The effect of surgery type on mortality in elderly patients with pertrochanteric femoral fracture: A Korean nationwide cohort study

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Asian Journal of Surgery xxx (xxxx) xxx

Available online at www.sciencedirect.com

ScienceDirect journal homepage: www.e-asianjournalsurgery.com

ORIGINAL ARTICLE

The effect of surgery type on mortality in elderly patients with pertrochanteric femoral fracture: A Korean nationwide cohort study Suk-Yong Jang a, Yong-Han Cha b,*, Kap-Jung Kim b, Ha-Yong Kim b, Won-Sik Choy b a b

Department of Preventive Medicine, Eulji University College of Medicine, Daejeon, South Korea Department of Orthopaedic Surgery, Eulji University Hospital, Daejeon, South Korea

Received 18 March 2019; received in revised form 7 June 2019; accepted 18 June 2019

KEYWORDS Hemiarthroplasty; Internal fixation; Mortality; Pertrochanter fracture; Treatment

Summary Background/Objective: The purpose of this study is to analyze the effect of surgical methods on mortality and the relative risk of patients who underwent internal fixation (IF) or hemiarthroplasty (HA) after being diagnosed as a pertrochanteric fracture over 65 years old in a Korean nationwide cohort with a single insurance medical system. Methods: The Korean National Health Insurance Service-Senior cohort (NHIS-Senior, NHIS-20182-111) was used in this study. The eligibility criteria for incident hip fracture patients were the following: (1) first-time admission to acute care hospitals (index admission) with pertrochanteric fracture (ICD-10 S721), (2) three years of hip fracture-free period, (3) recipients of typical surgeries including IF, HA, (4) age between 65 and 99. Results: a total of 7223 patients were enrolled in the cohort. There were 1662 patients (23%) in the HA group and 5561 patients (77%) in the IF group. Mortality rates of the IF group and HA group were 13.46 and 17.94 cases per 100 person-years, respectively. In the multivariableadjusted Cox proportional hazard model, the HA group had 1.22 times more hazard of allcause mortality than IF group (aHR 1.22, 95% CI 1.13e1.32). In subgroup analysis, aged 65 e79 and female patients showed a prominent association between surgery type and mortality (aHR 1.52, 95% CI 1.29e1.79). Conclusions: In patients with pertrochanter fracture over 65 years, 1.22-fold mortality rate was observed when HA was performed compared to that of IF, and the difference in mortality was particularly prominent within 1-year after surgery.

* Corresponding author. Department of Orthopaedic Surgery Eulji University hospital, 95 Dunsan Seoro, Seo-gu, Daejeon, 35233, South Korea. Fax: þ82 42 611 3283. E-mail address: [email protected] (Y.-H. Cha). https://doi.org/10.1016/j.asjsur.2019.06.006 1015-9584/ª 2019 Asian Surgical Association and Taiwan Robotic Surgery Association. Publishing services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Please cite this article as: Jang S-Y et al., The effect of surgery type on mortality in elderly patients with pertrochanteric femoral fracture: A Korean nationwide cohort study, Asian Journal of Surgery, https://doi.org/10.1016/j.asjsur.2019.06.006

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S.-Y. Jang et al. ª 2019 Asian Surgical Association and Taiwan Robotic Surgery Association. Publishing services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

