Cochrane in CORR®: Tourniquet Use For Knee Replacement Surgery

Importance of the Topic Nearly 1 million patients per year will undergo TKA in a typical year in the United States, and estimates suggest that rates of TKA will continue to rise worldwide [6, 9-11]. The large majority—perhaps 90% or more of these [2, 5]—will be performed under tourniquet control in an attempt to decrease intraoperative blood loss, increase visualization during surgery, and improve cement fixation [8]. However, several concerns remain about tourniquet use, including reduced early ROM, increased postoperative pain, increased postoperative thromboembolic events, and hypoxia-related wound complications [12]. In this Cochrane review of 41 randomized controlled trials (RCTs; 2819 participants), the authors compared tourniquet use to no tourniquet in TKA [1]. The authors found that the use of a tourniquet is associated with an increased risk of serious adverse events. However, adverse events of varying severity and clinical importance were pooled together, making it difficult to draw conclusions. Tourniquet use may increase postoperative pain, although the effect size of this finding was slight and probably not clinically important. No difference in overall blood loss or transfusion rates were seen between groups. Proponents of the tourniquet find that a drier bone surface allows for improved cement interdigitation. However, implant durability was not adequately addressed in the present review. Given the prevalence and expected growth of TKAs performed annually, potential differences in TKA outcomes attributed to tourniquet use are of great interest to orthopaedic surgeons and their patients. Upon Closer Inspection When broken into type of serious adverse events, both infection and venous thromboembolic events were higher in the tourniquet group. The authors calculated that the number needed to treat for additional harm was 48, indicating that for every 48 TKAs performed with a tourniquet, one serious adverse event occurred compared with the no tourniquet group. Projections suggest that approximately 1 million TKAs occurred in 2020 in the United States alone [10]. Based on the estimates that 90% of surgeons use a tourniquet, this represents up to 18,750 serious adverse events that could be potentially avoided each year by avoiding tourniquet use [2, 5]. However, what “counted” as an adverse event in this Cochrane review warrants closer inspection. For example, the risk of postoperative wound infection was higher in patients undergoing TKA with a tourniquet compared with no tourniquet use. Although the risk of wound infections was higher in patients who had surgery under tourniquet control, the review did not specify whether these were inconsequential episodes of superficial cellulitis or potentially limb- threatening periprosthetic joint infections. Pooling such disparate complications is not methodologically appropriate, and on the basis of what was presented in this Cochrane review regarding infection, it is not possible to conclude in favor of or against use of a tourniquet. Although total venous thromboembolic event rates were higher in the tourniquet group, this too requires a closer look. Pooling rates of deep vein thrombosis (DVT) and pulmonary embolism (PE) is not methodologically appropriate, given the that the impact of these complications is vastly different. When symptomatic DVTs and PEs were evaluated independently, no statistically significant differences were found in event rates between the two groups. Given this, one cannot conclude in favor of or against the use of tourniquet on the basis of this endpoint. Postoperative day 1 pain scores were found to be lower in the no tourniquet group compared with the tourniquet group. The effect size ranged from 3.1 to 21.9 mm on a 100-mm scale. Given the wide CIs, heterogeneity, and the fact that the lower boundary of the CI is below the minimum clinically important difference of 10 to 20 mm, it’s unlikely that this difference is noticeable to patients [3]. Importantly, this review did not adequately address an important endpoint—the durability of the prosthesis. Given that a major reason cited by proponents of tourniquet use is improved cement fixation and that aseptic loosening continues to be a leading cause of revision, implant durability is an important outcome that must be considered. The current review, and the literature it draws upon, had short follow-up that did not adequately capture rates of aseptic failure. Appropriately powered studies with longer-term follow-up will be required to answer this important question. Take-home Messages This is an exhaustive and up-to-date review, including 41 RCTs and more than 2800 patients. However, methodologic flaws limit the overall applicability of its findings. Although the authors found that adverse effects were overall higher with tourniquet use, the data were pooled inappropriately and should not serve as the basis for a change in clinical practice. The differences in postoperative pain scores failed to reach a difference that is likely to be meaningful to patients. Importantly, a major question still remains surrounding implant durability and cement fixation with or without tourniquet use. As with most research in arthroplasty, the results in this review were based on small studies and were likely not powered to find differences in adverse events [4, 7]. Future studies in this area must be appropriately powered with adequate follow-up to ensure that important differences, or lack thereof, in clinical outcomes are captured.

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