Abstract
Background
The use of chemoprophylaxis to prevent thromboembolic disease after primary THA and TKA can be associated with postoperative bleeding complications. Mechanical prophylaxis has been studied as an alternative to chemoprophylaxis with greater safety in patients undergoing THA, but no data have been published comparing the safety of chemoprophylaxis versus mechanical methods for patients undergoing TKA. The risk of readmission resulting from bleeding and venous thromboembolism (VTE) has also not been determined for patients undergoing THA or TKA when treated with low-molecular-weight heparin (LMWH) alone compared with mechanical prophylaxis plus aspirin (ASA).
Question/purposes
We sought to answer four questions: For the THA and TKA cohorts, respectively, (1) was the incidence of readmission resulting from VTE and bleeding complications higher with LMWH than mobile compression plus ASA; and (2) was the incidence of wound bleeding complications higher with LMWH than mechanical compression plus ASA? For the TKA cohort specifically, (3) was the frequency of systemic bleeding events and complications related to chemical prophylaxis higher with LMWH compared with mechanical compression plus ASA? (4) Was there a difference in symptomatic VTEs between LMWH and mechanical compression plus ASA?
Methods
Between November 2008 and April 2011, 632 patients underwent primary THA and TKA. Seventy-two patients (11%) were identified before surgery as being at high risk for VTE (31 patients) or bleeding (41 patients) and were excluded from the study. Five hundred sixty patients (89%) were considered to be at standard risk for VTE and bleeding and comprise the study cohort. Between November 2008 and November 2009, 252 patients (76 THAs, 176 TKAs) underwent THA and TKA and were treated with LMWH (5 mg dalteparin given subcutaneously daily for 14 days) and in-hospital nonmobile mechanical compression. Between November 2009 and April 2011, a total of 308 patients undergoing THA and TKA (108 THAs, 200 TKAs) were treated using a mobile compression device plus oral aspirin once daily for 2 weeks after surgery. All complications and readmissions that occurred within 6 weeks of surgery were noted. There were no differences between the VTE treatment groups with regard to age, sex, or body mass index.
Results
For the THA cohort, there was no difference in the frequency of readmission for a bleeding complication (wound or systemic) between the two groups (2.6% for LMWH versus 0.9% for mobile compression; p = 0.57; odds ratio [OR], 2.9). Patients undergoing TKA treated with LMWH had higher readmission rates within 6 weeks of surgery because of a bleeding complication, a wound infection, or the development of a VTE (6.8% for LMWH versus 1.5% for mobile compression; p = 0.015; OR, 4.8). For the THA cohort, there was higher wound bleeding complication frequency with LMWH (9.2% for LMWH versus 0.9% for mechanical compression; p = 0.009; OR, 10.9). Patients undergoing TKA treated with LMWH had a higher frequency of wound bleeding complications or infection (3.9% for LMWH versus 0.5% for mobile compression; p = 0.028; OR, 8.2). Patients undergoing TKA treated with LMWH had higher rates of systemic bleeding or a complication secondary to LMWH administration (2.8% for LMWH versus 0% for mobile compression; p = 0.022; OR, 12.8). No difference was noted in the rate of symptomatic VTEs between either group (for THA: 2.6% for the LMWH group versus 1.9% for the mechanical compression group; p = 1; for TKA: 1.1% versus 0%, respectively; p = 0.22).
Conclusions
Based on these results, we advocate for routine use of mobile mechanical compression devices in the prevention of VTEs and complications associated with more potent chemical anticoagulants. However, more focused randomized clinical trials are needed to validate these findings.
Level of Evidence:
Level III, therapeutic study.
Introduction
Venous thromboembolic disease (VTE), although rarely fatal, is considered by the Centers for Medicare & Medicaid Services to be a “never event” complication after THA and TKA. The best treatment remains unknown, but surgeons and patients must be aware of the risk–benefit analysis relating to the safety and efficacy of each prophylaxis protocol [14]. The American College of Chest Physicians (ACCP) guidelines for patients undergoing total joint arthroplasty include chemoprophylactic agents that have been shown to be very effective in prevention of VTE, but are also associated with postoperative complications including major bleeding and wound complications [1, 7, 8, 11, 12]. Portable intermittent pneumatic compression alone has been studied as an alternative to chemoprophylactic agents and was included as a recommended means of prophylaxis for patients undergoing both hip and knee arthroplasty in the 2012 ACCP and American Academy of Orthopaedic Surgeons (AAOS) guidelines [7, 13].
