Orthopedics

Feature Article 

The Effectiveness of Aspirin for Venous Thromboembolism Prophylaxis for Patients Undergoing Arthroscopic Rotator Cuff Repair

Eric Alyea, DO; Tara Gaston, DO; Luke S. Austin, MD; Charles Wowkanech, BS; Bret Cypel, BS; Manuel Pontes, PhD; Gerald Williams, MD

Abstract

Venous thromboembolic disease (VTED) is a rare complication following arthroscopic rotator cuff repair (RCR). The American Academy of Orthopaedic Surgeons and the American College of Chest Physicians have no prophylaxis guidelines specific to shoulder arthroscopy, yet many surgeons prescribe aspirin following RCR. The purpose of this study was to evaluate the effectiveness of aspirin and mechanical prophylaxis compared with mechanical prophylaxis alone in preventing VTED following RCR. A total of 914 patients underwent RCR between January 2010 and January 2015. A retrospective case-control study was performed. The control group (n=484) consisted of patients treated with compression boots and early mobilization. The study group (n=430) used compression boots, early mobilization, and 81 mg/d of aspirin. The primary outcome was symptomatic VTED, including deep venous thrombosis (DVT) and pulmonary embolism (PE). A total of 7 VTED events occurred during the study period: 6 DVTs and 1 PE; 1 patient experienced both DVT and PE. The percentage of patients with VTED, DVT, and PE was 0.66%, 0.66%, and 0.11%, respectively. There was no significant difference for DVT or PE between the 2 groups. The incidence of DVT and PE was 0.62% and 0.00%, respectively, for the control group (no aspirin) and 0.70% and 0.23%, respectively, for the study group (aspirin). Aspirin does not lead to a clinically significant reduction in either DVT or PE rate in patients undergoing RCR. The authors conclude that the use of mechanical prophylaxis and early mobilization is a sufficient method of VTED prophylaxis in this low-risk population. [Orthopedics. 201x; xx(x):xx–xx.]

Abstract

Venous thromboembolic disease (VTED) is a rare complication following arthroscopic rotator cuff repair (RCR). The American Academy of Orthopaedic Surgeons and the American College of Chest Physicians have no prophylaxis guidelines specific to shoulder arthroscopy, yet many surgeons prescribe aspirin following RCR. The purpose of this study was to evaluate the effectiveness of aspirin and mechanical prophylaxis compared with mechanical prophylaxis alone in preventing VTED following RCR. A total of 914 patients underwent RCR between January 2010 and January 2015. A retrospective case-control study was performed. The control group (n=484) consisted of patients treated with compression boots and early mobilization. The study group (n=430) used compression boots, early mobilization, and 81 mg/d of aspirin. The primary outcome was symptomatic VTED, including deep venous thrombosis (DVT) and pulmonary embolism (PE). A total of 7 VTED events occurred during the study period: 6 DVTs and 1 PE; 1 patient experienced both DVT and PE. The percentage of patients with VTED, DVT, and PE was 0.66%, 0.66%, and 0.11%, respectively. There was no significant difference for DVT or PE between the 2 groups. The incidence of DVT and PE was 0.62% and 0.00%, respectively, for the control group (no aspirin) and 0.70% and 0.23%, respectively, for the study group (aspirin). Aspirin does not lead to a clinically significant reduction in either DVT or PE rate in patients undergoing RCR. The authors conclude that the use of mechanical prophylaxis and early mobilization is a sufficient method of VTED prophylaxis in this low-risk population. [Orthopedics. 201x; xx(x):xx–xx.]

Patients undergoing orthopedic surgery are at risk for venous thromboembolic disease (VTED). It is well documented in major orthopedic surgery, such as total hip arthroplasty, total knee arthroplasty, and hip fracture surgery, that thromboprophylaxis is indicated. In a systematic review evaluating aspirin use for preventing deep venous thrombosis (DVT) following major elective lower limb surgery, 5 of 8 studies found aspirin to be an effective method of DVT prophylaxis. Of 43,012 patients prescribed aspirin postoperatively, 283 (0.66%) went on to have a symptomatic DVT.1 For non-major orthopedic surgery, such as arthroscopic surgery, the use of thromboprophylaxis is not as well studied. Currently, surgeons vary in their thromboprophylaxis following arthroscopic shoulder surgery in the immediate postoperative period and in the first few months following surgery. Therapies range from no prophylaxis to mechanical prophylaxis alone to combined mechanical and chemical prophylaxis.2 To date, no study has evaluated the efficacy of aspirin following arthroscopic rotator cuff repair (RCR).

