Minimizing the Risk of Surgical Site Infection Following Hip Fracture Operation

Abstract

Introduction:

Hip fractures are the most common serious injury in the elderly, associated with disability, morbidity, and mortality. Surgical site infection (SSI) is a serious post-operative complication. This prospective cohort study outlines how our center made cumulative improvements in SSI incidence rates, reaching a 12-month average of 0.5%.

Methods:

All patients undergoing hip fracture operation between 2016 and 2021 were included. The primary outcome measure was confirmed SSI, according to the Public Health England definition. Results were compared with the baseline recordings by an independent SSI team in 2013. Demographic data were compared with National Hip Fracture Database records. Peri-operative infection control and wound management tactics introduced between 2014 and 2021 were collated to gain an overview care bundle.

Results:

Baseline recordings identified a 9.0% SSI rate in a three-month observation period. In our study, 3,138 hip fracture operative cases were completed between October 2016 and December 2021. There were 9 superficial and 32 deep infections identified, yielding an overall infection rate of 1.3%. However, when analyzing the 12-month average, there was consistent decline in SSI from the baseline 9.0% in 2013 to 0.5% in 2021 (p < 0.05). A peri-operative care bundle included pre-operative bleeding risk assessment. Intra-operatively, double preparation and draping is used for arthroplasty. Broad-spectrum antibiotic agents and tranexamic acid are administered. Meticulous hemostasis and watertight wound closure are observed. Anti-coagulated patients received negative pressure dressings. Post-operatively, a dedicated senior lead team provided daily inpatient review of patients, with urgent consultant review of all wound healing concerns.

Conclusion:

Patients with a hip fracture have numerous risk factors for SSI. A dedicated multi-focal tactic, adopted by a multi-disciplinary department, can yield substantial risk reduction. Each intervention is evidence based and contributes to cumulative improvement. By prioritizing infection prevention, we have minimized the need for complex infection management interventions and achieved an annual saving of £860,000 for our trust.

Hip fractures are the most common serious injury occurring in the elderly population, associated with disability, morbidity, and mortality.¹ In the United Kingdom, 60,000–75,000 hip fractures occur each year, resulting in an annual cost (including medical and social care) of £2 billion.²

Surgical site infection (SSI) is a serious post-operative complication following hip fracture operation. SSI can result in increased length of hospital stay, greater rate of revision operation, prolonged use of antibiotic agents, increased inpatient mortality, and reduced rates of returning to original place of residence.^3,4 The financial cost of treating an SSI is also more than triple that of an uncomplicated case.^4,5 Therefore, the impact of SSI is detrimental and costly to both the patient and the healthcare service.

The current accepted incidence of SSI following hip fracture operation is between 0.8% and 4%.^6,7 Efforts have been made to audit and improve infection rates at different centers, with substantial improvements being observed,⁸ resulting in an optimum incidence around 1%.

In this review, we outline the means in which our center has made cumulative improvements in SSI incidence rates, reaching a 12-month average of 0.5%.

Patients and Methods

Following a mandatory SSI surveillance service (SSISS) review obtaining a baseline departmental infection rate over a three-month observation period in 2013, a care bundle of peri-operative infection control and wound management interventions was implemented in the coming years. This care bundle was introduced with a step-wise and continuous approach, with regular monitoring of performance.

In this prospective cohort study, all patients undergoing hip fracture operation (arthroplasty and internal fixation) in our center between 2016 and 2021, following the introduction of the SSI care bundle, were included for analysis. Local data collection was performed by two highly trained clinical nurse specialists (CNSs). Data from the national clinical audit of hip fracture care in England, Wales, and Northern Ireland, the National Hip Fracture Database (NHFD), were also included. The NHFD records outcomes for >95% of all patients >60 years of age who present with hip fracture to all 175 trauma units in these countries.⁹

The primary outcome measure was a confirmed superficial or deep SSI in keeping with Public Health England/Centers for Disease Control and Prevention (PHE/CDC) definition. Patient demographics were recorded for each confirmed SSI case, in addition to potential SSI risk factors. Infection rates were compared between operation type (arthroplasty [total hip arthroplasty (THA) and hemiarthroplasty (HA)] and internal fixation (dynamic/compression hip screw, intramedullary nail, and cannulated screw fixation]).

To ensure consistency of evaluating our center’s outcomes, and to draw comparison with data in the literature, we use pre-defined definitions for SSI outlined by PHE.¹⁰ This protocol defines SSIs according to standard clinical criteria for infections that affect the superficial tissues (skin and subcutaneous layer) of the incision and those that affect the deeper tissues (deep incisional or organ/space). These are based on the definitions established by the CDC.¹¹

Peri-operative infection control and wound management methods in place at our center were also summarized to gain an overview understanding of the interventions put into practice between 2016 and 2021.

