H IS C
N o r t h er n Ir e la n d
H ea lt h c a r e - A s so c ia t e d
In f e c tio n S u r v eilla n c e
C en tre
Pan Celtic Collaborative Surveillance Report
Surveillance of surgical site infection related to procedures performed by
orthopaedic surgeons in Scotland, Wales and Northern Ireland
2005 Data
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
1
Executive summary
In 2005, there were 17,781 valid orthopaedic procedures recorded in the four
mandated categories, i.e. arthroplasty of the knee, arthroplasty of the hip,
hemiarthroplasty of the hip, open reduction of the trochanteric region of the femur
with internal fixation. This represents an overall increase of 88.3% when
comparing 2005 with 2004.
Between 2003 and 2005, data on 35,197 procedures from the four mandated
categories of orthopaedic procedures were collected by hospitals in Scotland,
Wales and Northern Ireland.
The crude SSI rates in 2005 were:
•
•
•
•
•
All procedures
Hip prosthesis
Hemiarthroplasty of hip
# neck of femur
Knee prosthesis
SSI rate
2.1
1.8
2.8
2.1
2.2
95% confidence intervals
1.9 – 2.3
1.5 – 2.1
2.2 – 3.6
1.6 – 2.8
1.9 – 2.6
The SSI rate for hemiarthroplasty of the hip was significantly higher than the
SSI rate for hip prosthesis [p ≤ .001).
Two-thirds of emergency procedures (66.3%) were performed within a day of
admission.
The SSI rate of 2.7% for emergency procedures was significantly higher than
the SSI rate of 1.9% for elective procedures [p<0.003).
The NNIS basic risk index was a useful method of risk adjustment. SSI rates
increased as the number of risk factors increased (RI 0 & RI 1) for all procedure
categories [p<0.05].
Consultant surgeons performed the majority of hip and knee prostheses.
Specialist registrars performed the majority of hemiarthroplasty of hip and #
neck of femur procedures.
Consultant surgeons had a significantly lower SSI rate (1.9%) than nonconsultant surgeons (SSI rate 2.5%) [p<0.02].
Of all procedures, 85% were performed by a consultant or a consultant was
present in the theatre suite.
The SSI rate in patients with a pre-operative stay of four or more days was
4.4% and for patients with a pre-operative stay of three or less days the SSI
rate was 1.9%. There was a greater risk of developing an SSI in orthopaedic
patients with a preoperative stay of four or more days.
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
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Foreword to the Third Report
Healthcare Associated Infection (HCAI) is now recognised more and more by
patients and public alike as an issue with the capacity to touch everyone’s life. There
has been an increasing demand for consistent valid data regarding HCAIs not only
from the Government and the Public but also from the Healthcare Professions
themselves. It is only by monitoring and trying to understand why HCAIs occur that
we can put in place measures to reduce the occurrence of such untoward events.
Orthopaedic surgery has made great progress over the past couple of decades.
Most of the public will identify with someone who has experienced first-hand the
difference that orthopaedic surgery has made to his or her life. Therefore, it is not
surprising that orthopaedic surgery should be among the first specialties to have
mandatory surgical site infection (SSI) surveillance in the UK.
This Third Pan Celtic Collaborative Report builds on the standards set by the
previous two reports and demonstrates the value of the Pan Celtic Collaboration.
This is a major initiative involving hospitals in Scotland, Wales and Northern Ireland.
The success of the Pan Celtic Collaboration is demonstrated by the 88.3% increase
in recorded procedures in 2005 compared to 2004. Standardized methodology and
definitions of infection across the three countries have made national and
international comparisons possible. This enables benchmarking to occur.
The information gained by this initiative will be invaluable to healthcare workers as
they strive to reduce the occurrence of SSIs in orthopaedic surgery and will serve to
inform Governments and the Public of the state of play that currently exists within
our orthopaedic services regarding SSIs.
This report would not have been possible without the active assistance of all the
orthopaedic and infection prevention & control teams from the participating
hospitals. In addition, the activities of the surveillance centres are to be commended
in making this report possible: the Scottish Surveillance of Healthcare Associated
Infection Programme (SSHAIP), the Welsh Healthcare Associated Infection
Programme (WHAIP) and the Northern Ireland Healthcare-Associated Infection
Surveillance Centre (HISC). Support has also been supplied in abundance from the
members of the Pan Celtic Surveillance Centres Steering Group. Finally, mention
must be made of HISC staff, Gerard McIlvenny and Geraldine Reid, whose
dedication and expertise have resulted in the production of the Third Pan Celtic
Collaborative Report.
