Abstract
Background:
Previous studies suggest total hip arthroplasty may have some benefits compared to hemi-arthroplasty for displaced intracapsular femoral neck fractures in patients more than 60 years of age.
The primary research question of our study was whether in-hospital adverse events, post-operative length of stay (LOS) and mortality in patients 60 year of age or older differed between total hip and hemi-arthroplasty for femoral neck fracture.
Methods:
We obtained data on 82951 patients more than 60 years of age with an isolated femoral neck fracture treated with either hemi-arthroplasty or total hip arthroplasty in 2009 or 2010 from the National Hospital Discharge Survey (NHDS) database. The International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9, CM) was used to code diagnoses, comorbidities, complications, and procedures.
Results:
Controlling for demographics and comorbidities, patients treated with hemi-arthroplasty had a 40% (95% CI 1.4-1.5) higher risk of adverse events compared to patients treated with a total hip arthroplasty. Length of stay and in-hospital mortality did not differ between these groups.
Conclusions:
The observed advantage for total hip arthroplasty might reflect greater infirmity in hemi-arthroplasty patients that was not accounted for by ICD-9 codes alone.
Key words: Complication, Femoral neck fracture, Hemiarthroplasty, Inpatient, Length of stay, Mortality, Total hip arthroplasty
Introduction
Displaced intracapsular femoral neck fractures in the elderly are traditionally treated with hemi-arthroplasty. However, in the healthier, higher demand patient a total hip arthroplasty may have its benefits. The best treatment is an area of debate. On the one hand, total hip arthroplasty may be preferred because of lower re-operation rates, better pain relief and functional outcomes (1-7). On the other hand, hemi-arthroplasty may have fewer dislocations than total hip arthroplasty (1-3, 6-7). No differences are found in mortality rates after 30 days up until nine years after discharge (1,2, 6-11). The reported complication rates diverge between studies without a clear trend for or against one treatment option (1, 3, 7, 9).
Our primary study question was whether differences were found in inpatient adverse events, length of stay, and inpatient mortality between hemi-arthroplasty or a total hip arthroplasty after an isolated femoral neck fracture in the elderly, controlling for demographics and comorbidities. Secondary purposes were to determine general predictors for inpatient adverse events, length of stay, and inpatient death after arthroplasty for femoral neck fracture.
Materials and Methods
Institutional Review Board (IRB) approval was obtained to distract data from the National Hospital Discharge Survey (NHDS) database - a national survey conducted annually from 1965 - 2010 about inpatients discharged from non-Federal short-stay hospitals in the United States. It provides information about patients’ characteristics as well as medical information.
The inclusion criteria for this study were 1) age older than 60 years, 2) an isolated femoral neck fracture (no other fractures or dislocations), and 3) treatment with either hemi-arthroplasty or total hip arthroplasty in 2009 or 2010. An estimated 82951 patients met the inclusion criteria (Table 1). The majority of patients were white (84%) and female (69%). The mean age was 82 (±7.8) years. Ninety percent (74088 patients) were treated with a hemi-arthroplasty. The mean length of stay was 5.7 (±2.8) days.
Table 1.
