Safety and feasibility evaluation of tourniquets for total knee replacement (SAFE- TKR)

The objective of the research and data request is to look for surgical complications including episodes of postoperative venous thromboembolism (VTE) and cerebrovascular accident (CVA) in patients undergoing total knee replacement (TKR) surgery with or without a tourniquet. The research relates to one component of a much larger feasibility study, which is an observational study only and is not a trial. Therefore, this agreement relates to this one component only.

The data required for this research study is hospital episode statistics (HES) including diagnostic codes and length of hospital stay for the initial surgery for patients who underwent TKR surgery in 2003. HES diagnostic codes are required for these patients up to a year after surgery i.e. up to 2004.

The National Joint Registry (NJR) will provide NHS digital with a list of identifiers (NHS number, date of birth, and postcode) for patients who had TKR surgery from April 2003 to December 2003. The NJR collected data on the use of tourniquets for TKR surgery in England and Wales from April 2003 and December 2003 only which is why this time period has been selected. This dataset can then be linked to the HES data requested to undertake the research at the University of Warwick.

Many lower limb orthopaedic operations, including TKR surgery, are undertaken with the aid of a tourniquet around the thigh during the procedure. A tourniquet is an occlusive device which holds air under pressure (when inflated) and squeezes the thigh (including the blood vessels within the thigh). A survey in 2010 found that 95% of surgeons in the USA use a tourniquet for TKR surgery, and the National Joint Registry (NJR) reported that 93% of primary TKRs were done with a tourniquet in 2003. The reasons for such widespread use of tourniquets for TKR surgery are not clear. Anecdotally, surgical custom and practice has always involved a tourniquet when carrying out orthopaedic surgery below the level of the thigh and use of a tourniquet may improve the surgical field of view by limiting intraoperative blood loss. The majority of TKR components are cemented in situ to hold and stabilise them in the correct position on the bone. Cement which is initially soft when it is inserted interdigitates into the porous bone forming a strong bond to the bone as it sets. Some surgeons believe that using a tourniquet helps reduce bleeding from the porous bone ends and allows the soft cement to bond more effectively, but this is not supported by any research evidence. It is true that better cementation should reduce the chance of a TKR loosening and failing, but effective, and identical, cementation is routinely achieved in hip replacement surgery where the use of a tourniquet is not possible. In such surgery it is accepted that the absence of a tourniquet does not compromise the surgical field of view, cause excessive intraoperative blood loss or lead to long term problems with implant survivorship.

In TKR a tourniquet causes both arterial and venous stasis within the lower leg for the duration that it is inflated (typically over an hour). The increased risk of symptomatic Venous Thromboembolism (VTE) following major surgery, whether joint replacement or other has been known for many years. Routine measures including low molecular weight heparin, anti-embolism stockings and pneumatic calf compression devices following all such surgery are recommended by National Institute for Health and Care Excellence (NICE), subject to contraindications. It is therefore unsurprising that the use of a surgical tourniquet might increase the risk of post-operative symptomatic VTE. VTE is a spectrum of disease, ranging from deep vein thrombosis (DVT), through to potentially fatal pulmonary embolism (PE). The risk of VTE is already known to be higher amongst hospital inpatients, including those who have not had a surgical procedure, and brings a considerable risk of morbidity and mortality. Even non-fatal VTE may produce long-term morbidity including chronic venous insufficiency, which may cause venous ulceration and development of a post-thrombotic limb (chronic pain, swelling and skin changes in the affected limb following a DVT). Considerable efforts are made to minimise the risk of VTE in TKR surgery using all or some of the measures already described. Crucially, empirical data indicates no measurable reduction in VTE or mortality after TKR surgery despite increased prescribing of low molecular weight heparin following NICE guidelines published in 2007.

The pseudonymised data received from NHS digital will be processed by the research team based at Warwick Clinical Trials Unit at the University of Warwick. The data will be stored on secure University Servers based at Warwick Clinical Trials Unit. Data will only be accessed by individual study team members, who have authorisation from the Chief Investigator to access the data for the purposes described, all of whom are substantive employees of the University of Warwick.

The data will be imported in to STATA statistics programme and processed to look for surgical complications up to 12 months including episodes of postoperative venous thromboembolism (VTE) and cerebrovascular accident (CVA). Once analysed a report will be prepared based upon the data findings and submitted to NIHR and for peer review publication.