Ethics approval statement

This study was approved by the Sheffield Teaching Hospitals NHS Foundation Trust Clinical Effectiveness Unit (reference 9982).

Results

In total, 3,138 cases were completed in the study period between October 2016 and December 2021. Cases were completed by numerous surgeons with various experience levels (from Core Surgical Trainee to Senior Consultant). Trainees received appropriate senior supervision depending on experience.

In total, 53% of our patient cohort presenting with a hip fracture underwent arthroplasty (THA or HA). The mean American Society of Anesthesiologists (ASA) grade was 2.97. Population data from the NHFD identify 77% of all cases recorded nationally had ASA scores 1–3 and 54% of patients nationally underwent arthroplasty. This outlines our local cohort is on average at least as comorbid as the national population, and an almost identical proportion has arthroplasty versus fixation. Table 1 demonstrates that there was no change in our patient cohort demographics during the study period.

Table 1.

Demographic Data of All Patients with Hip Fracture per Year of Presentation.

Year	AgeMean (SD)p = 0.51	AMTSMean (SD)p = 0.90	ASAMean (SD)p = 0.62
2013	81.8 (±7.40)	6.0 (±4.00)	2.67 (±0.58)
2016 (Oct–Dec)	82.9 (±8.64)	6.3 (±3.81)	3.02 (±0.67)
2017	82.1 (±8.97)	6.5 (±3.84)	2.99 (±0.72)
2018	82.9 (±8.38)	6.4 (±3.92)	2.95 (±0.69)
2019	83.0 (±8.20)	6.4 (±3.79)	2.97 (±0.70)
2020	82.5 (±8.86)	6.6 (±3.70)	2.96 (±0.65)
2021	82.3 (±8.57)	6.6 (±3.72)	2.99 (±0.68)

ASA = American Society of Anesthesiologists; SD = standard deviation; ANOVA = analysis for variance; AMTS = Abbreviated Mental Test Score.

Nationally, 50.3% of patients undergo an operative procedure within 36 hours of presentation. In comparison, 75% of patients in our cohort had their surgical procedure within the same time frame, outlining our relative success in prioritizing this patient group.

SSI rates

SSI data were compared with baseline recordings by an independent specialist team in 2013, which identified that in a three-month observation period, 67 cases were assessed and 6 SSI episodes were identified. This gave a baseline SSI rate before intervention implementation of 9.0%.

Between October 2016 and December 2021, there was a total of 9 superficial infections and 32 deep infections, yielding an overall infection rate of 1.31%. However, when analyzing the 12-month rolling average, there was a consistent decline in infection rates from the baseline 9.0% in 2013 to 0.5% in 2021 (χ² = 20.259, p < 0.00) (Table 2).

Table 2.

Incidence of Superficial and Deep Surgical Site Infection Following Hip Fracture Operation

Year	Number of cases (n)	Superficial infection (n)	Deep infection (n)	Total infection (n)	12-month average (%)
2013 (May–Jun)	69	1	5	6	9.0
2016 (Oct–Dec)	183	1	4	5	2.7
2017	567	2	7	9	1.6
2018	606	2	7	9	1.6
2019	640	1	7	8	1.3
2020	552	2	5	7	1.3
2021	590	1	2	3	0.5
Total	3,207	10	37	47

p = 0.0025; χ² = 20.26.

Demographics and risk factors for all 41 identified cases of SSI were analyzed. The mean age at time of operation was 82.5 years, with a mean ASA grade of 2.9. Twenty-eight (59.6%) patients who developed an SSI were operated within 36 hours of presentation to hospital. Ten (21.3%) patients were on pre-operative anti-coagulation (Warfarin or Direct-Acting Oral Anticoagulant [DOAC]).

Of the SSI cases, 31 patients (65.9%) underwent hip HA, with 24 (87.1%) of these patients ultimately having a deep infection. The average operating time for all HA cases was 91 minutes.

Post-operatively, six SSI cases (12.8%) presented with a dislocation of their HA, with subsequent tissue sampling in theater identifying a positive growth on microbiological analysis. All remaining patients (87.2%) presented with a leaking surgical wound. Of those who presented a wound concern, the average time to senior review was 0.6 days. Ultimately, 65.9% (n = 31) of all identified SSI cases underwent additional surgical procedure within 90 days of the initial operation. Overall post-operative mortality for the SSI cases was 4.3% at 30 days and 12.8% at 90 days.

