There has been extensive discussion about the effect of delay to surgery on mortality in patients sustaining a fracture of the hip. Despite the low level of evidence provided by many studies, a consensus has been accepted that delay of > 48 hours is detrimental to survival. The aim of this prospective observational study was to determine if early surgery confers a survival benefit at 30 days.
Between 1989 and 2013, data were prospectively collected on patients sustaining a fracture of the hip at Peterborough City Hospital. They were divided into groups according to the time interval between admission and surgery. These thresholds ranged from < 6 hours to between 49 and 72 hours. The outcome which was assessed was the 30-day mortality. Adjustment for confounders was performed using multivariate binary logistic regression analysis. In all, 6638 patients aged > 60 years were included.
Worsening American Society of Anaesthesiologists grade (p < 0.001), increased age (p < 0.001) and extracapsular fracture (p < 0.019) increased the risk of 30-day mortality.
Increasing mobility score (p = 0.014), mini mental test score (p < 0.001) and female gender (p = 0.014) improved survival. After adjusting for these confounders, surgery before 12 hours improved survival compared with surgery after 12 hours (p = 0.013). Beyond this the increasing delay to surgery did not significantly affect the 30-day mortality.
Cite this article: Bone Joint J 2015;97-B:104–8.
Each day almost 200 elderly patients sustain a fracture of the hip in England and Wales.1 The rate of 30-day mortality associated with this injury is 8.2%.1 National Institute for Health and Care Excellence (NICE) guidelines2 and the National Hip Fracture Database (NHFD)1 are part of an initiative to manage these vulnerable patients, improving their return to their pre-injury level of function and decreasing mortality. Various factors relating to the patient have been attributed to an increased risk of mortality, most notably increasing age, male gender and worsening American Society of Anesthesiologists (ASA) grade.3-5 While aspects of care such as the provision of pressure relieving mattresses and venous thromboembolism prophylaxis have reduced the complications following a fracture of the hip,6-8 no modifiable factors have been convincingly proven to decrease mortality. Reducing the period of time between admission and operation has been proposed as a means of improving survival. Many articles have assessed this and despite the low level of evidence provided by many, a consensus has been agreed upon that a delay of > 48 hours is detrimental to survival.9,10 The Best Practice Tariff11 is driving the rationalisation of treatment of patients with a fracture of the hip in the UK and we are seeing a decrease in delay to surgery and further prioritisation of these patients.1 With streamlining of dedicated trauma lists and the appointment of trauma co-coordinators,12,13 trusts are beginning to have the ability to deliver same-day surgery for these patients.
The aim of this prospective observational study was to determine if early surgery confers an additional survival benefit at 30 days after correcting for a range of potentially confounding patient factors.
Patients and Methods
The senior author (MJP) co-ordinates and delivers the care for patients sustaining a fracture of the hip within Peterborough and Stamford NHS trust. Between 1989 and 2013, data pertaining to this care were prospectively collected using a standard proforma. The collection of data began on admission and continued until one year from injury.
The data included patient age, gender and ASA grade.3 Mobility was scored using a scale from 0 (immobile) to 9 points (independently mobile).14 Residence was divided into patients living in their own home and those living in institutional accommodation. Mental function was calculated using a standard Mini Mental Test Score (MMTS)15 as recommended by NICE.2 Fractures were classified as intra- or extracapsular. The type of operation was defined as either fixation or replacement. Extracapsular fractures were treated with an intramedullary nail or sliding hip screw. Intracapsular fractures were treated with cannulated screws or a plate and sliding screw device, and replacement was with a hemiarthroplasty or total hip arthroplasty. Delay to surgery was calculated from the time of admission to the Emergency Department (ED) to the time of operation. This time was divided into: one to six hours, seven to 12 hours, 13 to 18 hours, 19 to 24 hours, 25 to 36 hours, 37 to 48 hours and 49 to 72 hours. The outcome which was assessed was the 30-day mortality.