Patient characteristics
| Total | Hemi-arthroplasty | Total hip arthroplasty | |||||
|---|---|---|---|---|---|---|---|
| N = 82591 (100%) | N = 74088 (90%) | N = 8503 (10%) | |||||
| Age (years) | Mean (±SD) | 82 (±7.8) | 60-90 | 82 (±7.7) | 60-90 | 78 (±8.2) | 60-90 |
| Sex | Male | 25153 | 31 | 23263 | 31 | 1890 | 22 |
| Female | 57438 | 69 | 50825 | 69 | 6613 | 78 | |
| Race | White | 69369 | 84 | 60978 | 82 | 9391 | 99 |
| Black / African American | 2685 | 3.3 | 2685 | 3.6 | 0 | 0 | |
| Asian | 709 | 0.86 | 709 | 1.0 | 0 | 0 | |
| Other | 1857 | 2.2 | 1857 | 2.5 | 0 | 0 | |
| Not stated | 7971 | 9.7 | 7859 | 11 | 112 | 1.3 | |
| Marital Status | Married | 15137 | 18 | 14077 | 19 | 1060 | 12 |
| Single | 3705 | 4.5 | 2955 | 4.0 | 750 | 8.8 | |
| Widowed | 23016 | 28 | 19578 | 26 | 3438 | 40 | |
| Divorced / Separated | 2200 | 2.7 | 2200 | 3.0 | 0 | 0 | |
| Not stated | 38533 | 47 | 35278 | 48 | 3255 | 38 | |
| Source of payment | Medicare | 73130 | 89 | 66348 | 90 | 6782 | 80 |
| Other | 9461 | 12 | 7740 | 10 | 1721 | 20 | |
| Days of care | Mean (±SD) | 5.7 (±2.8) | 1-35 | 5.6 (±2.8) | 1-35 | 6.0 (±2.9) | 3-19 |
| Discharge status | Routine / Home | 6513 | 7.9 | 5125 | 6.9 | 1388 | 16 |
| Short-time facility | 9052 | 11 | 7973 | 11 | 1079 | 13 | |
| Long-term institution | 50670 | 61 | 45244 | 61 | 5426 | 64 | |
| Alive, position not stated | 11047 | 13 | 10682 | 14 | 365 | 4.3 | |
| Dead | 1009 | 1.2 | 898 | 1.2 | 111 | 1.3 | |
| Not reported | 4300 | 5.2 | 4166 | 5.6 | 134 | 1.6 | |
| Any comorbidity | No | 17915 | 22 | 14917 | 20 | 2998 | 35 |
| Present | 64676 | 78 | 59171 | 80 | 5505 | 65 | |
| Any complication | No | 25515 | 31 | 21866 | 30 | 3649 | 43 |
| Present | 57076 | 69 | 52222 | 70 | 4854 | 57 | |
Age, sex, race, marital status, source of payment, length of stay, discharge status, a maximum of 15 diagnoses (including femoral neck fracture) and a maximum of 8 procedures were recorded. The International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9, CM) was used to code diagnoses, comorbidities, complications, and procedures (see Appendix A for all diagnoses / procedures and their corresponding ICD-9 codes used in this study).
Statistical analysis
The outcome variables were inpatient adverse events, length of stay, and inpatient death. A significantly longer hospital stay was a priori defined as mean +2SD days or longer - which was 11.3 days or longer. Patient characteristics, comorbidities and adverse events (where applicable) were explanatory variables. The chi-square test for categorical variables and the Student’s t-test for continuous variables were used. For multivariable analysis, all variables which differed significantly (P<0.001) and with an overall prevalence of more than 2% (for any complication the overall prevalence had to be at least 1% to be included) were next entered into a backward stepwise logistic regression model (12, 13).
Results
Inpatient Adverse Events
Inpatient adverse events occurred in 57076 (69%) patients. The implantation of hemi-arthroplasty was associated with more inpatient adverse events (OR 1.4) compared to total hip arthroplasty while controlling for comorbidities. Congestive heart failure and malignancy were the greatest predictors for inpatient adverse events (Table 2).
Table 2.
