Tourniquet use for knee replacement surgery

Postoperative management following osteotomies around the knee: a narrative review

The present narrative review provides a summary of postoperative therapy modalities and their effectiveness following osteotomies around the knee. The topics that are discussed in the scientific discourse include support of cartilage cell regeneration, pain management, drainage insertion, tourniquet use, pharmacological and mechanical thromboembolism prophylaxis, weight-bearing protocols and bone consolidation. There is evidence for the use of pharmacological thromboembolism prophylaxis and weight-bearing protocols. A standardized postoperative treatment concept following osteotomies around the knee cannot be derived due to lack of evidence for the other topics in current literature.

Mesoporous Bioactive Glass-Graphene Oxide Composite Aerogel with Effective Hemostatic and Antibacterial Activities

Hemorrhage and infection after emergency trauma are two main factors that cause deaths. It is of great importance to instantly stop bleeding and proceed with antibacterial treatment for saving lives. However, there is still a huge need and challenge to develop materials with functions of both rapid hemostasis and effective antibacterial therapy. Herein, we propose the fabrication of a composite aerogel mainly consisting of mesoporous bioactive glass (MBG) and graphene oxide (GO) through freeze-drying. This composite aerogel has a three-dimensional porous structure, high absorption, good hydrophilicity, and negative zeta potential. Moreover, it exhibits satisfactory hemostatic activities including low BCI, good hemocompatibility, and activation of intrinsic pathways. When applied to rat liver injury bleeding, it can decrease 60% hemostasis time and 75% blood loss amount compared to medical gauze. On the other hand, the composite aerogel shows excellent photothermal antibacterial capacity against Staphylococcus aureus and Escherichia coli. Animal experiments further verify that this composite aerogel can effectively kill bacteria in wound sites via photothermal treatment and promote wound healing. Hence, this MBG-GO composite aerogel makes a great choice for the therapy of emergency trauma with massive hemorrhage and bacterial infection.

A systematic review of tourniquet use in paediatric orthopaedic surgery: can we extrapolate from adult guidelines?

Purpose

Tourniquets are commonly used intraoperatively in orthopaedic surgery to control bleeding and improve visibility in the surgical field. Recent evidence has thrown into question the routine use of tourniquets in the adult population resulting in a British Orthopaedic Association standard for intraoperative use. This systematic review evaluates the evidence on the practice, benefits, and risks of the intraoperative use of tourniquets for trauma and elective orthopaedic surgery in the paediatric population.

Methods

A prospectively registered systematic review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (PROSPERO: CRD42022359048). A search of MEDLINE, Embase, the Cochrane Library and a Grey literature search was performed from their earliest record to 23 March 2023. Studies reporting tourniquet data in paediatric patients undergoing orthopaedic surgery were included. Data extracted included demographics, involved limb, trauma versus elective use, tourniquet use as primary or secondary measure, and tourniquet parameters and complications.

Results

Thirty-nine studies were included. Tourniquet practices and information reporting varied considerably. Tourniquets were used uneventfully in the majority of patients with no specific benefits reported. Several physiological and biochemical changes as well as complications including nerve injury, compartment syndrome, skin burns, thrombosis, post-operative limb swelling, and pain were reported.

Conclusions

Tourniquets are routinely used in both trauma and elective paediatric orthopaedic surgery with no high-quality research affirming benefits. Severe complications associated with their use are rare but do occur. High-quality studies addressing their benefits, the exact indication in children, and the safest way to use them in this population are necessary.

Use of a tourniquet is not associated with increased risk of venous thromboembolism after fast-track total knee arthroplasty: a prospective multicenter cohort study of 16,250 procedures

BACKGROUND AND PURPOSE

Venous thromboembolism (VTE) is a serious postoperative complication after total knee arthroplasty (TKA). Use of a tourniquet has shown conflicting results for risk of VTE after TKA. We aimed to investigate the associated risk of VTE after TKA using tourniquet in a fast-track set-up as no previous data exists.