Prior studies on mobile compression have shown improved compliance [9] compared with nonportable devices and lower rates of major bleeding compared with low-molecular-weight heparin (LMWH) with noninferior efficacy compared with oral or parenteral anticoagulants [2, 3, 6, 10]. One study demonstrated that mobile compression prophylaxis was cost-effective in comparison to chemoprophylaxis [5]. Although mobile compression prophylaxis has been shown to reduce major bleeding events after THA from 6% to 0% [3], there have been no data presented on the effect of adopting mobile compression prophylaxis with regard to hospital readmissions because of bleeding complications. At our hospital in November 2009, the use of subcutaneous LMWH for routine thromboembolism prophylaxis in patients undergoing THA and those undergoing TKA who were at standard risk for VTE was changed to mobile mechanical compression combined with oral aspirin.
Therefore, we sought to answer four questions: For the THA and TKA cohorts, respectively, (1) was the incidence of readmission resulting from VTE and bleeding complications higher with LMWH than mobile compression plus aspirin; and (2) was the incidence of wound bleeding complications higher with LMWH than mechanical compression plus aspirin? For the TKA cohort specifically, (3) was the frequency of systemic bleeding events and complications related to chemical prophylaxis higher with LMWH compared with mechanical compression plus aspirin? (4) Was there a difference in symptomatic VTEs between LMWH and mechanical compression plus aspirin?
Patients and Methods
Between November 2008 and April 2011, 632 patients underwent primary THA and TKA. Preoperatively, patients were assessed for risk of VTE and bleeding and stratified according to AAOS guidelines from 2007 [18]. Based on this, 72 patients (11%) were deemed either at high risk for VTE (31 patients) or at high risk for bleeding (41 patients) and were excluded from the study. This left 560 patients (89%) considered to be at standard risk for VTE and bleeding and comprise the study cohort. Between November 2008 and November 2009, 252 patients (76 THAs, 176 TKAs) underwent THA and TKA and were treated with LMWH (5 mg dalteparin given subcutaneously daily for 14 days) and in-hospital nonmobile mechanical compression using a single-chamber device that was used while patients were in bed. Starting in November 2009, VTE prophylaxis for standard-risk patients who underwent THA and TKA was changed from LMWH to mechanical mobile compression plus oral aspirin. Between November 2009 and April 2011, a total of 308 patients underwent THA and TKA (108 THAs, 200 TKAs) and these patients were treated using a mobile sequential intermittent pneumatic compression device (ActiveCare; Medical Compression Systems, Or Akiva, Israel) plus oral aspirin once daily for 2 weeks after surgery. One compression sleeve was placed on the nonoperative extremity during surgery and then sleeves were used on both legs immediately after surgery.
Either 81 or 325 mg aspirin was given orally each day. Eight patients received mechanical compression alone as a result of a history of aspirin intolerance and were included in this study group. For the remainder of the patients (n = 299), it was intended that all patients were to receive 81 mg aspirin daily; however, 57 patients (19%) inadvertently received 325 mg once daily.
No other changes occurred in the postoperative protocols between groups except the VTE prophylaxis protocol, including the type of anesthesia or the physical therapy or pain protocols. The two senior authors (NJG, STW) were the surgeons in all cases and both used the same surgical approaches (posterolateral for hips and a nonminimally invasive surgical technique for both hips and knees). Cementless fixation was used in all hips and all knees had cemented posterior-stabilized designs. All patients had a drain that was removed on the first postoperative day and no patient in either group was treated with tranexamic acid therapy.
The proportion of patients in each group experiencing bleeding complications and hospital readmissions for bleeding reasons within 6 weeks were compared in this retrospective study. A bleeding complication was defined as (1) a wound hematoma that required a prolonged hospital stay (> 3 days); (2) prolonged wound drainage that persisted > 5 days or that led to a superficial or deep infection; or (3) a systemic bleeding episode involving either the urinary or gastrointestinal tracts. These endpoints were assessed by the attending surgeons. The development of a pulmonary embolus diagnosed by CT angiography or a deep venous thrombosis diagnosed by ultrasound was noted for all patients, but VTE surveillance was not performed routinely.
There were no differences between the VTE treatment groups with regard to age, sex, or body mass index (Table 1).
Table 1.
Patient demographics
Statistical Analysis
Statistical analysis was performed using SAS software, Version 9.2 (SAS Institute Inc, Cary, NC, USA). Descriptive statistics were reported using mean (range) and frequency (percentage). A two-sample t-test was used to compare differences in continuous variables between the LMWH and mechanical compression groups. Chi-square tests were used when comparing categorical variables between both groups.
Fisher’s exact test was used to compare the frequency of complications, readmissions, wound complications, and VTE events. The α level was set at 0.05 for statistical significance.