Expert opinion has been guiding VTED prophylaxis after shoulder arthroscopy. Currently, the American Academy of Orthopaedic Surgeons has no guidelines specific to shoulder arthroscopy.2 This is likely due to the low rate of VTED following arthroscopic shoulder surgery. The rate of VTED after elective shoulder surgery has been reported to range from 0.01% to 5.7%.3–6 Three of these studies reported rates between 0.01% and 0.31%,4–6 whereas Takahashi et al3 reported a rate of 5.7%. A systematic review by Dattani et al4 analyzed 8 articles on shoulder arthroscopy surgery and reported a rate of 0.038%, including both DVT and pulmonary embolism (PE). More than half of the DVTs were in the upper limb.4 Jameson et al5 reported a rate of 0.01% for DVT and PE following 65,302 shoulder arthroscopy surgeries. They found that patients with diabetes or who were older than 70 years were at higher risk of VTED.5 However, they did not report whether any and what type of anticoagulation was used postoperatively. Kuremsky et al6 evaluated 1908 patients who underwent elective shoulder arthroscopy. They reported a rate of 0.31% (6 of 1908) VTED events. All postoperative DVTs occurred on the ipsilateral side of the operative limb, with 3 being upper and 2 being lower limb.6 On the other hand, Takahashi et al3 reported a rate of postoperative VTED events of 5.7%. In that study, each patient's upper and lower limbs were evaluated by ultrasound both pre- and postoperatively. Most of the DVTs were asymptomatic and found in the lower limb.3 The discrepancy in rates of VTED after shoulder arthroscopy is likely because both symptomatic and asymptomatic VTED events were reported by Takahashi et al,3 whereas only symptomatic VTED events were reported in the former 3 studies.4–6 Takahashi et al3 also had a patient population of 175, whereas the other 3 studies had populations of 92,440,4 65,302,5 and 19086 patients. With these larger study populations, it becomes more difficult to obtain pre- and postoperative ultrasound scans of all 4 limbs. The rates may have also been higher if each patient in the other 3 studies had also been checked by ultrasound for asymptomatic DVTs.

Research shows that although VTED is rare after primary shoulder arthroscopy, it is one of the top 3 reasons for hospital readmission following primary shoulder arthroplasty.7,8 To reduce or eliminate VTED following arthroscopic shoulder surgery, many orthopedic surgeons in the authors' and other practices have adopted aspirin as thromboprophylaxis; it was suggested that mechanical prophylaxis combined with aspirin may be adequate for most shoulder arthroscopy patients.2 Aspirin is a suitable agent because it has been shown to be effective in joint arthroplasty,9 is low cost, and is not associated with significant bleeding complications, as compared with more aggressive chemical prophylaxis.10 However, aspirin has unknown efficacy in preventing VTED following arthroscopic shoulder surgery and is associated with potential complications. Although decreased compared with many other prophylactic medications, gastrointestinal discomfort and bleeding are associated with continued use of aspirin. Furthermore, many effective pain medications, such as most nonsteroidal anti-inflammatory medications, are contraindicated during aspirin use. Indeed, it was reported that many members of the American Shoulder and Elbow Surgeons routinely used only mechanical prophylaxis or no prophylaxis for preventing venous thromboembolism after arthroscopic shoulder surgery.2

As the current evidence supporting aspirin as an effective chemoprophylaxis agent for patients undergoing arthroscopic shoulder surgery is limited, this study sought to evaluate the specific need for thromboprophylaxis in patients undergoing elective arthroscopic RCR. The primary aim of this study was to compare the effectiveness of aspirin chemoprophylaxis in combination with mechanical prophylaxis to mechanical prophylaxis alone in preventing VTED. The secondary aim was to ascertain the rate of PE and DVT following arthroscopic RCR.