PATIENTS AND METHODS

We performed an observational cohort study from 9 fast-track centers including unilateral primary TKA from 2010-2017 with prospective collection of preoperative risk-factors and complete 90-day follow-up. Use of a tourniquet was registered in the Danish Knee Arthroplasty Register. Postoperative VTE was identified from health records. We performed risk analyses using a mixed-effects logistic regression model adjusting for previously identified risk factors.

RESULTS

Of the 16,250 procedures (39% males, mean age 67.9 [SD 10.0] years, median LOS 2 [interquartile range 2-3]) 12,518 (77%) were performed with a tourniquet. The annual tourniquet usage varied greatly between departments from 0% to 100%, but also within departments from 0% to 99%. There was no significant difference between the 2 groups with 52 (0.42%) VTEs in the tourniquet group vs. 25 (0.67%) in the no-tourniquet group (p = 0.06 for cumulative 90-day incidence of VTE). This association remained statistically insignificant for VTE using tourniquet after adjustment for previously identified risk factors.

CONCLUSION

We found no association between the use of a tourniquet and increased risk of 90-day VTE after primary fast-track TKA, irrespective of the length of time for which the tourniquet was applied.

Measuring the impact of zero-cases studies in evidence synthesis practice using the harms index and benefits index (Hi-Bi)

OBJECTIVES

In evidence synthesis practice, dealing with studies with no cases in both arms has been a tough problem, for which there is no consensus in the research community. In this study, we propose a method to measure the potential impact of studies with no cases for meta-analysis results which we define as harms index (Hi) and benefits index (Bi) as an alternative solution for deciding how to deal with such studies.

METHODS

Hi and Bi are defined by the minimal number of cases added to the treatment arm (Hi) or control arm (Bi) of studies with no cases in a meta-analysis that lead to a change of the direction of the estimates or its statistical significance. Both exact and approximating methods are available to calculate Hi and Bi. We developed the "hibi" module in Stata so that researchers can easily implement the method. A real-world investigation of meta-analyses from Cochrane reviews was employed to evaluate the proposed method.

RESULTS

Based on Hi and Bi, our results suggested that 21.53% (Hi) to 26.55% (Bi) of Cochrane meta-analyses may be potentially impacted by studies with no cases, for which studies with no cases could not be excluded from the synthesis. The approximating method shows excellent specificity (100%) for both Hi and Bi, moderate sensitivity (68.25%) for Bi, and high sensitivity (80.61%) for Hi compared to the exact method.

CONCLUSIONS

The proposed method is practical and useful for systematic reviewers to measure whether studies with no cases impact the results of meta-analyses and may act as an alternative solution for review authors to decide whether to include studies with no events for the synthesis or not.

Defining tourniquetless total knee arthroplasty: A systematic review

Introduction

Performing total knee arthroplasty (TKA) without the use of tourniquet is gaining popularity. However, performing a "tourniquetless TKA" has a variety of meanings regarding the timing and application of a tourniquet and associated techniques. The purpose of this systematic review was to evaluate the literature and more accurately define "tourniquetless TKA."

Methods

A systematic review following PRISMA guidelines was performed of the PubMed, Web of Science, and Cochrane databases for articles published from 2016 to 2021. Inclusion criteria included papers that used "tourniquetless" or a similar term to describe their TKA procedure, original clinical studies, English language, and full-text studies.

Results

A total of 1,096 studies were identified, of which 84 full text studies with 9,349 total patients were included. Overall, 17 (20.2%) of the studies performing tourniquetless TKA never applied a tourniquet, 17 (20.2%) applied a tourniquet but kept it deflated throughout the entire procedure, 2 (2.4%) applied a tourniquet and inflated during cementation only, and 48 (57.1%) did not specify. Ultimately, of the studies that did specify tourniquet use, only 17 studies (47.2%) truly never applied a tourniquet throughout the procedure. A review of 7 recommended techniques to control blood loss in tourniquetless TKA found that no one technique was performed in more than 10.6% of patients.