Dr Edward TM Smyth
Chair,
Pan Celtic Surveillance Centres Steering Group
& Director, HISC
12th December 2006
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Contents
Executive summary
1
Foreword to the third report
3
Contents
5
List of figures
6
List of tables
7
Surveillance methodology
8
Abbreviations
8
Results
9
Conclusions
26
References
27
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
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Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
List of figures
Figure 1: Statistical process control P chart SSI
Figure 2: Age and SSI
2003 – 2005
– 2005
Figure 3: Age by gender and SSI
10
11
– 2005
Figure 4: Circumstance of operation by procedure category
11
– 2005
12
Figure 5: Circumstance of operation by procedure category & SSI – 2005
13
Figure 6: Distribution of RI for procedure category – 2005
14
Figure 7: Distribution of RI for procedure category by country – 2005
14
Figure 8: Type of SSI by procedure category – 2005
16
Figure 9: Grade of surgeon by procedure category – 2005
17
Figure 10: Supervision of non-consultants – 2005
19
Figure 11: Pre-operative stay for procedure category – 2005
20
Figure 12: Pre-operative stay for procedure category by country – 2005
20
Figure 13: Post-operative stay and procedure category – 2005
22
Figure 14: Cumulative incidence of SSI by procedure category – 2005
23
Figure 15: Incidence density of in-hospital SSI procedure category – 2005
23
Figure 16: Post-operative stay for procedure category (RI 0) 2003 - 2005
24
6
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
7
List of tables
Table 1: SSI by category of procedure – 2005
9
Table 2: SSI by category of procedure 2003 – 2005
9
Table 3: Age and SSI – 2005
11
Table 4: Gender and SSI – 2005
11
Table 5: Circumstance of operation and SSI – 2005
13
Table 6: Procedure category by RI and SSI
15
2003 – 2005
Table 7: Grade of surgeon by RI and SSI 2003 – 2005
17
Table 8: Grade of surgeon by procedure category and SSI 2003 – 2005
18
Table 9: Surgeon performing procedure and supervision – 2005
19
Table 10: Pre-operative stay for procedure category by country and RI
21
Table 11: Comparative SSI rates by procedure category and RI
25
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
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8
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Surveillance methodology
The surveillance methodology is largely based on the National Nosocomial Infection
Surveillance (NNIS) System developed by Centers for Disease Control and
Prevention (CDC), Atlanta, Georgia, USA.1
This report contains data collected from hospitals in Scotland, Wales and Northern
Ireland performing orthopaedic surgery. It contains data on the four mandatory
orthopaedic procedures, i.e. arthroplasty of the hip, hemiarthroplasty of the hip,
open reduction of the trochanteric region of the femur with internal fixation (hence
forth referred to as ‘# neck of femur’) and arthroplasty of the knee.
Primary data collection related to the first 30 days post-surgery and if an implantable
device was involved for at least one year post surgery.
The following were excluded from the analysis:
• Day cases, i.e. patients with post-operative stay less than 24 hours;
• No indication of the presence or absence of SSI;
• Procedure not recorded.
Post-discharge surveillance was not routinely performed. However, patients
readmitted to hospital with a SSI were included in the surveillance. The report
indicates where SSI identified on readmission is included in the analysis.
Missing data is not routinely included in this report. Totals and percentages given
are valid totals and percentages, i.e. excluding missing data. The report indicates
where figures for missing data are included in the analysis.
Abbreviations
CI
Confidence intervals
HCAI
Healthcare Associated Infection
LCL
Lower control limit
LWL
Lower warning limit
NI
Northern Ireland
NNIS
National Nosocomial Infection Surveillance (United States)
OR
Odds ratio
RI
Risk index
SC
Scotland
SPC
Statistical Process Control P-chart
SSI
Surgical site infection
UCL
Upper control limit
UWL
Upper warning limit
WA
Wales
8
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
9
Results
In 2005, there were 17,781 orthopaedic procedures in the four mandated
procedures recorded, i.e. 7,141 arthroplasty of the hip, 2,331 hemiarthroplasty of the
hip, 2,534 open reduction of the trochanteric region of the femur and 5,775
arthroplasty of the knee.
In 2004, there were 9,444 procedures recorded in the four mandated categories.
This represents an increase of 88.3% when comparing 2005 with 2004.
SSI by procedure category
Table 1 provides crude SSI infection rates and confidence intervals for four
mandated categories of orthopaedic surgery in 2005.
Table 1
Procedure category
All procedures
Hip prosthesis
Hemiarthroplasty of hip
# neck of femur
Knee prosthesis
SSI by category of procedure – 2005
Number of
procedures
17781
7141
2331
2534
5775
Number of
SSI
373
125
66
54
128
SSI rate
95% CI
2.1
1.8
2.8
2.1
2.2
1.9 – 2.3
1.5 – 2.1
2.2 – 3.6
1.6 – 2.8
1.9 – 2.6
The SSI rate for hemiarthroplasty of the hip was significantly higher than the SSI
rate for hip prosthesis in 2005 [p ≤ .001].
