Версия для печати Milyukov A.Yu., Ustyantsev D.D., Gilev Ya.Kh., Mazeev D.V.

PREDICTIVE SIGNIFICANCE OF COMORBID STATUS IN DEVELOPMENT OF COMPLICATIONS IN SURGICAL TREATMENT OF PATIENTS WITH INJURIES TO THE PROXIMAL FEMORAL BONE

Regional Clinical Center of Miners’ Health Protection, Leninsk-Kuznetsky, Russia

Comorbidity influences on the prediction of life and increases the possibility of lethal outcome. The presence of comorbid disease promotes the increasing amount of bed-days, disability and prevents the conduction of rehabilitation, increases the number of postsurgical complications and causes the increase in probability of fallings in older patients [1, 2, 3].
Comorbid pathology makes the multifactorial and individual influence on the clinical manifestations, diagnostics and treatment of many diseases. The interaction of diseases, age and drug therapy significantly changes the clinical picture of the main nosology, characteristics and severity of complications, worsens the quality of life, limits or impedes the medical and diagnostic process [5. 6].
As the last works show, the problem of comorbidity is quite common for traumatologists-orthopedists during formation of a diagnostic and medical concept with consideration of potential risks for a patient and his/her remote prognosis [3, 7, 8].
The presence of comorbidity should be considered when selecting a diagnostic algorithm or a scheme of surgical treatment in locomotor system injuries [9, 10].
However in most conducted randomized clinical studies the authors include patients with separate traumatological pathology and present comorbidity as an exclusion criterion [3, 8, 10]. For this category of patients it is necessary to confirm a degree of functional disorders and the morphological status for all identified nosological forms.
Currently, the significance of comorbidity does not raise any doubts. There are 12 uniform techniques for measuring comorbidity [1, 2, 11, 12]. But how it can be measured in an individual patient? Each day any clinician meets such difficulties regardless of clinical experience and medical knowledge.
Absence of a uniform complex approach to estimation of comorbidity causes some gaps in clinical practice of a traumatologist-orthopedist [2, 12]. The main blocks on the way to implementation of comorbidity estimation systems into a many-sided medical and diagnostic process is their inconsistency and narrow directionality despite of variety of techniques for comorbidity estimation [2, 10].
After analyzing a comorbidity status in a certain patient with use of the most common international scales for comorbidity estimation, one can receive the essentially different results.
So, a recent study by Lakomkin N. et al. showed a statistically significant relationship between the increasing Charlson Comorbidity Index (CCI) and duration of postsurgical hospital stay for patients with single fractures of the lower extremities as compared to patients with hip joint injuries and pelvic fractures [13].
Min L., Burruss S., Morley E. et al. (2013) published the retrospective analysis of concurrent pathology in 280,000 trauma patients according to the data from US National Bank of Trauma Data including the trauma centers of the levels 1-3 [10]. The authors identified a close relationship between the age and complications in patients with three or more concurrent diseases. The risk of mortality increased in patients at the age > 45 [10].
The use of primary data acquired at the moment of admission (age, gender, chronic diseases and simple calculation of comorbidity categories) was successfully used for development of a nomogram of estimation of risk of complications and mortality in older trauma patients [10].
As result, the potentially wider use of such approach can be useful for stratifying the risk of complications, mortality with consideration of a comorbidity status for development of more efficient approaches in complex surgical treatment of patients with injuries and multiple chronic concurrent diseases.
The development of nomograms can be a starting point for estimating the risk of possible complications and for timely use of intensive prevention of infections in surgical treatment of some categories of patients with traumatic musculoskeletal injuries.
The objective of the study – to analyze and separate the values (age, gender, Injury Severity Score, length of hospital stay after surgery, complications) of the comorbid status and to develop a simple nomographic chart for clinical estimation of the risk of complications in patients with the proximal femoral bone injuries.

