- Email: [email protected]
In Reply: Tranexamic Acid Benefits Total Joint Arthroplasty Patients Regardless of Preoperative Hemoglobin Value
The Journal of Arthroplasty 31 (2016) 1128e1135
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Letters to the Editors Letter to the Editor on “Tranexamic Acid Benefits Total Joint Arthroplasty Patients Regardless of Preoperative Hemoglobin Value”
To the Editor: We would like to congratulate the authors of recently published article “Tranexamic Acid Benefits Total Joint Arthroplasty Patients Regardless of Preoperative Hemoglobin Value” [1]. The authors have presented a very valid topic, and to us, the strength of the study is the high volume of patients that authors have presented in each group. However, we have some concerns regarding the study design, and it would be kind of the authors to clear our doubts. First of all, there are 6 surgeons performing surgeries with 3 using tranexamic acid and 3 do not. Now our basic understanding for any scientific study is that as far as possible, the confounding factors should be distributed randomly among comparative groups. Since our interest is the study of blood transfusion, which is a direct consequence of blood loss in surgery that is dependent on the surgical technique. Now different surgeons may have different techniques which may in themselves result in differential blood loss. For instance, if we assume that one of the surgeon’s technique in the nonetranexamic acid group results in comparatively higher blood loss than all other surgeons, then higher transfusion in the nonetranexamic group would be the result of the technique of that surgeon than tranexamic acid use. How have authors accounted for such a bias? Second, no criterion for discharge or length of stay is mentioned. Who decided the length of stay? Again, if it were decided by the operating surgeon, it becomes very subjective. And because each surgeon is strictly in one particular group, surgeon’s bias cannot be accounted in this study design. What if a particular surgeon is little conservative in discharging the patients. His decision would affect the entire study and not the tranexamic acid use. Furthermore, the authors have mentioned that they divided patients into various groups, one of which was hemoglobin <11 g/dL. However, this group is omitted from the results section. What were the results of tranexamic acid use in such patients is not mentioned. Because the purpose of the study was to look for a threshold value of hemoglobin beyond which tranexamic acid has no role, the lower hemoglobin values are very important. Fibrinolytic response after surgical trauma is known to be biphasic with an increased activity during the first 3 hours, followed by a shutdown that peaks at about 24 hours. So an
DOI of original article: http://dx.doi.org/10.1016/j.arth.2015.12.040. No author associated with this paper has disclosed any potential or pertinent conflicts which may be perceived to have impending conflict with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2015.12.035. No source of funding was received for this study. 0883-5403/© 2016 Elsevier Inc. All rights reserved.
injectable dose in the postoperative period preferably after 3 hours (which is the half-life of tranexamic acid) is effective [2]. There is literature evidence to support that a regime of pre-op, intra-op, and post-op was superior to other regimes [3]. Was there a particular reason that authors chose to omit this dose. We believe that tranexamic acid helps in decreasing transfusion requirement, but tranexamic acid by itself may not be a very important factor in decreasing length of stay. Length of stay depends on patient factors, surgeon’s perception of the clinical status of the patient, and institutional policies. A more random set of 2 groups with minimal confounding factors may be able to show whether the difference in the length of stay shown in this study was clinically relevant. Jatin Prakash, MBBS, MS (Ortho), DNB* Department of Orthopaedics Lady Hardinge Medical College New Delhi, India * Reprint requests: Jatin Prakash, MBBS, MS (Ortho), DNB, Department of Orthopaedics, Lady Hardinge Medical College, H-19/82, Sec-7, Rohini, New Delhi, 110085, India.
http://dx.doi.org/10.1016/j.arth.2015.12.035 References 1.
2. 3.
Whiting Daniel R, Duncan Christopher M, Sierra Rafael J, et al. Tranexamic acid benefits total joint arthroplasty patients regardless of preoperative hemoglobin value. J Arthroplasty 2015;30:2098. Nilsson IM. Clinical pharmacology of aminocaproic and tranexamic acids. J Clin Pathol Suppl (R Coll Pathol) 1980;14:41. Maniar RN, Kumar G, Singhi T, et al. Most effective regimen of tranexamic acid in knee arthroplasty: a prospective randomized controlled study in 240 patients. Clin Orthop Relat Res 2012;470(9):2605.