1. Introduction Pertrochanter fractures involve between both trochanters of the femur and have been reported to have a high rate of mortality and morbidity.1 In order to reduce these problems, fractures should be early, firmly fixed and early ambulation should be performed. Internal fixation (IF) using a dynamic hip screw or proximal femoral nail is preferred as a primary treatment for this fracture and good clinical results are reported.2 However, if fracture site has severe comminution and reduction of the fracture is difficult, or if there is a fracture of the basi-cervical neck, or if there is severe osteoporosis, IF can result in cutout of the screw or excessive collapse of the fracture leading to shortening, implant breakage and pull out. Therefore, there have been reports of studies on hemiarthroplasty (HA) in some types of pertrochanteric fracture.3e5 In a previous study of pertrochanteric fractures, HA allowed early weight bearing and complications due to immobilization. On one hand, when compared to IF, intraoperative blood loss is greater and perioperative morbidity is higher.5,6 On the other, some recent studies have shown that HA has a better functional score and lower complication rate than IF, and has the advantage of enabling early ambulation, reducing reoperation risk, and reducing pain early in the postoperative period.7,8 Nevertheless, other studies have reported that intraoperative complications and mortality were higher when HA was performed, and there is still a debate on whether HA in pertrochanter fractures can decrease the patient’s mortality and morbidity.9,10 The above-mentioned studies were limited to specific types of pertrochanteric fractures and had a small group of patients. These studies did not analyze patients with all types of older pertrochanteric fractures. And it is difficult to assess the impact on mortality in the long period and the effectiveness of HA for patients exposed to various social environments.7 Thus, the purpose of this study is to analyze the effect of surgical methods on mortality and the relative risk of patients who underwent IF or HA after being diagnosed as a pertrochanteric fracture over 65 years old in a Korean nationwide cohort with a single insurance medical system. In addition, this study aims to investigate factors to be considered when choosing treatment.

2. Methods 2.1. Data source The Korean National Health Insurance Service-Senior cohort (NHIS-Senior, NHIS-2018-2-111) was used in this study. The NHIS-Senior was compiled by the Korean NHIS, and data can be accessed through the Korean NHIS website (https://

nhiss.nhis.or.kr/bd/ay/bdaya001iv.do). Through simple random sampling, 10% of the population of about 5.5 million South Korean enrollees older than 60 years of age in 2002; a total of 588,147 participants were selected into the NHIS- Senior. The NHIS-Senior was constructed to represent the elderly living in South Korea. Unless there was a disqualification for National Health Insurance, such as emigration or death, all the individuals included in the NHIS-Senior were followed until 2015. As a single payer under the single-insurer system of universal health coverage, the NHIS maintains all information containing personal information, demographics and medical treatment data for Korean citizens, who were categorized as insured employees, insured self-employed individuals or medical aid beneficiaries.11,12 The information in the data set included all inpatient and outpatient medical claims data, including treatment procedure codes and primary and secondary diagnostic codes. The protocol of this study was approved by the Institutional Review Board (IRB, No: EMC 2017-01-002-001).

2.2. Incident hip fracture cohort and all-cause mortality To identify incident hip fracture patients, inclusion criteria proposed by prior studies were applied with some modifications.13,14 The eligibility criteria for incident hip fracture patients were the following: (1) first-time admission to acute care hospitals (index admission) with diagnosis codes of pertrochanteric fracture (ICD-10 S721), (2) at least three years of hip fracture-free period, (3) recipients of typical surgeries including open reduction of fractured extremity (femur), closed pinning (femur), hemiarthroplasty (hip), (4) age between 65 and 99 at the time of a hip fracture.14 To ensure a minimum of 180-day follow-up period, patients were further excluded if they were enrolled in the incident hip fracture cohort 180 days before the end of observation period (June 31, 2015). The incidence date (index date) of hip fracture was defined as the date of admission to the acute care hospital fulfilling the eligibility criteria. The type of surgery was categorized into internal IF (open reduction of fractured extremity-femur and closed pinningfemur) and HA. In the NHIS-Senior, each subject’s unique de-identified number was linked to mortality information provided by the Korean National Statistical Office.12 The dates of death from the mortality information were used to calculate survival times.

2.3. Statistical analysis Baseline characteristics were identified at the time of hip fracture (time zero). Survival time used in survival analyses

Please cite this article as: Jang S-Y et al., The effect of surgery type on mortality in elderly patients with pertrochanteric femoral fracture: A Korean nationwide cohort study, Asian Journal of Surgery, https://doi.org/10.1016/j.asjsur.2019.06.006

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Mortality and surgery in pertrochanter Fx.