Patients aged < 60 years, those with pathological fractures and patients treated non-operatively were excluded from the study. As we were examining the effects of early surgery on survival, we excluded patients waiting > 72 hours for surgery. We also excluded patients delayed for correctable medical reasons when the surgical or anaesthetic team felt optimisation would significantly improve their chance of surviving an anaesthetic. These mirrored the immediately correctable reasons identified by NICE.2
All statistical analysis was performed with IBM SPSS Statistics v.21 (IBM, Armonk. New York). A p-value < 0.05 was considered to be significant. Patient characteristics grouped by time to surgery were compared using analysis of variance (ANOVA) for the continuous variables and Pearson’s chi-squared test for the categorical variables. Univariate analysis was performed comparing each recorded factor with 30-day mortality. The variables were tested for collinearity using linear regression diagnostics. Backward multivariate binary logistic regression was performed using 30-day mortality as the dependent variable. Multivariate binary logistic regression analysis was performed looking at the odds (with 95% confidence intervals (CI)) of 30-day mortality before each delay to surgery threshold versus delay beyond this threshold. The Hosmer–Lemeshow test was used to compare the expected (predicted by the model) and observed mortality results to suggest how well the regression model fitted the data. The Nagelkerke pseudo-R2 was calculated to indicate how much the independent variables improved the predictive ability of the model relative to the null model.
A total of 7872 fractures of the hip were managed during the study period. After applying the exclusion criteria, 6656 remained. Of these, 18 patients were lost to follow-up leaving 6638 patients for analysis (Fig. 1). The reasons for delay were due to an operating theatre or theatre team being unavailable and most commonly reflected an excessive trauma workload. A MMTS was not recorded pre-operatively for 430 patients and 24 did not have an ASA grade recorded. The mean age of the patients was 82 years (60 to 106), 5406 (78%) were female. Table I shows the characteristics of the patients for each delay to surgery group. Age, ASA grade, MMTS and pre-fracture mobility differed significantly between the groups.
|Hours to operation||0 to 6||7 to 12||13 to 18||19 to 24||25 to 36||36 to 48||48 to 72||Total||p-value|
|Mean delay (sd) (hrs)||4.7 (1.2)||9.7 (1.8)||16.0 (1.7)||21.4 (1.7)||28.1 (3.1)||42.7 (3.2)||57.5 (7.7)||22.9 (12.2)||< 0.001|
|Number of patients (%)||433 (6.5)||576 (8.7)||1385 (20.9)||2252 (33.9)||1085 (16.3)||611 (9.2)||296 (4.5)||6638||< 0.001|
|Mean age (sd) (yrs)||81.1 (8.8)||82.0 (9.0)||82.1 (8.0)||81.67 (8.1)||82.3 (8.1)||81.5 (8.2)||82.6 (8.0)||81.9 (8.2)||0.045|
|Female (%)||345 (79.7)||444 (77.1)||1093 (78.9)||1785 (79.3)||845 (77.9)||467 (76.4)||236 (79.7)||5406 (78.4)||0.675|
|Mean mobility score (sd)||5.5 (2.7)||5.1 (2.6)||5.2 (2.6)||5.4 (2.7)||5.2 (2.6)||5.3 (2.6)||4.6 (2.6)||5.3 (2.7)||< 0.001|
|Own home (%)||323 (74.6)||422 (73.3)||982 (70.9)||1672 (74.2)||781 (72.0)||450 (73.6)||203 (68.6)||4833 (72.8)||0.179|
|Mean ASA (sd)||2.6 (0.8)||2.6 (0.7)||2.6 (0.7)||2.6 (0.7)||2.7 (0.7)||2.7 (0.7)||2.9 (0.7)||2.6 (0.7)||< 0.001|
|Mean MMTS (sd)||7.2 (3.1)||6.8 (3.3)||6.9 (3.3)||7.0 (3.3)||6.8 (3.4)||7 (3.4)||6.4 (3.5)||6.9 (3.3)||0.033|
|Extracapsular fractures (%)||168 (38.8)||254 (44.1)||575 (41.5)||938 (41.7)||474 (43.7)||245 (40.1)||118 (39.9)||2772 (41.8)||0.459|
|Replacement (%)||119 (27.5)||189 (32.8)||491 (35.5)||780 (34.6)||358 (33.0)||223 (36.5)||102 (34.5)||2262 (34.1)||0.053|
|30-day mortality (%)||23 (5.3)||22 (3.8)||84 (6.1)||132 (5.9)||81 (7.5)||35 (5.7)||25 (8.4)||402 (6.1)||0.051|
sd, standard deviation; Replacement, hemiarthroplasty or total hip arthroplasty; ASA, American Society of Anesthesiologists grade; MMTS, mini mental test score
Age, gender, pre-fracture mobility, MMTS, fracture type, ASA grade, pre-fracture residence and delay to surgery were significantly correlated with 30-day mortality on univariate analysis (Table II). The type of operation was not significantly associated and was excluded from the final model. The variable inflation factor was < 2 for all independent variables in the final model suggesting that there was no significant collinearity between them.