Table 2 shows crude SSI rates with confidence intervals for the period 2003 – 2005.
Table 2
SSI by category of procedure 2003 – 2005
Procedure category
All procedures
Hip prosthesis
Hemiarthroplasty of hip
# neck of femur
Knee prosthesis
Number of
procedures
35197
16141
3388
3672
11996
Number of
SSI
730
299
102
87
242
SSI rate
95% CI
2.1
1.9
3.0
2.4
2.0
1.9 – 2.2
1.7 – 2.1
2.5 – 3.6
1.9 – 2.9
1.8 – 2.3
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
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10
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Although Tables 1 and 2 give an indication of the SSI rate for a given time period
they do not indicate trends in SSI rates over time.
Figure 1 is a Statistical Process Control P-chart (SPC) that shows the trend in SSI
rates by month over the 3-year period of the Pan Celtic orthopaedic surveillance.
Figure 1 presents the rates of occurrence of SSI in relation to what would be
expected (the average or mean rate) and what is unusual. The vertical or Y-axis in
the SPC is scaled in terms of proportions. Data were analysed using SSI/valid
surgical procedures with ±2 standard deviations (σ) representing upper and lower
warning limits (UWL and LWL) respectively and ±3σ representing upper and lower
control limits (UCL and LCL) respectively above and below the mean.
Pan Celtic Orthoapedic SSI Surveillance
Jan 2003 - Dec 2005
N=35177
0.06
Moving average
Surgical Site Infections per Valid Orthopaedic Procedures
0.05
0.04
UCL
0.03
UW L
Mean 0.021
0.02
LW L
0.01
LCL
0.00
-0.01
Jan
Apr
Figure 1
Jul
Oct
Jan
Apr
Jul
Oct
Jan
Apr
Jul
Oct
Statistical process control P chart SSI 2003 – 2005
The monthly SSI rate has remained within acceptable parameters (i.e. under the
UWL) throughout 2003 to 2005; except for two months in 2003 (June and
September) when the proportion of SSI slightly exceeded the UWL. At no point has
the proportion of SSI exceeded the UCL.
10
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
11
Age and gender
The median age for females was 74-years and for males 70-years. Increasing age
leads to an increased risk of developing SSI in males and females (Figures 2 & 3).
2.8
2.2
1.9
2
55 - 64
65 - 74
SSI rate
1.5
<55
75 - 84
85 and over
Age groups
Figure 2
Age and SSI – 2005
Table 3 shows the under 65-years and 65+ population and SSI. There was no
relationship between these age groups and the risk of developing SSI [p>0.08].
Table 3
Age
Number of
procedures
4631
13042
< 65
65 +
Age and SSI - 2005
% of
procedures
26.2
73.8
Number of
SSI
83
289
SSI rate
95% CI
1.8
2.2
1.9 – 2.6
1.8 – 2.3
Females accounted for 62.6% of the patient population. Table 4 shows the patient
population by gender and SSI. There was no relationship between gender and the
risk of developing SSI [p=0.35].
Table 4
Gender
Number of
procedures
6648
11120
Male
Female
Gender and SSI – 2005
% of
procedures
37.4
62.6
Number of
SSI
147
223
SSI rate
95% CI
2.2
2.0
1.9 – 2.6
1.8 – 2.3
2.6
2.2
SSI rate
2.1
2.1
1.7
2.3
1.9
2.8
2.1
1
<55
55 - 64
65 - 74
75 - 84
85 and over
Age groups
Male
Figure 3
Female
Age by gender and SSI – 2005
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
11
12
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Circumstance of operation (elective vs. emergency)
The circumstance of operation (elective vs. emergency) was recorded reflecting the
urgency of the surgery. The majority of hip prosthesis (98.5%) and knee prosthesis
(99.5%) operations were elective, i.e. planned in advance. The timing of
hemiarthroplasty of hip (67.9%) and # neck of femur (77.8%) were predominantly
classed as emergency, i.e. in response to an injury.
Figure 4 shows the circumstance of operation (elective vs. emergency) for each of
the mandated procedures.
Percentage of procedures
1.5
0.5
67.9
77.8
99.5
98.5
32.1
22.2
Hip prosthesis
Hemiarthroplasty
Elective
Figure 4
# neck of femur
Knee prosthesis
Emergency
Circumstance of operation by procedure category – 2005
The length of pre-operative stay (See Table 10) indicates that approximately 2/3 of
emergency procedures (66.3%) were performed within a day of admission; the
remaining 1/3 wait longer. The possible reason for delay in operation of more than
one day after admission for 1/3 of all emergency procedures could be due to the
underlying state of health of the patient. Another possible explanation for the delay
is that the procedures were not actually ‘true emergency’ procedures, i.e. life
threatening, but rather they were ‘urgent’ procedures, i.e. should be operated on as
soon as possible.
