In this study, the construction of hip fracture patients with prolonged hospital stay risk prediction model, whether the model construction or the internal verification of the data have good sensitivity and specificity, indicating that the prediction effect of the model is good and the result is stable (AUC = 0.794). The model can directly reflect the risk factors of delayed hospitalization in the formula, which can not only predict the risk of delay in patients with clinical hip fracture, but also provide a basis for the follow-up medical staff to systematically evaluate the influencing factors of discharge delay. According to this line map, nurses can evaluate the hospitalization time of patients with hip fracture in advance, according to their ACCI, bone traction, refracture, anemia, venous thrombosis, pneumonia, pulmonary infection and other influencing factors, to speculate that patients may have delayed discharge risk, so as to shorten hospital stay, reduce the occurrence of postoperative complications, promote postoperative rehabilitation, and optimize the rational allocation of medical resources.
In this study, it was found that the hospitalization delay of patients with hip fracture with CCI ≥ 8 increased by 3.326 times. The ACCI score includes the patient's age and various complications, reflecting the patient's overall health at the time of admission. Similar to the conclusions of this study, wei[9] et al. [9] found that the co-disease weight of elderly patients with hip fracture (based on age-adjusted CCI assessment) was associated with increased length of stay. A meta analysis also showed that there was a positive correlation between comorbid disease and length of stay of patients with hip fracture[10]. It is possible that patients with severe comorbidities may be more prone to complications and require multiple medication, so they will be given longer hospital stay for treatment and care[11, 12]. In addition, these patients with a variety of chronic diseases lead to poor self-care ability, but also need a longer recovery period to return to their original self-care level. Bone traction is generally used in patients with hip fractures who are unable to tolerate surgery and receive conservative treatment. Yoo et al[5]found that most of the postoperative patients in secondary and primary surgical hospitals can be discharged early. Hip arthroplasty can replace the damaged site with artificial hip joint, and walk on the ground as soon as possible to reduce the complications caused by long-term bedridden. In addition, patients after hip arthroplasty can take early rehabilitation exercise to reduce the risk of infection, venous thrombosis and delayed healing, and reduce the length of stay of patients with hip fracture [13]. As bone traction patients can not tolerate surgery, need to stay in bed for a long time, prone to infection, bedsores and other complications, resulting in prolonged hospitalization.
This study found that refracture is closely related to the prolonged hospitalization of patients with hip fracture. Compared with the primary fracture, the secondary fracture has a higher mortality and incidence of complications, often has limited function, and has worse self-care ability after operation[14]. The study reported that the admission function and activity level of patients with secondary fracture of hip fracture was significantly worse than that of patients with primary fracture, and the difference of Basel index between the two groups was almost 20 points[15].Due to the complex injury and many complications in patients with secondary fracture, it is very difficult to treat, which seriously affects the prognosis and requires a longer hospital stay to restore their function.
This study found that anemia is closely related to prolonged hospitalization in patients with hip fractures. Nissenholtz et al.[16]found that anemia has a significant effect on the length of stay of elderly patients with hip fracture. On the one hand, because anemic patients need to supplement blood volume and give allogeneic blood transfusion after operation, allogeneic blood transfusion will cause a variety of adverse reactions, affect the patient's immune system and blood coagulation system, and increase the incidence of complications [17] .On the other hand, the degree of postoperative anemia in patients with preoperative anemia of hip fracture is relatively severe, which affects the transport of nutrients in the fracture site, weakening the body's defense barrier and hindering the ability of self-repair, resulting in the invasion of pathogenic microorganisms. the final manifestation is an increase in the incidence of complications[18]. uncorrected anemia after hip fracture may hinder the functional recovery of patients with hip fracture and affect medical complications and length of stay [19] .
This study found that pneumonia and pulmonary infection were independent risk factors for delayed discharge in patients with hip fractures. Pneumonia and pulmonary infection are common in elderly patients with hip fracture due to the weakening of movement and respiratory muscle ability. SalarbaksAM et al. [20]found that the hospitalization time of elderly patients with hip fracture treated with anti-pneumonia was 1.6 times longer than that of patients with hip fracture observed. The study found that elderly patients with hip fractures who received anti-pneumonia treatment spent an average of 1.6 times longer in hospital than those with observed hip fractures. On the one hand, pulmonary infection can damage the immune system and lead to the decline of the body's physiological function, which requires further clinical treatment[21]. On the other hand, the longer the patient stays in the hospital, the longer the time of exposure to pathogens in the hospital, thus increasing the risk of infection.The study found that lower limb venous thrombosis is also a risk factor for delayed discharge of hip fractures. It is reported in foreign literature that venous thrombosis is related to prolonging hospitalization time and increasing hospitalization expenses[22]. On the one hand, venous thrombosis will increase the probability of pulmonary embolism. In order to prevent fatal pulmonary embolism, clinicians will give antithrombotic preventive measures for a period of time. Even the minimum dose of antithrombotic regimen takes 10–14 days[23]. On the other hand, the longer the hospitalization time of patients with hip fracture, the longer the immobilization time, resulting in slow blood flow and hypercoagulable state, thus increasing the risk of venous thrombosis.
Limitations: this study is a retrospective, single-center study, some indicators are not available; the inclusion of disease heterogeneity, underlying diseases, different etiology of primary diseases, these confounding factors to establish predictive models. The effectiveness of the prediction model still needs to be further verified by multicenter, prospective studies.