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was defined by days from the index date to dates of death or December 31 2015, whichever comes first. Denominators for the calculation of incidence rate were defined by survival time as unit of days divided by 365.25. The cumulative survival probabilities and survival curves were estimated and graphed by a KaplaneMeier method using the productlimit formula. Comparison of survival curves was performed by using the log-rank test of the null hypothesis of a common survival curve. A multivariable-adjusted Cox proportional hazards model was used to investigate the effects of surgery type on all-cause mortality. Proportional hazard assumption was checked by comparing logelog survival curves graphically. Effect sizes were presented as hazard ratios (HRs) and 95% confidence intervals (CIs). Included covariates were; age group, gender, household income level, residential area, Charlson Comorbidity Score (CCS), anesthesia types, number of hospital beds, and calendar year of the hip fracture incidence. Each subject’s number

Table 1

of comorbidities was assessed by diagnostic codes during the 3 years before the index date, using the Quan’s ICD-10 coding algorithm of the CCS.15 The presence of diseaseconstituting disease categories of the CCS was defined by at least two outpatient visits or one admission upon the primary or first secondary diagnosis. In addition to main analyses, subgroup analyses according to sex, age group, and a combined group of sex and age were performed. The statistical analyses were conducted using SAS Enterprise Guide version 7.1 (SAS Institute, Cary, NC, USA). P values < 0.05 were considered statistically significant.

3. Results Between January 1 2002, and December 31 2015, a total of 8540 pertrochanteric hip fracture patients were admitted to hospitals and received surgery. The 921 patients who first

Baseline characteristics of study participants at the time of hip fracture. Hemiarthroplasty

Variables 1662 Age group 65-69 37 70-74 216 75-79 372 80-84 468 85-89 355 >90 214 Mean(SD) 81.8 (6.59) Sex Female 1343 Male 319 Income High 705 Mid-high 398 Mid-low 321 Low 238 Charlson Comobidity score 0 361 1-2 756 3-6 445 >6 100 Anesthesia General 388 Spinal 1149 Unknown 125 Hospital beds >800 368 500-799 326 200-499 639 <200 329 Calendar year 2005e2006 221 2007e2008 279 2009e2010 317 2011e2012 386 2012e2015 459

Internal fixation

p-value

23%

5561

77%

2.23% 12.99% 22.38% 28.16% 21.36% 12.88%

279 938 1411 1443 1037 453 80.1 (6.6)

5.02% 16.87% 25.37% 25.94% 18.64% 8.15%

80.81% 19.19%

4056 1505

72.94% 27.06%

42.42% 23.95% 19.31% 14.32%

2528 1328 992 713

45.46% 23.88% 17.84% 12.82%

21.72% 45.49% 26.78% 6.017%

1227 2407 1555 372

22.06% 43.28% 27.97% 6.69%

23.35% 69.13% 7.52%

1243 4009 309

22.35% 72.09% 5.56%

22.14% 19.61% 38.45% 19.80%

1290 991 1923 1357

23.20% 17.82% 34.58% 24.40%

13.30% 16.79% 19.07% 23.23% 27.61%

773 868 1084 1207 1629

13.90% 15.61% 19.49% 21.70% 29.29%

<0.001

<0.001 <0.001

0.095

0.388

0.006

<0.001

0.385

SD: standard deviation.

Please cite this article as: Jang S-Y et al., The effect of surgery type on mortality in elderly patients with pertrochanteric femoral fracture: A Korean nationwide cohort study, Asian Journal of Surgery, https://doi.org/10.1016/j.asjsur.2019.06.006

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S.-Y. Jang et al. Table 2 Variables

Incidence rate and comparison of hazard for death according to type of pertrochanteric fracture surgery. Mortality ratea

Surgery type Internal fixation 13.46 Hemiarthroplasty 17.94 Age group 65-69 5.89 70-74 9.12 75-79 11.97 80-84 16.39 85-89 20.53 >90 30.81 Sex Female 12.95 Male 19.34 Income High 13.68 Mid-high 15.35 Mid-low 13.94 Low 15.90 Residential area Metropolitan 14.40 Non-metropolitan 14.40 Charlson Comobidity score 0 12.22 1-2 13.68 3-6 16.38 >6 21.33 Anesthesia General 14.05 Spinal 14.18 Unknown 19.29 Hospital beds >800 14.77 500-799 14.36 200-499 14.88 <200 13.39 Calendar year 2005e2006 14.37 2007e2008 13.62 2009e2010 14.90 2011e2012 14.77 2012e2015 14.44