Conclusion

Variation in the definition of tourniquetless TKA and the utilization of augmented techniques to control blood loss remains. We propose the terms "tourniquetless" for no tourniquet application, "tourniquet-available" for tourniquet applied but kept deflated throughout surgery, and "tourniquet-assisted" for tourniquet inflation during cementation only. These terms can help better differentiate the literature, guide surgeons as they transition to tourniquetless TKA, and assist in the development of more definitive protocols for tourniquetless TKA.

Tourniquet use in total knee arthroplasty and the risk of infection: a meta-analysis of randomised controlled trials

Purpose

The intra-operative use of tourniquets during Total Knee Arthroplasty (TKA) is common practice. The advantages of tourniquet use include decreased operating time and the creation of a bloodless visualisation field. However, tourniquet use has recently been linked with increased post-operative pain, reduced range of motion, and slower functional recovery. Importantly, there is limited evidence of the effect of tourniquet use on infection risk. The purpose of this systematic review and meta-analysis is to fill this gap in the literature by synthesising data pertaining to the association between tourniquet use and infection risk in TKA.

Methods

A systematic literature search was performed on Pubmed, Embase, Cochrane and clinicaltrials.gov up to May 2021. Randomized control trials were included, comparing TKA outcomes with and without tourniquet use. The primary outcome was overall infection rate. Secondary outcomes included superficial and deep infection, skin necrosis, skin blistering, DVT rate, and transfusion rate.

Results

14 RCTs with 1329 patients were included. The pooled incidence of infection in the tourniquet group (4.0%, 95% CI = 2.7–5.4) was significantly higher compared to the non-tourniquet group (2.0%, 95% CI = 1.1–3.1) with an OR of 1.9 (95% CI = 1.1–3.76, p = 0.03). The length of hospital stay, haemoglobin drop (0.33 95% CI =0.12–0.54), P = 0.002) and transfusion rates (OR of 2.7, 95%CI = 1.4–5.3, P = < 0.01) were higher in the tourniquet group than the non-tourniquet group. The difference in the length of inhospital stay was 0.24 days favouring the non-tourniquet group (95% CI = 0.10–0.38, P = < 0.01). The incidence of skin blistering (OR 2.6, 95% CI = 0.7–9.9, p = 0.17), skin necrosis (OR 3.0, 95% CI = 0.50–19.3, p = 0.25), and DVT rates (OR 1.5, 95% CI = 0.60–3.60, p = 0.36) did not differ between the two groups.

Conclusion

Quantitative synthesis of the data suggested tourniquet use was associated with an increased overall risk of infection, intraoperative blood loss, need for blood transfusion and longer hospital stay. Findings of this meta-analysis do not support the routine use of tourniquet in TKA and arthroplasty surgeons should consider any potential additional risks associated with its use.

Level of evidence

meta-analysis, Level II.

The mid-term and long-term effects of tourniquet use in total knee arthroplasty: systematic review

Purpose

A tourniquet is routinely used during total knee arthroplasty (TKA) to reduce intra-operative hemorrhage, though surgery without a tourniquet is becoming popular. To address concerns about the effect of blood at cement interfaces on long-term implant stability, we conducted a systematic review among patients undergoing total knee arthroplasty to determine if TKA with a tourniquet, compared to TKA without a tourniquet or with reduced tourniquet duration, is associated with better mid-term and long-term implant stability.

Methods

A literature search was conducted without language restriction in PubMed, Cochrane database and Web of Science from conception to 17th March, 2021. Prospective cohorts, randomized and observational, that compared tourniquet use with a control group, followed patients for 3 months or more and reported outcomes concerning implant stability, limb function, pain and inflammation. Article selection, quality assessment according to the Revised Cochrane risk assessment scale and Newcastle Ottawa Scale, and data extraction were conducted in duplicate. PROSPERO: CRD42020179020.