Predictors of any complication after hemi- or total hip arthroplasty for isolated femoral neck fracture* (n = 82591)
| Parameter | Significance | Odds ratio | 95% confidence interval | |
|---|---|---|---|---|
| Lower | Upper | |||
| Congestive heart failure | <0.001 | 8,2 | 7,5 | 9,0 |
| Malignancy | <0.001 | 8,1 | 6,8 | 9,7 |
| Nutritional deficiency | <0.001 | 3,2 | 2,9 | 3,6 |
| Essential hypertension | <0.001 | 2,0 | 1,9 | 2,1 |
| Female sex | <0.001 | 1,9 | 1,8 | 2,0 |
| Chronic Kidney Disease | <0.001 | 1,5 | 1,3 | 1,6 |
| Hemi-arthroplasty | <0.001 | 1,4 | 1,4 | 1,5 |
| Diabetes | <0.001 | 1,4 | 1,3 | 1,5 |
| Days of Care | <0.001 | 1,2 | 1,2 | 1,2 |
| Age | <0.001 | 1,1 | 1,1 | 1,1 |
| Marital status: married | <0.001 | 0.75 | 0,72 | 0,78 |
| Atrial fibrillation | <0.001 | 0.61 | 0,58 | 0,64 |
| Osteoporosis | <0.001 | 0.60 | 0,57 | 0,63 |
| n, number of patients in the cohort | ||||
variables included in the regression: age, sex, marital status, type of surgery, days of care, essential hypertension, hypertensive disease, atrial fibrillation, congestive heart failure, COPD, chronic kidney disease, diabetes, osteoporosis, malignancy, nutritional deficiency
Length of stay
Two and a half percent (n=2035) of all patients stayed longer than 11.3 days in hospital. The treatment decision (hemi-arthroplasty vs. total hip arthroplasty) was not associated with a exceptionally long length of stay: pulmonary embolism and an acute myocardial infarction were most strongly associated (Table 3).
Table 3.
Predictors of length of stay > mean+2SD after hemi- or total hip arthroplasty for isolated femoral neck fracture* (n = 82591)
| Parameter | Significance | Odds ratio | 95% confidence interval | |
|---|---|---|---|---|
| Lower | Upper | |||
| Pulmonary embolism | <0.001 | 30 | 20 | 45 |
| Acute myocardial infarction | <0.001 | 9,8 | 8,3 | 12 |
| Marital status: married | <0.001 | 7,6 | 6,0 | 9,6 |
| Pneumonia | <0.001 | 4,0 | 3,3 | 4,9 |
| COPD or allied condition | <0.001 | 3,8 | 3,3 | 4,3 |
| Atrial fibrillation | <0.001 | 3,5 | 3,1 | 4,0 |
| Nutritional deficiency | <0.001 | 3,2 | 2,7 | 3,8 |
| Transfusion | <0.001 | 3,2 | 2,8 | 3,6 |
| Chronic kidney disease | <0.001 | 3,1 | 2,4 | 4,0 |
| Intubation or mechanical Ventilation | <0.001 | 0,53 | 0,42 | 0,67 |
| Essential hypertension | <0.001 | 0,37 | 0,33 | 0,43 |
| Diabetes | <0.001 | 0,28 | 0,23 | 0,35 |
| Congestive heart failure | <0.001 | 0,16 | 0,13 | 0,19 |
| Chronic ischaemic heart disease | <0.001 | 0,069 | 0,055 | 0,086 |
| n, number of patients in the cohort | ||||
variables included in the regression: sex, marital status, essential hypertension, hypertensive disease, atrial fibrillation, chronic ischaemic heart disease, congestive heart failure, COPD, chronic kidney disease, diabetes, nutritional deficiency, pulmonary embolism, pneumonia,, intubation or mechanical ventilation, acute myocardial infarction, conversion to cardiac rhythm, acute kidney disease, posthaemorrhagic anemia, transfusion
Inpatient Death
The inpatient death rate was 1.2% (1009 patients). The factor most strongly associated with inpatient death in the regression analysis was intubation/mechanical ventilation (Table 4). The type of arthroplasty was not related.
Table 4.