Cases

Person years

aHR

95% CI

p-value

2531 900

18,803.62 5016.32

1 1.22

1.13

1.32

<0.001

115 433 747 949 762 425

1953.67 4746.87 6239.61 5789.14 3711.08 1379.58

1 1.67 2.35 3.46 4.56 7.35

1.36 1.93 2.84 3.73 5.94

2.06 2.87 4.22 5.58 9.11

<0.001 <0.001 <0.001 <0.001 <0.001

2383 1048

18,401.87 5418.06

1 1.81

1.68

1.95

<0.001

1480 851 612 488

10,817.61 5544.26 4389.13 3068.94

1 1.16 1.07 1.18

1.07 0.97 1.06

1.26 1.17 1.30

<0.001 0.186 0.002

1401 2030

9726.83 14,093.1

1 1.00

0.93

1.07

0.920

718 1465 977 271

5875.57 10,710.43 5963.56 1270.38

1 1.19 1.59 2.31

1.09 1.44 2.00

1.30 1.76 2.66

<0.001 <0.0001 <0.0001

785 2416 230

5586.08 17,041.57 1192.29

1 0.96 1.24

0.88 1.07

1.04 1.43

0.276 0.005

844 601 1217 769

5713.89 4184.79 8176.10 5745.15

1 1.02 1.06 1.00

0.92 0.97 0.91

1.14 1.16 1.11

0.705 0.220 0.954

737 749 800 685 460

5127.16 5498.88 5370.22 4637.41 3186.27

1 0.83 0.82 0.74 0.61

0.75 0.734 0.66 0.54

0.92 0.91 0.82 0.69

<0.0001 <0.0001 <0.0001 <0.0001

SD, standard deviation; aHR, adjusted hazard ratio; CI, confidence interval. Adjusted for age group, sex, income level, residential area, Charlson Comorbidity Score, anesthesia type, hospital beds, and calendar year. a Cases per 100 person-years, Denominators for the calculation of incidence rate were defined by survival time as unit of days divided by 365.25.

developed a hip fracture before December 31 2004, were excluded to make sure of at least 3-year hip fracture-free period. Additionally, 71 patients <65 or >99 years of age and 357 patients whose index date was within 180 days prior to December 31 2015, were excluded. Finally, a total of 7223 patients were enrolled in the cohort as elderly pertrochanteric hip fracture patients (Table 1). There were 1662 patients (23%) in the HA group and 5561 patients (77%) in the IF group. Female were 1343 (80.81%) in the HA group and 4056 (72.94%) in the IF group. There was statistical

difference in age, sex, type of anesthesia, and hospital bed between two groups (p < 0.05). Median survival time was 1451 days for HA group and 1908 days for the IF group. HA patients were older and consisted of more female subjects than IF patients (p < 0.05). However, Charson Comorbidity Index was not different between the two groups (p > 0.05). Mortality rates of the IF group and HA group were 13.46 and 17.94 cases per 100 person-years, respectively (Table 2). Thirty-day cumulative mortality rate was 2.51% (HA

Please cite this article as: Jang S-Y et al., The effect of surgery type on mortality in elderly patients with pertrochanteric femoral fracture: A Korean nationwide cohort study, Asian Journal of Surgery, https://doi.org/10.1016/j.asjsur.2019.06.006

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Mortality and surgery in pertrochanter Fx.

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Figure 1 Kaplan-Meyer curve of pertrochanteric hip fracture patients according to the type of surgery. P-value of Log-rank test was <0.001.

