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Medicine (Baltimore)
Medicine (Baltimore)
MD
Medicine
0025-7974
1536-5964
Lippincott Williams & Wilkins Hagerstown, MD

39312315
MD-D-24-09443
00016
10.1097/MD.0000000000039825
3
7100
Research Article
Observational Study
Construction and validation of a predictive model for preoperative lower extremity deep vein thrombosis risk in elderly hip fracture patients: An observational study
https://orcid.org/0009-0001-4495-0011
Yang Chang-Song MM a*
Tan Zhe MM 462378436@qq.com
b
a Ya’an Mingshan District Hospital of Traditional Chinese Medicine, Ya’an, China
b Ya’an Hospital of Traditional Chinese Medicine, Ya’an, China.
* Correspondence: Chang-Song Yang, Ya’an Mingshan District Hospital of Traditional Chinese Medicine, Ya’an, China (e-mail: axqw648@163.com).
20 9 2024
20 9 2024
103 38 e3982514 8 2024
01 9 2024
02 9 2024
Copyright © 2024 the Author(s). Published by Wolters Kluwer Health, Inc.
2024
https://creativecommons.org/licenses/by-nc/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial License 4.0 (CCBY-NC), where it is permissible to download, share, remix, transform, and buildup the work provided it is properly cited. The work cannot be used commercially without permission from the journal.

The aim of this study was to identify independent risk factors for preoperative lower extremity deep vein thrombosis (DVT) in elderly hip fracture patients and to construct a nomogram prediction model based on them. We collected clinical data from elderly hip fracture patients from Ya’an Hospital of Traditional Chinese Medicine (2021–2023), and used univariate and multivariate logistic regression analyses to identify independent risk factors for preoperative DVT. In this way, a nomogram prediction model was established. In addition, external validation of the model was performed by patient data from Ya’an Mingshan District Hospital of Traditional Chinese Medicine. Receiver operating characteristic curve analysis was used to calculate the area under the curve, and calibration and decision curves were plotted to assess the predictive performance of the model. Of the 223 elderly hip fracture patients, 23 (10.31%) developed DVT of the lower extremities before surgery. A total of 6 variables were identified as independent risk factors for preoperative lower extremity DVT in elderly hip fracture patients by logistic regression analysis: age > 75 years (OR = 1.932; 95% CI: 1.230–3.941), diabetes mellitus (OR = 2.139; 95% CI: 1.149–4.342), and prolonged duration of disease (OR. 2.535; 95% CI: 1.378–4.844), surgical treatment (OR = 1.564; 95% CI: 1.389–3.278), D-dimer > 0.5 mg/L (OR = 3.365; 95% CI: 1.229–7.715) fibrinogen > 4 g/L (OR = 3.473; 95% CI: 1.702–7.078). The constructed nomogram model has high accuracy in predicting the risk of preoperative DVT in elderly hip fracture patients, providing an effective tool for clinicians to identify high-risk patients and implement early intervention.

fracture
hip
nomogram
thrombus
OPEN-ACCESSTRUE
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pmc 1. Introduction

Hip fracture is a common osteoporotic fracture in the elderly.[1–3] With the aggravation of population aging in China, the incidence, disability, as well as fatality rates of hip fractures have been increasing year by year.[4,5] Complications of these fractures include deep vein thrombosis (DVT) of the lower extremities, which is caused by the long-term hypercoagulable state of the patient’s blood.[6] DVT not only affects the therapeutic efficacy and prognosis, but also imposes a heavy psychological and economic burden on the elderly patients, and has become 1 of the main causes of perioperative death.[7] Studies have shown that identifying and preventing risk factors affecting the preoperative occurrence of DVT in hip fracture patients can improve the success rate of surgery and the quality of postoperative recovery.[8] However, the lack of obvious early symptoms of DVT and the general lack of relevant knowledge among patients make early diagnosis difficult, and treatment is often ineffective, affecting prognosis. Therefore, exploring the risk factors for preoperative DVT in elderly hip fractures is crucial for clinical screening and early prevention. nomogram, as a predictive tool, has been successfully applied to risk prediction of postoperative blood transfusion, and after fracture surgery, demonstrating good predictive results.[9–11] The aim of this study was to identify independent risk factors for preoperative DVT formation in hip fracture patients and to develop a nomogram prediction model accordingly to reduce the risk of DVT in elderly hip fracture patients.

2. Information and methods

2.1. Data sources and data collection

The present study retrospectively analyzed the data of patients aged > 60 years and hospitalized for hip fracture in Ya’an Hospital of Traditional Chinese Medicine from January 2021 to December 2023. Single-factor and multifactorial logistic regression analyses were used to determine the independent risk factors for preoperative lower extremity DVT in elderly hip fracture patients and to establish the corresponding nomogram.In addition, data from elderly hip fracture patients at Ya’an Mingshan District Hospital of Traditional Chinese Medicine were collected for external validation. The study was retrospective and complied with the relevant standards of the Hospital Ethics Committee.