12
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
13
Table 5 shows the number of patients, the infection rates, and the 95% confidence
intervals for elective and emergency operations. The SSI rate of 2.7% for
emergency procedures was significantly higher than the SSI rate of 1.9% for elective
procedures [p<0.003].
Table 5
Circumstance
of operation
Elective
Emergency
Circumstance of operation and SSI – 2005
Number of
procedures
13942
3638
% of
total
79.3
20.7
Number of
SSIs
265
98
SSI rate
95% CI
1.9
2.7
1.7 – 2.1
2.2 – 3.3
Figure 5 shows the circumstance of operation for each of the mandated procedures
and the SSI rate. There is an increased risk of developing an SSI when comparing
elective and emergency operations in all procedure categories.
7.8
SSI rate
6.7
2.6
2.9
2
1.6
Hip prosthesis
Hemiarthroplasty
Elective
Figure 5
2.2
2.2
# neck of femur
Knee prosthesis
Emergency
Circumstance of operation by procedure category and SSI – 2005
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
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14
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
NNIS risk index (RI)
In 1991, the Centers for Disease Control and Prevention published the NNIS
System risk index (RI) to stratify populations of surgical patients by the risk of
acquiring SSI.3
The RI is computed from the wound contamination class (one point if >2;
contaminated or dirty/infected wounds); the ASA physical status classification (one
point if >2: severe systemic disease to moribund patient) and the duration of the
operation (>75th percentile of NNIS distribution). Procedures score from zero to
three according to the number of risk factors present at the time of surgery.
Figure 6 shows the distribution of RI by procedure category.
2.9
2.1
2.5
Percentage of procedures
6
31.1
33.6
67.1
68.4
66.4
60.1
Hip prosthesis
30.1
29.5
Hemiarthroplasty
# neck of femur
RI 0
Figure 6
Knee prosthesis
RI 1
RI 2
Distribution of RI for procedure category – 2005
The comparison of RI by procedure category and by country (Figure 7) shows slight
variation between countries within the same procedure category.
Hip prosthesis
Percentage of procedures
100%
Hemiarthroplasty
prosthesis
Knee prosthesis
# neck of femur
80%
60%
40%
20%
0%
SC
WA
RI 0
Figure 7
14
NI
SC
WA
RI 1
NI
SC
WA
NI
SC
RI 2
WA
NI
RI 3
Distribution of RI for procedure category by country – 2005
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
15
Table 6 displays SSI rates by operative procedure and RI for 2003 - 2005.
When the SSI rates for adjacent risk categories for a particular operation were not
statistically different, they were combined into a single risk category. For example,
because the SSI rates for knee prosthesis with 2 or 3 risk factors were similar, the
data were combined into a new category 2,3. Thus, the numbers of risk index
categories in the tables will differ depending upon the operation. In categories with
less than 30 procedures, the SSI rate is not given; indicated by --.
Table 6
Procedure category by risk index and SSI 2003 – 2005
Procedure category
RI
Number of
operations
SSI rate
95% CI
0
1
2
3
17642
12197
1272
55
1.5
2.7
3.8
5.5
1.4 – 1.7
2.4 – 3.0
2.9 – 5.0
1.9 – 14.9
0
1
2,3
8801
4688
836
1.4
2.5
3.1
1.2 – 1.7
2.1 – 3.0
2.1 – 4.5
0
1
2,3
887
2025
77
1.7
3.7
1.3
1.0 – 2.8
2.9 – 4.6
0.2 – 7.0
0
1
2
3
966
2136
59
0
1.8
2.3
5.1
--
1.1 – 2.8
1.8 – 3.1
1.7 – 13.9
--
0
1
2,3
6988
3348
355
1.7
2.5
5.9
1.4 – 2.0
2.0 – 3.1
3.9 – 8.9
All procedures
Hip prosthesis
Hemiarthroplasty of hip
Open reduction # neck
of femur
Knee prosthesis
The NNIS basic risk index was a useful method of risk adjustment. SSI rates
increased as the number of risk factors increased (RI 0 & RI 1) for all procedure
categories [p<0.05].
The numbers in RI 2 & RI 3 were too small to make meaningful comparisons.
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
15
16
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Type of SSI
Three types of SSI were identified depending on whether the incisional site
(superficial incisional SSI or deep incisional SSI) or other structures (organ/space
4
SSI) were involved.
Figure 8 gives the proportion of SSI type by procedure category.
