° and 98 knees were sorted into group non-valgus with HKAA ≤ 180°. Logistic regression was performed to analyze risk factors including age, gender, BMI, side, preoperative limb alignment HKAA, preoperative LDFA, MPTA, FTFA, thickness of polyethylene bearing insert, tibial prothesis size, femoral prothesis size, medial tibial cut thickness, thickness of distal femoral mill, prothesis angle of coronal, and sagittal plane.
The mean mechanical preoperative HKAA of 174.39°±4.23° was corrected to 178.18°±3.49° postoperatively (t = − 13.45, p = 0.000). The mean of postoperative HKAA in valgus group and non-valgus group was 183.45 ± 2.21° and 176.88 ± 2.35°, respectively (t = 12.44, p = 0.000). After statistical analysis with univariate analysis, eight risk factor variables among 16 independent variables were identified as potential predictors with p value ≤ 0.1. Multivariate logistic regression analysis for these eight potential predictors revealed that tibial cut (p = 0.046), LDFA (p = 0.003), MPTA (p = 0.011), and FTFA (p = 0.008) were significant risk factors predicting postoperative valgus malalignment after mobile-bearing UKA.
Preoperative smaller LDFA, FTFA, larger MPTA and less medial tibial cut thickness were significantly associated with postoperative valgus malalignment in mobile-bearing UKA.
KeywordsUnicompartmental knee arthroplasty Risk factor Alignment Radiologic Surgical technique
We would like to thank the patients included in the study for their cooperations. We would also like to thank Mr Omar M. Fakhr, Department of Biological Science, The University of Tulsa, Tulsa, OK, 74104, USA, for the English improvement.
This study was funded by Beijing municipal science and technology commission (Grant number Z171100001017209), National Natural Science Foundation of China (Grant number 81703896), and the Capital Health Research and Development of Special (Grant number 2016-2-4062).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
Informed consent for study participation was obtained from each patient.
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