Frailty is a well-established risk factor in patients undergoing total knee arthroplasty (TKA). How age modifies the impact of frailty on outcomes in these patients, however, remains unknown. In this study, we aimed to describe and evaluate the applicability of a novel risk stratification tool—the age-adjusted modified Frailty Index (aamFI)—in patients undergoing TKA. A national database was queried for all patients undergoing primary TKA from 2015 to 2019. There were 271,271 patients who met inclusion criteria for this study. First, outcomes were compared between chronologically young and old frail patients. In accordance with previous studies, the 75th percentile of age of all included patients (73 years) was used as a binary cutoff. Then, frailty was classified using the novel aamFI, which constitutes the 5-item mFI with the addition of 1 point for patients ≥73 years. Multivariable logistic regressions were then used to investigate the relationship between aamFI and postoperative outcomes. Frail patients ≥73 years had a higher incidence of complications compared to frail patients <73 years. There was a strong association between aamFI and complications. An aamFI of ≥3 (reference aamFI of 0) was associated with an increased odds of 30-day mortality (odds ratio [OR] 8.6, 95% CI 5.0-14.8), any complication (OR 3.1, 95% CI 2.9-3.3), deep vein thrombosis (OR 1.5, 95% CI 1.2-1.8), and nonhome discharge (OR 6.1, 95% CI 5.8-6.4; all < .001). Although frailty negatively influences outcomes following TKA in patients of all ages, chronologically old, frail patients are particularly vulnerable. The aamFI accounts for this and represents a simple, but powerful tool for stratifying risk in patients undergoing primary TKA.

中文翻译：

---

对于接受初次全膝关节置换术的患者来说，衰弱的影响取决于年龄：年龄调整后的改良衰弱指数

虚弱是接受全膝关节置换术（TKA）患者的一个公认的危险因素。然而，年龄如何改变虚弱对这些患者预后的影响仍然未知。在这项研究中，我们的目的是描述和评估一种新型风险分层工具——年龄调整的改良衰弱指数（aamFI）——在接受 TKA 的患者中的适用性。查询了 2015 年至 2019 年所有接受初次 TKA 的患者的国家数据库。共有 271,271 名患者符合本研究的纳入标准。首先，比较了年轻和年老体弱患者的结果。根据之前的研究，所有纳入患者的年龄（73 岁）的第 75 个百分位数被用作二元截止值。然后，使用新型 aamFI 对衰弱进行分类，该方法构成 5 项 mFI，对于≥73 岁的患者加 1 分。然后使用多变量逻辑回归来研究 aamFI 与术后结果之间的关系。与<73岁的体弱患者相比，≥73岁的体弱患者并发症发生率更高。 aamFI 与并发症之间存在很强的相关性。 aamFI ≥3（参考 aamFI 为 0）与 30 天死亡率（比值比 [OR] 8.6，95% CI 5.0-14.8）、任何并发症（OR 3.1，95% CI 2.9-3.3）的几率增加相关。 ）、深静脉血栓（OR 1.5，95% CI 1.2-1.8）和非回家出院（OR 6.1，95% CI 5.8-6.4；全部 < 0.001）。尽管虚弱会对所有年龄段的患者进行全膝关节置换术后的结果产生负面影响，但年龄较大、虚弱的患者尤其容易受到影响。 aamFI 解释了这一点，并代表了一个简单但强大的工具，用于对接受初次 TKA 的患者进行风险分层。