Abstract
Background
To better define the optimal alignment target for medial fixed-bearing unicompartmental
knee arthroplasty (UKA), this study compares the postoperative mechanical alignment
of well-functioning UKAs against 2 groups of failed UKAs, including revisions for
progression of lateral compartment osteoarthritis (“Progression”) and revisions for
aseptic loosening or subsidence (“Loosening”).
Methods
From our prospective institutional database of 3351 medial fixed-bearing UKAs performed
since 2000, we identified 37 UKAs revised for Progression and 61 UKAs revised for
Loosening. Each of these revision cohorts was matched based on age at surgery, gender,
body mass index, and postoperative range of motion with unrevised UKAs that had at
least 10 years of follow-up and a Knee Society Score of 70 or greater without subtracting
points for alignment (“Success” groups). Postoperative alignment was quantified by
the hip-knee-ankle (HKA) angle measured on long-leg alignment radiographs.
Results
The mean HKA angle at 4-month follow-up for the Progression group was 0.3° ± 3.6°
of valgus compared to 4.4° ± 2.6° of varus for the matched Success group (P < 0.001). For the Loosening group, the mean HKA angle was 6.1° ± 3.1° of varus versus
4.0° ± 2.7° of varus for the matched Success group (P < 0.001).
Conclusions
Patients with well-functioning UKAs at 10 years exhibited mild varus mechanical alignment
of approximately 4°, whereas patients revised for progression of osteoarthritis averaged
more valgus and those revised for loosening or subsidence averaged more varus. The
optimal mechanical alignment for medial fixed-bearing UKA survival with contemporary
polyethylene is likely slight varus.
Keywords
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Article info
Publication history
Published online: September 28, 2019
Accepted:
September 24,
2019
Received in revised form:
August 29,
2019
Received:
June 27,
2019
Footnotes
Funding: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. The Inova Health System provides financial support for the Anderson Orthopaedic Research Institute (AORI) but does not restrict or define the scope of the research undertaken by AORI.
One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to https://doi.org/10.1016/j.arth.2019.09.038.
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