Abstract
Background
A forgotten joint is considered the ultimate goal of joint replacement. We aim to
explore the predictive factors of a forgotten joint after fixed-bearing unicompartmental
knee arthroplasty (UKA).
Methods
This retrospective cohort study used prospectively collected data from 302 cases of
medial-compartment UKA with a minimum of 2-year follow-up. The primary outcome was
the achievement of a forgotten joint after UKA, according to the Forgotten Joint Score
(FJS-12) at the last follow-up. Patients with FJS-12 > 84 were considered to have
forgotten UKA. Univariate and multivariate logistic regression analyses were conducted
with preoperative patient characteristics and surgery-related factors as potential
predictors.
Results
Of patients, 94 (31.1%) achieved a forgotten joint post-surgery. Multivariate logistic
regression analysis revealed that preoperative hip-knee-ankle angle (HKAA), anatomic
lateral distal femoral angle (aLDFA), and postoperative HKAA and HKAA changes were
independent predictors of a forgotten joint. The probability of achieving a forgotten
joint increased by 29% (OR = 1.29, 95% CI: 1.12–1.51) with a 1° increase in aLDFA.
Preoperative HKAA, postoperative HKAA, HKAA changes (ΔHKAA), and outcomes exhibited
a non-linear relationship. The probability of achieving a forgotten joint was the
highest with preoperative HKAA > 172.0°, postoperative HKAA of 176.0–178.5°, and ΔHKAA < 5.5°.
Conclusion
To achieve the forgotten joint state, the ideal HKAA range after medial fixed-bearing
UKA is 176.0–178.5° and ΔHKAA should be <5.5°. Patients with smaller preoperative
aLDFA and HKAA have a lower probability of achieving a forgotten joint after UKA.
Keywords
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Article info
Publication history
Published online: June 23, 2022
Accepted:
June 9,
2022
Received:
March 27,
2022
Identification
Copyright
© 2022 Elsevier B.V. All rights reserved.