Results
For the THA cohort, there was no difference in the frequency of readmission for a bleeding complication (wound or systemic) between the two groups (2.6% for LMWH versus 0.9% for mobile compression; p = 0.57; odds ratio [OR], 2.9; confidence interval [CI], 0.26–32.5) (Table 2). For the TKA cohort, readmission within 6 weeks of surgery because of a bleeding complication, wound infection caused by prolonged wound drainage, or the development of a VTE was more frequent in the LMWH group (6.8% for LMWH versus 1.5% for mobile compression; p = 0.015; OR, 4.8; CI, 1–67.7) (Table 3).
Table 2.
THA results
Table 3.
TKA results
Patients undergoing THA treated with LMWH had a higher wound bleeding complication frequency (9.2% for LMWH versus 0.9% for mechanical compression; p = 0.009; OR, 10.9; CI, 1.3–90.2) (Table 2).
Similarly for the TKA cohort, there was a higher frequency of wound bleeding complications or infection in the LMWH group compared with those patients in the mobile compression group (3.9% for LMWH versus 0.5% for mobile compression; p = 0.028; OR, 8.2; CI, 1–67.7) (Table 3).
Specifically, for the patients undergoing TKA treated with LMWH, the frequency of systemic bleeding or a complication secondary to LMWH administration (nephrotoxicity from dalteparin in one patient) was greater compared with the mobile compression group (2.8% for LMWH versus 0% the mobile compression; p = 0.022; OR, 12.8; CI, 0.7–234.2) (Table 3).
There was no difference in the rate of symptomatic VTE disease between either group for the THA cohort (2.6% for the LMWH group versus 1.9% for the mechanical compression group; p = 1) and for the TKA cohort (1.1% versus 0%, respectively; p = 0.22) (Tables 2, 3).
Discussion
VTE prophylaxis for patients undergoing THA and TKA includes both oral and parenteral chemotherapeutic drugs as well as mechanical prophylaxis. Chemoprophylaxis is effective in the prevention of venous thromboembolism [11], but the benefits in efficacy of anticoagulants must be weighed against the potentially serious risks from postoperative bleeding that include prolonged wound drainage, infection, reoperation, and readmission [15, 19]. The results of our study indicate that (1) the frequency of VTE and bleeding-related hospital readmissions was approximately five times higher in patients undergoing TKA treated with LMWH versus mechanical compression plus aspirin but no difference was noted in patients undergoing THA; (2) the incidence of wound bleeding complications was approximately 11 times higher in patients undergoing THA and approximately eight times higher in patients undergoing TKA treated with LMWH versus mechanical compression plus aspirin; (3) the incidence of systemic bleeding events and complications resulting from chemical prophylaxis was approximately 13 times higher in patients undergoing TKA treated with LMWH versus mechanical compression plus aspirin; and (4) there was no difference in the rate of symptomatic VTEs between LMWH and mechanical compression plus aspirin in patients undergoing THA and TKA.
This study has definite limitations. It is retrospective in nature and data collection was performed through electronic chart review. However, the Veterans Administration (VA) system has been an early adopter and leader in the use of electronic medical records and it is unlikely that we have under- or overreported the rates of readmission and complications because, in general, VA patients do not have ready access to civilian medical resources and typically followup within the VA system. Although we report and compare VTE rates between the LMWH and mechanical compression groups, the study is underpowered to detect any meaningful differences. The outcomes with regard to VTEs was not a focus of our study and we refer to a 2014 registry study by Colwell et al. of > 3000 hip and knee patients who had portable mechanical compression with or without aspirin [2]. They found that the efficacy of mobile compression was noninferior to that of two oral antithrombin XI drugs, warfarin and LMWH, with respect to both patients undergoing THA and those undergoing TKA. We also note that within the mobile compression group, different dosages of aspirin were used with 19% of eligible patients receiving 325 mg once daily despite the surgeon’s preference for 81 mg once daily. The significance of this with regard to VTEs and bleeding complications remains unclear, but in a previous study by Colwell et al. [3], 63% of patients within the mobile compression group were allowed additional daily use of 81 mg aspirin, whereas the remainder of patients received no chemical VTE prophylaxis at all. The authors noted no difference in VTE rates in patients treated with mobile compression with or without the use of daily aspirin, but acknowledge that the study was underpowered to come to a conclusion. In a more recent retrospective study by Park et al., 375 patients undergoing TKA were treated with mechanical compression only for 10 to 14 days compared with 401 patients undergoing TKA treated with mechanical compression plus LMWH [17]. Their results showed no differences in VTE rates between both groups but increased rates of hematomas and postoperative Hemovac drainage in patients who were treated with LMWH in addition to mechanical compression. Our study did not attempt to study the individual effects of either mobile compression or aspirin alone. We also did not perform an a priori power analysis to determine the sample size. Another limitation was that the patient population analyzed in this study was overwhelmingly male, reflecting the sex distribution of patients undergoing total joint arthroplasty at VA medical centers. Lack of social support, psychiatric illness, and an increased comorbidity burden are known factors that distinguish the VA patient population from the community patient population [20, 22]. These factors may contribute to increased complication and readmission rates and, therefore, the results of this study may not be applicable to other patient populations [4, 21]. Nevertheless, the results can give us some insight into outcomes of THA and TKA in this challenging patient population.
