Objectives

to describe the increase in orthogeriatrician involvement in hip fracture care in England and its association with improvements in time to surgery and mortality.

Study design

analysis of Hospital Episode Statistics for 196,401 patients presenting with hip fracture to 150 hospitals in England between 1 April 2010 and 28 February 2014, combined with data on orthogeriatrician hours from a national organisational survey.

Methods

we examined changes in the average number of hours worked by orthogeriatricians in orthopaedic departments per patient with hip fracture, and their potential effect on mortality within 30 days of presentation. The role of prompt surgery (on day of or day after presentation) was explored as a potential confounding factor. Associations were assessed using conditional Poisson regression models with adjustment for patients’ sex, age and comorbidity and year, with hospitals treated as fixed effects.

Results

between 2010 and 2013, there was an increase of 2.5 hours per patient in the median number of hours worked by orthogeriatricians—from 1.5 to 4.0 hours. An increase of 2.5 hours per patient was associated with a relative reduction in mortality of 3.4% (95% confidence interval 0.9% to 5.9%, P = 0.01). This corresponds to an absolute reduction of approximately 0.3%. Higher numbers of orthogeriatrician hours were associated with higher rates of prompt surgery, but were independently associated with lower mortality.

Conclusion

in the context of initiatives to improve hip fracture care, we identified statistically significant and robust associations between increased orthogeriatrician hours per patient and reduced 30-day mortality.

Introduction

Older people who fall and fracture a hip are often frail with multiple health problems. In the UK in 2015, their average age was 83, and just over a fifth were aged 90 years or older [1]. Cognitive problems and comorbidities such as hypertension, heart disease and diabetes are common. Hip fracture causes severe pain and immobility, which can precipitate a rapid decline in fitness and complications such as pressure ulcers and pneumonia [2]. In England, around a third of people die within a year of a hip fracture, and 8–10% die within 30 days [3].

Orthogeriatrics is a subspecialty that has developed to improve outcomes of older people with fractures by providing medical care alongside orthopaedic surgeons within multidisciplinary teams. Orthogeriatricians provide specialist medical support and a holistic approach to care [4]. In addition, orthogeriatricians often initiate and lead the development of protocols and practices to improve collaboration between surgeons, anaesthetists, nurses, physiotherapists and occupational therapists to provide better pain relief, prompt surgery and effective rehabilitation.

Compared to surgeon-delivered care alone, orthogeriatric care adds reductions in medical complications and mortality, and also improves mobility and independence [57]. A meta-analysis including 18 studies (9,094 patients) concluded that multidisciplinary care involving an orthopaedic surgeon and a geriatrician reduced in-hospital mortality and mortality at 6–12 months [8]. In 2011, the National Institute for Health and Care Excellence (NICE) summarised evidence for an orthogeriatrician-led ‘hip fracture programme’, concluding that it improved mortality, length of stay and long-term dependency, making such an approach cost-saving [9]. Since then, a further Norwegian study has showed how orthogeriatric care delivered on a dedicated ward can improve mobility, activities of daily living and cost-effectiveness [10].

Orthogeriatric models of care have been widely adopted within the UK. A collaboration between an orthopaedic surgeon and a geriatrician was first developed in Hastings in the 1960s [11]. By 2004, two-fifths of NHS hospitals in England reported involvement of orthogeriatricians in hip fracture care, but only four reported having an orthogeriatrician working full time on the fracture ward [12]. In 2007, the British Geriatrics Society (BGS) and the British Orthopaedic Association (BOA) published guidance on the care of patients with fragility fractures, specifying access to acute orthogeriatric care and prompt surgery as two of six national clinical standards, and launching the National Hip Fracture Database (NHFD) to support their implementation [13].

In England, a further sharp rise in orthogeriatrician staffing followed the introduction of financial incentives under the Best Practice Tariff (BPT) scheme in April 2010 [14]. The BPT scheme required assessment by a geriatrician within 72 hours and surgery within 36 hours as two of the conditions for additional payment.