Results

The search yielded 4868 articles, from which 16 randomized controlled trials (RCT) and four prospective cohort studies, evaluating outcomes of 1884 knees, were included. Eleven RCTs were evaluated to be low overall risk of bias, five RCTs had some concerns and four cohort studies were good quality. Few studies showed benefits of tourniquet use in mid-term implant stability (1/6), pain (1/11) and limb inflammation (1/5), and long-term implant stability (1/1). One study reported a significantly improved range of motion (1/14) while another reported significantly reduced quadriceps strength (1/6) in the tourniquet group. The remaining studies reported non-significant effect of tourniquet use.

Conclusion

Although few studies indicated benefits of tourniquet use in mid-term pain, limb inflammation, implant loosening and function, and long-term implant loosening, the majority of studies report no significant advantage of tourniquet use in total knee arthroplasty.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40634-022-00471-1.

Peri-articular administration of tranexamic acid is an alternative route in total knee arthroplasty: a systematic review and meta-analysis

Background

As an antifibrinolytic agent, tranexamic acid (TXA) is increasingly used in total knee arthroplasty (TKA) to reduce blood loss. The administration of intravenous and intra-articular TXA has been well explored, but the most efficient way to administer TXA remains in question. Peri-articular injection (PAI) of TXA is a recently mentioned method. A meta-analysis of the efficacy of PAI TXA in patients after TKA should be performed.

Methods

A systematic search was performed within PubMed, Embase, and the Cochrane Library up to November 8, 2021. Two authors independently screened studies for eligibility and extracted data for analysis. The primary outcome was haemoglobin change. The secondary outcomes were haematocrit change, total drainage volume, thromboembolic events, and blood transfusion.

Results

A total of ten studies were included in this meta-analysis. The results indicated that there was a significant decrease in haemoglobin change when using PAI TXA compared with no TXA (mean difference − 1.05; 95% CI − 1.28 to − 0.81; P < 0.00001; I² = 0%), but it had no significant differences compared with IA and IV (mean difference − 0.01; 95% CI − 0.17 to − 0.14; P = 0.85; I² = 39%). There were no significant differences between the TXA < 1.5 g subgroup (0.10, 95% CI − 0.27 to 0.46; P = 0.60; I² = 0%) and the TXA ≥ 1.5 g subgroup (0.18, 95% CI − 0.12 to 0.48; P = 0.24; I² = 74%). In addition, the combined group (PAI plus IV or IA) was superior to the IV or IA group in terms of haemoglobin change (mean difference − 0.51; 95% CI − 0.76 to − 0.27; P < 0.0001; I² = 19%). Regarding haematocrit change, the pooled result showed it was significantly less in the PAI group than the non-TXA group. Similarly, comparing it against the IV subgroup, the result revealed a difference in favour of the PAI group, with a mean difference of − 1.89 g/dL (95% CI − 2.82 to − 0.95; P < 0.0001; I² = 67%). For total drainage volume, the pooled result was in favour of PAI TXA over no TXA (297 ml, 95% CI − 497.26 to − 97.23; P = 0.004; I² = 87%), but it had no significant difference compared with IA and IV (mean difference − 37.98; 95% CI − 115.68 to 39.71; P = 0.34; I² = 95%). There was no significant difference in thromboembolic events (OR 0.74; 95% CI 0.25 to 2.21; P = 0.59; I² = 0%). Blood transfusion was not significantly different between the PAI group and the non-TXA group (OR 0.50; 95% CI 0.23 to 1.06; P = 0.07; I² = 21%), and there was no significant difference between PAI and the other two TXA injection methods (OR 0.72; 95% CI 0.41 to 1.25; P = 0.24; I² = 19%).

Conclusion

PAI has comparable effects to IV and IA injections. PAI is an alternative injection route of TXA for patients who have undergone TKA.