Microbiological samples were obtained from 85% of SSI cases. The most commonly occurring organisms were Staphylococcus epidermidis (39%), Enterococcus (20%), and Escherichia coli (12%).

SSI prevention care bundle

In order to gain an overview of the peri-operative infection control and wound management methods, we have summarized the key interventions below.

Pre-operative

Each patient with hip fracture is clinically assessed on presentation, including clotting function blood tests and a medication history to ascertain the presence of an oral anti-coagulant in use. If a patient is anti-coagulated with a DOAC or Warfarin, they are deemed at an increased risk for post-operative surgical wound leaking. Their clotting is appropriately reversed according to published national advice¹² and a plan made to use a closed incision negative pressure wound therapy device. Also, as it was identified that the pre-dominant infectious microorganism was of staphylococcal origin, in keeping with National Institute for Health and Care Excellence (NICE) guidelines for prevention of SSI,¹³ nasal mupirocin ointment in combination with a chlorhexidine body wash is utilized before all surgical procedures for this patient cohort. This is administered by the trained nursing staff on the admitting ward.

Intra-operative

Patients undergoing arthroplasty (THA or HA) are prepped with a chlorhexidine skin solution (iodine if allergic contraindication) and sterile drapes applied in the anesthetic room before being moved to the operating theater and the preparation process re-applied. Those undergoing internal fixation are prepped and draped only in the operating theater.

All operations are performed in a laminar flow theater. All patients received broad-spectrum prophylactic intravenous antibiotic agents at induction. No further doses are routinely prescribed post-operatively. Patients are also routinely administered a single dose of tranexamic acid at induction. In all cemented arthroplasty cases, high-dose dual antibiotic bone cement, Heraeus Copal G + C cement (Hanau, Germany), containing gentamicin 1 g and clindamycin 1 g per 40 gm mix of cement, is utilized, as it has been demonstrated to minimize the risk of SSI in this patient population.¹⁴

Careful surgical techniques, with meticulous hemostasis, are always observed. Watertight wound closure using an absorbable monofilament is a standard practice. A PICO (Smith & Nephew Inc, UK) dressing is utilized according to the assessment of risk for post-operative wound leaking. If a patient meets any of the following criteria, the negative pressure wound therapy device is used: -

Admitted on anti-coagulation therapy including DOACs

Long-term steroid use

Recipient of renal dialysis or presence of chronic kidney disease (creatinine >200)

Methotrexate or other immune modulator use

Heart or liver failure

Presence of soft tissue edema

Recipient of an organ transplant

In all other cases, a Mepilex (Mölnlycke Health Care Limited, UK) dressing is utilized.

Post-operative

Following completion of the procedure, a clear venous thromboembolism (VTE) prophylaxis plan is documented and prescribed. Patients not on an oral anti-coagulant before admission are routinely prescribed 35 days of prophylactic dose low molecular weight heparin, and those on an oral anti-coagulant are prescribed a bridging protocol.

A dedicated senior-led team provided a daily inpatient review of all patients. All ward nurses caring for these patients receive clear education on the early recognition of signs of wound leaking or infection. Any suspicion for wound issues is escalated directly to a dedicated CNS who completes an urgent review within 24 hours and then escalates to one of two senior consultant surgeons for urgent review as required. Decisions and interventions on VTE prophylaxis management and dressing care are only made by these CNS/senior consultant reviewers. Any decision to return to theater for further operation is prioritized early on the next available theater list.

Discussion

In this study, we have shown a reduction in SSI following hip fracture operation using a SSI care bundle. Various studies and reviews have previously outlined the risk factors associated with SSI in hip fracture operation. In the emergency trauma setting, the luxury of pre-operative optimization of a patient is not always possible, and surgical delay has been shown to lead to increased risk of SSI.¹⁵ We identified our trust is far better than the national average at operating on patients within 36 hours of presentation; however, in the cohort of confirmed SSI, there was a lower proportion receiving a timely procedure. This further supports the evidence that surgical delay influences SSI rates.

Other non-modifiable risk factors for SSI in the hip fracture trauma setting are increased age,¹⁶ increased body mass index,¹⁷ and a low pre-operative serum albumin.¹⁷ It is also understood that a greater ASA physical status classification is associated with increased SSI risk.¹⁸ We identified that our cohort was generally more comorbid than the general UK population on review of data present on the NHFD, and the patients with confirmed SSI carried a greater degree of comorbidity still.

