This study demonstrates that various factors such as fracture site, surgical type, comorbidities and pre-fracture functional status significantly influence physical function outcomes and QoL 6 months after fragility hip fracture surgeries, thus, providing an integrated, rather than fragmentary, view of the patient's recovery after hip fracture surgery.
First of all, our results are concordant with previous studies showing the association between age and gait recovery in patients with fragility hip fractures. In this study, FAC scored lower in older patients at 6 months post-surgery, meaning that older patients had less gait recovery than younger patients. This finding is similar to that by Takahashi et al. [24] who used the same scale of FAC. They concluded that old age negatively affects ambulatory functional outcomes in patients with hip fractures. Wong et al. [25] also argued that risk of ambulation deterioration increased for every 10 years of age.
In addition, our study showed that K-IADL scored higher in older patients at 6 months post-surgery, meaning that older patients had less independent in daily life than younger patients. Many studies have shown that older patients had poor recovery to the pre-fracture ADL [26–28]. Mayoral et al. [26] argued that comorbidities, cognitive status and previous physical state affect poor recovery of older patients. Considering the above hypothese and that there was no significant difference in MMSE scores by age in our study, the negative effect of age on the FAC and K-IADL score in our study can be considered to be due to the combination of physical state and comorbidities.
There have been relatively many studies on mortality and ambulatory function after surgery according to fracture type [24, 29–36]. There was study that showed no difference in mortality or function according to fracture type [36], and there were rare reports that intertrochanteric fracture had worse function [29, 35], but overall, intertrochanteric fracture reported worse initial function [24, 30], mortality [31, 32] and functional outcomes [24, 30, 33, 34].
Consistent with past reports, Intertrochanteric fracture had a significantly higher Koval’s grade in this study and it indicates that patients with intertrochanteric fracture have significantly poor recovery of walking ability. A possible explanation of this finding may be biologically older age of patients with intertrochanteric fracture. Lawton et al. [37] reported that patients with intertrochanteric fractures had poorer prefracture ambulatory function and more associated medical conditions, such as anemia, that affected fracture management than patients with femoral neck fractures. Similarly, Jarnlo et al. [38] also reported that patients with intertrochanteric fractures seemed to be less active than patients with femoral neck fractures. Another possible explanation may be pain, reduced knee-extension strength and larger edema in the thigh with intertrochanteric fracture [39, 40].
There was a significant difference in functional outcome according to operation type in our study. Several studies have investigated the relationship between postoperative functional outcomes and surgical type, and the results have been varied [36, 41–46]. There were reports that there was no difference in functional outcome depending on the surgical method [36], or that internal fixation produced better results [41], but in most cases, arthroplasty showed better results than internal fixation and total hip replacement showed better results than bipolar hemiarthroplasty among arthroplasty.
Chammout et al. [45] who compared the results of total hip replacement with those of internal fixation over a long-term follow-up period of seventeen years concluded that total hip replacement provided better hip function and significantly fewer reoperations compared with internal fixation without increasing mortality. Alexiou et al. [46] assessed forty-nine randomized controlled trials or prospective cohort studies reporting the QoL and psychological outcomes and demonstrated that arthroplasty had better functional outcomes than internal fixation, including QoL and health status.
In our study, total hip replacement arthroplasty and bipolar hemiarthroplasty showed significantly higher EQ-5D and FAC, respectively. In other words, arthroplasty showed better results compared to internal fixation in quality of life and ambulatory function, so the results were consistent with the literature.
In terms of the relationship between hypertension and fragility hip fractures, EQ-5D related to QoL scored lower in patients with hypertension in our study. The association between hypertension and QoL has been has been proven through many studies [47–49]. Bardage et al. [47] demonstrated that hypertensive patients had significantly lower quality of life, with lower health-related quality of life (HRQL) and 36-item short form questionnaire (SF-36) scores. Previous studies explained that hypertensive individuals have reported lower social and psychological functioning [50, 51] and have been associated with symptoms [52, 53] and/or side effects of antihypertensive medication [54, 55] such as headache, dizziness, depression, anxiety, and tiredness.
A link between hypertension and frailty has also been established in many studies [56–58]. Kang et al. [56] argued that uncontrolled hypertension can cause serious cardiovascular events and hypertension is related to future ADL/IADL limitation or disability. In this regard, in patients with hip fractures, it can be considered that hypertension-related deterioration of social and psychological function, symptoms and frailty will cause a decrease in QoL.
With respect to the relationship between diabetes mellitus and fragility hip fractures, K-IADL scored higher in patients with diabetes mellitus in our study. It is well known that diabetes is a risk factor for fragility hip fractures [59] and several studies on the effects of diabetes mellitus on functional outcomes and mortality post-surgery in patients with fragility hip fractures showed negative effect [60–62].
Yoon et al. [60] found that diabetes negatively affected a variety of functional outcomes, including not only K-IADL and also the FAC, EQ-5D, K-FRAIL and GDS related to depression. Lieberman et al. [61] concluded that the rehabilitation outcome of diabetic patients was significantly worse than that of non-diabetic patients among older patients with hip fractures using the FIM scale. The explained diabetic patients have an increased risk for medical complications such as cerebrovascular and cardiovascular event and surgical site infection. Rutenberg et al. [62] demonstrated that higher mortality, more medical complications and longer rehabilitation duration in diabetic patients with fragility hip fractures.