Safety of Total Knee Arthroplasty without Using a Tourniquet in Elderly Patients

This study retrospectively compared the perioperative bleeding, hemodynamics, and clinical outcomes of total knee arthroplasty (TKA) performed with and without a tourniquet between two age groups. We grouped 103 patients with knee osteoarthritis who underwent primary TKA based on age at surgery: <76 years and ≥76 years. Tourniquet was used for TKA until March 2010 and stopped thereafter; hence, the patients were further classified according to TKA performed with or without a tourniquet. The differences in the operation time; perioperative bleeding; estimated bleeding; and hemoglobin (Hb) and hematocrit (Ht) levels immediately, 1 day, and 7 days postoperatively were evaluated. The clinical outcomes for range of motion, and Knee Society Knee Scores preoperatively and at 4 weeks postoperatively were assessed. Operation time was longer in the ≥76-year-old non-tourniquet group. No difference was observed in estimated bleeding among the groups. Changes in the Hb and Ht levels at postoperative days 1 and 7 were negatively correlated with age but were not different for TKA performed with or without a tourniquet in the ≥76-year-old-patient group. There were no differences in clinical outcomes among the groups. TKA can be performed with or without a tourniquet in patients aged ≥ 76 years with careful assessment of postoperative anemia.

Effect of tourniquet use on the risk of revision in total knee replacement surgery: an analysis of the National Joint Registry Data Set

OBJECTIVE

Tourniquet use in total knee replacement (TKR) is believed to improve the bone-cement interface by reducing bleeding, potentially prolonging implant survival. This study aimed to compare the risk of revision for primary cemented TKR performed with or without a tourniquet.

DESIGN

We analysed data from the National Joint Registry (NJR) for all primary cemented TKRs performed in England and Wales between April 2003 and December 2003. Kaplan-Meier plots and Cox regression were used to assess the influence of tourniquet use, age at time of surgery, sex and American Society of Anaesthesiologists (ASA) classification on risk of revision for all-causes.

RESULTS

Data were available for 16 974 cases of primary cemented TKR, of which 16 132 had surgery with a tourniquet and 842 had surgery without a tourniquet. At 10 years, 3.8% had undergone revision (95% CI 2.6% to 5.5%) in the no-tourniquet group and 3.1% in the tourniquet group (95% CI 2.8% to 3.4%). After adjusting for age at primary surgery, gender and primary ASA score, the HR for all-cause revision for cemented TKR without a tourniquet was 0.82 (95% CI 0.57 to 1.18).

CONCLUSIONS

We did not find evidence that using a tourniquet for primary cemented TKR offers a clinically important or statistically significant reduction in the risk of all-cause revision up to 13 years after surgery. Surgeons should consider this evidence when deciding whether to use a tourniquet for cemented TKR.

Time to reconsider the routine use of tourniquets in total knee arthroplasty surgery

Aims

Many surgeons choose to perform total knee arthroplasty (TKA) surgery with the aid of a tourniquet. A tourniquet is a device that fits around the leg and restricts blood flow to the limb. There is a need to understand whether tourniquets are safe, and if they benefit, or harm, patients. The aim of this study was to determine the benefits and harms of tourniquet use in TKA surgery.

Methods

We searched MEDLINE, EMBASE, Cochrane Central Register of Controlled trials, and trial registries up to 26 March 2020. We included randomized controlled trials (RCTs), comparing TKA with a tourniquet versus without a tourniquet. Outcomes included: pain, function, serious adverse events (SAEs), blood loss, implant stability, duration of surgery, and length of hospital stay.

Results

We included 41 RCTs with 2,819 participants. SAEs were significantly more common in the tourniquet group (53/901 vs 26/898, tourniquet vs no tourniquet respectively) (risk ratio 1.73 (95% confidence interval (CI) 1.10 to 2.73). The mean pain score on the first postoperative day was 1.25 points higher (95% CI 0.32 to 2.19) in the tourniquet group. Overall blood loss did not differ between groups (mean difference 8.61 ml; 95% CI -83.76 to 100.97). The mean length of hospital stay was 0.34 days longer in the group that had surgery with a tourniquet (95% CI 0.03 to 0.64) and the mean duration of surgery was 3.7 minutes shorter (95% CI -5.53 to -1.87).