MATERIALS AND METHODS

The study is based on the analysis of the results of the complex examination and the surgical treatment of 161 patients with injuries to the proximal femoral bone. The patients received the treatment in the traumatology and orthopedics unit No.2, Regional Clinical Center of Miners’ Health Protection in 2013-2016. The study data was obtained from the computer basis of the Medical Information System (MIS) of Regional Clinical Center of Miners’ Health Protection.
The inclusion criteria for the patients with the proximal femoral bone injuries were the age ≥ 18, Injury Severity Score (ISS) ≤ 15 [14]. The increase in the amount of points corresponded to the increasing severity of injury since ISS is a continuous variable and can vary from 0 to 75 points [14]. The study excluded the cases when the patients were transferred to other hospital or a lethal outcome was registered during 24 hours after admission.
In concordance with ICD-10, the proximal femoral bone injuries were verified on the basis of complaints, the results of physical examination and X-ray examination of the hip joint in two standard planes.
119 patients (74 %) had the medial fractures of the proximal femoral bone, with the basal, medial and subcapital fractures of the femoral neck in 34, 50 and 35 patients correspondingly. 42 cases (26 %) were associated with the lateral fractures of the proximal femoral bone. The transtrochanteric and subtrochanteric fractures were identified in 28 and 14 patients with the injuries according to the classification by A.V. Kaplan (1967).
The study was conducted in concordance with the ethical principles of World Medical Association Declaration of Helsinki – Ethical Principles for Medical Research Involving Human Subjects, 2013 and the Rules for Clinical Practice in the Russian Federation (the Order No.266 by RF Health Ministry, June 19, 2003) after receiving the written consent from a patient and approval from the local ethical committee of the center.
The age of the patients was selected as a stratified variable: the age of 18-64 was considered as young one, ≥ 65 – as older age (the table 1). Initially, the values were analyzed and separated (age, gender, injury mechanism, injury type, ISS, duration of hospital stay after surgery). The comorbidity status was estimated with the amount of concurrent diseases (among 16 possible diseases) (the table 1).

Table 1. The characteristics of patients with proximal femoral bone injuries in the examined age groups

Values		Young age (18–64 years) (n = 39)	Older age (65+ years) (n = 122)	p-value
Men, %		65	43	< 0.001
Injury mechanism, %	Road traffic accidents	46.2	9.0	< 0.001
	Falling from height*	23.0	83.6	< 0.001
	Others (home injury, diving)	30.8	7.4	< 0.001
Injury Severity Score (ISS), mean		15 (10.0)	13 (8.2)
Hospital stay, mean (SD), days		11.2 (16.0)	16.5 (19.3)	< 0.001
Comorbidity (concurrent diseases before injury), %1	No concurrent diseases (0)	12.8	5.7	< 0.001
	1-2 and more concurrent diseases	53.8	54.1	< 0.001
	3+ concurrent diseases	33.3	40.2	< 0.001
	Hypertension	28.2	70.5	< 0.001
	Coronary heart disease	25.6	59.0	< 0.001
	Coagulopathy and anticoagulant therapy	30.8	69.7	< 0.001
	Chronic pulmonary diseases including obstructive pulmonary disease and asthma	12.8	24.6	< 0.001
	Previous cardiosurgical operations	2.6	9.0	< 0.001
	Arrhythmia (also installed cardiac stimulators)	12.8	26.2	< 0.001
	Deep venous thrombosis, lymphostasis	23.1	23.0	0.563
	Diabetes mellitus	19.7	23.1	< 0.001
	Obesity (degrees 3-4)	11.5	28.2	< 0.001
	Neurological diseases (including hemiparesis, stroke, chronic demyelinating diseases)	1.6	5.5	< 0.001
	Chronic renal insufficiency (including hemodialysis, urinary tract infections)	5.1	9.0	< 0.001
	Systemic diseases (RA, SLE)	2.6	7.4	< 0.001
	Senile dementia	0.3	5.0	< 0.001
	Bed sores	2.6	4.9	< 0.001
	Oncological diseases	2.6	4.1	< 0.001
	Alcoholism	30.8	7.4	< 0.001
	Hepatitis, HIV	23.1	14.8	< 0.001
	Drug addiction, toxicomania (smoking)	43.6	19.7	< 0.001

Note: p – value in comparison with the groups of young and older age (χ² – for the qualitative signs, t-test for the quantitative signs); * – falling from low height – falling from low furniture (a chair, a bed, an arm-chair, curbs, stairs); ¹ – percentage ratio for each item of comorbidity has been calculated with consideration of all patients with at least one concurrent disease.

