**1. Introduction**

The incidence of distal femur fracture increases markedly with age [1]. Elderly patients with distal femur fracture were reported to have similar demographic characteristics and outcomes to elderly patients with hip fracture [2]. Elderly patients with distal femur fracture have poor postoperative outcomes because of their many perioperative complications caused by preoperative immobilization [2,3], which is similar to the case for elderly patients with hip fracture [4]. In elderly patients with hip fracture, systematic reviews have

**Citation:** Yamamoto, N.; Ohbe, H.; Tomita, Y.; Yorifuji, T.; Nakajima, M.; Sasabuchi, Y.; Miyamoto, Y.; Matsui, H.; Noda, T.; Yasunaga, H. Associations between Early Surgery and Postoperative Outcomes in Elderly Patients with Distal Femur Fracture: A Retrospective Cohort Study. *J. Clin. Med.* **2021**, *10*, 5800. https://doi.org/10.3390/jcm10245800

Academic Editor: Gianluca Testa

Received: 25 September 2021 Accepted: 8 December 2021 Published: 11 December 2021

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demonstrated the beneficial effects of early surgery on postoperative outcomes, including mortality and postoperative complications [5,6].

However, prior studies have provided mixed results regarding the association between the timing of surgery and postoperative mortality in elderly patients with distal femur fracture. Several observational studies found that early surgery was associated with reduced mortality [7–9], while other studies showed no such association [10–13]. One of the reasons for these conflicting results may be small patient numbers used in previous studies (*n* = 88 to 392) [2,3,7–12]. In addition, confounding factors may not have been sufficiently adjusted for because of the small numbers of patients.

The purpose of the present study was to examine the associations between early surgery and postoperative outcomes in elderly patients with distal femur fractures using data from a nationwide inpatient database. We hypothesized that early surgery is associated with a lower in-hospital mortality, a lower proportion of postoperative complications, and lower medical costs. By clarifying these associations, we suggest a better treatment strategy for geriatric distal femur fracture that will improve patient outcomes and the social economy of healthcare.

#### **2. Materials and Methods**

This study was a retrospective cohort study using a national administrative inpatient database under the REporting of studies Conducted using Observational Routinelycollected Data (RECORD) statement reporting guidelines [14]. This study was conducted in accordance with the Declaration of Helsinki and was approved by the Institutional Review Board of The University of Tokyo (approval number: 3501-(3); 25 December 2017). The requirement for informed consent was waived because of the anonymous nature of the data.