Conclusion

TKA with a tourniquet is associated with an increased risk of SAEs, pain, and a marginally longer hospital stay. The only finding in favour of tourniquet use was a shorter time in theatre. The results make it difficult to justify the routine use of a tourniquet in TKA surgery.

Cite this article: Bone Joint J 2021;103-B(5):830–839.

Tourniquet use in total knee replacement surgery: a feasibility study and pilot randomised controlled trial (SAFE-TKR study)

INTRODUCTION

Tourniquets are routinely used during total knee replacement (TKR) surgery. They could increase the risk of thromboembolic events including cerebral emboli, cognitive decline, pain and other adverse events (AEs). A randomised controlled trial to assess whether tourniquet use might safely be avoided is therefore warranted but it is unclear whether such a trial would be feasible.

METHODS

In a single-site feasibility study and pilot randomised controlled trial, adults having a TKR were randomised to surgery with an inflated tourniquet versus a non-inflated tourniquet. Participants underwent brain MRI preoperatively and within 2 days postoperatively. We assessed cognition using the Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA) and Oxford Cognitive Screen (OCS) and thigh pain using a Visual Analogue Scale at baseline and days 1 and 2, and 1 week postsurgery. AEs related to surgery were recorded up to 12 months.

RESULTS

We randomised 53 participants (27 tourniquet inflated and 26 tourniquet not inflated). Fifty-one participants received care per-protocol (96%) and 48 (91%) were followed up at 12 months. One new ischaemic brain lesion was detected. Of the cognitive tests, MoCA was easy to summarise, sensitive to change with lower ceiling effects compared with OCS and MMSE. There was a trend towards more thigh pain (mean 49.6 SD 30.4 vs 36.2 SD 28 at day 1) and more AEs related to surgery (21 vs 9) in participants with an inflated tourniquet compared with those with a tourniquet not inflated.

CONCLUSION

A full trial is feasible, but using MRI as a primary outcome is unlikely to be appropriate or feasible. Suitable primary outcomes would be cognition measured using MoCA, pain and AEs, all of which warrant investigation in a large multicentre trial.

TRIAL REGISTRATION NUMBER

ISRCTN20873088.

Tourniquet use for knee replacement surgery

BACKGROUND

Many surgeons prefer to perform total knee replacement surgery with the aid of a tourniquet. A tourniquet is an occlusive device that restricts distal blood flow to help create a bloodless field during the procedure. A tourniquet may be associated with increased risk of pain and complications.

OBJECTIVES

To determine the benefits and harms of tourniquet use in knee replacement surgery.

SEARCH METHODS

We searched MEDLINE, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) up to 26 March 2020. We searched clinicaltrials.gov, the World Health Organization trials portal, and several international registries and joint registries up to March 2020.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) comparing knee replacement with use of a tourniquet versus without use of a tourniquet and non-randomised studies with more than 1000 participants. Major outcomes included pain, function, global assessment of success, health-related quality of life, serious adverse events (including venous thromboembolism, infection, re-operation, and mortality), cognitive function, and survival of the implant. Minor outcomes included blood loss, economic outcomes, implant stability, and adverse events.