On the other hand, Tian et al. [63] argued that diabetes does not affect post-fragility hip fracture functional outcomes and mortality. However, they also reported the higher incidence of postoperative complications, such as urinary tract infections and deep vein thrombosis in patients with diabetes. Therefore, decreased ability of diabetic patients to perform daily activities can be thought to be primarily due to medical complications.
Initial functional status is one of the most well-known predictive factors of functional outcome after hip fracture surgery. Many studies have already reported associations between various initial functional statuses, such as cognition [64–74], gait [24, 64, 68, 71, 75–77], and ADL [78–82], and postoperative functional outcomes using various evaluation tools.
It has been reported that poor cognitive function significantly adversely affects functional recovery of gait and ADL after hip fracture surgery [64–74]. Liang et al. [72] demonstrated that patients who had cognitive impairment showed significantly less improvement in ambulatory status than reference patients and significantly lower MBI score after hip fracture rehabilitation. Söderqvist et al. [74] found that cognitive dysfunction of patients with hip fracture effectively predicted their outcome with regard to the ability to walk and perform ADL.
It has also been studied that the initial ambulatory state and ADL state significantly affect gait and ADL function recovery after hip fracture surgery. Several studies reported that patients with better score of Timed up and go test [77], BBS [71], and FAC [24] showed significantly good recovery of ambulatory function after hip fracture surgery. Other studies found that patients with good ambulatory ability after hip fracture surgery have also been more likely to regain their prefracture independent living status. Initial ADL function was found that independent predictor of ADL and QoL after hip fracture surgery. Ishidou et al. [79] showed that an increased risk of Barthel Index (BI) deterioration was associated with worse BI at discharge and Chang et al. [82] reported that poor baseline ADL could predict poor QoL 6 month after hip fracture surgery.
Based on these results, it can be seen that the functional state does not affect cognition, gait and ADL separately, but complexly influences each other. Thus, our findings support previous studies. It was found that cognition, gait, and ADL influence each other in this study. Among them, initial 4MWT showed a significant difference in the most functional outcomes (Koval, BBS, 4 MWT, K MMSE and K MBI) and MMSE also showed a significant difference in BBS, MMSE, MBI. Therefore, evaluating cognition, gait speed, and ADL will be a simple and useful method for predicting prognosis and preparing for rehabilitation strategy in clinical practice.
Previous studies demonstrated that there is a direction of loading in which a hip fracture easily occurs [83, 84] and several studies have been conducted on the fall characteristics as a risk factor of hip fracture [85, 86]. Hwang et al. [86] reported that sideway falls and backward falls were associated with 12.8- to 15.2- and 9.86- to 10.8-fold increased risks of hip fractures, respectively. Cumming et al. [87] hypothesized that a sideways fall would likely absorb the impact directly because there is less soft tissue such as skin, fat, and muscle.
However, no study was conducted on whether the fall characteristics such as direction and location affect the functional outcomes after hip fracture surgery. In this study, fall direction and didn’t reveal any significant impact on functional outcomes. This suggest that the fall direction has a significant effect on the direction and value of the load and therefore affects the risk of hip fracture, but once a load above the threshold sufficient to induce a hip fracture is applied, the fall direction does not significantly affect the functional outcome.
The fall location showed different indoor and outdoor ratios in various studies [87, 88], and to our knowledge, it was not reported as an independent risk factor for hip fracture. In our study, outdoor was about three times of indoor, but it did not have a significant effect on functional outcomes. However, further studies are needed to determine the relationship between fall characteristics and postoperative functional outcomes in patients with fragility hip fractures. It can be helpful to study the relationship between the fall direction and fall location as well as the situation or behavior at the time of the fall and functional outcomes.
Limitation
Our study has several limitations. First, because the study was conducted on Korean patients who received rehabilitation treatment at a tertiary hospital, the study population may not represent the general community-dwelling older adults who have suffered from fragility hip fractures. Second, the prefracture functional status was not evaluated in this study. Prefracture functional status is one of the best-known predictive factors of functional outcome after hip fracture surgery [26, 89–92]. Since preoperative functional status is likely to be poor in patients with older age, comorbidities and intertrochanteric fracture, further studies are needed to evaluate the effect of this on postoperative functional outcomes. Third, among the numerous comorbidities, only comorbidities with a relatively high frequency could be studied. Therefore, larger studies are needed to evaluate the effects of these factors on the functional outcome post-fragility hip fracture surgeries.
Despite the limitations, this study has several strengths. First, this study has identified and clarified which factors can affect the postoperative functional outcomes. Therefore, clinicians can focus on intervening certain factors such as comorbidities as well as impaired initial function that should be intensively controlled and providing individualized rehabilitation strategies. Second, we investigated the effects of various factors and used a lot of functional outcome tools at once. This provided an integrated, rather than fragmentary, view of the patient's recovery after hip fracture surgery.