In Reply: Tranexamic Acid Benefits Total Joint Arthroplasty Patients Regardless of Preoperative Hemoglobin Value
We thank the authors of the letter for their thoughts on our recently published article “Tranexamic acid benefits total joint arthroplastic patients regardless of preoperative hemoglobin DOI of original article: http://dx.doi.org/10.1016/j.arth.2015.12.035. One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2015.12.040.
Letters to the Editors
value” [1] and the editors for the opportunity to respond to the concerns presented in the letter. The study includes results from 6 fellowship-trained adult reconstruction surgeons, 3 of whom used tranexamic acid (TXA) and 3 who did not as a matter of standard practice during the years 2007-2009. All total knee arthroplasties were performed through a standard paramedian approach with the use of a tourniquet which was deflated during the operation to assess for bleeding and perform electrocautery appropriately. For total hip arthroplasty, the 3 surgeons using TXA routinely used the posterior approach, whereas 2 of the surgeons in the non-TXA group routinely used the anterolateral approach and the third used the posterior approach. Closed suction drains were used routinely in both total knee arthroplasty and total hip arthroplasty and were removed on postoperative day 1. No surgeries were computer navigated during this study period. Anesthesia was provided through a standardized total joint arthroplasty protocol regardless of the surgeon. Thus, we feel that the standardization of the surgical and anesthesia protocols for the preoperative, intraoperative, and postoperative periods decreased the likelihood of differing techniques leading to differences in blood transfusion. In addition, as noted in the article, all decisions regarding transfusion were made with a standard transfusion trigger throughout the group. The letter writers are correct to note that the determination of length of stay (LOS) may be very subjective, and this subjectivity may be a confounding factor when directly correlating TXA with LOS because of the fact that each surgeon falls solely into a single group. This is certainly a limitation of this retrospective review which we recognize. However, there were also other providers, namely nursing, physical therapy, and social work, involved in deciding the timing of dismissal. They provided their input without regard for TXA status and based on the progress of each individual patient in meeting goals standardized throughout the total joint practice. During the formulation of the study, we recognized this potential confounding factor when trying to directly correlate TXA with LOS, which is why we further assessed for any relationship between LOS and transfusion. As noted in our study, patients who received a transfusion had a longer mean LOS by 0.69 days (P < .0001, 95% confidence interval: 0.57-0.81), and this increase remained consistent when controlling for the surgeon involved [1]. This increase in LOS with transfusion is also consistent with the results of 2 studies examining data from the nationwide inpatient sample from 2000 to 2009 [2,3], providing evidence across a large sample of surgeons. Thus, we feel that the strong association between transfusion and increased LOS in conjunction with the strong association between TXA and decreased transfusion provide support for our results of decreased LOS with the use of TXA. The letter writers correctly point out that the patients with a preoperative hemoglobin (Hgb) value <11 g/dL were omitted from our results section. These patients were omitted for 2 reasons. First, this was a rather small group, including 31 patients with a large range of preoperative Hgb (8.6-10.9 g/dL); 17 of these patients received TXA. Thus, analysis of this small group with such a wide variance in Hgb would be difficult to perform in any meaningful way. Second, this was not the group of focus in our study question. We sought to determine whether there was an Hgb value above which TXA was no longer beneficial, or in other words, whether TXA was clinically beneficial in healthy patients with normal preoperative Hgb. The fact that this group of patients with Hgb <11 g/dL includes only 31 patients, or 1.5% of the entire cohort, demonstrates to us that our selection criteria were valid in finding our desired patient population. Throughout the literature, there are many varied dosing regimens for TXA, with variances including route of administration (intravenous, topical, oral), number of doses (1, 2, 3, continuous