|Wald||p value||OR||95% CI|
|Age||75.620||< 0.001||1.063||1.049 to 1.078|
|Female gender||10.380||0.001||0.689||0.550 to 0.864|
|ASA grade||166.301||< 0.001||2.901||2.467 to 3.410|
|Mobility score||121||< 0.001||0.768||0.733 to 0.805|
|MMTS||115.362||< 0.001||0.850||0.825 to 0.875|
|Extracapsular fracture||511.844||0.001||1.462||1.165 to 1.744|
|Delay to surgery||5.887||0.015||1.091||1.017 to 1.170|
|Residence||62.021||< 0.001||2.276||1.855 to 2.793|
|Operation type (replacement)||0.575||0.448||1.087||0.876 to 1.348|
OR, odds ratio; CI, confidence interval; Wald, Wald test statistic; ASA, American Society of Anesthesiologists; MMTS, Mini Mental test Score; Replacement, hemiarthroplasty or total hip arthroplasty
Age, gender, pre-fracture mobility, MMTS and ASA grade were statistically significant predictors of 30-day mortality on backward multivariate binary logistic regression. Pre-fracture residence and delay to surgery thresholds were not significantly associated with 30-day mortality after correcting for confounding factors. The Hosmer–Lemeshow test denoted a good model fit (chi-squared test, chi = 5.468, p = 0.707). The variables included in the model predicted 13.1% of the variance in 30-day mortality (Nagelkerke r-square = 0.131). Overall the model strongly rejected the null hypothesis that none of the factors are associated with 30-day mortality (p < 0.001). The validity of the model was upheld with 402 events (deaths within 30 days of admission). This was above the required ten per variable included in the regression model.
The adjusted odds ratios (ORs) with 95% confidence intervals (CIs) for each independent variable in the final model are shown in Table III. The model suggests that ASA grade is the strongest predictor of 30-day mortality with every increase in ASA grade increasing the odds of mortality by 2.52 (95% CI 2.01 to 3.04; p < 0.001). Each additional year in age increased the odds by 1.04 (95% CI 1.03 to 1.06; p < 0.001). Sustaining an extracapsular fracture also increased mortality with an OR of 1.31 (95% CI 1.05 to 1.64; p = 0.019). Female gender, increasing MMTS and mobility score decreased the 30-day mortality with an OR of 0.725 (95% CI 0.56 to 0.94; p = 0.014), 0.906 (95% CI 0.87 to 0.94; p < 0.001) and 0.925 (95% CI 0.87 to 0.98; p = 0.014), respectively.
|Wald||p-value||Adjusted OR||95% CI|
|Age||21.479||< 0.001||1.039||1.023 to1.056|
|Female gender||6.072||0.014||0.725||0.561 to 0.936|
|ASA grade||93.561||< 0.001||2.517||2.088 to 3.035|
|Mobility score||6.08||0.014||0.925||0.869 to 0.984|
|MMTS||27.762||< 0.001||0.906||0.873 to 0.940|
|Extracapsular fracture||5.517||0.019||1.307||1.045 to1.634|
|Delay to surgery||2.69||0.101||1.066||0.988 to 1.151|
|Constant||86.6||< 0.001||< 0.001|
OR, odds ratio; CI, confidence interval; Wald, Wald test statistic; ASA, American Society of Anesthesiologists; MMTS, Mini Mental test Score
Surgery within 12 hours appeared to improve survival significantly, after adjusting for confounders, with patients undergoing surgery after 12 hours having a 1.59 (95% CI 1.11 to 2.29) increased odds of death within 30 days (p = 0.013). While there were benefits for the other thresholds examined they were not statistically significant (Table IV).