With regard to peri-operative medications, oral steroid use is associated with a greater SSI risk.⁵ However, the consensus on the overall risks associated with anti-coagulant use in hip fracture operation is less clear.^19,20 It has been demonstrated that anti-coagulated patients are up to five times more likely to experience post-operative wound leaking,²¹ with such prolonged wound drainage and hematoma formation increasing the risk of infection.^22,23 The collection or leaking of fluids from a surgical incision provides a medium for bacterial growth and has effects on impairing wound healing and reducing tissue perfusion.²⁴ Although the use of negative pressure dressings is not known to be of benefit in all lower limb trauma²⁵ or in elective joint arthroplasty,²⁶ their use in patients with geriatric hip fracture is shown to reduce SSIs.¹⁷ Therefore, we continue to advocate the use of negative pressure wound therapy devices for all anti-coagulated patients. Post-operatively, early recognition and senior intervention and decision-making are key. We have demonstrated our trust has achieved an average delay of 0.6 days from recognition of wound problem to senior review. Given 86% of infected HA cases were identified to be deep SSIs, a high degree of suspicion and early, aggressive management of SSI is preferred.

Intra-operative practice of double skin preparation is not widely performed; however, when included as part of a care bundle for hip fracture operation, it has been shown to contribute to a substantial improvement in SSI²⁷ and hence continues to have a role in our practice.

Our mean operative time for our identified infected cases was 91 minutes, slightly above the average reported rate of 86 minutes for cemented HAs in a recent meta-analysis.²⁸ This demonstrates the need for safely reducing operative time to reduce the risk of SSI.^17,22,29

Our microbiological data were in keeping with previous literature outlining that prosthetic joint infections in HAs completed for hip fractures differ from organisms identified following elective arthroplasty.³⁰ Polymicrobial infection is common, with Enterococcus frequently identified. Other studies have outlined that in similar cohorts, the two main causative micro-organisms were methicillin-resistant Staphylococcus aureus and Pseudomonas aeruginosa³¹; however, population and geographical differences may influence this.

Ultimately, our multi-focal tactic, for managing hip fracture procedures, has resulted in a favorably low SSI rate. This has minimized the burden of morbidity and mortality for our patient cohort and allowed our center to most efficiently manage our resources. By prioritizing prevention of infection, we have minimized the need for complex infection management interventions and procedures, which have previously been found to be of high failure rate. Studies outlining the efficacy of managing hip fracture deep infections showed success rates between 13% and 54%.^30,32

Finally, reducing the infection risk after hip fracture operation has led to substantial cost-efficiency improvements for our center. The average reported increase in cost of managing an infected case is £16,931.^4,5 Our trust treats an average of 600 hip fracture cases each year. By reducing our infection rate from 9.0% to 0.5%, this has resulted in an annual saving of more than £860,000 for our National Health Service (NHS) trust.

Limitations

We appreciate that we cannot define which of our interventions is most effective, or even if they all contribute a positive role in reducing SSI rates. However, we have selected interventions previously described in the literature to form part of our care bundle. A care bundle is defined by The Institute for Healthcare Improvement as “a collection of processes needed to effectively and safely care for patients undergoing particular treatments with inherent risks. Several interventions are bundled together and, when combined, improve patient care outcomes”³³—a management tactic, supported by NICE guidelines on the prevention and treatment of SSIs.³⁴

Also, under-reporting of SSI is a recognized limitation of similar studies³⁵ as some patients may have developed complications following discharge, without representing to our services.

Conclusion

SSI is a devastating post-operative complication following hip fracture operation, with detrimental effects on patients and healthcare systems. The prioritization of preventing infection is essential, and a multi-disciplinary approach must be adopted within a treating department. We recommend the use of a tailored and evidence-based SSI prevention care bundle, aiming for progressive cumulative positive improvement. This peri-operative infection control and wound management tactic must be senior led and incorporate early senior involvement and decision-making.

Footnotes

Acknowledgments

The authors would like to thank Mr. Wayne Russell, CNS, for his assistance in data curation.

Authors’ Contributions

M.M.: Conceptualization, methodology, formal analysis, investigation, writing—original draft, and visualization. A.W.: Validation, formal analysis, and writing—reviewing and editing. K.W.: Investigation, resources, and data curation. K.R.: Writing—reviewing and editing and supervision. E.M.: Conceptualization, resources, data curation, writing—reviewing and editing, and supervision.

Funding Information

No funding or financial support was received for the research.

Author Disclosure Statement

The authors declare no conflicts of interest.

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