1129
infusion), and timing of doses (preoperative, intraoperative, postoperative). Many different combinations of these variables have demonstrated good results in decreasing blood loss in various settings. Tanaka et al [4] found that 2 intravenous doses, 1 given before incision and 1 before deflation of the tourniquet, were more effective than a single dose given at either of the same time points. The article cited by the letter writers [5] prospectively compared 5 different TXA groups with various timing combinations. They found that all TXA dosing regimens were effective compared to the control group and that 3 intravenous doses were better than a single intravenous dose, but did not find any significant differences between regimens including 2 or 3 doses. When comparing 3 doses to 2 doses administered preoperatively and intraoperatively, Maniar et al [5] reported decreases in drain output (58 mL, P ¼ .792) and total blood loss (94 mL, P ¼ .944) in the group receiving 3 doses. However, these differences were far from statistically significant and, furthermore, may not be clinically significant even if they had been statistically significant. Per their protocol, the number of patients who were recommended to receive a transfusion was the same in these 2 groups. We believe this, transfusion, to be the clinically relevant outcome measure for blood loss in total joint arthroplasty because it carries its own risks and costs. Therefore, although there may be a theoretical benefit to administering a third dose of TXA, we are unaware of any clinical evidence demonstrating its superiority to 2 doses administered preoperatively and intraoperatively, as is our routine. We again thank the editors and the letter writers for the opportunity to further clarify these points of our study. The body of evidence supporting the use of TXA in total joint arthroplasty continues to grow and includes a wide array of effective dosing regimens. We encourage surgeons to find a regimen that fits within their system and surgical routine to provide the benefits of TXA to all patients regardless of their preoperative Hgb value. Daniel R. Whiting, MD Department of Orthopedic Surgery Mayo Clinic Rochester, Minnesota Christopher M. Duncan, MD Department of Anesthesiology Mayo Clinic Rochester, Minnesota Rafael J. Sierra, MD* Department of Orthopedic Surgery Mayo Clinic Rochester, Minnesota Hugh M. Smith, MD Department of Anesthesiology Mayo Clinic Rochester, Minnesota * Reprint requests: Rafael J. Sierra, MD, Mayo Clinic, 200 First Street South West, Rochester, MN 55905
http://dx.doi.org/10.1016/j.arth.2015.12.040 References 1.
2.
Whiting D, Duncan C, Sierra R, et al. Tranexamic acid benefits total joint arthroplasty patients regardless of preoperative hemoglobin value. J Arthroplasty 2015;30:2098. Klika A, Small T, Saleh A, et al. Primary total knee arthroplasty allogenic transfusion trends, length of stay, and complications: nationwide inpatient sample 2000-2009. J Arthroplasty 2014;29:2090.
1130 3.
4.
5.
Letters to the Editors
Saleh A, Small T, Pillai A, et al. Allogenic blood transfusion following total hip arthroplasty: results from the nationwide inpatient sample 2000 to 2009. J Bone Joint Surg 2014;96(1-10):e155. Tanaka N, Sakahashi H, Sato E, et al. Timing of the administration of tranexamic acid for maximum reduction in blood loss in arthroplasty of the knee. J Bone Joint Surg Br 2001;83-B:702. Maniar R, Kumar G, Singhi T, et al. Most effective regimen of tranexamic acid in knee arthroplasty: a prospective randomized controlled study in 240 patients. Clin Orthop Relat Res 2012;470(9):2605.