Materials and Methods

Data Source

After obtaining institutional review board approval, the authors performed a retrospective case-control study of VTED, including DVT and PE, that occurred after arthroscopic RCR surgery. Patient charts were obtained from the database of a regional orthopedic center. Cases of RCR were identified by the presence of the Current Procedural Terminology code 29827.

Study Population

This was a consecutive, retrospective case-control study. Data were collected and evaluated from 914 consecutive RCR surgeries between January 2010 and January 2015 at 2 regional hospitals and 1 associated outpatient surgical center performed by 2 fellowship-trained shoulder and elbow surgeons (L.S.A., G.W.). All identified RCR surgeries that occurred during this period were included in the study.

Patient demographics were obtained from the charts, including age, sex, smoking status, cancer history, primary vs revision repair, and laterality of repair. Smoking status was defined as “former smoker,” “current smoker,” or “never smoked,” although approximately 20% of the patient records did not have smoking status noted. To account for this, the authors created an additional smoking status category—“unknown.” Laterality of repair was included to determine if there was a correlation between the side of the body on which surgery was performed (left vs right) and the side of the body on which a DVT or PE occurred (Table 1).

Preoperative Demographics

Table 1:

Preoperative Demographics

Study Design

The surgical technique did not differ between the 2 surgeons. A standard arthroscopic RCR approach in the beach chair position was used. Intermittent pneumatic compression device sleeves were applied to bilateral lower extremities in the preoperative holding area and removed just prior to discharge. No patient had a significant intraoperative complication.

The decision to place patients in the control group vs the study group was surgeon dependent. In regular practice, the 2 surgeons use different methods of VTED prophylaxis after RCR surgery. This practice was not altered. Those operated on by surgeon A received 81 mg/d of aspirin for 4 weeks, whereas those operated on by surgeon B did not. Both groups used intermittent pneumatic compression devices during the perioperative period, meaning that they were initiated in the preoperative holding area and continued until discharge home less than 24 hours later. Early ambulation was encouraged in both groups. All postoperative complications were identified through review of physician notes at 2- and 6-week and at 3-, 4.5-, and 6-month follow-up visits.

Outcomes

The primary outcome was VTED, including DVT and PE. Venous thromboembolic disease events were recorded up until the 6-month follow-up visit. For each individual VTED event identified, the limb and laterality, postoperative day, and associated symptoms were specified.

Statistical Analysis

Rates of DVT and PE were calculated for each group. Statistical analysis was performed between the control group and the study group to evaluate the effectiveness of aspirin in preventing VTED events after arthroscopic RCR surgery. Further multivariate analysis evaluating risk factors for DVT and PE was performed.

For this research, SAS version 9.4 software (SAS Institute Inc, Cary, North Carolina) was used. The Wilson method was employed to estimate confidence intervals (CIs) for proportions, and the Newcombe method (based on the Wilson score) was employed to estimate CIs for differences in proportions.11,12 For all proportions, CIs with continuity corrections were reported. Odds ratios were estimated with logistic regression, using the Firth method.13

Results

Preoperative demographics were analyzed between the study group (aspirin) and the control group (no aspirin) (Table 1). Mean age and percent revision rate were significantly greater in the study group. The rate of smoking was significantly greater in the control group. Both groups had a low complication rate, and there were no significant differences between the groups (Table 2).

Postoperative Complications

Table 2:

Postoperative Complications

Incidence of VTED, DVT, and PE

In the study group (aspirin), the incidence of DVT was 0.70% (95% CI, 0.18%–2.20%) and the incidence of PE was 0.23% (95% CI, 0.01%–1.49%). In contrast, in the control group (no aspirin), the incidence of DVT was 0.62% (95% CI, 0.16%–1.96%) and the incidence of PE was 0.00% (95% CI, 0.00%–0.98%). For DVT, the risk difference between the study group and the control group was 0.08% (95% CI, −1.36% to 1.65%). For PE, the risk difference between the study group and the control group was 0.23% (95% CI, −0.77% to 1.50%) (Figure 1). A total of 7 venous thromboembolic events occurred during the study period: 6 DVTs and 1 PE. Three of the DVTs were found in the operative upper extremity. The other 3 DVTs were found in the lower extremity, with 2 of the 3 being on the ipsilateral side of surgery (Table 3). Of note, the 1 PE that did occur was not an isolated event, but instead was found concomitantly with a lower extremity DVT on the contralateral side of surgery. Results of penalized logistic regression (Firth method) showed that the odds ratio for the effect of aspirin was 1.13 (95% CI, 0.24–5.33; P=.88) for DVT and 3.38 (95% CI, 0.18–494.36; P=.45) for PE. Thus, there was no significant difference in the rate of DVT or PE between the study group and the control group in this pool of patients.