Our study addressed the question: has the increased involvement of orthogeriatricians in hip fracture care led to the intended improvements in patient outcomes? We documented trends in numbers of hours worked by orthogeriatricians in orthopaedic departments in England between 2010 and 2013, and then estimated the association between increased hours per patient with hip fracture and 30-day mortality. Finally, we examined the role of prompt surgery (on the day of, or day after presentation with hip fracture) as a potential confounder of the relationship between orthogeriatrician hours and mortality.

Methods

Intervention—orthogeriatrician involvement in hip fracture care

Orthogeriatrician involvement is primarily clinical but can also extend to system change, audit and leadership of clinical and service development. For this reason, we defined exposure to orthogeriatrician involvement broadly, and estimated it at a hospital level—using the number of hours worked by orthogeriatricians in orthopaedic departments. These data are collected annually via the NHFD Facilities Survey. For each hospital, the average number of hours per patient was estimated by multiplying weekly hours worked by orthogeriatricians by 52 and dividing by the annual number of patients presenting with hip fracture. In a separate analysis, we used the hospital proportion of patients assessed by an orthogeriatrician within 72 hours as an alternative measure of their involvement. The results of this separate analysis, along with further details about the data used in the main analysis, are given in

.

Patient cohort

We identified a cohort of patients admitted to hospital with hip fracture between 1 April 2010 and 28 February 2014 using non-audit data from Hospital Episode Statistics (HES), which covers all NHS hospitals in England [15]. This was linked at individual level to Office for National Statistics (ONS) data on all registered deaths [16]. HES includes information about patients’ diagnoses, coded using the International Classification of Diseases, 10th Revision (ICD-10).

Patients with hip fracture were identified using the ICD-10 codes S72.0 (fracture of neck of femur), S72.1 (pertrochanteric fracture) and S72.2 (subtrochanteric fracture). Records were extracted for all patients aged 60 years or older with a diagnosis of hip fracture in any of 14 diagnosis fields in the first record (episode) of their first admission with hip fracture. Records that indicated a planned rather than an emergency admission were excluded.

Individual hospitals were identified in HES using data fields containing the provider and site of treatment. These were matched to hospitals that participated in the NHFD throughout the study period using a spreadsheet available from the NHFD website (http://www.nhfd.co.uk), which was manually checked and corrected. Our final cohort included 196,401 patients admitted with hip fracture to 150 NHS hospitals.

Patient-level variables

Prompt surgery was defined as surgery performed on the day of or day following presentation. This is the NICE clinical guideline, and closely matches the 36-hour target that is the BPT standard. This was calculated using the dates of hospital admission and of first surgery for hip fracture since exact times are not recorded in HES. Procedures are coded using the UK Office for Population Censuses and Surveys (OPCS) version 4. The codes we used included internal or external fixation (W19, W20, W22, W24), hemiarthroplasty (W46–W48) and total hip replacement (W37–W39; W93–W95).

Mortality was measured at 30 days after hip fracture, including deaths in hospital and in the community, based on the date of death recorded in the HES-ONS linked data set. The number of comorbidities was measured using a method developed for HES data based on the Charlson Score, which includes selected diagnosis codes for present and past admissions within the previous year [17].

Statistical analyses

For the main analysis, we grouped the HES-ONS patient-level data by age group (60–69 years, 70–79 years, 80–89 and 90 years or older), sex, number of comorbidities (0, 1 or ≥ 2), financial year of admission (2010–11 to 2013–14) and hospital.

The primary outcome variable was 30-day mortality in each group. The average number of orthogeriatrician hours per patient varied by hospital and year, and the relationship between this and mortality was modelled using Poisson regression modelling, with other variables included as additional explanatory variables. Financial year was included to examine annual variation in mortality. To adjust for impacts of variation in hospital hip fracture populations, we included age group, sex and number of comorbidities as categorical explanatory variables. Further between-hospital variations were treated as time-constant differences and modelled using a fixed-effects specification of the Poisson model [18].

