Background 

Staphylococcus aureus is a common organism implicated in prosthetic joint infection after THA and TKA, prompting preoperative culturing and decolonization to reduce infection rates. It is unknown whether colonization is associated with other noninfectious outcomes of THA or TKA.

Questions/purposes 

(1) What is the association between preoperative S. aureus colonization (methicillin-sensitive S. aureus [MSSA] and methicillin-resistant S. aureus [MRSA]) and the noninfectious outcomes (discharge destination, length of stay, Hip/Knee Disability and Osteoarthritis Outcome Score [HOOS/KOOS] pain score, HOOS/KOOS physical function score, 90-day readmission, and 1-year reoperation) of THA and TKA? (2) What factors are associated with colonization with S. aureus?

Methods 

Between July 2015 and March 2019, 8078 patients underwent primary THA in a single healthcare system, and 17% (1382) were excluded because they were not tested preoperatively for S. aureus nasal colonization, leaving 6696 patients in the THA cohort. Between June 2015 and March 2019, 9434 patients underwent primary TKA, and 12% (1123) were excluded because they were not tested for S. aureus colonization preoperatively, leaving 8311 patients in the TKA cohort. The goal of the institution’s standardized care pathways is to test all THA and TKA patients preoperatively for S. aureus nasal colonization; the reason the excluded patients were not tested could not be determined. Per institutional protocols, all patients were given chlorhexidine gluconate skin wipes to use on the day before and the day of surgery, and patients with positive S. aureus cultures were instructed to use mupirocin nasal ointment twice daily for 3 to 5 days preoperatively. Adherence to these interventions was not tracked, and patients were not rescreened to test for S. aureus control. The minimum follow-up time for each outcome and the percentage of the cohort lost for each was: for discharge destination, until discharge (0 patients lost); for length of stay, until discharge (0.06% [4 of 6696] lost in the THA group and 0.01% [1 of 8311] lost in the TKA group); for HOOS/KOOS pain score, 1 year (26% [1734 of 6696] lost in the THA group and 24% [2000 of 8311] lost in the TKA group); for HOOS/KOOS physical function, 1 year (33% [2193 of 6696] lost in the THA group and 28% [2334 of 8311] lost in the TKA group); for 90-day readmission, 90 days (0.06% [4 of 6696] lost in the THA group and 0.01% [1 of 8311] lost in the TKA group); and for 1-year reoperation, 1 year (30% [1984 of 6696] lost in the THA group and 30% [2475 of 8311] lost in the TKA group). Logistic regression models were constructed to test for associations between MSSA or MRSA and nonhome discharge, length of stay greater than 1 day, improvement in the HOOS/KOOS pain subscale (≥ the minimum clinically important difference), HOOS/KOOS physical function short form (≥ minimum clinically important difference), 90-day readmission, and 1-year reoperation. We adjusted for patient-related and hospital-related factors, such as patient age and hospital site. Variable significance was assessed using the likelihood ratio test with a significance level of p < 0.05. To assess factors associated with S. aureus colonization, we constructed a logistic regression model with the same risk factors.

Results 

Among the THA cohort, after controlling for potentially confounding variables such as patient age, smoking status, and BMI, S. aureus colonization was associated with length of stay greater than 1 day (MSSA: odds ratio 1.32 [95% CI 1.08 to 1.60]; MRSA: OR 1.88 [95% CI 1.24 to 2.85]; variable p < 0.001 by likelihood ratio test) but not the other outcomes of THA. Male sex (OR 1.26 [95% CI 1.09 to 1.45]; p = 0.001) and BMI (OR 1.02 for a one-unit increase over median BMI [95% CI 1.01 to 1.03]; p = 0.003) were patient-related factors associated with S. aureus colonization, whereas factors associated with a lower odds were older age (OR 0.99 [95% CI 0.98 to 0.99]; p < 0.001) and Black race compared with White race (OR 0.64 [95% CI 0.50 to 0.82]; p < 0.001). Among the TKA cohort, S. aureus colonization was associated with 90-day readmission (MSSA: OR 1.00 [95% CI 0.99 to 1.01]; MRSA: OR 1.01 [95% CI 1.00 to 1.01]; variable p = 0.007 by likelihood ratio test). Male sex (OR 1.19 [95% CI 1.05 to 1.34]; p = 0.006) was associated with S. aureus colonization, whereas factors associated with a lower odds of colonization were older age (OR 0.99 [95% CI 0.98 to 0.99]; p < 0.001), Veterans RAND-12 mental component score (OR 0.99 [95% CI 0.99 to 1.00]; p = 0.027), Black race compared with White race (OR 0.70 [95% CI 0.57 to 0.85]; p < 0.001), and being a former smoker (OR 0.86 [95% CI 0.75 to 0.97]; p = 0.016) or current smoker (OR 0.70 [95% CI 0.55 to 0.90]; p = 0.005) compared with those who never smoked.

Conclusion 

After controlling for the variables we explored, S. aureus colonization was associated with increased length of stay after THA and 90-day readmission after TKA, despite preoperative decolonization. Given that there is little causal biological link between colonization and these outcomes, the association is likely confounded but may be a proxy for undetermined social or biological factors, which may alert the surgeon to pay increased attention to outcomes in patients who test positive. Further study of the association of S. aureus colonization and increased length of stay after THA and readmission after TKA may be warranted to determine what the confounding variables are, which may be best accomplished using large cohorts or registry data.

Level of Evidence 

Level III, therapeutic study.

