Tourniquet is now widely used in TKA, but its latent adverse effects are problems that we cannot neglect. Some researchers recommend regular tourniquet application in TKA because of its advantage in reducing intraoperative blood loss and operation time. Other researchers hold an opposite idea. They believe that tourniquet application has obvious damage to quadriceps and extra side effects such as pain, swelling and blood loss, which may go against patients’ enhanced recovery after surgery (ERAS), so they resist using tourniquet in TKA. After years of studies including meta-analysis and randomized controlled trials, tourniquet application in TKA is still in dispute.
Tourniquet effects on quadriceps morphology and function is controversial. It is generally considered that tourniquet does have certain damage to quadriceps but how bad it can be and what effects it will have on patients are confusing. Leurcharusmee et al[6] hold the point that tourniquet application can cause ischemia reperfusion injury to quadriceps, which leads to the release of both oxygen free radicals and inflammatory cytokines. Dennis et al[26] found in a prospective trial that tourniquet application can reduce quadriceps strength in 3 months after surgery. Guler et al[27] found that tourniquet use in TKA can decrease the thigh and quadriceps muscle volumes. However, Jawhar et al[13] reported that tourniquet has no significant effects on quadriceps strength and function. Ayik et al[28] also reported that avoiding tourniquet cannot improve quadriceps strength after TKA. It is obvious that more studies about quadriceps morphology and function are needed.
It is generally considered that tourniquet application can significantly reduce intraoperative blood loss, but its effects on total blood loss is not explicit. Zhao et al[29] found out in a randomized controlled trial that tourniquet application may increase hidden blood loss and total blood loss. However, Liu et al[10] conducted a meta-analysis and found that tourniquet has no significant effects on total blood loss. Herndon et al[3] hold another idea that tourniquet may reduce total blood loss but has no effects on postoperative blood transfusion rate.
Postoperative pain is an important outcome for TKA patients. It can be evaluated by VAS score as well as opioid consumption. Tourniquet effects on postoperative pain is also controversial. Liu et al[7] hold the point tha6yt tourniquet application can increase postoperative pain, which may be caused by ischemia reperfusion injury and the release of cytokines. Ajnin et al[30] and Dong et al[9] both reported that not using tourniquet in TKA can reduce patient’s postoperative pain and beneficial to their recovery. While a randomized controlled trial conducted by McCarthy et al[4] reported that tourniquet application had no significant effect on thigh pain. Palanne et al[31] also reported that tourniquet application could not affect pain management and postoperative opioid consumption.
Lower limb swelling is also related to postoperative recovery. It can be measured by circumference of thigh. Tourniquet effects is still disputable in respect of swelling. Ajnin et al[30] and Wang et al[32] both reported that patients without tourniquet application showed less lower limb swelling. However, Alexandersson et al[33] reported that tourniquet application had no significant effects on limb swelling.
Postoperative inflammation process is also in association with tourniquet application. It can be reflected by CRP level in blood. A randomized controlled trial conducted by Cao[34] reported an increase in inflammatory mediators in tourniquet application such as TNF-α, PTX3, CCL2, PGE-2 and SOD-1 and its degree of elevation is positively correlated with the tourniquet time, which is considered relative to ischemia reperfusion injury caused by tourniquet. Zhao et al[29] also reported that the absence of tourniquet application could reduce postoperative inflammation process.
Above all, there is still no consensus on tourniquet effects on quadriceps morphology and function, blood loss, postoperative pain, lower limb swelling and other outcomes for patients undergoing TKA. Tourniquet-related side effects are mainly about quadriceps injuries, so we decide to concentrate ourselves on tourniquet effects on quadriceps morphology and function and design this single blind randomized controlled trial to offer advice for tourniquet application in clinical practice.
In this study, quadriceps thickness and stiffness are essential primary outcomes. These indicators can effectively reflect quadriceps morphology after tourniquet application. Quadriceps thickness is measured by ultrasound test. Innovatively, we use shear wave elastography (SWE) to evaluate quadriceps stiffness. SWE is an evolving ultrasound technique which is progressively used in musculoskeletal system to evaluate tissue elasticity[35–37]. It is reported to evaluate the stiffness of soft tissues such as quadriceps tendon or medial collateral ligament in healthy people[38, 39], but it has never been used to assess quadriceps stiffness of patients undergoing TKA. Shear waves propagate faster through stiffer tissue so we decide to measure shear wave velocity along the long and short axis of quadriceps to represent quadriceps stiffness[40, 41]. Additionally, we include three tests of rehabilitation department. Isokinetic muscle strength proved to be valid in assessment of muscle function in TKA[42, 43]. Three-dimensional gait analysis is a useful clinical test to evaluate gait abnormality which can be captured by cameras placed around a walkway[44]. Posture stability testing is also used in our study to monitor displacement of plantar pressure center[45]. These tests can provide important indicators to evaluate quadriceps function for TKA patients.
As for secondary outcomes, thigh circumference, VAS score, opioid consumption in morphine equivalent, knee function score, postoperative satisfaction score, operation time, blood loss, blood transfusion rate, D-Dimer, CRP and complications in tourniquet group and non-tourniquet group will be evaluated. These outcomes work as effective supplements to our study to further evaluate tourniquet effects on TKA patients.
What’s more, tourniquet time is also a meaningful indicator. As tourniquet is used throughout the whole operation period, it can be represented by operation time. Quadriceps injury and many other side effects may be time-related, so we hope to further investigate the relationship between tourniquet time and tourniquet effects in this study.
Indeed, there are several limitations in our study. First, ultrasound test is examiner dependent. Though all the patients are tested by the same ultrasound examiner, it may still affect the validity of the assessment to some degree. Second, tourniquet effects on patients maybe too subtle to be reflected by chosen outcomes like VAS score or knee function score. More sensitive outcomes for patients after TKA are needed. Third, this study mainly focuses on clinical outcomes of tourniquet effects. There is a lack of deeper study of mechanism of ischemia reperfusion and inflammation.
This study is precisely designed to clarify the effect of tourniquet application on the morphology and function of quadriceps in patients undergoing total knee arthroplasty and offer advice for tourniquet use in clinical practice. Indeed, tourniquet application cannot be determined by one single trial, but we believe that more high-quality studies will be conducted and tourniquet impact will be clarified in the foreseeable future.