Results are presented as relative percentage changes in outcomes, with 95% confidence intervals (CIs) for a 2.5-hour increase in average orthogeriatrician hours per patient, i.e. the increase in median hours per patient we observed between 2010 and 2013. Corresponding absolute changes were calculated using the 2010 rate as a baseline. Full results are given in

online. Reported P values are from two-sided Wald tests.

We carried out secondary analyses to explore the role of prompt surgery. First, we examined the association between orthogeriatrician hours and prompt surgery as an outcome variable also using fixed-effects Poisson regression. Second, we re-examined the association between orthogeriatrician hours and mortality, adjusting for prompt surgery as a binary explanatory variable. We restricted these analyses to patients who had surgery.

Results

Trends in orthogeriatrician hours reported in NHFD annual facilities survey

The median annual number of orthogeriatrician hours per patient with hip fracture increased by 2.5 hours between 2010 and 2013, from 1.5 to 4.0 hours. The percentage of hospitals reporting zero orthogeriatrician hours fell from 8.5% (8/94 hospitals) to 2.0% (3/150 hospitals).

Figure 1 shows the distribution of orthogeriatrician hours per patient across hospitals each year, revealing increasing variation between hospitals over time. In 2013, the interquartile range (the difference between the bottom 25% and top 25% of hospitals) was approximately 4.9 hours.

Figure 1.

Distribution of per-patient hours worked by orthogeriatricians in orthopaedic departments by year. Source: NHFD annual facilities survey.

Figure 1.

Distribution of per-patient hours worked by orthogeriatricians in orthopaedic departments by year. Source: NHFD annual facilities survey.

Trends in patients’ characteristics, care and mortality after hip fracture

The sex and age breakdown of patients with hip fracture did not change substantially over the study period. The percentage of women decreased from 72.8% to 71.6%, while that of patients aged 90 years or older increased from 20.2% to 21.5%. The percentage of patients with two or more documented comorbidities increased from 30.8% to 36.1% (Table 1).

Table 1

Characteristics of patients admitted with hip fracture and mortality at 30 days by financial year, HES-ONS linked mortality data for 150 hospitals included in study.

 Financial year 
2010–11 (%) 2011–12 (%) 2012–13 (%) 2013–14 (%) 
Female 72.8 73.4 72.0 71.6 
Age group 
 60–69 years 8.9 8.7 9.2 9.3 
 70–79 years 23.1 22.5 22.2 22.2 
 80–89 years 47.8 47.9 47.1 46.9 
 90 years and older 20.2 20.9 21.5 21.6 
Number of comorbiditiesa 
 None 34.3 32.7 31.0 29.7 
 1 comorbidity 34.9 34.9 35.1 34.2 
 2 or more comorbidities 30.8 32.4 34.0 36.1 
Surgery 91.7 92.2 92.3 92.4 
 of which, prompt surgery 68.2 72.4 76.1 77.3 
30-day mortality 8.7 8.5 8.6 7.9 
Number of patientsb 48,945 49,784 50,468 47,204b 
 Financial year 
2010–11 (%) 2011–12 (%) 2012–13 (%) 2013–14 (%) 
Female 72.8 73.4 72.0 71.6 
Age group 
 60–69 years 8.9 8.7 9.2 9.3 
 70–79 years 23.1 22.5 22.2 22.2 
 80–89 years 47.8 47.9 47.1 46.9 
 90 years and older 20.2 20.9 21.5 21.6 
Number of comorbiditiesa 
 None 34.3 32.7 31.0 29.7 
 1 comorbidity 34.9 34.9 35.1 34.2 
 2 or more comorbidities 30.8 32.4 34.0 36.1 
Surgery 91.7 92.2 92.3 92.4 
 of which, prompt surgery 68.2 72.4 76.1 77.3 
30-day mortality 8.7 8.5 8.6 7.9 
Number of patientsb 48,945 49,784 50,468 47,204b 

aDocumented comorbidities in HES for current admission and hospital admissions over the past year.

bThe data extract for the financial year 2013–14 was restricted to the 11 months up to 28 February 2014 to allow for 30-day follow-up.