Most prior studies lack a detailed comparison of bleeding complications and readmission data related to the various modes of prophylaxis and have rather focused on prevention of deep vein thromboses (DVTs). With regard to hospital readmission as a result of major bleeding events, Colwell et al. noted a 6% major bleeding rate in patients undergoing THA who were treated with LMWH compared with a 0% major bleeding rate in patients treated with mobile mechanical compression with or without oral aspirin [3]. The rates of complications and readmissions that our patients experienced with LMWH prophylaxis before changing our protocol were similar to those reported by Burnett et al. [1]. Our results expand on the TKA patient population indicating that utilization of mobile mechanical compression decreases the rate of hospital readmissions as a result of bleeding complications, wound infection, and symptomatic VTEs in standard-risk patients undergoing TKA. To our knowledge, no other study reports on these findings specifically.
With regard to wound bleeding complications, we are not aware of any studies that directly compare patients undergoing THA and those undergoing TKA treated with LMWH versus mechanical compression plus oral aspirin. As mentioned previously, Park et al. noted a 4% hematoma rate in 401 patients undergoing TKA treated with mechanical compression and LMWH versus no hematoma formation in 375 patients undergoing TKA treated with mobile mechanical compression alone [17]. Nam et al. enrolled 1502 patients in anticipation of primary and revision THA and TKA, unicompartmental knee arthroplasty, and surface arthroplasty [16]. Their group risk-stratified all patients into routine-risk and high-risk patients for VTE. Routine-risk patients received a mobile compression device for 10 days in addition to 325 mg aspirin twice daily for 6 weeks. High-risk patients were placed on warfarin for an international normalized ratio goal of 1.8 to 2.2. The results of the study showed that routine-risk patients with VTE on aspirin and mobile compression had lower rates of wound complications within 2 weeks of surgery and a lower percentage of patients presenting with wound drainage > 7 days.
The same study noted higher rates of systemic bleeding events in high-risk patients with VTE on warfarin compared with routine-risk patients on aspirin plus mobile compression [16]. We acknowledge that the study by Nam et al. does not exactly resemble our patient population, but in general, it appears that switching from a more potent chemical anticoagulant to a less potent one plus mobile mechanical compression will mitigate systemic and local bleeding complications.
Finally, there was no difference in symptomatic VTE rates in our study and because of the numbers of patients available, we cannot confirm the finding that mobile compression with aspirin is noninferior to chemoprophylaxis as noted by Colwell et al. [2] in their multicenter registry study of 3000 hip and knee patients.
Two additional studies looked at the effect of mobile compression and rates of DVTs and pulmonary embolus. Gelfer et al. studied two groups of patients undergoing total joint arthroplasty [10]. One group was treated with mobile compression and 100 mg aspirin daily (61 patients) and the other group was treated with LMWH alone (60 patients). Patients in the mobile compression group had lower rates of venographically detected DVTs (7% versus 28%) at a followup of 5 to 8 days. Multivariate analysis determined that patients on LMWH had a seven times higher likelihood to develop a DVT (95% CI, 1.95-21.4; p = 0.002). Froimson et al. compared the same mobile compression device used in our study in 223 patients with 1354 patients treated with a nonmobile, nonsequential compression device [9]. In addition, both groups received LMWH. Patients in the mobile compression group had lower rates of DVTs (1.3% versus 3.6%) and a decrease in symptomatic pulmonary embolus (0% versus 0.7%).
This study was done because there was a unique opportunity to compare the frequencies of bleeding complications (systemic and local) and its effect on hospital readmission between a chemoprophylaxis regime (LMWH) that at one time was the gold standard for standard-risk patients undergoing THA and TKA with a newer mechanical prophylaxis protocol. Based on our results and other findings in the literature, we believe that there is a role for routine use of mobile mechanical compression devices in the prevention of VTEs and complications associated with more potent chemical anticoagulants. However, more focused randomized clinical trials are needed to validate these findings.
Footnotes
One of the authors (STW) owns stock in the compression device studied in this article (Medical Compression Systems, Inc, Or Akiva, Israel).
All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research® editors and board members are on file with the publication and can be viewed on request.
Clinical Orthopaedics and Related Research® neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDA-approval status, of any drug or device prior to clinical use.
Each author certifies that his institution approved the human protocol for this investigation, that all investigations were conducted in conformity with ethical principles of research, and that informed consent for participation in the study was obtained.
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