DATA COLLECTION AND ANALYSIS

Two review authors screened abstracts and full texts, extracted data, performed risk of bias assessments, and assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

We included 41 RCTs with 2819 participants. Trials included from 20 to 199 participants. Mean age ranged between 58 and 84 years. More than half of the RCTs had unclear risk of selection bias and unclear risk of performance and detection bias due to absence of blinding of participants and surgeons. Major outcomes Pain: at postoperative day 1, pain (on a scale from zero to 10, with higher scores indicating worse pain) was ranked at 4.56 points after surgery without a tourniquet and at 1.25 points (MD) higher (95% CI 0.32 higher to 2.19 higher) with a tourniquet (8 studies; 577 participants), for an absolute difference of 12.5% higher pain scores (95% CI 3.2% higher to 21.9% higher) and a relative difference of 19% higher pain scores (95% CI 3.4% higher to 49% higher) with a tourniquet. Evidence for these findings was of moderate certainty, downgraded due to risk of bias. Knee replacement with a tourniquet probably led to higher postoperative pain scores at day 1, although this difference may or may not be noticeable to patients (based on a minimal clinically important difference (MCID) of 1.0). Function: at 12 months, tourniquet use probably makes little or no difference to function, based on an MCID of 5.3 for Knee Society Score (KSS) and 5.0 for Oxford Knee Score (OKS). Mean function (on a scale from 0 to 100, with higher scores indicating better outcomes) was 90.03 points after surgery without a tourniquet and was 0.29 points worse (95% CI 1.06 worse to 0.48 better) on a 0 to 100 scale, absolute difference was 0.29% worse (1.06% worse to 0.48% better), with a tourniquet (5 studies; 611 participants). This evidence was downgraded to moderate certainty due to risk of bias. Global assessment of success: low-certainty evidence (downgraded due to bias and imprecision) indicates that tourniquet use may have little or no effect on success. At six months, 47 of 50 (or 940 per 1000) reported overall successful treatment after surgery without a tourniquet and 47 of 50 (or 940 per 1000) with a tourniquet (risk ratio (RR) 1.0, 95% CI 0.91 to 1.10) based on one study with 100 participants. Health-related quality of life: at six months, tourniquet may have little or no effect on quality of life. The 12-Item Short Form Survey (SF-12) score (mental component from zero to 100 (100 is best)) was 54.64 after surgery without a tourniquet and 1.53 (MD) better (95% CI 0.85 worse to 3.91 better) with a tourniquet (1 study; 199 participants); absolute difference was 1.53% better (0.85% worse to 3.91% better). Evidence was of low certainty, downgraded due to risk of bias and small number of participants. Serious adverse events: the risk of serious adverse events was probably higher with tourniquet; 26 of 898 (29 per 1000) reported events following surgery without a tourniquet compared to 53 of 901 (59 per 1000) with a tourniquet (RR 1.73, 95% CI 1.10 to 2.73) in 21 studies (1799 participants). Twenty-nine more per 1000 patients (95% CI 3 to 50 more per 1000 patients) had a serious adverse event with a tourniquet. Forty-eight (95% CI 20 to 345) participants would need to have surgery without a tourniquet to avoid one serious adverse event. This evidence was downgraded to moderate certainty due to risk of bias. Cognitive function: one study reported cognitive function as an outcome; however the data were incompletely reported and could not be extracted for analysis. Survival of implant: it is uncertain if tourniquet has an effect on implant survival due to very low certainty evidence (downgraded for bias, and twice due to very low event rates); 2 of 107 (19 per 1000) required revision surgery in the surgery with a tourniquet group compared to 1 of 107 (9 per 1000) without a tourniquet group at up to two years' follow-up (RR 1.44, 95% CI 0.23 to 8.92). This equates to a 0.4% (0.7% lower to 7% more) increased absolute risk in surgery with a tourniquet.

AUTHORS' CONCLUSIONS

Moderate certainty evidence shows that knee replacement surgery with a tourniquet is probably associated with an increased risk of serious adverse events. Surgery with a tourniquet is also probably associated with higher postoperative pain, although this difference may or may not be noticeable to patients. Surgery with a tourniquet does not appear to confer any clinically meaningful benefit on function, treatment success or quality of life. Further research is required to explore the effects of tourniquet use on cognitive function and implant survival, to identify any additional harms or benefits. If a tourniquet continues to be used in knee replacement surgery, patients should be informed about the potential increased risk of serious adverse events and postoperative pain.