4.3
2.6
5.9
9.8
Percentage of infections
14
14.8
17.6
23
81.7
Hip prosthesis
Superficial
Figure 8
82.6
76.5
67.2
Hemiarthroplasty
# neck of femur
Deep
Knee prosthesis
Organ / Space
Type of SSI by procedure category – 2005
The majority of SSIs were superficial incisional (78.7%). However, 21.3% of SSIs
were identified as the more serious deep incisional or organ/space infections.
In the combined dataset, covering 2003 – 2005, 22.2% of SSIs were classified as
deep incisional or organ/space infections; of these 15.5% were identified on
readmission to hospital.
16
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
17
Grade of surgeon
Consultant surgeons performed the majority of hip and knee prostheses.
Specialist registrars performed the majority of hemiarthroplasty of hip and # neck of
femur procedures (Figure 9).
0.6
Percentage of procedures
2.9
9.8
5
14.6
0.6
5.5
13.1
16.6
3.5
52.9
61.5
82.1
77.4
32.3
20.1
Hip prosthesis
Hemiarthroplasty
Consultant
Figure 9
# neck of femur
Specialist Registrar
Knee prosthesis
Career grade
SHO
Grade of surgeon by procedure category – 2005
Table 7 shows the SSI rates for grades of surgeon stratified by RI 2003 - 2005. SSI
rate is not shown for categories with less than 30 procedures (indicated by --).
Table 7
Grade of surgeon by RI and SSI 2003 – 2005
Grade of surgeon
performing procedure
Consultant
Non-consultant surgeons,
i.e. Specialist registrars,
SHOs and non-consultant
career grades
Specialist registrar
Non-consultant career
grade
Senior house officer
RI
0
1
2
3
0
1
2
3
0
1
2
3
0
1
2
3
0
1
2
3
Number of
operations
13002
7392
968
52
4490
4581
298
3
3371
3432
237
3
750
573
32
0
369
576
29
0
SSI rate
95% CI
1.4
2.5
4.2
5.8
2.0
3.0
2.3
-1.5
2.8
2.5
-4.3
3.8
3.1
-1.9
3.3
---
1.2 – 1.6
2.2 – 2.9
3.1 – 5.7
2.0 – 15.6
1.6 – 2.5
2.5 – 3.5
0.3 – 2.9
-1.2 – 2.0
2.3 – 3.4
1.2 – 5.4
-3.0 – 6.0
2.6 – 5.7
0.6 – 15.7
-0.9 – 3.9
2.1 – 5.1
---
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
17
18
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Grade of surgeon performing the procedure had an impact on SSI rates (Table 8).
Table 8
Grade of surgeon by procedure category and SSI 2003 – 2005
Grade of surgeon
Consultant
Non-consultant
surgeons, i.e. Specialist
registrars, SHOs and
non-consultant career
grades
Specialist registrar
Senior house officer
Non-consultant career
grade
Procedure
category
All procedures
Hip prosthesis
Hemiarthroplasty
# neck of femur
Knee prosthesis
All procedures
Hip prosthesis
Hemiarthroplasty
# neck of femur
Knee prosthesis
All procedures
Hip prosthesis
Hemiarthroplasty
# neck of femur
Knee prosthesis
All procedures
Hip prosthesis
Hemiarthroplasty
# neck of femur
Knee prosthesis
All procedures
Hip prosthesis
Hemiarthroplasty
# neck of femur
Knee prosthesis
Number of
procedures
24066
13122
965
723
9256
10460
2812
2256
2780
2612
7923
2263
1695
2024
1941
1099
123
343
517
116
1438
426
218
239
555
SSI
rate
1.9
1.8
1.3
2.5
2.0
2.5
1.9
3.9
2.3
2.3
2.2
1.6
3.5
2.3
1.8
2.7
1.6
4.4
2.1
1.7
4.0
3.5
5.5
2.9
4.3
95% CI
1.7 – 2.1
1.6 – 2.1
0.8 – 2.3
1.6 – 3.9
1.7 – 2.3
2.3 – 2.9
1.5 – 2.5
3.1 – 4.7
1.8 – 2.9
1.8 – 3.0
1.9 – 2.6
1.2 – 2.3
2.8 – 4.5
1.7 – 3.0
1.3 – 2.4
1.9 – 3.9
0.5 – 5.7
2.7 – 7.1
1.2 – 3.8
0.5 – 6.1
3.1 – 5.2
2.2 – 5.7
3.2 – 9.4
1.4 – 5.9
2.9 – 6.4
Consultant surgeons had a significantly lower SSI rate (1.9%) than non-consultant
surgeons (SSI rate 2.5%) [p<0.02].