Statistical analysis

Choice of predictive parameters

The preliminary analysis demonstrated 21 values, which are presented in the table 1 and could be used as the predictive parameters for estimating the risk of complications in patients with the proximal femoral bone injuries. We considered each value (total of 21) as a dichotomized variable in relation to the variants – gender, ISS, the amount of concurrent diseases (among 16 possible diseases).
The statistical analysis of the results was conducted with IBM SPSS Statistics 20. Student’s test and Mann-Whitney U-test were used for estimating the reliability of intergroup differences in dependence of the type of distribution of the variables.
The quantitative variables were presented as mean arithmetic values (M) and quadratic deviation of mean arithmetic values (SD) in the amplitude of the ordered sample as Me (LQ-UQ), where Me – is the median, (LQ-UQ) is interquartile range (LQ – 25 %, UQ – 75 %).
The extensive coefficients (%) describing the relationship between members and the integral were measured during the process of statistical analysis. The qualitative signs were presented as absolute and relative (%) values. Fisher’s exact test and χ² (chi-square) test were used for estimating the significance of differences of frequency of observation of the studied values in the study groups. The critical level of significance (p) was less 0.05 during testing the statistical hypotheses.
The randomized heterogeneous combined sample was used as a way of formation of the sampling population. The relationships were identified with multiple logistic regression for each concurrent disease, distinct from 0, with consideration of gender, ISS and amount of concurrent diseases.
The risk of complications was estimated with the comorbidity parameters, when the incidence of a concurrent disease was 2-3 times higher than the similar value in the young patients.

The model for development of a nomogram of clinical risk of complications

Multiple logistic regression was used for creation of a nomogram for predictive estimation of clinical risk of development of complications. First of all, we used three variables received at the moment of admission (age, gender, concurrent pathology). The variability was controlled with estimating the severity of injuries with use of ISS. The concurrent pathology was considered as a variable consisting of three categories: healthy persons (0 – absence of concurrent diseases), mean chronic state (1-2 and more concurrent diseases), multiple morbidity (3+ concurrent diseases). All types of interaction of the variables were analyzed (mutual influence between age, gender and the concurrent pathology). The statistically significant values (p < 0.05) were included into the final multivariate model.
We used the ISS = 15 (mean severity of an injury) for predictive estimation of risk of complications. Then we estimated the predictive risk of complications in relation to increasing age and categories of comorbidity for men and women. The analytic sample predicting the risk of complications was limited by at least three various preexisting states (Fig. 1).

Figure 1. The nomographic chart for calculation of risk of development of complications after surgical treatment of the patients with the proximal femoral bone fractures with consideration of the age, gender and the concurrent diseases. The complications included the infectious (wound infection, periprosthetic infection, urinary tract infection, pneumonia) and non-infectious complications (metal construct instability, thrombosis in the femoral artery and lower extremity veins, thrombophlebitis, thromboembolism, infarction, cerebral perfusion, sciatic nerve neuritis, renal insufficiency, contact dermatitis).
The nomographic chart is presented separately for the men and the women. The potential risk of complications in the coordinate axis (Y) is presented in concordance with the age (in the axis of abscissas (X) and comorbidity categories (0 – absent concurrent diseases, 1-2 concurrent disease, 3+ concurrent diseases).
The horizontal direct line (30 %) risk demonstrates the use of the nomographic chart for calculating the potential risk of complications. So, all values, which are higher than the values of the direct line of 30 % risk show the high risks of complications with consideration of gender and the age of the patients with injuries. For example, the men at the age of 50 with more than 3 concurrent diseases show 30 % risk of complications, as well as the men at the age of 55 with at least 2 concurrent diseases and the men at the age of 70 and older. The predictor risk with is presented in the similar manner with consideration of the age and concurrent pathology in the women (55 years and 3 concurrent disease; 60 years and 1-2 concurrent diseases; the women older than 75).