|Delay to surgery||Wald||p-value||Adjusted OR||95% CI|
|After six hours vs within six hours||0.205||0.651||1.122||0.683 to 1.843|
|After 12 hours vs within 12 hours||6.227||0.013||1.589||1.105 to 2.287|
|After 18 hours vs within 18 hours||1.356||0.244||1.151||0.908 to 1.459|
|After 24 hours vs within 24 hours||0.059||0.808||0.972||0.776 to 1.219|
|After 36 hours vs within 36 hours||0.020||0.888||1.023||0.750 to 1.394|
|After 48 hours vs within 48 hours||0.302||0.582||1.140||0.715 to 1.818|
OR, odds ratio; CI, confidence interval; Wald, Wald test statistic
The incidence of fragility fracture of the hip is rising globally16 and there is some evidence that within this group of patients the incidence of unstable peri-trochanteric fractures is increasing.17 Whilst mortality remains high, the medical community will endeavour to understand and improve it. A number of guidelines recommend that the balance between prolonged medical optimisation and early surgery should favour the latter. It has been suggested by various bodies that 24 hours,18 48 hours19 and most recently suggested by NICE, 36 hours, is the acceptable limit of the delay from admission to operation.2 This figure lacks substantiated evidence. Two recent meta-analyses have loosely recommended early surgery as beneficial but have acknowledged that a lack of prospective studies and poor adjustment for confounding factors prevent definite conclusions, especially when related to 30-day mortality.8,9 In 2013, Uzoigwe et al20 published results of a retrospective review of prospectively collected data, which examined the effects of early surgery on in-patient mortality. They found that sequential 12-hour thresholds significantly improved in-patient mortality after adjusting for evidence-based confounders. The 12-hour threshold conferred the greatest benefit; this is much earlier than other published studies examining the effects of delayed surgery on early mortality.21,22
Our study validates these results with a larger sample size and a greater range of relevant confounders. Where possible, each of these confounders has been recorded in a continuous fashion rather than dichotomously; this reduced the significance of our results but produced a statistically robust regression model. We believe our study is also more widely applicable as it excludes patients aged < 60 years and so represents the fragility fracture group examined by the NHFD. It also examines 30-day mortality, which is easily interpreted and less likely to be influenced by local factors such as hospital discharge policies.
Our results support a growing body of evidence that the ASA grade is a powerful predictor of short-term mortality following a fracture of the hip (p < 0.001). Due to its wide spread use and ease of interpretation, we believe it should represent the minimum level of confounding adjustment for studies examining survival after a fracture of the hip. We accept that it is a subjective measure but have found that studies struggle to produce an effective method of stratifying specific co-morbidities against survival.21 We found increasing age (p < 0.001) and extracapsular fracture (p = 0.019) predict 30-day mortality. Protective factors are female gender (p = 0.014), increasing MMTS (p < 0.001) and an increasing mobility score (p = 0.014). These are easily reproducible, commonly recorded (as recommended by NICE) and should be included in future survival analyses.
Our aim was to examine the effects of early surgery on 30-day mortality in patients sustaining a fracture of the hip. Our model did not demonstrate an overall benefit of six hourly early watersheds (six hours, 12 hours, 18 hours and 24 hours), nor did it find a significant benefit of later watersheds on survival (36 hours or 48 hours) that previous studies have demonstrated. This is probably due to our comprehensive adjustment for confounding variables. Our study did support the findings by Uzoigwe et al20 that early surgery before 12 hours does significantly decrease short-term mortality in patients sustaining a fracture of the hip (p = 0.013) but not that immediate surgery (< 6 hours) confers a significant survival benefit.
We acknowledge that our study had missing data (24 missing ASA grade and 430 missing MMTS score), lost 18 patients to follow-up and that data from a single centre may not reflect national trends. Another limitation is that our model predicted 13.1% in the variability of mortality, suggesting that there are more factors affecting survival yet to be elucidated. Furthermore, despite the recent surge of resources and streamlining of services towards the care of these patients, most trusts will be unable to provide surgery within 12 hours for most of them. This makes it difficult to incorporate our results into a guideline for the acceptable operative delay in patients with a fracture of the hip. Our results support the benefits of early surgery and justify the allocation of resources to this vulnerable group.
Ethical reasons have precluded any effective randomised control trials looking at the effect of operative delay on survival in patients who sustain a fracture of the hip. Our results will inform future studies assessing whether early surgery confers a survival benefit. As proposed by The Hip Fracture Accelerated Surgical Treatment and Care Track (HIP ATTACK) Investigators,23 early surgery versus routine care would appear to be an ethically appropriate method of examining this question, which still has considerable clinical equipoise.9 This remains an issue of great importance as displacing patients with other injuries from the trauma list without definitive evidence of a benefit may not be ethically justified.
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C. P. Bretherton: Study Design, Refinement of the study protocol, Data analysis, Wrote the manuscript.
M. J. Parker: Study design, Refinement of the study protocol, Study Implementation, Data collection, Approved final manuscript.
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.
This article was primary edited by G. Scott and first proof edited by J. Scott.