18
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
19
Supervision of non-consultant surgeons
Guidance from the Specialist Advisory Committee of the Joint Committee on Higher
Surgical Training suggests that when a consultant does not perform the procedure,
one should be present in the operating theatre in order to minimise the risk of
5
infection.
Figure 10 shows the proportion of procedures performed by consultant surgeons, by
non-consultant surgeons when a consultant was present in the operating theatre
and by non-consultant surgeons when a consultant was not present.
A consultant was not present in the theatre suite for only 15% of all procedures.
Specialist Registrars (75.1%) performed the majority of these procedures; Nonconsultant career grades (14.4%) and Senior House Officers (10.5%) performed the
remaining procedures.
15%
Consultant operating
18%
Figure 10
67%
Consultant present
Consultant not present
Supervision of non-consultant surgeons – 2005
Table 9 shows the SSI rate for consultants, for supervised surgeons and where
there was no supervision.
Table 9
Surgeon performing procedure and supervision – 2005
Supervision
Consultant operating
Consultant present
Consultant not present
Number of
procedures
11371
2995
2442
Number of
SSI
217
70
58
SSI rate
1.9
2.3
2.4
95% CI
1.6 – 2.2
1.9 – 2.9
1.8 – 3.1
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
19
20
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Pre-operative stay
Pre-operative stay is an important risk factor in orthopaedic patients for the
6
development of SSI. In the observed patient population 6.7% of patients had a preoperative stay of four or more days. The SSI rate in patients with a pre-operative
stay of four or more days was 4.4% and for patients with a pre-operative stay of less
than four days the SSI rate was 1.9%. There was a significant risk of developing an
SSI for orthopaedic patients with a preoperative stay of four or more days compared
to patients with a pre-operative stay of less than 4 days.
There were differences in the pre-operative stay by procedure category (Figure 11),
by country (Figure 12) and by RI (Table 10).
2.8
1.2
2.7
Percentage of procedures
4.2
18.8
19.2
23.4
24.1
96.1
93
Hip prosthesis
57.8
56.7
Hemiarthroplasty
# neck of femur
0 to 1 days
Figure 11
2 to 3 days
Knee prosthesis
4 or more days
Pre-operative stay for procedure category – 2005
Figure 12 shows variations in the distribution of pre-operative stay by country for
each of the procedure categories.
Hip prosthesis
Percentage of procedures
100%
Hemiarthroplasty
prosthesis
# neck of femur
Knee prosthesis
80%
60%
40%
20%
0%
SC
WA
NI
0 to 1 days
Figure 12
20
SC
WA
NI
SC
2 to 3 days
WA
NI
SC
WA
NI
4 or more days
Pre-operative stay for procedure category by country – 2005
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
21
Table 10 Pre-operative stay for procedure category by country and SSI – 2005
Procedure
category
Hip prosthesis
Country
All
SC
WA
NI
Hemiarthroplasty
of hip
All
SC
WA
NI
# neck of femur
All
SC
WA
NI
Knee prosthesis
All
SC
WA
NI
Pre-operative
stay (days)
0 to 1
2 to 3
4 or more
0 to 1
2 to 3
4 or more
0 to 1
2 to 3
4 or more
0 to 1
2 to 3
4 or more
0 to 1
2 to 3
4 or more
0 to 1
2 to 3
4 or more
0 to 1
2 to 3
4 or more
0 to 1
2 to 3
4 or more
0 to 1
2 to 3
4 or more
0 to 1
2 to 3
4 or more
0 to 1
2 to 3
4 or more
0 to 1
2 to 3
4 or more
0 to 1
2 to 3
4 or more
0 to 1
2 to 3
4 or more
0 to 1
2 to 3
4 or more
0 to 1
2 to 3
4 or more
Number of
procedures
6584
293
200
4039
146
97
1313
49
43
1232
98
60
1334
542
433
1116
255
99
147
77
74
71
210
260
1415
603
478
1068
280
100
192
119
97
155
204
281
5507
154
71
3317
91
42
1312
40
20
878
23
9
Number
of SSI
107
2
11
61
0
2
38
1
5
8
1
4
31
13
22
25
7
6
4
3
3
2
3
13
21
16
16
12
7
5
8
5
3
1
4
8
116
7
3
36
1
2
58
5
1
22
1
0
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
SSI
rate
1.6
7.0
5.5
1.5
0.0
2.1
2.9
2.0
11.6
0.6
1.0
6.7
2.3
2.4
5.1
2.2
2.5
6.1
2.7
3.9
4.1
2.8
1.4
5.0
1.5
2.7
3.3
1.7
2.5
5.0
4.2
4.2
3.1
0.6
2.0
2.8
2.1
4.5
4.2
1.1
1.1
4.8
4.4
12.5
-2.5
---
21
22
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Post-operative stay
A major factor influencing the detection of SSI is the duration of post-operative stay
in hospital. After discharge, the detection of SSI is entirely dependent on the
intensity of post discharge surveillance.