Rate of venous thromboembolic disease (deep venous thrombosis [DVT], pulmonary embolism [PE], or both) in the study group (aspirin) vs the control group (no aspirin). A single patient in the study group was found to have a DVT and an associated PE. The PE was not an isolated event. Thus, the rate of DVT is equal to the rate of venous thromboembolic disease. Abbreviation: VTE, venous thrombosis.

Figure 1:

Rate of venous thromboembolic disease (deep venous thrombosis [DVT], pulmonary embolism [PE], or both) in the study group (aspirin) vs the control group (no aspirin). A single patient in the study group was found to have a DVT and an associated PE. The PE was not an isolated event. Thus, the rate of DVT is equal to the rate of venous thromboembolic disease. Abbreviation: VTE, venous thrombosis.

Venous Thromboembolic Disease Events

Table 3:

Venous Thromboembolic Disease Events

Discussion

On the basis of this study of 914 patients, the addition of 81 mg/d of aspirin for 4 weeks did not reduce the odds of a thromboembolic event following arthroscopic RCR. The study group, receiving aspirin chemoprophylaxis as well as mechanical bilateral compression boots, had an incidence rate of 0.70% for DVT and 0.23% for PE (3 patients with DVT, with 1 also having a PE). Bleeding events, peptic ulceration, and gastric irritation were among the complications experienced more frequently by the study group than by the control group, although these data were not statistically significant. The control group, receiving only mechanical prophylaxis with compression boots, had an incidence rate of 0.62% for DVT and 0.00% for PE. These data suggest that the addition of aspirin chemoprophylaxis does not provide a protective effect of reducing the incidence of VTED, nor is it without risk. In this study, the use of aspirin resulted in a nonsignificant increase in complications, thus reiterating the benign nature of aspirin use. However, the sample size was underpowered to detect significant differences given the low rates of complications in the study and control groups. A sample size in excess of 300,000 would be needed to have adequate power to detect significant differences.14

The American Academy of Orthopaedic Surgeons and the American College of Chest Physicians currently have no recommendations for prophylaxis for patients undergoing upper limb surgery.15 Guidelines from the National Institute for Clinical Excellence recommend no routine prophylaxis for upper limb surgery, whereas the Scottish Intercollegiate Guidelines Network recommends that patients undergoing “less invasive” orthopedic procedures, such as arthroscopy, be assessed for their risk of developing VTED and that prophylaxis be administered accordingly.16 The Japanese Circulation Society suggested in their 2009 recommendations that patients undergoing upper extremity surgery are not at risk for DVT if no risk factors exist.3 Finally, many members of the American Shoulder and Elbow Surgeons routinely use no prophylaxis for prevention of venous thromboembolism after shoulder arthroscopy.2

Multiple studies have indicated a low rate of VTED following shoulder arthroscopy. The VTED burden in the current study fell within the range of incidence of DVT and PE reported in prior studies,3–6 with a DVT rate of 0.70% in the study group compared with 0.62% in the control group (P=.88) and a PE rate of 0.23% in the study group vs 0.00% in the control group (P=.71). The low rate of VTED in this study, and that in the current literature, calls into question any routine use of aspirin prophylaxis in addition to mechanical prophylaxis following arthroscopic RCR, as it is unlikely to lead to any clinically significant difference in VTED.