     

The nomographic chart for calculation of risk of development of complications after surgical treatment of the patients with the proximal femoral bone fractures with consideration of the age, gender and the concurrent diseases.
The complications included the infectious (wound infection, periprosthetic infection, urinary tract infection, pneumonia) and non-infectious complications (metal construct instability, thrombosis in the femoral artery and lower extremity veins, thrombophlebitis, thromboembolism, infarction, cerebral perfusion, sciatic nerve neuritis, renal insufficiency, contact dermatitis).
The nomographic chart is presented separately for the men and the women. The potential risk of complications in the coordinate axis (Y) is presented in concordance with the age (in the axis of abscissas (X) and comorbidity categories (0 – absent concurrent diseases, 1-2 concurrent disease, 3+ concurrent diseases).
The horizontal direct line (30 %) risk demonstrates the use of the nomographic chart for calculating the potential risk of complications. So, all values, which are higher than the values of the direct line of 30 % risk show the high risks of complications with consideration of gender and the age of the patients with injuries. For example, the men at the age of 50 with more than 3 concurrent diseases show 30 % risk of complications, as well as the men at the age of 55 with at least 2 concurrent diseases and the men at the age of 70 and older. The predictor risk with is presented in the similar manner with consideration of the age and concurrent pathology in the women (55 years and 3 concurrent disease; 60 years and 1-2 concurrent diseases; the women older than 75).

RESULTS AND DISCUSSION

Results

161 patients with the proximal femoral bone injuries who were admitted to the traumatology unit No.2, Regional Clinical Center o Miners’ Health Protection, were included into the study in compliance with the criteria (ISS ≤ 15, age ≥ 18, absence of transfer to other hospitals, duration of stay in the clinic ≥ 24 hours). The general mortality was absent in the patients included into the study.
The table 1 demonstrates the characteristics of the young and older patients with the proximal femoral bone injuries.
The amount of the men was higher (65 %) among the young patients. The mean age was 48.9 ± 1, ISS (SD) ≤ 15 (10.0). The main causes of the injuries were road traffic accidents (46.2 %), falling from low height (30.8 %), home injuries and diving (23 %) (the table 1).
Amongthe older patients, the amount of the men was lower (43 % vs. 65 %, p > 0.001), whereas the presence of at least one concurrent disease was more common for the older patients than the young ones (94.3 % vs. 87.2 %, p < 0.001). Falling from low height was more common for the older patients (83.6 % vs. 23 %, p < 0.001). The severity of the injuries was evidently lower in the older patients than in the young ones (ISS = 13 vs. ISS = 15, p < 0.001).
The types of operations and their amount in the patients with the proximal femoral bone injuries are presented in the table 2.

Table 2. Types and amount of performed surgeries in the patients of the examined groups with proximal femoral bone injuries

Groups of patients	Young patients (18-64 years) (n = 39)			Older patients (65+ years) (n = 122)
Proximal femoral bone fractures	Medial	Lateral	n	Medial	Lateral	n
Вид операции / Surgery type:
Total hip joint replacement	6	1	7	83	7	90
Fixation with cannulated screws	13	1	14	10	1	11
PFN fixation	1	17	18	6	15	21
Amount of operations, abs.	20	19	39	99	23	122

The table shows that the young patients (age of 18-64) with the medial and lateral injuries to the proximal femoral bone received 7 procedures of primary total hip joint replacement, 14 patients received the femoral bone fixation with the cannulated screws, 18 patients – the femoral bone osteosynthesis with PFN (18 %, 36 % and 46 % of operations in this group correspondingly).
The older patients (≥ 65 years) received the hip joint replacement in 74 % of the cases (the table 2). The feature of these operations included 2 cases of the acetabular defect replaced with bone automass from the resected and blenderized femoral head, 1 case of a supporting ring fixed to the pelvic bone according to Bursh-Schneider, 1 case of a prosthesis cup fixed with bone cement (Fig. 2).