Figure 13 shows the percentage of patients in hospital post-surgery by procedure
category.
100
% patients in hospital
90
80
Hip prosthesis
70
Hemiarthroplasty
60
# neck femur
50
Knee prosthesis
40
30
20
10
28
26
24
22
20
18
16
14
12
10
8
6
4
2
0
0
Post-operative stay - Days
Figure 13
Post-operative stay and procedure category – 2005
Approximately 76% of hip prosthesis patients and 78% of knee prosthesis patients
were discharged from hospital within 8 days of operation. In contrast, 50%
hemiarthroplasty of hip patients and 47% of # neck of femur patients were
discharged within the same time scale.
Ideally, SSI surveillance should be performed 30-days post operatively or for one
year if an implant is involved. Although information is gathered on patients
readmitted to hospital with an SSI this is confined to the more serious deep
incisional and organ/space infections
The numbers of infections detected in hospital will be affected by the length of
postoperative stay. The median post surgery stay in hospital for hip and knee
prostheses patients is 6 days, for those undergoing hemiarthroplasty of hip it is 8
days and for # neck of femur surgery it is 9 days.
The percentage of procedures that resulted in SSI in the postoperative in-patient
period (cumulative incidence) is shown in Figure 14. It is possible to allow for length
of postoperative stay by calculating the rate of in-patient SSI as an incidence
density, i.e. the number of in-patient SSI per 1000 post-operative days (Figure 15).
22
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
23
In the absence of post discharge surveillance, the post-operative stay is the
observation period. This differs between procedures, countries, hospitals and units.
Incidence density partially removes the observation bias caused by the differing
lengths of observation periods.
The effect that increased length of post-operative follow-up has on the rates of SSI
for the procedure categories is demonstrated when the cumulative in-patient
incidence (Figure 14) is compared with the incidence density (Figure 15).
Knee pros thes is
1.9
# neck of fem ur
1.9
Hemiarthroplas ty
2.7
Hip pros thes is
1.5
In-patient SSI rate
Figure 14
Cumulative incidence of SSI by procedure category – 2005
Knee prosthesis
# neck of femur
2.7
1.8
Hemiarthroplasty
Hip prosthesis
2.5
2
Incidence density per 1000 post-operative days
Figure 15
Incidence density of in-hospital SSI per 1000 postoperative inpatient days by procedure category – 2005
In procedures with a comparatively short post-operative stay, i.e. hip and knee
prosthesis the cumulative incidence SSI rate (Figure 14) is lower than the incidence
density rate (Figure 15) and conversely for procedures with a comparatively longer
post-operative stay, i.e. hemiarthroplasty of hip and # neck of femur, the cumulative
incidence SSI rate is higher than the incidence density rate.
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
23
24
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Prolongation of in-patient stay due to SSI
Patients who developed an SSI in hospital stayed 11 days longer in hospital than
patients who did not develop an SSI, i.e. median procedure to discharge was 7 days
without SSI and 18 days with SSI (2003 - 2005).
Patients with a number of risk factors may have a poor state of health that may lead
to prolongation of stay that may not be solely attritbutale to the development of SSI.
Patients with a RI 0 may give a better indication of prolongation of stay due to SSI;
as they appear to have no predisposing risk for the development of SSI. Any
prolongation of post-operative stay for patients with a RI 0 who develop an SSI can
probably be attributed to complications resulting from the development of the SSI.
Patients with a RI 0 who developed an SSI in hospital stayed 8 days longer in
hospital than patients who did not develop an SSI, i.e. median procedure to
discharge was 6 days without SSI and 14 days with SSI (2003 - 2005).
Procedure RI 0 2003-2005
Figure 16 shows considerable variation in the prolongation of stay for patients with
and without an SSI between procedure categories with a RI0.
13
Knee prosthesis
6
12
# neck of femur
7
13
Hemiarthroplasty
7
14
Hip prosthesis
6
Median post-operative stay (days)
Patients without SSI
Figure 16
24
Patients with SSI
Post-operative stay for procedure category (RI 0) 2003 – 2005
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
25
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
Comparative results
Table 11 displays SSI rates by procedure category and RI for:
• Pan Celtic data – combined for Scotland, Wales and Northern Ireland;
• England 7;
• U.S.A. 8.
When the SSI rates for adjacent risk categories for a particular procedure were not
statistically different, they were combined into a single risk category. For example,
because the SSI rates for hip prosthesis with 2 or 3 risk factors were similar, the
data were combined into a new category 2,3. Thus, the number of risk index
categories in the tables will differ depending on the procedure.
