A total of 60 (3.8%) older hip fracture patients occurred AIS in all 1577 cases. Among 60 AIS patients, the number of female was higher than that of male, but the incidence was higher in male than female. The most common cause of fall was limb weakness or instability. The most cerebral infarction type was PACI and the most infarction lesion was single cerebral infarction in 60 AIS patients. Most of them were located on the left side. 81.7% of AIS patients had mild (NIHSS 0-4) AIS. Older patients with AIS after hip fracture were more frequently complicated by hypertension, previous stroke, diabetes and were more likely to have hypoproteinemia, electrolyte imbalance, anemia, deep vein thrombosis, cardiac complications and pneumonia. Combined with hypertension and male sex were independent risk factors of the AIS after hip fracture in the elderly.
There were significantly more female among AIS cases in our study, which is due to the reason that female tend to live longer and are more likely to develop stroke and fracture in older people[16, 17]. The AIS incidence was higher in male than female in older fracture people in our study. Studies have shown that male sex is a significant risk factor for stroke[18], and the incidence of stroke in male before the age of 85 is higher than in female[19]. 75-84 years was the most common age group in our study. This may be due to the largest number of fracture patients in this age group. Fall is a major cause of fracture in older adults, and the most common fall-related injury was hip fracture[20].Elderly people often fall due to instability and weakness, which may be related to the decline of physical functions such as vision and movement, as well as the impairment of balance in the elderly[21]. The infarctions were solitary cerebral infarction and were located on the left side in our study. The result was consistent with previously published results of Hedna VS et al[22]. Left-sided strokes might be mentioned more often because they cause obvious symptoms like aphasia, while strokes on the right side can cause less obvious symptoms like hemineglector spatial disorientation[23].We think that this can also be applied to patients with AIS after fracture.
The prevalence of AIS after hip fracture was 3.8% in our study, which was consistent with prior study[24]. In our study, it was found that AIS patients after hip fracture were more frequently comorbid with chronic medical illness diseases, including hypertension, prior stroke and diabetes. Hypertension and diabetes are significant risk factors for the occurrence of cerebrovascular accidents (CVA) after hip fracture[25]. It has been observed that the carotid arteries of patients with diabetes are thicker and harder than those of the general population[26]. In addition, it has been reported that the carotid stiffness index of hypertensive patients is significantly higher than that of the general population[27]. Hypertension and diabetes accelerate the progression of atherosclerosis. Atherosclerosis is an important pathological cause of ischemic stroke. 30% of ischemic stroke are caused by carotid atherosclerosis[28]. The pathogenesis of ischemic stroke is considered to be arterial embolism caused by rupture of carotid plaque, ulceration, and platelet activation.
A study has shown that hip fracture is associated with increased risk of stroke[29]. Physical inactivity, fear and pain are common in the elderly hip fracture patients. In this case, the pre-existing cerebrovascular risk may be exacerbated. This may be associated with traumatic stress response. Fracture can lead to the release of stress hormones such as glucocorticoids, glucagon, epinephrine, thyroxine and others, which is called the “stress response”[30]. Stress response induces platelet aggregation and promotes microcirculation dysfunction and thrombosis[30]. A large number of inflammatory mediators caused by stress are released after hip fracture, and inflammation in the acute phase can affect thrombosis. Inflammation is usually related to oxidative stress. The strong oxidative activity can also destroy normal cell structure and promote the progress of cardiovascular and cerebrovascular diseases[31].
Patients with both fractures and strokes have a worse prognosis than those with single injury[32], and this may be related to their stronger traumatic stress response. Our observations showed that AIS patients after hip fractures suffered other adverse events such as hypoproteinemia, anemia, electrolyte disturbances, pneumonia, lower limb venous thrombosis and cardiovascular complications. Complications also affected each other, resulting in worse prognosis.
Hypoalbuminemia, electrolyte imbalance, and anemia were common complications after bone fracture in our study. Factors such as excessive blood loss and pain after the fracture induce stress response. Stress response puts the body in a state of enhanced catabolism and decreased anabolism, which may be related to the occurrence of hypoproteinemia and electrolyte disorder[33]. Stroke related disorders such as cognitive dysfunction, impaired consciousness, neurogenic vomiting, neurogenic dysphagia, and motor dysfunction also contribute to the development of hypoalbuminemia and electrolyte imbalance[34]. One study has shown that hypoalbuminemia occurs more frequently in patients with bone fracture and stroke and is associated with a poor prognosis[35]. Several studies have shown that human albumin therapy can combat thrombosis, stagnation and leukocyte adhesion of the microcirculation in the early stage of stroke, and provide neuroprotection for stroke patients[36, 37].
The traumatic stress response leads to the release of hormones such as catecholamines[38], which increase pulmonary artery systolic pressure and initiate pulmonary vasoconstriction and pulmonary interstitial edema. Moreover, an excessive stress response would impair organism immunity. These factors lead to the occurrence of pneumonia. In addition, swallowing difficulty, immune deficiency, nasogastric tube feeding, and poor oral hygiene from stroke can increase the risk of pneumonia. The occurrence of pneumonia increases the risk of in-hospital death[39]. In addition, after traumatic fracture, stress can activate the endogenous and exogenous coagulation system, resulting in hypercoagulability and coagulation dysfunction. This significantly increases the risk of deep vein thrombosis.
The persistent stress of older hip fracture patients can cause myocardial hypoxia and increase the imbalance between oxygen supply and myocardial demand. This is a common and complex pathophysiological mechanism that causes the occurrence of cardiac complications[40]. There are several common risk factors for stroke and ischemic heart disease. Underlying heart diseases, such as atrial fibrillation, valve defects, or congestive heart failure, increase the risk of stroke. Stroke interferes with autonomic control and can easily lead to cardiac complications in patients[41].Cardiac complications in patients with fracture or stroke can be fatal for the patients[42]. All the occurrence of these complications after hip fracture is associated with traumatic stress, and we need to strengthen the management of patients' breathing, circulation, blood, and thrombus to attenuate the stress response and improve the quality of patients' survival.
Furthermore, after we performed multivariate logistic regression on patients participated in this study, the data showed that comorbid with hypertension and male sex were significant risk factors for the AIS after hip fracture in the elderly. The mechanism of stroke caused by hypertension was discussed above. For this reason, we propose the following recommendations. Firstly, elderly patients comorbid with hypertension should prevent falls and fractures in their daily life. Secondly, Elderly patients comorbid with hypertension should pay attention to monitoring blood pressure, blood lipids, and preventing the occurrence and development of cerebrovascular disease. In addition, for these elderly patients who develop fracture, we should strengthen management to reduce the stress reaction and avoid the occurrence of stroke and other complications.