2.2. Inclusion exclusion criteria

Inclusion criteria: first, patients must meet the clinical diagnostic criteria of hip fracture; second, patients must be older than 60 years old; third, patients must complete the color Doppler ultrasound examination of the lower extremity veins after admission to the hospital, which is used to screen for venous thrombosis; fourth, the clinical data of the patients must be complete; fifth, the patients and their family members must agree to participate in the study and sign the informed consent form. Exclusion criteria: first, patients with pathological fractures; second, patients with severe dysfunction of liver, kidney and other vital organs; third, patients with severe edema.

2.3. Collection of relevant variables

Relevant information of elderly hip fracture patients was collected, including patients’ age, gender, body mass index (BMI), hypertension, diabetes, hyperlipidemia, cardiovascular disease, smoking, alcohol consumption, disease duration, lateralization, cause of fracture, type of fracture, ASA grading, surgical treatment, D-dimer and fibrinogen.

2.4. Statistical analysis

The data of elderly hip fracture patients collected in Ya’an Traditional Chinese Medicine Hospital were used as the modeling group, and the data of elderly hip fracture patients collected in Ya’an Mingshan Traditional Chinese Medicine Hospital were used as the validation group. In the modeling group, SPSS26.0 software was used for 1-way analysis to compare the differences between the 2 groups, and the chi-square test was applied to statistically test the categorical data. Variables that were statistically significant (P < .05) were screened by univariate analysis, and then these variables were included in multifactorial logistic regression analysis in order to determine the independent risk factors for preoperative lower extremity DVT in elderly hip fracture patients. The independent risk factors screened by the multifactorial logistic regression analysis were plotted on a nomogram in R software. Meanwhile, receiver operating characteristic curves were plotted in the modeling and validation groups, and the area under the curve was calculated to assess the diagnostic efficacy of the model. In addition, calibration curves and decision curves were plotted to further assess the clinical applicability and performance of the model.

3. Results

3.1. General situation

In this study, data were collected from 223 hip fracture patients in Ya’an Hospital of Traditional Chinese Medicine, and a total of 23 hip fracture patients had preoperative lower extremity DVT, with an incidence rate of 10.31%. In addition, data of 86 hip fracture patients were collected in Ya’an Mingshan District Hospital of Traditional Chinese Medicine as external validation.

3.2. Independent risk factors for preoperative lower extremity deep vein thrombosis in elderly hip fracture patients

In the modeling group, 17 variables were analyzed by univariate logistic regression analysis, and the results showed that 9 variables were potential risk factors for preoperative lower extremity DVT in elderly hip fracture patients, including age, BMI, diabetes mellitus, hyperlipidemia, duration of disease, cause of fracture, surgical treatment, D-dimer and fibrinogen (Table 1). Age > 75 years (OR = 1.932; 95% CI: 1.230–3.941), diabetes mellitus (OR = 2.139; 95% CI: 1.149–4.342), long duration of disease (OR = 2.535; 95% CI: 1.378–4.844), and surgical treatment (OR = 1.564; 95% CI: 1.389–3.278), D-dimer > 0.5 mg/L (OR = 3.365; 95% CI: 1.229–7.715) and fibrinogen > 4 g/L (OR = 3.473; 95% CI: 1.702–7.078) were the independent risk factors for preoperative lower extremity deep venous thrombosis in patients with hip fractures (Table 2).

Table 1 Univariate analysis of preoperative lower extremity deep vein thrombosis in elderly hip fracture patients.

Risk factor	DVT group (n = 23)	No DVT group (n = 200)	P	
Sex			.926	
 Male	10	89		
 Female	13	111		
Age			.017	
 ≤75 years	5	96		
 ＞75 years	18	104		
BMI			.040	
 ≤24 kg/m2	7	106		
 ＞24 kg/m2	16	94		
Smoking			.188	
 Yes	12	76		
 No	11	124		
Drinking			.253	
 Yes	13	88		
 No	10	112		
Hypertension			.466	
 Yes	13	97		
 No	10	103		
Diabetes			.002	
 Yes	15	66		
 No	8	134		
Hyperlipidemia			.022	
 Yes	13	65		
 No	10	135		
Cardiovascular disease			.401	
 Yes	12	86		
 No	11	114		
Disease duration			.004	
 ≤48 h	7	123		
 ＞48 h	16	77		
Lateral			.439	
 Left	10	104		
 Right	13	96		
Causes of fractures			.044	
 High energy	14	78		
 Low energy	9	122		
Type of fracture			.496	
 Femoral neck fracture	8	56		
 Intertrochanteric fracture	15	144		
ASA classification			.246	
 II or III	13	137		
 IV	10	63		
Surgery			.038	
 Yes	22	154		
 No	1	46		
D-dimer			.037	
 ≤0.5 mg/L	6	98		
 ＞0.5 mg/L	17	102		
Fibrinogen			.032	
 ≤4 g/L	7	108		
 ＞4 g/L	16	92		

Table 2 Multivariate analysis of preoperative lower extremity deep vein thrombosis in elderly hip fracture patients.

