Background and purpose: Microplasty instrumentation was introduced for a more consistent surgical implantation technique, especially component alignment and tibial resection level, of the Oxford medial unicompartmental knee replacement (UKA) and thereby aims to improve UKA survival. This study aimed to assess the 5-year risk for revision and reasons for revision of the Oxford medial UKA using the new instrumentation (Microplasty) with its predecessor, i.e., conventional instrumentation (Phase 3). Patients and Methods: Data of all medial UKAs from the Dutch Arthroplasty Register (LROI) between 2007-2019 were collected. Type of instrumentation was divided into new (Microplasty) and conventional instrumentation. Kaplan-Meier analysis was performed to calculate 5-year cumulative revision percentage with any reason for revision as endpoint. A multivariable Cox regression with outcome revision of UKA adjusted for age, gender, American Society of Anesthesiologists-score, surgical history, and type of fixation was performed. Additionally, reasons for revision at 3-year were assessed and tested through Fisher’s exact tests. Results: 12,867 Oxford medial UKAs, 8,170 using new and 4,697 using conventional instrumentation, were included. The 5-year revision percentage was 9.2% (CI 8.4-10.1%) for UKAs using the conventional and 6.1% (CI 5.4-6.7%) for new instrumentation. The adjusted hazard ratio for revision at 5-year follow-up was 0.68 (CI 0.59-0.79) in favor of UKAs using the new instrumentation. Malalignment was less frequently registered as reason for revision in UKAs using the conventional compared to the new instrumentation (16.2% versus 7%; p=0.001). Interpretation: Our results show a reduced 5-year risk for revision of the medial Oxford UKAs using the new compared to the conventional instrumentation. This might be the result of a lower revision rate for malalignment in UKAs using the new instrumentation.

背景和目的：微整形器械的引入是为了使牛津内侧单间室膝关节置换术 (UKA) 的手术植入技术更加一致，特别是组件对齐和胫骨切除水平，从而提高 UKA 的生存率。本研究旨在评估使用新器械（微整形）及其前身（即传统器械）对牛津内侧 UKA 进行翻修的 5 年风险和原因（第 3 阶段）。患者和方法：收集了 2007 年至 2019 年荷兰关节置换术登记册 (LROI) 中所有内侧 UKA 的数据。仪器类型分为新型（微整形）仪器和传统仪器。进行 Kaplan-Meier 分析以计算 5 年累积修订百分比，以任何修订原因作为终点。进行多变量 Cox 回归，并根据年龄、性别、美国麻醉医师协会评分、手术史和固定类型调整 UKA 结果修正。此外，还通过 Fisher 精确检验评估和测试了 3 年修订的原因。结果：纳入 12,867 名牛津医学 UKA，其中 8,170 名使用新仪器，4,697 名使用传统仪器。使用传统仪器的 UKA 的 5 年修订百分比为 9.2% (CI 8.4-10.1%)，而新仪器的 5 年修订百分比为 6.1% (CI 5.4-6.7%)。5 年随访时修正的调整后风险比为 0.68 (CI 0.59-0.79)，有利于 UKA 使用新仪器。与新仪器相比，使用传统仪器的 UKA 中，由于排列不正而被记录为修正原因的频率较低（16.2% 与 7%；p=0.001）。解释：我们的结果显示，与传统器械相比，使用新器械修复内侧 Oxford UKA 的 5 年风险降低了。这可能是由于使用新仪器对 UKA 中的排列不齐修正率较低的结果。