Letter to the Editor on “Preoperative Mapping in Unicompartmental Knee Arthroplasty Using Computed Tomography Scans Is Associated With Radiation Exposure and Carries High Cost”
To the Editor: I read with interest the article by Ponzio and Lonner [1] regarding preoperative mapping in unicompartmental knee arthroplasty (UKA) using computed tomographic (CT) scans. The authors reported that preoperative CT mapping yielded a mean effective dose (ED) of 4.8 mSv in patients undergoing robot-assisted UKA. They concluded that robotic assistance improves UKA accuracy although reasonable efforts should be taken to reduce unnecessary ionizing radiation exposure to maximize the medical benefit of CT-based preoperative mapping to the patient. The authors highlighted the association of ionizing radiation exposure with cancer risk although the context of this discussion was quite broad. In fact, risks of medical imaging at EDs below 50 mSv for single procedures or 100 mSv for multiple procedures over short time periods are too low to be detectable and may be nonexistent [2]. Even when using the most conservative models that assume a linear no-threshold relationship of ionizing radiation exposure with cancer risk, a mean ED of 4.8 mSv has a negligible influence on cancer risk, particularly in the typical UKA patient. For example, a 65-year-old male has a 44.9% risk of developing cancer during his lifetime. A single exposure to an ED of 4.8 mSv increases lifetime cancer risk from 44.9% to 44.92%. Similarly, at the same ED in a 65-year-old female, lifetime cancer risk increases from 37.5% to 37.52% using the most conservative no-threshold assumptions [3]. Therefore, the risks associated with a single CT scan used for preoperative mapping in robot-assisted UKA appear to be grossly overstated in this article, and the benefits of robotics asserted by the authors likely outweigh this risk, should any exist. The issue of cumulative lifetime exposure to ionizing radiation warrants further discussion. In this study, additional CT examinations unrelated to the UKA procedure comprised the vast majority of ionizing radiation exposure to patients, with 1 in 4 patients exposed to EDs ranging from 6 to 103 mSv. Although the authors attempt to associate radiation exposure from preoperative CT mapping with radiation exposure from unrelated CTs, patients treated with image-free UKA robotic technology would still be exposed to this more significant radiation burden. It is unclear why the authors try to confound the impact of a single CT of the hip, knee, and ankle by using a patient population that received a large burden of unrelated studies. As noted by the authors, there were also significant disparities in radiation exposure with CT protocols at different hospitals. Collectively, these findings suggest that cumulative lifetime exposure to ionizing radiation would be best managed by
avoiding medically unwarranted CT scans and by optimizing CT protocols using the “as low as reasonably achievable” principle. In agreement with the authors, robot-assisted UKA is a promising technology that has demonstrated superior midterm patient outcomes compared with standard UKA. One study demonstrated lower 2-year revision rates for robot-assisted UKA compared with standard UKA [4]. A randomized controlled trial of robot-assisted vs manual UKA found less pain and higher functioning for the robotic-assist cohort [5]. The authors present no cost data in this study despite the assumption of such data given the title of the article. It would be interesting to examine cost effectiveness of robot-assisted UKA over the long term. Finally, the reader should note that the single surgeon in this case series is also a stockholder in the company that manufacturers the image-free robotic UKA system. One should remain vigilant when reviewing study findings that are critical of a technology when authored by competitors of the technology. Ideally, this study could be replicated by independent investigators in a multicenter setting. Larry E. Miller, PhD* Miller Scientific Consulting, Inc Asheville, North Carolina * Reprint requests: Larry E. Miller, PhD, Miller Scientific Consulting, Inc, 1854 Hendersonville Road, #231, Asheville, NC 28803.
http://dx.doi.org/10.1016/j.arth.2016.01.003 References 1.
2.
3.
4.
5.
Ponzio DY, Lonner JH. Preoperative mapping in unicompartmental knee arthroplasty using computed tomography scans is associated with radiation exposure and carries high cost. J Arthroplasty 2015;30:964. AAPM position statement on radiation risks from medical imaging procedures. [http://www.aapm.org/org/policies/details.asp?id¼318&type¼PP¤t¼true] [accessed 20.11.15]. National Research Council. Health risks from exposure to low levels of ionizing radiation: BEIR VII phase 2. In: Book Health risks from exposure to low levels of ionizing radiation: BEIR VII phase 2 (Editor ed.∧eds.). Washington. D.C.: National Academies Press; 2006. Coon T, Roche M, Buechel F, et al. Short to mid term survivorship of robotic arm assisted UKA: a multicenter study. Kona, HI: Pan Pacific Orthopaedic Congress; 2014. Jones B, Blyth M, MacLean A, et al: Accuracy of UKA implant positioning and early clinical outcomes in a RCT comparing robotic assisted and manual surgery. In 14th Annual Meeting of CAOS e International; Orlando, FL. 2013.
