In what appears to be the first study to explore whether the tourniquet is beneficial to patients undergoing robot-assisted TKA, our data suggest that using a tourniquet in robot-assisted TKA does not decrease total blood loss and instead leads to more severe pain, slower functional recovery, longer hospital stay, and more frequent complications.
Perhaps the most important finding of our study is that the tourniquet in robot-assisted TKA does not significantly decrease total blood loss. While the tourniquet appears to reduce intraoperative blood loss and shorten the operation, it fails to decrease hidden blood loss. Similarly, a study involving conventional TKA [24] found that the tourniquet can effectively control intraoperative blood loss but not reduce postoperative or total blood loss. On the contrary, a randomized controlled trial suggested that tourniquet use during conventional TKA significantly decreases blood loss without adversely affecting early postoperative outcomes[25]. We may need a high-quality meta-analysis to assess whether the tourniquet can significantly reduce total blood loss.
Whatever the case, it seems clear enough that using a tourniquet during robot-assisted TKA increases hidden blood loss. Hidden blood loss arising from postoperative hyperfibrinolysis accumulates in the third anatomic space and has been associated with postoperative inflammation, lower limb swelling, subcutaneous ecchymosis, and pain[26]. Our swelling data are consistent with this. Since swelling is associated with quadricep weakness and slower gait[27], interventions to reduce knee swelling after TKA may strengthen quadriceps and improve gait speed.
Numerous studies have shown that using a tourniquet during conventional TKA does not reduce total blood loss, but instead it appears to increase risk of more severe pain, longer length of stay, slower functional recovery, and complications[21, 25, 28–30], similar to our results. Since robot-assisted TKA takes significantly longer than conventional surgery[31], and since risk of tourniquet-associated complications increase with tourniquet time[32], we suspect that at least some of the adverse effects of tourniquet use in robot-assisted TKA relate to the relatively long operation time.
Our study demonstrated that tourniquets are associated with more severe pain soon after robot-assisted TKA, especially pain in the thigh. In fact, the pain appears to be higher than that reported for tourniquet use during conventional TKA[33]. Pain in the early postoperative period can strongly affect outcomes because it can compromise functional recovery[34]. Using a tourniquet can cause pain due to ischemia-reperfusion injury[35], particular when the tourniquet is used longer. The use of registration pins in robot-assisted TKA increases pain even more.
We found that range of motion on PODs 1-3 was significantly restricted when a tourniquet was used, which is consistent with a report that tourniquets slow functional recovery after routine TKA[36]. Indeed, we found that using a tourniquet in robot-assisted TKA led to longer time to achieve the first straight-leg raise than what has been reported for patients after conventional TKA[37], which likely reflects muscle damage as a result of prolonged tourniquet use. Indeed, the ischemia-reperfusion injury associated with tourniquets may significantly reduce the number of skeletal muscle fibers[38]. With a tourniquet may damage quadriceps, thereby delaying the recovery of muscle function, prolonging hospitalization and giving rise to long-lasting functional deficits[39]. However, we found no significant difference between the tourniquet and non-tourniquet groups in functional recovery up to 3 months after robot-assisted TKA. Studies with longer follow-up should verify and extend our results.
The use of a pneumatic tourniquet in conventional TKA may increase risk of postoperative complications[40, 41], although there is some evidence that it can protect against DVT[42, 43]. We found that a tourniquet significantly increased the risk of tension blisters but not of other complications, even DVT. More work is needed to clarify the effects of tourniquet use on DVT and other complications after TKA, especially since the literature shows substantial heterogeneity of samples and study designs[33]. Clarifying these effects is particularly important for robot-assisted TKA because it involves longer operation and tourniquet time than routine TKA.
One of the strengths of our study is that it is a randomized, controlled, double-blinded trial. Another advantage is that all patients received the same standardized perioperative treatment, including multimodal analgesia, surgical procedure and blood loss management. This should reduce heterogeneity that could confound our analysis. On the other hand, our study was small and did not examine long-term clinical outcomes. The small sample may have failed to detect significant effects of a tourniquet on the incidence of complications, especially the DVT and pulmonary embolism. Large, multi-center studies are needed to evaluate the safety and efficacy of tourniquet use in robot-assisted TKA, especially now that robot-assisted surgery is becoming popular