SSI rate is not shown for categories with less than 30 procedures (indicated by --).
Table 11
Procedure
category
Hip prosthesis
Hemiarthroplasty
of hip
Comparative SSI rates by procedure category and RI
RI
Pan Celtic data 2003 - 2005
All
SC
WA
NI
England7
NNIS 8
*
Overall
0
1
2,3
1.9
1.4
2.5
3.1
1.9
1.4
2.7
3.2
3.1
2.9
3.1
4.3
1.0
0.7
1.7
2.0
1.2
0.8
1.6
4.5
**
NA
0.9
1.7
2.5
Overall
0
1
2,3
3.0
1.7
3.7
1.3
2.6
0.9
3.5
1.8
3.6
3.7
3.6
--
3.4
2.2
3.8
--
Overall
0
1
2
3
2.4
1.8
2.3
5.1
--
1.8
0.7
2.3
0.0
--
3.8
3.4
3.6
---
2.5
2.3
2.1
---
4.0
3.3
4.1
7.1
***
2.0
1.1
2.8
6.3
--
***
NA
0.8
1.4
2.8
5.0
Overall
0
1
2,3
2.0
1.7
2.5
5.9
1.5
1.1
2.0
5.4
4.2
3.9
4.1
12.8
1.8
1.5
3.0
2.5
1.0
0.8
1.4
2.5
NA
0.9
1.3
2.3
# neck of femur
Knee prosthesis
*
In England the Surgical Site Infection Surveillance Service use an adapted
version of the NNIS definitions of infection.
** NNIS procedure category of ‘Hip prosthesis’ combines hip prosthesis and
hemiartroplasty of hip.
*** ‘Open reduction of fracture’ procedure category, in England and in the NNIS
system, includes all open reduction of long bones not just open reduction of #
neck of femur.
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
25
26
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Conclusions
The Pan Celtic Collaborative Report provides data on orthopaedic SSI surveillance
in areas with similar practice and offers an opportunity to examine these areas of
practice.
The programme has provided risk adjusted measures of performance over time.
The results can be compared with other internationally published data relating to
orthopaedic procedures.
Rates of SSI were higher for hemiarthroplasty of hip and # neck of femur, which are
generally undertaken following a traumatic injury to the hip. This association may
reflect a number of risk factors for SSI such as the underlying state of health of the
patient or illness that predisposes to, or increases the risk of infection.
Pre-operative stay is an important risk factor in orthopaedic patients for the
development of SSI.
The post-operative stay in hospital for hemiarthroplasty of hip and # neck of femur
patients was longer than those patients undergoing elective hip or knee replacement
and therefore the chance that SSI will be detected by this surveillance is increased.
The grade of surgeon performing the procedure has an impact on the SSI rate.
Most of the SSIs reported affected the superficial layers of the wound.
Approximately a quarter involved the deeper tissues and these infections are more
difficult to treat and may require re-admission to hospital and/or subsequent reoperation.
The consistent nature of the results supports validity of the methodology and
provides a basis for evaluating hospital/unit/surgeon performance over time and the
impact of any interventions introduced to reduce infections.
This collaborative report should be used, with reports from the relevant country,
hospital and surgeon specific reports, to review orthopaedic practice in conjunction
with other infection control activities in order to reduce the burden of SSI.
26
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 data
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
27
References
1. National Nosocomial Infections Surveillance (NNIS) Manual. U.S.
Department of Health & Human Services, Public Health Service, Centers for
Disease Control and Prevention (CDC), 1999.
2. National Confidential Enquiry into Perioperative Death (NCEPOD),
Classification of Interventions. NCEPOD, December 2004.
3. Culver et al. Surgical wound infection rates by wound class, operative
procedure and patient risk index. Am J Med 1991; 91(Suppl B): 3B -152S157S.
4. Horan et al., CDC Definitions of Surgical Site Infections, 1992: A
Modification of CDC Definitions of Surgical Wound Infections. Infect Control
Hosp Epidemiol 1992; 13: 606-608.
5. Manual of Higher Surgical Training in the UK and Ireland. Joint Committee
on Higher Surgical Training, ninth report, April 2005.
6. de Boer et al. Risk Assessment for Surgical-Site Infections in Orthopedic
Patients. Infect Control Hosp Epidemiol 1999; 20: 402–407.
7. Health Protection Agency. Mandatory surveillance of surgical site infection
in orthopaedic surgery: April 2004 to March 2005. London: Health Protection
Agency, October 2005.
8. National Nosocomial Infections Surveillance (NNIS) System Report, data
January 1992 to October 2004. Am J Infect Control 2004; 32: 470-85.
Pan Celtic Collaborative Surveillance – Orthopaedic Procedures Report: 2005 Data
27
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