Figure 2. The surgical techniques for the patients with the proximal femoral bone fractures: a) fixation with the cannulated screws; b) total hip joint replacement; c) PFN fixation

      

The postsurgical complications included the infectious (wound infection, periprosthetic infection, urinary tract infection, pneumonia) and non-infectious (instable metal constructs, thrombosis, thromboembolism, infarction, cerebral perfusion disorders, sciatic nerve neuritis, renal insufficiency, contact dermatitis) complications (the table 3).

Table 3. The predictive factors of risk of infectious and non-infectious complications in patients with proximal femoral bone injuries after surgery and multiple logistic regression analysis (OR – odds ratio, CI – confidence interval)

Comorbidity categories Values	Absence of concurrent diseases		All concurrent diseases			1-2 and more concurrent diseases		3+ concurrent diseases
	OR (95 % CI)	p	OR (95 % CI)		p	OR (95 % CI)	p	OR (95 % CI)	p
Age a	1.01 (0.98–1.03)	< 0,001	1.04 (1.03–1.05)		< 0.001	1.02 (1.01–1.03)	< 0.001	1.005 (0.89–1.01)	< 0.04
Men	0.61 (0.47–0.89)		0.67 (0.49–0.92)		<0.012	0.62 (0.44–0.88)	< 0.05	0.64 (0.46–0.92)	< 0.007
Value of ISS b	1.54 (1.44–1.64)	< 0.001	1.47 (1.38–1.56)		< 0.001	1.37 (1.33–1.46)	< 0.001	1.51 (1.41–1.61)	< 0.001
All complications	1.04 (1.03–1.05)	< 0.001	2.30 (1.9–2.7)		< 0.025	1.67 (1.44–1.8)	< 0.029	2.81 (1.18–6.66)	< 0.019
Infectious complications
Pyoinflammatory(wound infection) b			2.67 (2.34–2.8)	< 0.025				3.55 (3.20–3.90)	< 0.001
Periprosthetic infection b			2.07 (1.74–2.20)	< 0.025				3.49 (3.13–3.84)	< 0.001
Urinary tract infection b			1.43 (1.13–1.65)	< 0.025				3.28 (3.00–3.56)	< 0.001
Pneumonia b			1.27 (1.04–1.53)	< 0.025				3.13 (2.79–3.46)	< 0.001
Non-infectious complications
Metal construct instability b			1.87 (1.64–1.96)	< 0.025				3.63 (3.33–3.93)	< 0.001
Femoral artery thrombosis b								3.34 (3.12–3.56)	< 0.001
Thrombophlebitis and thrombosis in lower extremity veins b								3.22 (2.89–3.56)	< 0.02
Thromboembolismb								2.78 (2.38–3.18)	< 0.02
Infarction b								2.20 (1.46–2.94)	0.4
Cerebral perfusion disorders b								1.93 (1.67–2.2)	0.2
Sciatic nerve neuritis b								1.61 (1.36–1.86)	0.2
Renal insufficiency b								1.38 (1.28–1.48)	0.08
Contact dermatitis b								1.07 (1.03–1.11)	0.2

Note: ^a – odds ratio for annual increase; ^b – odds ratio for the moment of increase; ^* – p < 0.05.

As compared to the young patients, the older patients demonstrated the higher duration of hospital stay (24 % vs. 13 %, p < 0.001) and 2.4-fold increase in the risk of complications (p < 0.001) such as wound infection, periprosthetic infection, urinary tract infection, pneumonia, instability of metal constructs, femoral artery thrombosis, deep venous thrombosis in the lower extremities, progression of neurological manifestations, renal insufficiency (the table 3).
The following values were used for creation of the multiple logistic model (Fig. 1): age, gender, ISS, preselected categories of comorbidity (0, 1-2, 3+). Each age increase by 5 years was accompanied by the average increasing risk of complications by 10 % (95 % CI, 8.7-10.5 %). The assessment of the comorbidity categories showed that 56 % the patients had the preexisting risks of concurrent pathology with three or more diseases (3+) (95 % CI, 36-78 %). 29 % of the patients received the comorbidity categories 1-2 (95 % CI, 15-47 %) as compared to the patients without concurrent diseases (0 – a comorbidity category).
The men had the higher probability of complications (increase by 18 %, 95 % CI, 14-22 %) as compared to the women (p < 0.001). The most positive and significant relationship was found between the age and comorbidity (OR, 1,005, p < 0.04 per year for patients with three and more concurrent diseases), because the relationship between the age and comorbidity was left in the final model (Fig. 1).
The area under the curve, which describes the corresponding model, was 74 % (Fig. 1). Therefore, it is possible to use the presented model for estimating the risk of complications in patients with injuries to the proximal femoral bone in clinical practice.

