Our main findings are various mortality rates of the study population (1-month, 3-month, 6-month, 1-year, 2-year, 5-year and 10-year cumulative mortality rates were 3.15%, 5.5%, 7.4%, 17.94%, 29.76%, 56.8% and 83.38%, respectively) (Table 2). Several other studies reported the short-term outcomes after hemiarthroplasty for unstable trochanteric fracture with various results [8–18]. Their sample sizes are rather small (from 29 to 277) and most (> 70%) of them had sample sizes < 100 [8–10, 12–14, 18, 22–28]. Discrepancy in mortality rates among studies could bedue to differences in selection criteria, distributions of gender and age in the populations, pre-fracture physical activity, bone quality, nutrition, and comorbidities, in addition to sample sizes. Our one-month mortality was 3.15% in Taiwan, lower than 4–13.8% of the previous reports [9–12, 14, 28]. One possible reason is the progressive improvement in general medical careand healthcare with time. Our cohort started from 2000 which is a time more recent than most of those in the literature. The similar cohort effects can also be found in the previous studies from Korean [9, 15, 28]. Our 3-month mortality was 5.5%, lower than 7.0–26.6% reported in the previous studies [10, 12, 28]. Our 6-month mortality of 7.42%, which is also lower than 23.5–26.4% reported in the literature [10, 22, 27]. Cornwall et al. investigated the short-term mortality rates of 4 types of hip fractures [29]. Their in-hospital and 6-month mortality rates were 0% and 5.7% for 70 nondisplaced femoral neck fractures, 2.2% and 15.8% for 181 displaced femoral neck fractures, 2.8% and 12.8% for 108 stable intertrochanteric fractures and 1.1% and 13.8% for 178 unstable intertrochanteric fractures [29]. However, our 1-year mortality rate was 17.9% higher than 2.5–14.6% of the previous studies [13, 25, 26], but still lower than 21.8–39.3% in most past studies [9–12, 14–18, 28]. Our 2-year mortality rate was 29.7%, which falls in the mid-range of 12.5–59.0%, as reported in the literature [8, 9, 12, 16, 25, 28]. One possible reason is the accessibility of the long-term healthcare services in Taiwan for theses fragile seniors and disables. Our long-term healthcare services were started first in 2017. Before that time, our long-term healthcare system/service was worse than those of the major developed countries or welfare states. Therefore, our mortality rates after 1-year follow-up jumped into the middle range of the previous reports. Our 5-year mortality rate was 56.8% which was slightly higher than 52–64%, as reported in the literature for all hip fractures [2, 3, 19, 30]. Few studies reported 5-year mortality rates after hemiarthroplasty for unstable intertrochanteric fracture [16, 17]. Camurcu et al. and Cobden et al. reported their 5-year mortality rates as high as 94.4% and 90.25%, respectively [16, 17]. One important reason for the large differences in mortality rates between studies of ours and others [16, 17] is related to their smaller sample sizes. For a study with a smaller sample size study containing high mortality elderly adults, only a few number of survival subjects were left toward the end of the study such that a small number of deaths would cause huge impact on the change of the mortality rate and cause a sharp rise for the mortality rate at the end of the study.
Our short-term mortality rates after hemiarthroplasty for unstable trochanteric fracture are not higher than those hemiarthroplasty reported for cervical fracture and internal fixation for trochanteric fracture. For example, Forte et al. found 1-, 2-, and 3-month mortality rates among 192,365 elderly after internal fixations for trochanteric fractures are 7.92%, 12.34% and 15.19%, respectively [31]. The meta analyses of Mundi and Li et al. for the outcomes after trochanteric fracturesfound the 1-year mortality rate being 23% and 17% [32, 33]. Tucker et al. conducted a prospective including 3,230 unstable trochanteric fractures with internal fixations and found the 1-year mortality rate being 22.6% [34]. Mattisson et al. reported a study for trochanteric fracture based on a database from Swedish fracture register and found that the overall 30-day and 1-year mortality rates being 7.7% and 26% [35]. In contrast, our 5-year and 10-year mortality rates after hemiarthroplasty for unstable trochanteric fracture were 56.8% and 83.3%, which areall higher than those reported in the literature after hemiarthroplasty for cervical fracture [2, 3, 19, 30]. Lin and Liang examined the outcomes of subjects after hemiarthroplasty for displaced cervical fracture. They reported the 5-and 10-year mortality rates being 46.9% and 71% [19]. Studies reported that subjects with trochanteric fractures tended to be older, in worse health conditions and higher short-term mortality rates than those with femoral neck fractures [27, 36]. We believe that unstable trochanteric fracture with sequelae and aging both of which impact on the high mortality one year after fractures.
Other main findings of our study are the significant risk factors for overall survival rate being male gender, older age, larger CCI score and lower insured amount. Few studies reported on the risk factors for hemiarthroplasty after unstable trochanteric fracture [17]. Camurcu et al. reported 106 subjects after cementer bipolar hemiarthroplasty for unstable trochanter fracture and found that risk factors for 1-year mortality being American Society of Anesthesiologists (ASA) scores ≧ 3, delayed postoperative mobilization ≧ 2 days and presence of ≧ 3 comorbidities. Camurcu et al. did not find age and male being risk factors for 1-year mortality. Several meta-analyses reported that older age, male gender and multiple preoperative comorbidities are significant risks for mortality and medical complications after hip fractures in the elderly [1, 37]. We found that males had a hazard 1.31 times of females and age had hazard yearly 1.05 times higher for the overall mortality. We used CCI score representing the number and severity of comorbidities. Other investigators used instead ASA score for unstable trochanteric fractures [11, 12, 14, 16, 23, 24, 28]. Higher CCI, aging, higher ASA scores and delayed surgery are highly correlated with one another. Multiple comorbidities and aging often result in high ASA scores.We found that CCI score had stronger association with mortality than ASA score (data not shown here). CCI score or ASA score are in positive and strong correlation. They are bothgood measures for the number and severity of comorbidities. Since several studies had shown CCI score as a significantrisk factor associated with the mortality after hip fractures [38, 39]. For this reason, we had chosen CCI score as the measure for the severity of multiple comorbidities.