Factors	β	SE	Wald χ2	P	OR	95% CI	
Age > 75 years	0.073	0.021	18.549	.001	1.932	1.230 to 3.941	
Diabetes	0.724	0.354	5.090	.014	2.139	1.149 to 4.342	
Disease duration＞48 h	0.574	0.226	7.761	.008	2.535	1.378 to 4.844	
D-dimer＞0.5 mg/L	1.145	3.213	35.922	.001	3.365	1.229 to 7.715	
FIB＞4 g/L	1.045	0.332	11.757	.001	3.473	1.702 to 7.078	
Surgery	0.523	0.043	63.483	.001	1.564	1.389 to 3.278	

3.3. Nomogram development and validation

A nomogram was developed to predict the risk of preoperative lower extremity DVT in hip fracture patients by using the independent risk factors screened by multifactorial logistic regression analysis (Fig. 1). To verify the predictive efficacy of this nomogram, we plotted ROC curves in the modeling and validation groups and calculated AUC values of 0.831 and 0.792, respectively (Fig. 2A and B). These results illustrate the high diagnostic accuracy of the nomogram. The plotting of the calibration curves showed good agreement between the risks predicted by the nomogram and the actual risks incurred by the patients, indicating that its predictive ability is reliable (Fig. 2C and D). Decision curve analysis further confirmed the usefulness of the nomogram in clinical practice, showing that it can provide physicians with useful reference information to aid decision-making (Fig. 2E and F).

Figure 1. Nomogram prediction model for preoperative lower extremity deep vein thrombosis (DVT) in elderly hip fracture patients.

Figure 2. ROC curves of nomograms for predicting preoperative lower extremity DVT in elderly hip fracture patients in training set (A) and validation set (B). Nomogram calibration curves for predicting preoperative lower extremity DVT in elderly hip fracture patients in training set (C) and validation set (D). Decision curves for nomograms used to predict preoperative lower extremity DVT in elderly hip fracture patients in training set (E) and validation set (F).

4. Discussion

With age, the physical functions of the elderly gradually decline, and problems such as osteoporosis and muscle atrophy make them prone to fall and lead to hip fracture in daily life.[12] The complications of hip fracture are numerous and seriously threaten the life and health of patients. DVT of the lower extremities is 1 of the common complications of hip fracture.[13] Elderly patients are prone to lower extremity DVT due to vascular injury, blood stasis, and hypercoagulable state of the blood, which may trigger pulmonary embolism, resulting in serious consequences such as respiratory distress and cardiac insufficiency.[14] If a large thrombus occurs and the patient is not treated in time, the patient may even face the risk of death, thus seriously affecting the prognosis of elderly hip fracture patients. Early symptoms of lower extremity DVT are not obvious, and the swelling and pain are similar to those of hip fracture itself, which makes the diagnosis difficult. Early identification and prevention of factors affecting preoperative lower extremity DVT in elderly hip fracture patients is crucial, which is important for improving the surgical success rate and postoperative prognosis of elderly hip fracture patients. In this study, we used some common predictors that are easily recognized in clinical practice and constructed a nomogram prediction model based on 6 independent risk factors identified among these predictors. After model validation, we confirmed that the model had good predictive ability.

The findings of this study suggest that advanced age is a significant risk factor for preoperative lower extremity DVT formation in hip fracture patients. In elderly patients undergoing hip fracture surgery, the incidence of lower extremity DVT is high, of which the age factor has been the focus of research.[15] Studies have shown that the older the patient with hip fracture the higher the incidence of lower extremity DVT.[16] The results of the study showed that patients in the DVT group were significantly older than those in the non-DVT group, suggesting that age is an independent risk factor for preoperative lower extremity DVT in elderly hip fracture patients in the emergency setting. This finding further confirms the association between increasing age and increased risk of lower extremity DVT in elderly hip fracture patients. It is hypothesized that increasing age leads to a decline in the body’s immunity, metabolic capacity, and cardiorespiratory function in elderly patients. These physiological changes may affect the repair capacity of blood vessels, resulting in a gradual thickening of the vessel walls and a reduction of elastin in the vessels, leading to a decrease in vascular elasticity and a weakening of venous reflux, thus increasing the risk of lower extremity DVT.[17] Therefore, for elderly hip fracture patients, especially those of advanced age, more attention should be paid to the prevention and early identification of DVT preoperatively in order to reduce the risk of postoperative complications. Some studies have reported that elderly patients with diabetes mellitus after hip fracture surgery are more likely to develop lower extremity DVT.