In Reply: Preoperative Mapping in Unicompartmental Knee Arthroplasty Using Computed Tomography Scans Is Associated With Radiation Exposure and Carries High Cost
To the Editor: We are happy to have an opportunity to reply to Dr Miller who expressed concern regarding the discussion of cancer risk associated with radiation exposure in our article “Preoperative Mapping DOI of original article: http://dx.doi.org/10.1016/j.arth.2016.01.003. Investigation performed at the Department of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, PA.
DOI of original article: http://dx.doi.org/10.1016/j.arth.2016.01.002. One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2016.01.003.
One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2016.01.002.
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Letters to the Editors Letter to the Editor on “Tranexamic Acid Benefits Total Joint Arthroplasty Patients Regardless of Preoperative Hemoglobin Value”
To the Editor: We would like to congratulate the authors of recently published article “Tranexamic Acid Benefits Total Joint Arthroplasty Patients Regardless of Preoperative Hemoglobin Value” [1]. The authors have presented a very valid topic, and to us, the strength of the study is the high volume of patients that authors have presented in each group. However, we have some concerns regarding the study design, and it would be kind of the authors to clear our doubts. First of all, there are 6 surgeons performing surgeries with 3 using tranexamic acid and 3 do not. Now our basic understanding for any scientific study is that as far as possible, the confounding factors should be distributed randomly among comparative groups. Since our interest is the study of blood transfusion, which is a direct consequence of blood loss in surgery that is dependent on the surgical technique. Now different surgeons may have different techniques which may in themselves result in differential blood loss. For instance, if we assume that one of the surgeon’s technique in the nonetranexamic acid group results in comparatively higher blood loss than all other surgeons, then higher transfusion in the nonetranexamic group would be the result of the technique of that surgeon than tranexamic acid use. How have authors accounted for such a bias? Second, no criterion for discharge or length of stay is mentioned. Who decided the length of stay? Again, if it were decided by the operating surgeon, it becomes very subjective. And because each surgeon is strictly in one particular group, surgeon’s bias cannot be accounted in this study design. What if a particular surgeon is little conservative in discharging the patients. His decision would affect the entire study and not the tranexamic acid use. Furthermore, the authors have mentioned that they divided patients into various groups, one of which was hemoglobin <11 g/dL. However, this group is omitted from the results section. What were the results of tranexamic acid use in such patients is not mentioned. Because the purpose of the study was to look for a threshold value of hemoglobin beyond which tranexamic acid has no role, the lower hemoglobin values are very important. Fibrinolytic response after surgical trauma is known to be biphasic with an increased activity during the first 3 hours, followed by a shutdown that peaks at about 24 hours. So an
DOI of original article: http://dx.doi.org/10.1016/j.arth.2015.12.040. No author associated with this paper has disclosed any potential or pertinent conflicts which may be perceived to have impending conflict with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2015.12.035. No source of funding was received for this study. 0883-5403/© 2016 Elsevier Inc. All rights reserved.
injectable dose in the postoperative period preferably after 3 hours (which is the half-life of tranexamic acid) is effective [2]. There is literature evidence to support that a regime of pre-op, intra-op, and post-op was superior to other regimes [3]. Was there a particular reason that authors chose to omit this dose. We believe that tranexamic acid helps in decreasing transfusion requirement, but tranexamic acid by itself may not be a very important factor in decreasing length of stay. Length of stay depends on patient factors, surgeon’s perception of the clinical status of the patient, and institutional policies. A more random set of 2 groups with minimal confounding factors may be able to show whether the difference in the length of stay shown in this study was clinically relevant. Jatin Prakash, MBBS, MS (Ortho), DNB* Department of Orthopaedics Lady Hardinge Medical College New Delhi, India * Reprint requests: Jatin Prakash, MBBS, MS (Ortho), DNB, Department of Orthopaedics, Lady Hardinge Medical College, H-19/82, Sec-7, Rohini, New Delhi, 110085, India.
http://dx.doi.org/10.1016/j.arth.2015.12.035 References 1.
2. 3.
