• Tomoyuki Kamenaga, Naoki Nakano, Kazunari Ishida, Masanori Tsubosaka, Yuichi Kuroda, Shinya Hayashi, Takehiko Matsushita, Takahiro Niikura, Ryosuke Kuroda, and Tomoyuki Matsumoto.
• Department of Orthopaedic Surgery, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan.
• Arch Orthop Trauma Surg. 2021 Sep 8.

IntroductionThe presence of tibiofemoral subluxation (TFS) in patients with unicompartmental arthritis, a potential contraindication to unicompartmental knee arthroplasty (UKA), remains controversial and is not commonly discussed. This study aimed to determine the predictability of postoperative TFS before surgery and the effect of TFS on clinical outcomes after fixed-bearing UKA.Materials And MethodsIn total, 70 patients with anteromedial osteoarthritis and osteonecrosis of the knee who underwent fixed-bearing UKA from January 2015 to January 2017 were included. The preoperative TFS was assessed using plain anteroposterior and valgus stress radiographs. The patients were classified into three groups as follows: group A (acceptable TFS, n = 36) comprising patients with preoperative TFS less than 5.0 mm; group C (correctable TFS, n = 17) comprising patients with preoperative TFS of more than 5.0 mm but corrected to less than 5.0 mm under valgus stress; and group U (uncorrectable TFS, n = 17) comprising patients with preoperative TFS of more than 5.0 mm under valgus stress. Patient-derived clinical scores were assessed with the 2011 Knee Society Score preoperatively and 2 years postoperatively. The results were compared among the three groups using analysis of variance.ResultsGroup U showed significantly higher postoperative TFS than groups A and C. Improvements in "symptoms" and "patient satisfaction" scores 2 years after surgery were significantly higher in groups A and C than in group U.ConclusionPreoperative assessment of TFS under valgus stress could be a predictor of postoperative TFS. Furthermore, preoperative uncorrectable TFS could increase pain and decrease patient satisfaction 2 years after undergoing fixed-bearing UKA.© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.

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