Several other studies reported readmission rates and reoperation rates after hemiarthroplasty for unstable trochanteric fracture [9–11, 13–15, 18, 22, 25, 28]. However these studies did not consider the interferences caused by the competing risk of deaths in estimating the cumulative incidence of the readmission and the reoperation rates. It is therefore difficult to compare their findings with ours. Other difficulties are the large variations in sample size across studies, the differences in the definition of causes for the readmissions, the follow-up times and the lost follow-up rates. We found that the 1-, 3-, and 6-month cumulative incidences of the first readmission after medical complications were 16.4%, 22.44% and 27.13%, respectively, using competing risk analysis. Previous studies reported the 1- to 6-month rates of medical complications ranged from 11.2–41.8% for subjects after hemiarthroplasty for unstable trochanteric fracture [9–11, 13, 18, 22, 25]. Several other studies reported the one-month readmission rates due to medical complications from 5.3–17.1% for all types of hip fractures [40–42]. Our cumulative incidences of the first readmission due to medical complications after hemiarthroplasty for trochanteric fracture seemhigher than those cervical fracture reported in literature [9–11, 13, 18, 19, 22, 25, 40]. Subjects with trochanteric fracture are older than those with cervical fracture of femur. Therefore, the first readmission rates are often higher in trochanteric fracture. We found that older age and larger CCI score are risk factors for the first readmission. In the literature review of Ali and Gobbons, they summarized that age, preoperative comorbidities are strong independent predictors of readmission after hip fracture operations [43]. Male gender, unlike for mortality, was not found to be a risk factor for readmission in our study. Pollock et al. did not find male gender being a risk for readmission in 1,486 subjects after hip fracture operations [44]. Lizaur-Utrilla et al. found that female gender, higher ASA score and more than 2 comorbidities are risk factors for readmission among 732 subjects after hip fractures [45]. And French et al. also found that female gender and multiple comorbidities are risk factors for readmission in 41,331 subjects after hip fractures [46]. That females have similar or higher risk for readmission might be due to the lower competing risk of death.Although Ali and Gibbons also found that ASA score being a predictor of readmission more robust than the CCI score or individual comorbidities [43]. However, we found the association with readmission was stronger with CCI score than with ASA score.
We found that 1-, 2-, 5-, and 10-years cumulative incidences of the first reoperation were 13.87%, 18.11%, 25.79%, and 38.24%, respectively. In the literature, large disparities existregarding surgical complications or reoperation rates after hemiarthroplasty for unstable trochanteric fractures [9–11, 13–15, 18, 22, 25, 28]. The 6-month surgical complication/reoperation rates arearound 2.2% [22]; one-year surgical complication/reoperation rates are from 2.6–20% [10, 13, 14] and 2-year surgical complication/reoperation rate are from 2.4–18.3% [9, 18, 25, 28]. Surgical site infection, dislocation and periprosthetic fracture are three major causes of the reoperations [9–11, 13–15, 18, 22, 25, 28]. The 1-year reoperation rates are from 2.9–16.3% after hemiarthroplasty for displaced femoral neck fracture in the literature [19, 47, 48]. By contrast, in our study, older age was a protective factor for reoperation. For each yearly increase in age, the sub-distribution hazard ratio (sHR) dropped by 1.4% (sHR: 0.986, 95% CI: 0.974–0.998) for reoperation. Again, the different directions of the risks between the long-term mortality and the reoperation were due to the competing risk of death. Therefore, the more healthy subjects would be left in the risk set for reoperation, resulting in lowering the risk for reoperation. The competing risk of death usually has a larger impact on the outcomes of long-term than of short-term. We did not identify other significant risk factors for reoperation apart from younger age. Competing risk of death partly explains for that.The reoperation rates of hemiarthroplasty for unstable trochanteric fractureare still comparable to hemiarthroplasty after femoral neck fracture. Therefore, we speculate that hemiarthroplasty is likely a robust alternative management for unstable trochanteric fracture among a heterogeneous elderly population.
Our retrospective population study has several limitations. The database, unlike hip fracture registry database or prospective study, does not contain all clinical parameters. Retrospective studies often are vulnerable to selection bias and unknown confounding factors. All the hemiarthroplasty operations were required to be approved in advance by 3 orthopedic surgeons through peer-review system of NIH program such that it could reduce large selection bias. However, no pre-approval was required for internal fixation. And no standard criteria or nor guidance existed for the diagnosis and implant selection of unstable trochanteric fracture for internal fixation. Therefore, we did not include internal fixation for trochanteric fracture as controls to avoid large selection bias. Subjects were enrolled from 2000 to 2010 and followed up from 2- to 10-year in the study. During the long study period and the long follow-up time, regular healthcare improvements take place in admission policy and postoperative period required. Therefore, some confounding factors or lurking factors were not completely controlled usingstatistical modeling approaches. The ICD codes for medical complications and surgical complications always had variations such that misclassifications existed to interfere in estimating the readmission rates and reoperation rates. The distinctions between medical complications and newly developed comorbidities were not well separated after a major surgery. We therefore interpreted a shorter time duration (from the index date to the date of the first medical readmission) reflecting a higher probability index surgery leading directly or indirectly to readmissions related to medical complications. Furthermore, extrapolations from the readmission rate and reoperation rate should be done with caution.