Whiting Daniel R, Duncan Christopher M, Sierra Rafael J, et al. Tranexamic acid benefits total joint arthroplasty patients regardless of preoperative hemoglobin value. J Arthroplasty 2015;30:2098. Nilsson IM. Clinical pharmacology of aminocaproic and tranexamic acids. J Clin Pathol Suppl (R Coll Pathol) 1980;14:41. Maniar RN, Kumar G, Singhi T, et al. Most effective regimen of tranexamic acid in knee arthroplasty: a prospective randomized controlled study in 240 patients. Clin Orthop Relat Res 2012;470(9):2605.
In Reply: Tranexamic Acid Benefits Total Joint Arthroplasty Patients Regardless of Preoperative Hemoglobin Value
We thank the authors of the letter for their thoughts on our recently published article “Tranexamic acid benefits total joint arthroplastic patients regardless of preoperative hemoglobin DOI of original article: http://dx.doi.org/10.1016/j.arth.2015.12.035. One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2015.12.040.
Letters to the Editors
value” [1] and the editors for the opportunity to respond to the concerns presented in the letter. The study includes results from 6 fellowship-trained adult reconstruction surgeons, 3 of whom used tranexamic acid (TXA) and 3 who did not as a matter of standard practice during the years 2007-2009. All total knee arthroplasties were performed through a standard paramedian approach with the use of a tourniquet which was deflated during the operation to assess for bleeding and perform electrocautery appropriately. For total hip arthroplasty, the 3 surgeons using TXA routinely used the posterior approach, whereas 2 of the surgeons in the non-TXA group routinely used the anterolateral approach and the third used the posterior approach. Closed suction drains were used routinely in both total knee arthroplasty and total hip arthroplasty and were removed on postoperative day 1. No surgeries were computer navigated during this study period. Anesthesia was provided through a standardized total joint arthroplasty protocol regardless of the surgeon. Thus, we feel that the standardization of the surgical and anesthesia protocols for the preoperative, intraoperative, and postoperative periods decreased the likelihood of differing techniques leading to differences in blood transfusion. In addition, as noted in the article, all decisions regarding transfusion were made with a standard transfusion trigger throughout the group. The letter writers are correct to note that the determination of length of stay (LOS) may be very subjective, and this subjectivity may be a confounding factor when directly correlating TXA with LOS because of the fact that each surgeon falls solely into a single group. This is certainly a limitation of this retrospective review which we recognize. However, there were also other providers, namely nursing, physical therapy, and social work, involved in deciding the timing of dismissal. They provided their input without regard for TXA status and based on the progress of each individual patient in meeting goals standardized throughout the total joint practice. During the formulation of the study, we recognized this potential confounding factor when trying to directly correlate TXA with LOS, which is why we further assessed for any relationship between LOS and transfusion. As noted in our study, patients who received a transfusion had a longer mean LOS by 0.69 days (P < .0001, 95% confidence interval: 0.57-0.81), and this increase remained consistent when controlling for the surgeon involved [1]. This increase in LOS with transfusion is also consistent with the results of 2 studies examining data from the nationwide inpatient sample from 2000 to 2009 [2,3], providing evidence across a large sample of surgeons. Thus, we feel that the strong association between transfusion and increased LOS in conjunction with the strong association between TXA and decreased transfusion provide support for our results of decreased LOS with the use of TXA. The letter writers correctly point out that the patients with a preoperative hemoglobin (Hgb) value <11 g/dL were omitted from our results section. These patients were omitted for 2 reasons. First, this was a rather small group, including 31 patients with a large range of preoperative Hgb (8.6-10.9 g/dL); 17 of these patients received TXA. Thus, analysis of this small group with such a wide