中文翻译：

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THA 术前金黄色葡萄球菌定植与住院时间增加相关

背景 

金黄色葡萄球菌是 THA 和 TKA 术后假体关节感染的常见微生物，提示术前培养和去定植以降低感染率。目前尚不清楚定植是否与 THA 或 TKA 的其他非感染性结果相关。

问题/目的 

(1) 术前金黄色葡萄球菌定植（甲氧西林敏感金黄色葡萄球菌[MSSA] 和耐甲氧西林金黄色葡萄球菌[MRSA]）与非感染性结局（出院目的地、住院时间、髋/膝残疾）之间有何关联THA 和 TKA 的骨关节炎结果评分 [HOOS/KOOS] 疼痛评分、HOOS/KOOS 身体功能评分、90 天再入院和 1 年再次手术）？(2)金黄色葡萄球菌定植与哪些因素有关？

方法 

2015 年 7 月至 2019 年 3 月期间，8078 名患者在单一医疗保健系统中接受了初次 THA，其中 17%（1382 名）因术前未接受金黄色葡萄球菌鼻定植检测而被排除在外，THA 队列中只剩下 6696 名患者。2015 年 6 月至 2019 年 3 月期间，9434 名患者接受了初次 TKA，其中 12%（1123 名）因术前未进行金黄色葡萄球菌定植检测而被排除，在 TKA 队列中剩下 8311 名患者。该机构标准化护理途径的目标是在术前测试所有 THA 和 TKA 患者的鼻腔金黄色葡萄球菌定植情况；无法确定被排除的患者未接受检测的原因。根据机构方案，所有患者在手术前一天和手术当天均使用葡萄糖酸氯己定皮肤湿巾，金黄色葡萄球菌培养呈阳性的患者被指示在术前每天使用莫匹罗星鼻软膏两次，持续 3 至 5天。没有跟踪对这些干预措施的遵守情况，也没有对患者进行重新筛查以测试金黄色葡萄球菌控制情况。每个结果的最短随访时间以及每个结果的队列丢失百分比为： 出院目的地，直至出院（0 名患者丢失）；住院时间，直至出院（THA 组中损失了 0.06% [6696 中的 4]，TKA 组中损失了 0.01% [8311 中的 1]）；HOOS/KOOS 疼痛评分，1 年（THA 组中 26% [6696 中的 1734] 丢失，TKA 组中 24% [8311 中的 2000] 丢失）；HOOS/KOOS 身体功能，1 年（THA 组中 33% [6696 中的 2193] 丧失，TKA 组中 28% [8311 中的 2334] 丧失）；90 天再入院，90 天（THA 组中损失 0.06% [6696 人中的 4 人]，TKA 组中损失 0.01% [8311 人中的 1 人）；1 年再次手术为 1 年（THA 组中 30% [1984 of 6696] 失访，TKA 组中 30% [2475 of 8311] 失访）。构建逻辑回归模型来测试 MSSA 或 MRSA 与非回家出院、住院时间大于 1 天、HOOS/KOOS 疼痛分量表的改善（≥最小临床重要差异）、HOOS/KOOS 身体功能简表（ ≥ 最小临床重要差异）、90 天再入院和 1 年再次手术。我们调整了患者相关和医院相关的因素，例如患者年龄和医院地点。使用似然比检验评估变量显着性，显着性水平为 p < 0.05。为了评估与金黄色葡萄球菌定植相关的因素，我们构建了具有相同风险因素的逻辑回归模型。

结果 

在 THA 队列中，在控制了患者年龄、吸烟状况和 BMI 等潜在混杂变量后，金黄色葡萄球菌定植与住院时间超过 1 天相关（MSSA：比值比 1.32 [95% CI 1.08 至 1.60] ；MRSA：OR 1.88 [95% CI 1.24 至 2.85]；通过似然比检验，变量 p < 0.001），但 THA 的其他结果则不然。男性（OR 1.26 [95% CI 1.09 - 1.45]；p = 0.001）和BMI（比中值BMI增加1个单位的OR 1.02 [95% CI 1.01 - 1.03]；p = 0.003）是患者相关因素与金黄色葡萄球菌定植相关，而与较低几率相关的因素是年龄较大（OR 0.99 [95% CI 0.98 - 0.99]；p < 0.001）和黑人种族与白人种族相比（OR 0.64 [95% CI 0.50 - 0.82] ]；p < 0.001）。在 TKA 队列中，金黄色葡萄球菌定植与 90 天再入院相关（MSSA：OR 1.00 [95% CI 0.99 至 1.01]；MRSA：OR 1.01 [95% CI 1.00 至 1.01]；按似然比计算，变量 p = 0.007测试）。男性（OR 1.19 [95% CI 1.05 至 1.34]；p = 0.006）与金黄色葡萄球菌定植相关，而与定植几率较低相关的因素是年龄较大（OR 0.99 [95% CI 0.98 至 0.99]；p = 0.006）。 p < 0.001），退伍军人 RAND-12 心理成分评分（OR 0.99 [95% CI 0.99 至 1.00]；p = 0.027），黑人种族与白人种族相比（OR 0.70 [95% CI 0.57 至 0.85]；p < 0.001 ），与从未吸烟者相比，曾经吸烟者（OR 0.86 [95% CI 0.75 至 0.97]；p = 0.016）或当前吸烟者（OR 0.70 [95% CI 0.55 至 0.90]；p = 0.005）。

结论 

在控制我们探索的变量后，尽管术前进行了去定植，但金黄色葡萄球菌定植与 THA 后住院时间的增加和 TKA 后 90 天的再入院有关。鉴于定植与这些结果之间几乎没有因果生物学联系，这种关联可能是令人困惑的，但可能是不确定的社会或生物因素的代表，这可能会提醒外科医生更多地关注检测呈阳性的患者的结果。可能有必要进一步研究金黄色葡萄球菌定植与全髋关节置换术后住院时间增加和全膝关节置换术后再入院之间的关系，以确定混杂变量是什么，这最好使用大型队列或登记数据来完成。

证据水平 

III级，治疗研究。