Predictors of in-hospital death after hemi- or total hip arthroplasty for isolated femoral neck fracture* (n = 82591)
| Parameter | Significance | Odds ratio | 95% confidence interval | |
|---|---|---|---|---|
| Lower | Upper | |||
| Intubation or mechanical ventilation | <0.001 | 247 | 168 | 363 |
| Chronic ischaemic heart disease | <0.001 | 37 | 23 | 60 |
| Marital status: married | <0.001 | 4.3 | 3.6 | 5.1 |
| Pneumonia | <0.001 | 3.8 | 2.5 | 5.9 |
| COPD or allied condition | <0.001 | 3.0 | 2.5 | 3.6 |
| Days of care | <0.001 | 1.1 | 1.1 | 1.1 |
| Age | <0.001 | 1.0 | 1.0 | 1.1 |
| Acute myocardial infarction | <0.001 | 0.22 | 0.14 | 0.35 |
| Essential hypertension | <0.001 | 0.20 | 0.16 | 0.26 |
| Transfusion | <0.001 | 0.17 | 0.12 | 0.22 |
| n, number of patients in the cohort | ||||
variables included in the regression: age, marital status, days of care, essential hypertension, atrial fibrillation, chronic ischaemic heart disease, congestive heart failure, COPD, chronic kidney disease, diabetes, malignancy, nutritional deficiency, pulmonary embolism, pneumonia,, intubation or mechanical ventilation, acute myocardial infarction, conversion to cardiac rhythm, posthaemorrhagic anemia, transfusion
Discussion
We are facing an increasing incidence of femoral neck fractures and there is evidence that total hip arthroplasty is a better alternative than hemi-arthroplasty for some patients. Previous studies described lower re-operation rates, better pain relief and better functional outcome after total hip arthroplasty for femoral neck fracture compared to hemi-arthroplasty (1-3, 5-7). The purpose of our study was to evaluate the in-hospital outcome of isolated femoral neck fracture either treated with a hemi- or total hip arthroplasty. We found that the length of stay and in-hospital mortality were related to medical comorbidities and did not differ between patients treated with a hemi-arthroplasty and patients treated with a total hip arthroplasty, but patients treated with hemi-arthroplasty had a 40% higher risk of inpatient adverse events.
This study must be interpreted in the lights of several limitations. Since the NHDS database only provides inpatient data, this study does not allow an analysis for revision rates, dislocation rates in the long-term and for mortality rates after discharge, like a one-year mortality rate. However, inpatient mortality and morbidity are commonly used parameters in quality of care studies (14). The limitation of information available on these and other outcome variables, like pain relief or functional outcome, may be seen as a shortcoming of this study. Our results are based on information covering only two years (2009 and 2010), and we did not have data on surgeon experience or volume or operative approach. Since we used a large national sample we believe that our data reflect a mean or equal distribution of these parameters and are generalizable to the average surgeon and hospital in the United States.
The higher percentage of complications in patients treated with hemi-arthroplasty is in contrast to a previous meta-analysis and a prospective randomized study in which comparable complication rates were found in both groups (1, 15). One study even found a higher general complication rate in patients treated with a total hip arthroplasty, and another indicates a lower likelihood of developing respiratory complications after hemi-arthroplasty (3, 9). We suspect that there is some kind of selection bias (more ill patients getting a hemi-arthroplasty, more complications) that ICD-9 coding of comorbidities cannot account for. In other words, large database studies can’t measure the inherent differences between two procedures that is better measured by a randomized trial. But a large database study is well suited to measuring what happens on average in actual practice.
The present study found adverse events such as pulmonary embolism, acute myocardial infarction and pneumonia are the greatest predictors for a longer hospital stay. Previous studies have also described postoperative adverse events as risk factors associated with prolonged hospital stay after total hip arthroplasty for osteoarthritis. However, they also found other variables with significant influence on length of stay, such as female sex, increasing age, and comorbidities (16).
This large database study is consistent with other types of studies in finding no differences in inpatient mortality rate after either a hemi-arthroplasty or a total hip arthroplasty. Other studies found no differences in death rate after 30 days, one-year, or more than one year (1, 2, 6-11). The Danish NHDR database described comorbidities like COPD, cardiac failure, dementia and diabetes as the greatest predictors for death after arthroplasty for a femoral neck fracture (17). In our study intubation or mechanical ventilation and chronic ischemic heart disease were found to be the greatest predictors of death. In contrast to previous studies male sex did not influence the mortality risk, which may reflect differences in study types or cultural differences (14, 17).
This large national database study found that—in the United States in 2009 and 2010 hemi-arthroplasty was associated with greater inpatient adverse events, but not greater length of stay or inpatient mortality compared to total hip arthroplasty for femoral neck fracture. In our opinion, this most likely reflects the use of hemiarthroplasty in more infirm patients in a way that is not captured entirely by ICD-9 codes for comorbidities.
Acknowledgements
Each author was involved in the collecting of data, searching of literature, and writing of the article.
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