In our study we evaluated the effect of two different ways of sealing the femoral canal on patients' postoperative coagulation status and blood loss. By comparing TEG indicators (preoperative, first postoperative day and seventh postoperative day), postoperative blood loss, transfusion rate and DVT incidence, we found that patients without bone cement sealing of the canal had a relatively hypocoagulable postoperative state and had more total and hidden blood loss in the postoperative period than the other group. These results were statistically significant. In addition, bone cement did not alter postoperative drainage, transfusion rates or the incidence of DVT.
The use of TEG for monitoring post-operative coagulation status in orthopaedic arthroplasty has become increasingly widespread in recent years [16, 17]. Compared to traditional coagulation tests, TEG focuses on the function of blood components and allows for a full picture of coagulation, providing a dynamic, comprehensive view of the entire coagulation response and providing better insight than conventional coagulation tests in assessing a patient's coagulation status [9, 18]. In our study there was a significant difference between the two groups in terms of postoperative CI, which in turn reflected the overall coagulation status, with the Bone Group and Bone&Cement group comparing relatively low coagulation, suggesting that the use of bone cement had an effect on the coagulation status of the patients in the postoperative period, which was further illustrated by the comparison of total and occult blood loss in the two groups in the postoperative period.
TKA blood loss can be divided into two components: visible blood loss and hidden blood loss[19, 20]. Visible blood loss consists mainly of intraoperative bleeding and postoperative drainage, whereas hidden blood loss refers to the accumulation of blood in the joint cavity and extravasation in the tissue spaces after major trauma or surgery, as well as haemoglobin loss due to haemolysis[21]. Tao Yuan et al [22] suggested that visible bleeding after arthroplasty is associated with a hemolytic reaction following attack on red blood cells by a large number of oxygen radicals produced by stress. In our review of previous similar articles, we found that the findings of Li X et al [7] were similar to the present experiment, with significant differences in total and hidden blood loss between the two groups of patients. Dikmen İ et al [4] also illustrated a difference in total blood loss between the empty tube and bone cement groups. The bone cement blocking of the femoral medullary canal in this experiment did reduce blood loss, probably because more gaps remained around the block after it was blocked. The bleeding from the femoral trophoblastic vessels in the medullary canal may enter the joint cavity or tissue space through these residual gaps. This stagnant blood in the joint cavity or tissue space may not only cause hidden blood loss, but also swelling and pain in the joint, which may affect the recovery of joint function.
There are also inconsistent results in terms of transfusion rates and drainage in previous articles, with Li et al. and Ko et al. finding lower transfusion rates in the bone cement group than in the empty tube group [6, 7], while other articles indicate no difference [3–5], which may be related to whether tranexamic acid was used intraoperatively. Tranexamic acid reduces bleeding and transfusion requirements in the perioperative period[23, 24].The transfusion rate in the study by Dikmen İ et al[4] was partly due to a decrease in the use of tranexamic acid.In addition,there is a difference in the results of drainage flow between Dikmen İ et al. and Batmaz AG et al.[3, 5]. We compared them and found that the time of drainage tube removal was different, and since drainage flow increases with time, it is closely related to the time of removal and also to the use of perioperative anticoagulants[25, 26]. In our study there was no difference in transfusion rates or drainage between the two groups. We also took into account the comparison of postoperative DVT. We performed a lower limb ultrasound on the seventh postoperative day and found no difference in the incidence of DVT between the two groups, and the patients who had DVT had no symptoms associated with it at the time of follow-up, and it eventually resolved with anticoagulation.
This study has several drawbacks, firstly it is a single central retrospective study with a high potential for bias. Secondly the sample size was relatively small and the experimental data lacked convincingness; a large prospective study would have better validated our conclusions. Also, we only performed Doppler ultrasound on patients preoperatively and on the seventh postoperative day, which may have been missed due to the fact that Doppler ultrasound was only performed on patients with DVT-related symptoms only in the postoperative follow-up of patients after discharge from hospital. In addition, Doppler ultrasound is not the gold standard for the diagnosis of lower limb venous thrombosis and the likelihood of false negatives increases. When the Gross equation method is used to estimate blood loss, the true calculated total blood loss may be compromised due to the transfer of body fluids and haemolytic reaction to transfusion.