variance in Hgb would be difficult to perform in any meaningful way. Second, this was not the group of focus in our study question. We sought to determine whether there was an Hgb value above which TXA was no longer beneficial, or in other words, whether TXA was clinically beneficial in healthy patients with normal preoperative Hgb. The fact that this group of patients with Hgb <11 g/dL includes only 31 patients, or 1.5% of the entire cohort, demonstrates to us that our selection criteria were valid in finding our desired patient population. Throughout the literature, there are many varied dosing regimens for TXA, with variances including route of administration (intravenous, topical, oral), number of doses (1, 2, 3, continuous
1129
infusion), and timing of doses (preoperative, intraoperative, postoperative). Many different combinations of these variables have demonstrated good results in decreasing blood loss in various settings. Tanaka et al [4] found that 2 intravenous doses, 1 given before incision and 1 before deflation of the tourniquet, were more effective than a single dose given at either of the same time points. The article cited by the letter writers [5] prospectively compared 5 different TXA groups with various timing combinations. They found that all TXA dosing regimens were effective compared to the control group and that 3 intravenous doses were better than a single intravenous dose, but did not find any significant differences between regimens including 2 or 3 doses. When comparing 3 doses to 2 doses administered preoperatively and intraoperatively, Maniar et al [5] reported decreases in drain output (58 mL, P ¼ .792) and total blood loss (94 mL, P ¼ .944) in the group receiving 3 doses. However, these differences were far from statistically significant and, furthermore, may not be clinically significant even if they had been statistically significant. Per their protocol, the number of patients who were recommended to receive a transfusion was the same in these 2 groups. We believe this, transfusion, to be the clinically relevant outcome measure for blood loss in total joint arthroplasty because it carries its own risks and costs. Therefore, although there may be a theoretical benefit to administering a third dose of TXA, we are unaware of any clinical evidence demonstrating its superiority to 2 doses administered preoperatively and intraoperatively, as is our routine. We again thank the editors and the letter writers for the opportunity to further clarify these points of our study. The body of evidence supporting the use of TXA in total joint arthroplasty continues to grow and includes a wide array of effective dosing regimens. We encourage surgeons to find a regimen that fits within their system and surgical routine to provide the benefits of TXA to all patients regardless of their preoperative Hgb value. Daniel R. Whiting, MD Department of Orthopedic Surgery Mayo Clinic Rochester, Minnesota Christopher M. Duncan, MD Department of Anesthesiology Mayo Clinic Rochester, Minnesota Rafael J. Sierra, MD* Department of Orthopedic Surgery Mayo Clinic Rochester, Minnesota Hugh M. Smith, MD Department of Anesthesiology Mayo Clinic Rochester, Minnesota * Reprint requests: Rafael J. Sierra, MD, Mayo Clinic, 200 First Street South West, Rochester, MN 55905
http://dx.doi.org/10.1016/j.arth.2015.12.040 References 1.
2.
Whiting D, Duncan C, Sierra R, et al. Tranexamic acid benefits total joint arthroplasty patients regardless of preoperative hemoglobin value. J Arthroplasty 2015;30:2098. Klika A, Small T, Saleh A, et al. Primary total knee arthroplasty allogenic transfusion trends, length of stay, and complications: nationwide inpatient sample 2000-2009. J Arthroplasty 2014;29:2090.
1130 3.
4.
5.
Letters to the Editors
Saleh A, Small T, Pillai A, et al. Allogenic blood transfusion following total hip arthroplasty: results from the nationwide inpatient sample 2000 to 2009. J Bone Joint Surg 2014;96(1-10):e155. Tanaka N, Sakahashi H, Sato E, et al. Timing of the administration of tranexamic acid for maximum reduction in blood loss in arthroplasty of the knee. J Bone Joint Surg Br 2001;83-B:702. Maniar R, Kumar G, Singhi T, et al. Most effective regimen of tranexamic acid in knee arthroplasty: a prospective randomized controlled study in 240 patients. Clin Orthop Relat Res 2012;470(9):2605.