The results of the study showed that the percentage of patients with hyperglycemia was significantly higher in the DVT group than in the non-DVT group. This suggests that having hyperglycemia is an independent risk factor for preoperative lower extremity DVT in elderly hip fracture patients in the emergency setting, which is consistent with previous findings.[18] Hyperglycemia may lead to damage of vascular endothelial cells and increased inflammatory response, thus promoting thrombosis.[19] In addition, hyperglycemia leads to decreased deformability of erythrocytes and reduced vascular elasticity, which can increase blood viscosity and slow down blood flow, further increasing the risk of venous thrombosis.[20] Therefore, for elderly hip fracture patients, especially those with hyperglycemia, prophylactic measures for DVT should be strengthened preoperatively and closely monitored postoperatively to reduce the occurrence of complications.

The results of this study showed that the percentage of surgical history and duration of disease were significantly higher in the DVT group than in the non-DVT group, and that surgery and long duration of disease were independent risk factors for preoperative lower extremity DVT in elderly hip fracture patients. This may be due to the fact that whether or not to perform surgical treatment is mainly determined by the presence or absence of contraindications to surgery and hip fracture in elderly patients, and that non-operated patients may have less severe hip fracture symptoms, less vascular damage and less impact on their own mobility, resulting in a lower probability of complication of lower extremity DVT. The longer the duration of the disease in elderly patients, the longer they are bedridden and the longer their limbs and trunks are in a passive static state, the more likely they are to experience slower blood flow and increased blood viscosity, which affects the adhesion ability of leukocytes and the number of coagulation factors, activates the coagulation system, and puts the body in a hypercoagulable state, which leads to the development of blood clots.

Fibrinogen (FIB) and D-dimer are important markers of the blood coagulation and fibrinolytic system, and they play a key role in the development of DVT in the lower extremities.[21] Elevated levels of FIB as a coagulation factor imply an increase in the number of fibrin monomers in the blood that can be used to form a thrombus, which in turn increases the risk of DVT formation.[22] In the case of DVT, there is an increase in fibrin polymers in the body, which are subsequently degraded through the action of the fibrinolytic system, and D-dimer is the specific degradation product produced during this process. Therefore, elevated levels of D-dimer can reflect the presence of DVT and its severity. In the present study, the levels of FIB and D-dimer were significantly higher in patients in the DVT group than in the non-DVT group, suggesting that elevated levels of both are independent risk factors for preoperative lower extremity DVT in elderly patients with hip fractures in the emergency setting. Elevated levels of FIB increase the tendency of the blood to agglutinate, whereas elevated levels of D-dimer are indicative of the presence of active thrombus formation and subsequent fibrinolytic activity in the body. The combined assessment of these 2 indicators can help physicians more accurately assess a patient’s risk of developing DVT and guide the development of clinical prevention and treatment strategies.

However, there are also shortcomings in this study. First, as this is a retrospective study, there will be some unavoidable errors arising. Second, the number of hip fracture patients included in this study is limited, so its validity needs to be verified by further multicenter large-sample studies.

5. Conclusion

The results of this study indicate that old age, high blood glucose, surgical treatment, long duration of disease, high level of FIB, and high level of D-dimer are independent risk factors for preoperative lower extremity DVT in elderly hip fracture patients in the emergency department. The nomogram of preoperative lower extremity DVT in hip fracture patients constructed in this study has good predictive accuracy and helps physicians to intervene in advance in patients at high risk of preoperative lower extremity DVT in hip fracture patients.

Author contributions

Conceptualization: Chang-Song Yang.

Data curation: Chang-Song Yang.

Funding acquisition: Zhe Tan.

Investigation: Zhe Tan.

Methodology: Zhe Tan.

Software: Zhe Tan.

Validation: Chang-Song Yang.

Visualization: Chang-Song Yang.

Writing – original draft: Chang-Song Yang.

Writing – review & editing: Chang-Song Yang.

Abbreviations:

BMI body mass index

DVT deep vein thrombosis

The authors have no funding and conflicts of interest to disclose.

Due to the non-experimental nature of the research, the study protocol did not need to be submitted for consideration and approval to an ethical review committee.

The datasets generated during and/or analyzed during the current study are not publicly available, but are available from the corresponding author on reasonable request.

How to cite this article: Yang C-S, Tan Z. Construction and validation of a predictive model for preoperative lower extremity deep vein thrombosis risk in elderly hip fracture patients: An observational study. Medicine 2024;103:38(e39825).
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