The percentage of patients who had surgery remained stable at 92.0%. The percentage of these who had prompt surgery (on day of, or day after, admission) increased from 68.2% to 77.3%.

Thirty-day mortality remained relatively stable between 2010–11 and 2012–13 at rates of 8.7% and 8.6% respectively, then falling to 7.9% in 2013–14.

Mortality was 40% lower among women than men. Mortality was four times higher among those aged 90 years or older compared to those aged 60–69 years; and four times higher among those with two or more comorbidities than those with none. There was no evidence of a difference in mortality trends by group (see

).

Relationship between number of orthogeriatrician hours and 30-day mortality

Figure 2 shows that higher numbers of orthogeriatrician hours per patient were associated with lower annual 30-day mortality (Spearman's rank correlation coefficient −0.11, P = 0.01).

Figure 2.

Association between average per-patient hours worked by orthogeriatricians in orthopaedic departments and annual 30-day mortality.

Figure 2.

Association between average per-patient hours worked by orthogeriatricians in orthopaedic departments and annual 30-day mortality.

After adjustment for age, sex and comorbidity, and for annual variation in mortality, the expected relative reduction in mortality for a 2.5-hour per-patient increase was 3.4% (95% CI 0.9–5.9%, P = 0.01). This corresponds to an absolute reduction of approximately 0.3% for this level of investment in a hospital with a baseline mortality rate of 8.7% (−3.4% × 8.7% ≈ −0.3%).

Relationship between orthogeriatrician hours, prompt surgery and 30-day mortality

Higher orthogeriatrician hours per patient were also associated with higher rates of prompt surgery. After adjustment for patient characteristics and annual variation, the expected relative increase in rates of prompt surgery was 1.3% (95% CI 0.0–2.6%, P = 0.05) for a 2.5-hour per-patient increase in orthogeriatrician hours. This corresponds to an absolute increase of 0.9% for a hospital with a baseline rate of 68.2% (1.3% × 68.2% ≈ 0.9%).

There was a large and significant association between having prompt surgery and lower 30-day mortality (relative reduction 12.9%, 95% CI 9.5–16.2%, P < 0.001; absolute reduction of 0.9% for baseline rate of 8.7%).

However, adjusting for prompt surgery very slightly reduced but did not explain the association between increased orthogeriatrician hours and reduced 30-day mortality (relative reduction 3.0%, 95% CI 0.2–5.8%, P = 0.03; absolute reduction of 0.26% from baseline rate of 8.7%).

Discussion

Main findings

Over the period 2010–2013, we found that higher numbers of orthogeriatrician hours per patient were consistently associated with lower 30-day mortality. This association persisted after adjustment for patient characteristics and annual variation in mortality.

Higher numbers of orthogeriatrician hours were also associated with higher rates of prompt surgery, and there was a strong association at the individual level between having prompt surgery and lower mortality. However, an independent association between increased orthogeriatrician hours and lower mortality persisted after adjusting for the effects of prompt surgery.

If the association were causal, then the 2.5-hour increase in orthogeriatrician hours would equate with the avoidance of nearly 200 deaths within 30 days of hip fracture across the 65,000 people presenting with this injury each year (absolute reduction 0.3% × 65,000 = 195). Even after adjustment for the effects of prompt surgery, it would equate with the avoidance of around 170 deaths per year.

Strengths and limitations of study

This is the first nationwide study to quantify orthogeriatrician involvement in hip fracture and describe its impact on patient care and outcomes. We used hospital-level data on orthogeriatrician involvement: hours worked by orthogeriatricians in orthopaedic departments reported in an annual organisational survey. We estimated a standardised measure of orthogeriatrician hours per patient with hip fracture as a clear and straightforward approach that would help in defining the job plan or business case for a new post.