Letter to the Editor on “Preoperative Mapping in Unicompartmental Knee Arthroplasty Using Computed Tomography Scans Is Associated With Radiation Exposure and Carries High Cost”
To the Editor: I read with interest the article by Ponzio and Lonner [1] regarding preoperative mapping in unicompartmental knee arthroplasty (UKA) using computed tomographic (CT) scans. The authors reported that preoperative CT mapping yielded a mean effective dose (ED) of 4.8 mSv in patients undergoing robot-assisted UKA. They concluded that robotic assistance improves UKA accuracy although reasonable efforts should be taken to reduce unnecessary ionizing radiation exposure to maximize the medical benefit of CT-based preoperative mapping to the patient. The authors highlighted the association of ionizing radiation exposure with cancer risk although the context of this discussion was quite broad. In fact, risks of medical imaging at EDs below 50 mSv for single procedures or 100 mSv for multiple procedures over short time periods are too low to be detectable and may be nonexistent [2]. Even when using the most conservative models that assume a linear no-threshold relationship of ionizing radiation exposure with cancer risk, a mean ED of 4.8 mSv has a negligible influence on cancer risk, particularly in the typical UKA patient. For example, a 65-year-old male has a 44.9% risk of developing cancer during his lifetime. A single exposure to an ED of 4.8 mSv increases lifetime cancer risk from 44.9% to 44.92%. Similarly, at the same ED in a 65-year-old female, lifetime cancer risk increases from 37.5% to 37.52% using the most conservative no-threshold assumptions [3]. Therefore, the risks associated with a single CT scan used for preoperative mapping in robot-assisted UKA appear to be grossly overstated in this article, and the benefits of robotics asserted by the authors likely outweigh this risk, should any exist. The issue of cumulative lifetime exposure to ionizing radiation warrants further discussion. In this study, additional CT examinations unrelated to the UKA procedure comprised the vast majority of ionizing radiation exposure to patients, with 1 in 4 patients exposed to EDs ranging from 6 to 103 mSv. Although the authors attempt to associate radiation exposure from preoperative CT mapping with radiation exposure from unrelated CTs, patients treated with image-free UKA robotic technology would still be exposed to this more significant radiation burden. It is unclear why the authors try to confound the impact of a single CT of the hip, knee, and ankle by using a patient population that received a large burden of unrelated studies. As noted by the authors, there were also significant disparities in radiation exposure with CT protocols at different hospitals. Collectively, these findings suggest that cumulative lifetime exposure to ionizing radiation would be best managed by
avoiding medically unwarranted CT scans and by optimizing CT protocols using the “as low as reasonably achievable” principle. In agreement with the authors, robot-assisted UKA is a promising technology that has demonstrated superior midterm patient outcomes compared with standard UKA. One study demonstrated lower 2-year revision rates for robot-assisted UKA compared with standard UKA [4]. A randomized controlled trial of robot-assisted vs manual UKA found less pain and higher functioning for the robotic-assist cohort [5]. The authors present no cost data in this study despite the assumption of such data given the title of the article. It would be interesting to examine cost effectiveness of robot-assisted UKA over the long term. Finally, the reader should note that the single surgeon in this case series is also a stockholder in the company that manufacturers the image-free robotic UKA system. One should remain vigilant when reviewing study findings that are critical of a technology when authored by competitors of the technology. Ideally, this study could be replicated by independent investigators in a multicenter setting. Larry E. Miller, PhD* Miller Scientific Consulting, Inc Asheville, North Carolina * Reprint requests: Larry E. Miller, PhD, Miller Scientific Consulting, Inc, 1854 Hendersonville Road, #231, Asheville, NC 28803.
http://dx.doi.org/10.1016/j.arth.2016.01.003 References 1.
2.
3.
4.
5.
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In Reply: Preoperative Mapping in Unicompartmental Knee Arthroplasty Using Computed Tomography Scans Is Associated With Radiation Exposure and Carries High Cost
To the Editor: We are happy to have an opportunity to reply to Dr Miller who expressed concern regarding the discussion of cancer risk associated with radiation exposure in our article “Preoperative Mapping DOI of original article: http://dx.doi.org/10.1016/j.arth.2016.01.003. Investigation performed at the Department of Orthopaedic Surgery, Rothman Institute, Thomas Jefferson University, Philadelphia, PA.
DOI of original article: http://dx.doi.org/10.1016/j.arth.2016.01.002. One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2016.01.003.
One or more of the authors of this paper have disclosed potential or pertinent conflicts of interest, which may include receipt of payment, either direct or indirect, institutional support, or association with an entity in the biomedical field which may be perceived to have potential conflict of interest with this work. For full disclosure statements refer to http://dx.doi.org/10.1016/j.arth.2016.01.002.