3.34%, IF 2.26%) and 1-year cumulative mortality rates was 17.3% (HA 21.8%, IF 16.0%), respectively. In the multivariable-adjusted Cox proportional hazard model, the HA group had 1.22 times more hazard of all-cause mortality than IF group (aHR 1.22, 95% CI 1.13e1.32). The difference in deaths between the two groups occurred rapidly within one year after surgery and is maintained thereafter (Fig. 1). As age increased, hazard of all-cause mortality increased and male had 1.81 times more hazard of all-cause mortality than female (aHR 1.81, 95% CI 1.68e1.95) (Table 2). In subgroup analysis, higher mortality of HA group than IF group was prominent among patient aged 65e79 (aHR

Table 3

1.35, 95% CI 1.18e1.54) and female patients (aHR 1.24, 95% CI 1.14e1.36) (Table 3). Among combined age-sex groups, younger (aged 65e79) and female patients showed a prominent association between surgery type and mortality (aHR 1.52, 95% CI 1.29e1.79).

4. Discussion The main results observed in this study is that HA has 1.22 times mortality rate compared to that of IF, in patients with pertrochanteric fractures older than 65 years, and the

Subgroup analyses of comparison of hazard for death according to type of pertrochanteric fracture surgery.

Subgroup

Age group 65-79 80 Sex Female Male Sex and age group Female and Age79 Male and Age79 Female and Age80 Male and Age80

Internal fixation

Hemiarthroplasty aHR

95% CI

p-value

Reference Reference

1.35 1.16

1.18 1.05

1.54 1.27

<0.001 0.003

Reference Reference

1.24 1.13

1.14 0.97

1.36 1.33

<0.001 0.123

Reference Reference Reference Reference

1.52 1.10 1.15 1.17

1.29 0.86 1.03 0.94

1.79 1.39 1.28 1.45

<0.001 0.445 0.012 0.152

aHR, adjusted hazard ratio; CI confidence interval. Adjusted for age group, sex, income level, residential area, Charlson Comorbidity Score, anesthesia type, hospital beds, and calendar year.

Please cite this article as: Jang S-Y et al., The effect of surgery type on mortality in elderly patients with pertrochanteric femoral fracture: A Korean nationwide cohort study, Asian Journal of Surgery, https://doi.org/10.1016/j.asjsur.2019.06.006

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6 difference between the two groups occurs mainly within 1 year after surgery. It is well known that both HA and IF are good treatments for elderly pertrochanteric fracture and that clinical results are satisfactory.16,17 However, many previous studies have reported that IF with proximal femoral nail or dynamic hip screw has advantages over HA in the treatment of pertrochanteric fracture patients. Golge et al. reported that the mortality of the HA group was 5.1 times higher than that of the proximal femoral nail at the 3-year follow-up of 202 patients over 60 years of age and Gormeli et al. reported that the mortality of the proximal femoral nail group was lower than that of the HA group in a comparative study of both groups at postoperative 30 months.17,18 Yang et al. also reported that mortality in the IF group was statistically significantly lower than that of the HA group during the 5-year follow-up period in 110 patients.19 The main results observed in this study also suggest that the use of HA in pertrochanteric fractures of 65 years of age or older would increase the risk of death by 1.22 times compared to that of IF. This is meaningful in that it reports the hazard ratio using big data, unlike the previous reports. Dobbs et al. reported that 30-day mortality did not differ between the two groups; however, the results of this study showed that there is a significant difference in early mortality between the two groups after the operation.9 Although Dobbs et al. reported different results of mortality from this study, they reported that the possibility of a complicated intraoperative course was higher in the HA group. Tang et al. also reported no difference in functional outcome between the two groups, but the HA group was less favorable in operative factors such as operation time, blood loss, blood transfusion and drainage.9,10 In the metaanalysis performed in China, the total complication rate of HA group was higher than that of IF group.20 The results of this study suggest that there is a difference in mortality at the initial stage of the surgery and that the surgical difference between IF and HA in older patients is likely to be one of the factors affecting the initial mortality difference. Another major observation in this study is that female patients who underwent HA (aged 65e79 years) had 1.52fold increased risk of death compared to those who underwent IF. The age-related hazard ratio of pertrochanteric fractures increases rapidly with age. However, age-related hazard ratios of patients who underwent HA compared to that of IF groups decreased with age. This means that age is the primary factor affecting mortality of pertrochanteric fracture in patients older than 80 years, not surgical procedures. In addition, the surgical method at age <80 years may have a greater impact on mortality. Many studies have been reported on the mortality of hip fractures, and these studies show differences in mortality rates due to the characteristics of each subjects.21e23 The meta-analysis also reported a 1-year cumulative mortality rate of 5.9e59% in elderly hip fractures.24 In this study, 30day cumulative mortality rate was 2.51% (HA 3.34%, IF 2.26%) and 1-year cumulative mortality rates was 17.3% (HA 21.8%, IF 16.0%), respectively. Recently, in many developing countries, populations are aging and many reports are expecting the increasing trends of the number of elderly hip fracture. Other reports are also expected that approximately 50% of all hip fractures in the world will occur in