Discussion

The older patients with the proximal femoral bone injuries showed more complicated and often unfavorable clinical course as compared to the young patients during the postsurgical period. Moreover, the registered infections (wound infection, periprosthetic and urinary tract infection, pneumonia) were associated with at least double risk of development of infectious complications in the older patients as compared to the young ones. Some non-infectious causes were also associated with the increasing risk of severe postsurgical course in the older patients, including instability of metal constructs, femoral artery thrombosis, thrombophlebitis, thrombosis in veins of the lower extremities, thromboembolism, infarction, cerebral perfusion disorder, sciatic nerve neuritis, renal insufficiency (the table 3).
In our study 14 % of the patients with the proximal femoral bone injuries experienced at least one complication during admission. As compared to younger patients, the older patients demonstrated 34 % risk of development of complications. These findings comply with the previous studies of the risk factors of mortality after traumatic injuries [3]. As result, early diagnostics and timely preventive measures are the main priorities in the treatment of older patients with the proximal femoral bone injuries.
In our study we used the estimation of comorbidity on the basis of three categories of the general amount of preexisting diseases. A close relationship was found between the age and the complications in the patients with 3 and more diseases (3+), which existed before an injury (the table 3). It corresponds to the previous observations that showed the increasing risk of mortality in trauma patients at the age > 45 [16]. Comorbidity can be a partial explanation of increasing risk of mortality [17].
The use of the primary information (acquired at the moment of admission, i.e. age, gender, chronic diseases) allowed developing the nomogram (Fig.1) for stratification of risk of complications in patients with the proximal femoral bone injuries. Such approach to estimating the clinical risk is supported by the modern guidance for treating trauma in older patients [7, 8].
The modern practical guidance does not recommend the use of the injury severity values for the treatment of individual patients, because these values are unknown up to the moment of discharge. However since the injury severity is a main predictive factor of complications and mortality in older patients, then the use of ISS was the necessary part of the design of our clinical study and was considered in compliance with the injury severity criteria – injuries of middle severity (ISS ≥ 15). The older patients had the lower value of ISS than the young ones, although this difference was not statistically significant. Probably, the cause of these differences can be the fact that the older patients are admitted with higher probability than younger patients, but with the same values of ISS. Other potential explanation is difference in the injury mechanism between two groups. Injuries after fallings from low height were the most common in the older patients.
For risk stratification it is necessary to conduct additional studies of the estimation methods, which can identify the injury mechanism and the injury severity degree at the early stage of inhospital treatment.

CONCLUSION

The conducted study has shown that the high risk of postsurgical complications has a close relationship between the age increase and the comorbidity index.
The perspective estimation of the functional status with consideration of preexisting concurrent diseases is a necessary screening measure for prediction of hospital complications in older patients. Finally, the complications, which were identified in the older patients with the proximal femoral bone injuries, should be interpreted as the complications with probable high risk of their development, but not as the complications causing such injuries.
The developed simple nomogram for clinical estimation of the risk of complications at the background of concurrent diseases in patients with the proximal femoral bone injuries can be used in combination with screening of the previous functional and physiological parameters for identification of older patients with maximal risk of complicated clinical course in the postsurgical period (Fig.1).
The perspective use of the offered nomogram requires the realization of future population-based studies that will confirm the possibility of its use and to define more efficient clinical approaches in the treatment of older patients with injuries and multiple chronic diseases.

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