There are several potential sources of error in the estimation of hours per patient. One source of error arises from the fact that data on weekly orthogeriatrician hours were collected via an annual survey, so that within-year changes are not captured. In addition, we estimated annual hours by multiplying reported weekly hours by 52, but we recognize that there will be variation in part-time work patterns, sickness leave, annual/study leave and arrangements for leave cover across different hospitals. Finally, the roles of orthogeriatricians vary between units, with some taking responsibility for all older patients with fractures and even for older elective orthopaedic surgery patients. Such factors are complex to define even within a department, but they will affect every post in England to some extent, so this lack of standardisation will contribute to measurement error in the exposure. In turn, measurement error in the exposure, if this error is independent of the outcome, will tend to contribute to underestimation of the true association [19].

We carried out a parallel analysis to check the validity of orthogeriatrician hours per patient as a measure of their involvement in clinical hip fracture care. Orthogeriatrician hours were strongly correlated with the proportion of patients assessed by an orthogeriatrician within 72 hours (Spearman's rank correlation coefficient 0.51, P < 0.001), as well as with other markers of orthogeriatrician involvement (see

).

There was a higher rate of missing data in the 2010 organisational survey; 62.7% of hospitals (94 out of 150) providing complete data compared to 93.3% in 2011, 99.3% in 2012 and 100.0% in 2013. However two sensitivity analyses, one restricted to the years 2011–13 and the other confined to 89 hospitals with complete data for all 4 years, both of which confirmed the association between increased orthogeriatrician hours and lower mortality. Given this we chose to report on the whole period 2010–13, since this captures the key investment following the introduction of BPT in April 2010.

Finally, although the contribution of orthogeriatric care is both broad and variable, our study used a limited measure of input (in hours) to measure it. The same number of hours worked by an orthogeriatrician will mask variations in the nature of their involvement, with some services providing continuity of care and others providing a reactive service. A previous qualitative study of four hip fracture services highlighted such variation: in the style and formalization of collaboration; the extent to which multidisciplinary team members engaged with one another through ward rounds and multidisciplinary team meetings; and in staff perceptions of teamwork [20].

Orthogeriatrics in the context of quality improvement in hip fracture care

Access to orthogeriatric care is just one component of quality improvement in hip fracture care, and increased orthogeriatrician involvement may be both a consequence and a driver for wider service improvements. For example, orthogeriatricians may improve care quality by improving the coordination of care, improving standardization of care by introducing protocols and by assessing complex issues in the care of older people such as decisions on the surgical or non-surgical management of the frailest, near-terminal patients. Any more detailed clarification of the impact of these factors, the impact of standards and audit, the availability of specialist nurses and audit coordinators and improved multidisciplinary teamwork would be complex.

Our study was limited to a hospital-level time-based measure of orthogeriatrician involvement. So our estimates represent a combination of individual effects of orthogeriatric assessment and care, averaged over patients who did and did not receive it, plus wider benefits of their involvement in the service. In addition, there is an important interplay between orthogeriatrician, surgeon and anaesthetist in the optimization of patients prior to surgery. Much of this is in the provision of a uniform approach to acceptable criteria for surgery with the adoption of national guidelines [9, 21]. Once the patient has been seen by an orthogeriatrician and has been assessed as optimized for surgery, a significant barrier to prompt surgery is removed. Future studies could explore individual- and service-level effects of orthogeriatric care, and relationships to prompt surgery, by using linked patient-level data from the NHFD and HES. They could also explore impacts on a wider range of important outcomes documented in NHFD, including restoration of pre-fracture levels of mobility and independence.