S.-Y. Jang et al. Asia at 2050.25,26 This phenomenon is also observed in Korean society.27 Ha et al. in 2016 reported that the total number of hip fractures was estimated to increase an overall of 1.4 times by 2025.27 They were concerned that this increase would serve as a serious socioeconomic burden in the future and a significant challenge for public health management. This increasing trend is also seen in this cohort. In the calendar year, the number of hip fracture patients in 2005e2006 was 994, but the number of hip fracture patients in 2011e2012 increased to 386. This demonstrates the tendency of hip fractures to increase in Korean society today. There are some limitations to this study. Because of the limitation of cohort data, we could not analyze the severity of pertrochanteric fracture or osteoporosis. This is an important factor in the decision of surgery and can determine the severity of the injury. However, the severity of comorbidity and types of anesthesia were included in an effort for adjustment for severity of hip fracture. Secondly, intrinsic limitations regarding administrative claims data are present. Disease codes listed for the cohort may not represent a participant’s true disease status, which is an inherent limitation of insurance databases. Nonetheless, the incidence of hip fracture in this study could be measured fairly well, because nearly all types of healthcare providers follow the fee-for-service system and all treatment procedures such as surgeries are claimed by hospitals. Thirdly, the functional evaluation of the patient was not performed after surgery. Death is not the only factor considered in evaluating the outcome of surgery. Therefore, we cannot conclude that the results of this study should not be used for HA. Forth, we could not investigate specific cause of death due to inherent limitation of insurance database. Despite the above weaknesses, this study has several strengths. First, the NHIS-Senior is a cohort with large sample size, with a relatively low rate of follow-up loss over 13 years, due to the nature of the national administration data. Secondly, the NHIS-Senior represents the entire South Korean population over 60 years of age and therefore hip fracture patients of this study could represent entire South Korean hip fracture patient older than 65 years of age.

5. Conclusion In patients with pertrochanter fracture over 65 years, 1.22fold mortality rate was observed when HA was performed compared to that of IF, and the difference in mortality was particularly prominent within 1-year after surgery. The risk of death in the HA was 1.52 times higher than that of IF, in the female of 65e79 age groups.

Funding There is no funding source.

Ethics statement The study design and protocol were approved by the institutional review board of the Eulji University Hospital (EMC-

Please cite this article as: Jang S-Y et al., The effect of surgery type on mortality in elderly patients with pertrochanteric femoral fracture: A Korean nationwide cohort study, Asian Journal of Surgery, https://doi.org/10.1016/j.asjsur.2019.06.006

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Mortality and surgery in pertrochanter Fx. IRB No 2018-01-002-001). Written informed consent was waived all patients involved in this study.

Conflicts of interest No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.

Acknowledgements This study is based on data from the Korean National Health Insurance Service (research administration number, NHIS2018-2-111), and the results of the study are not related to the National Health Insurance Service.

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Please cite this article as: Jang S-Y et al., The effect of surgery type on mortality in elderly patients with pertrochanteric femoral fracture: A Korean nationwide cohort study, Asian Journal of Surgery, https://doi.org/10.1016/j.asjsur.2019.06.006