Identifiers (NHS number, date of birth and postcode) from the NJR dataset will be securely transferred to NHS Digital for linkage to the HES admitted patient care and outpatient’s data for the cohort. Other variables will also be used for optimum linkage (study ID, gender and date of surgery). A pseudonymised dataset linked to the cohort will then be provided under this agreement to the University of Warwick by secure transfer. The study team at the University of Warwick will not have access to or process any patient identifiable information. The data will be linked at a record level to ensure details of surgical complications are accurate.

The data will not be made available to any third parties except in the form of aggregated outputs with small numbers supressed in line with the HES Analysis guide. The University of Warwick are requesting only two years’ worth of data to look for surgical complications which may have resulted due to using a tourniquet in knee replacement surgery.

All organisations party to this agreement must comply with the Data Sharing Framework Contract requirements, including those regarding the use (and purposes of that use) by "Personnel" (as defined within the Data Sharing Framework contract i.e. employees, agents and contractors of the Data Recipient who may have access to the data.)

HES data is held by NHS digital. Linkage of the two datasets (HES and NJR) will be undertaken by NHS digital. NJR data is controlled by the Healthcare Quality Improvement Partnership (HQIP) who acts as ‘host’ to the NJR. NJR data is processed by Northgate Public Services (UK) Ltd (NPS). NPS is contracted by HQIP to provide the data collection, aggregation, and reporting services for the NJR.

Under this agreement, only the University of Warwick is permitted to access and process the data provided by NHS Digital.

All outputs and publications will contain only aggregated data with small numbers suppressed in line with the HES Analysis Guide.

The main outcomes from the proposed research will be evidence of the safety or otherwise of the use of tourniquets in TKR surgery.

The results of this research will be disseminated to the following groups:

1. Patients and public

A public and patient workshop on the proposed research found consensus that the internet should be used whenever possible to disseminate the results. Led by a patient co-applicant and other PPI collaborators the University of Warwick will develop a study Facebook page and Twitter feed. These will track both the progress of the study and eventual results and will allow people with an interest to have access to our findings in a contemporary and user-friendly way. Results will be presented in magazines such as Arthritis Today, and the study team will work with NHS Choices to prepare patient information for use after the study.

2. Medical community

A large body of specialists including nurses, physiotherapists, occupational therapists, physicians, general practitioners, anaesthetists and orthopaedic surgeons typically manage patients before, during and after TKR surgery in secondary and tertiary care centres. These groups will be targeted through conferences, seminars and meetings. All key findings from the study will be presented at national and international conferences such as the British Orthopaedic Association (BOA); British Association of Specialist Knee Surgeons (BASK) and American Academy of Orthopaedic Surgeons (AAOS). The annual conferences of the BOA and the AAOS have attendances of 1,600 and 32,000 surgeons respectively. The results of the research are likely to attract significant attention at meetings; particularly as the presentation of RCT evidence in this field is rare.

The aim is to publish the results in at least one major peer-reviewed publication by the end of the study. The University will be working with the Cochrane Musculoskeletal Group to produce a full Cochrane Review on the safety and benefit of thigh tourniquets for TKR surgery. The review will incorporate data from this research.

This research will provide answers to important safety concerns about the use of tourniquets in knee replacement surgery. The safety concern of interest is whether using a tourniquet increase a patients' risk of developing bloods clots in the leg (DVT), lung (PE) or brain (CVA). Analysis of this historic data may prevent the need for further large prospective studies of patients to examine this safety concern. Furthermore if a serious safety concern is identified this is likely to lead to a recommendation to the Medicines & Healthcare products Regulatory Agency (MHRA) for a change in surgical practice and withdrawal of tourniquets for use in knee replacement surgery and ma. Such a change in practice would make surgery safer for future patients undergoing knee replacement surgery and avoid unnecessary risk. Not only will this help patients but it will reduce the costs to the NHS of managing surgical complications.

The aim is to publish the results in at least one major peer-reviewed publication by the end of the study. It is hoped that this research will assist NICE in updating the clinical pathway for VTE which includes guidance for elective hip and knee replacement surgery and the specific NICE clinical guideline “CG92 VTE: reducing the risk”. The University will be working with the Cochrane Musculoskeletal Group to produce a full Cochrane Review on the safety and benefit of thigh tourniquets for TKR surgery. The review will incorporate data from this research. Full Cochrane reviews which have an ethos of avoiding too much medical jargon and producing detailed “lay summaries” helps to ensure these open access reviews have significant impact not only within the research community but also amongst patients, the public and policy makers including NICE.

Yielded Benefits is not a requirement for new applications.