Policy implications

The rapid expansion of the subspecialty of orthogeriatrics reflects the strength of its parent specialty, geriatric medicine, within the UK's National Health Service. In other healthcare systems, a comparable expansion of orthogeriatricians may be less likely, with clear consequences for the generalisability of the developments and results this study describes.

Elsewhere, general physicians, internists, physician assistants and senior nurses might, to a greater or lesser extent, fulfil the various roles described for orthogeriatricians, and in some settings this already happens. This could be supported by the use of existing online learning modules covering a range of core orthogeriatric competencies, including the need to adapt treatment in line with ageing, recognition of comorbidities and polypharmacy, early rehabilitation and secondary prevention of osteoporosis and falls [22].

Key points

  • Orthogeriatrician involvement has been a key component of strategies to improve hip fracture care in England.

  • Increased orthogeriatrician hours in orthopaedic departments are associated with lower 30-day mortality after hip fracture.

  • Increased hours are also associated with higher rates of prompt surgery, but are independently associated with lower mortality.

Supplementary data

Acknowledgements

We thank Lynn Copley for providing the required HES data extract. We thank the NHFD audit team, in particular, Chris Boulton and Tim Bunning, for help accessing the NHFD data. We thank Nivi Singh, Vanessa Meiris, Celia Gregson and Alec Fraser for advice.

Hospital Episode Statistics were made available by the NHS Health and Social Care Information Centre. (Copyright 2012, reused with the permission of The Health and Social Care Information Centre. All rights reserved.)

Facilities survey data are collected as part of the National Hip Fracture Database. NHFD is commissioned by the Healthcare Quality Improvement Partnership (HQIP) and managed by the Clinical Effectiveness and Evaluation Unit (CEEU) of the Royal College of Physicians as part of the Falls and Fragility Fracture Audit Programme (FFFAP).

Authors’ contribution

All authors took part in the design of the study and interpretation of the results. J.N. and C.C. drafted the article. J.N., J.v.d.M. and B.D.S. designed the analysis. All authors revised the article.

Conflicts of interest

C.T. and D.A.C. are currently commissioned by the Royal College of Physicians to analyse data for the NHFD annual reports as part of the Falls and Fragility Fractures Audit Programme. R.W. and A.J. are the clinical leads for orthopaedic surgery and geriatric medicine, respectively, on the NHFD.

Funding

Jenny Neuburger is funded by a National Institute for Health Research Postdoctoral Fellowship (PDF-2013-06-078). The views expressed in this publication are those of the authors and not necessarily those of the NHS, the National Institute for Health Research or the Department of Health.

Ethics approval

The project does not require NHS Research Ethics Committee approval because it involves secondary analysis of anonymised data. The project meets the requirements of the Office for National Statistics (ONS) for release of mortality data under Section 42(4) of the Statistics and Registration Service Act 2007 as amended by Section 287 of the Health and Social Care Act 2012.

References

1
Royal College of Physicians
. National Hip Fracture Database annual report 2016.
London
:
RCP
,
2016
. Available at: http://www.nhfd.co.uk/.
2
Parker
M
,
Johansen
A
.
Hip fracture. Clinical review
.
BMJ
 
2006
;
333
:
27
.
3
Neuburger
J
,
Currie
C
,
Wakeman
R
et al
.
The impact of a national clinician-led audit initiative on care and mortality after hip fracture in England
.
Med Care
 
2015
;
53
:
686
691
.
4
Wilson
H
.
Multi-disciplinary care of the patient with acute hip fracture
.
Best Pract Res Clin Rhematol
 
2013
;
27
:
717
730
.
5
Hawley
S
,
Javaid
MK
,
Prieto-Alhambra
D
et al
.
Clinical effectiveness of orthogeriatric and fracture liaison service models of care for hip fracture patients: population-based longitudinal study
.
Age Ageing
 
2016
;
0
:
1
7
.
6
Friedman
SM
,
Mendelson
DA
,
Kates
SL
et al
.
Geriatric co-management of proximal femur fractures: total quality management and protocol-driven care result in better outcomes for a frail patient population
.
J Am Geriatr Soc
 
2008
;
56
:
1349
1356
.
7
Vidan
M
,
Serra
JA
,
Moreno
C
et al
.
Efficacy of a comprehensive geriatric intervention in older patients hospitalized for hip fracture: a randomized controlled trial
.
J Am Geriatr Soc
 
2005
;
53
:
1476
1482
.
8
Grigoryan
KV
,
Javedan
H
,
Rudolph
JL
.
Ortho-geriatric care models and outcomes in hip fracture patients: a systematic review and meta-analysis
.
J Orthop Trauma
 
2014
;
28
:
e49
e55
.
9
National Institute for Health and Clinical Excellence.
Hip Fracture: Management. Clinical Guideline.
2011
. Available at: https://www.nice.org.uk/guidance/cg124
10
Prestmo
A
,
Hagen
G
,
Sletvold
O
et al
.
Comprehensive geriatric care for patients with hip fractures: a prospective, randomised, controlled trial
.
Lancet
 
2015
;
385
:
1623
1633
.
11
Devas
MB
,
Irvine
R
.
The geriatric orthopaedic unit – a method of achieving return to independence in the elderly patient
.
Br J Geriatr Pract
 
1969
;
6
:
19
24
.
12
Wakeman
R
,
Sheard
PD
,
Jenner
GH
.
Ortho-geriatric liaison – the missing link
.
J Bone Joint Surg
 
2004
;
86-B
:
636
638
.
13
British Orthopaedic Association, British Geriatric Society
The Care of Patients with Fragility Fracture
 .
London
:
British Orthopaedic Association
,
2007
.
14
Department of Health
. A Simple Guide to Payment by Results.
2012
. Available at: https://www.gov.uk/government/publications/simple-guide-to-payment-by-results (17 December 2015, date last accessed).
15
The Health and Social Care Information Centre.
Hospital Episode Statistics: HES User Guide,
2010
. Available at: http://www.hesonline.nhs.uk/Ease/servlet/ContentServer?siteID=1937&categoryID=459 (17 December 2015, date last accessed).
16
The Information Centre.
A Guide to Linked HES-ONS Mortality Data. August 2011. Available at: http://www.hscic.gov.uk/article/2677/Linked-HES-ONS-mortality-data (17 December 2015, date last accessed)
13 Poisson
 
17
Armitage
JN
,
van der Meulen
JH
.
Identifying co-morbidity in surgical patients using administrative data with the Royal College of Surgeons Charlson Score
.
Br J Surg
 
2010
;
97
(
5
):
772
81
.
18
Angrist
JD
,
Pishke
J-S
Parallel worlds: fixed effects, differences-in-differences, and panel data. In:
Angrist
JD
,
Pishke
J-S
(eds.),
Mostly Harmless Econometrics; An Empiricist's Companion
 .
Princeton
:
Princeton University Press
.
2009
. pp.
221
246
.
19
Carroll
R
,
Ruppert
D
,
Stefanski
L
et al
.
Measurement Error in Nonlinear Models: A Modern Perspective
 ,
2nd ed
.
London
:
Chapman & Hall/CRC
,
2006
.
20
Tierney
AJ
,
Vallis
J
.
Multidisciplinary teamworking in the care of elderly patients with hip fracture
.
J Interprof care
 
1999
;
13
:
41
52
.
21
Association of Anaesthetists of Great Britain and Ireland
. Management of Proximal Femoral Fractures.
2011
. Available at: https://www.aagbi.org/sites/default/files/femoral%20fractures%202012_0.pdf
22
AO Foundation.
Educational Program: Orthogeriatrics. Available at: K https://aotrauma.aofoundation.org/Structure/education/educational-programs/orthogeriatrics/Pages/orthogeriatrics.aspx (17 December 2015, date last accessed).

Supplementary data

Comments

0 Comments