There is a scarcity of recommendations specific to prophylaxis for patients undergoing upper extremity arthroscopic surgery. As such, many of the current prophylaxis regimens are based on data from studies of hip and knee arthroplasty, for which the risk of VTED is arguably greater than with upper extremity surgery, let alone arthroscopic procedures. There is also limited evidence regarding VTED prophylaxis following lower extremity arthroscopy. A single randomized control study compared low-molecular-weight heparin with no prophylaxis following knee arthroscopy. It was concluded that low-molecular-weight heparin was an effective and safe form of chemical prophylaxis against DVT and PE following knee arthroscopy.17 Both DVT and PE were assessed by ultrasound postoperatively, regardless of whether the patient was symptomatic. When using the preceding lower limb arthroplasty and arthroscopy studies to help guide VTED prophylaxis following shoulder arthroscopy, it is likely that overtreatment would occur and that patients would be unnecessarily exposed to the inherent risks of anticoagulation.

Aspirin was chosen as the chemical prophylactic for a few reasons. Aspirin is a cost-effective medication that can be easily obtained at any pharmacy. Regarding patient compliance and reducing the cost burden on patients, this seemed to be within reason. In addition, 81 mg of aspirin has been studied in hip and knee arthroplasty as an effective method of anticoagulation postoperatively.9,10,15,18 Finally, aspirin is a relatively safe medication, with most side effects involving gastrointestinal disturbance. Of note, 1 patient in the study group developed peptic ulceration, as revealed by upper endoscopy, and 3 individuals developed severe dyspepsia, all of which resolved after discontinuation of aspirin therapy. Also, bleeding/hematoma did occur in 2 of the patients in the study group.

This study had some limitations. Despite there being a large cohort of 914 patients, this study was underpowered. Because of the relatively rare outcomes of DVT and PE and the negligible difference in DVT rates between the study group and the control group, a larger sample would be required to determine statistical significance. Despite this large cohort, aspirin did not show any clinical benefits for reducing the incidence of VTED, and it placed patients at a higher risk of gastrointestinal complications compared with the control. However, neither the rate of VTED nor the rate of postoperative complications, including bleeding and gastrointestinal disturbance, was statistically significantly different between the 2 groups (Table 2). It is possible that the effectiveness of aspirin was compromised in the study group because these patients were older and had longer operative times, as more of their surgeries were revisions. Owing to the low incidence of DVT in both the study group and the control group, this study had limited power to detect whether revision surgery, patient age, or surgical time was significantly related to the incidence of venous thromboembolism. Further, only symptomatic thromboembolic events were identified; as most DVTs are asymptomatic, it is possible that VTED was underreported.19 This study was unable to identify all risk factors for VTED. The risk factors identified included age, revision surgery, smoking history, and cancer. The study group was significantly older and had a greater number of revision surgeries. The control group had significantly greater proportions of current and former smokers. This study did not account for many inherited and acquired hypercoaguable states that place an individual at increased risk for developing a DVT or PE.2,20 Finally, this was a nonrandomized study. Each study arm was based on a single surgeon's routine practice for VTED prophylaxis. Although the rate of VTED was similar to those reported in other studies, it is possible that other surgeon-specific factors may play a role in this rate.

Conclusion

The purpose of this study was to evaluate the effectiveness of aspirin as chemical thromboprophylaxis for patients undergoing arthroscopic RCR. No standard protocol currently exists to guide surgeons in choosing prophylactic measures specific to patients undergoing arthroscopic upper extremity surgery. On the basis of the results of this study and a thorough evaluation of the literature, the authors cannot recommend aspirin administration for routine VTED prophylaxis following arthroscopic RCR.

References

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Preoperative Demographics

CharacteristicControl GroupStudy GroupP
Patients, No.484430NA
Age, mean (range), y57.7 (29–78)59.1 (22–82).01
Male64.46%65.58%.73
Right cuffa61.90%61.45%.89
Cancer history6.40%4.65%.71
Smoker8.68%3.72%.00
Revision1.86%4.67%.02

Postoperative Complications

ComplicationNo. of PatientsOdds Ratio (95% Confidence Interval)P

Control Group (N=484)Study Group (N=430)
Acute infection362.11 (0.59–8.90).26
Deep venous thrombosis331.13 (0.24–5.33).88
Wound drainage331.13 (0.24–5.33).88
Ecchymosis221.13 (0.02–7.31).89
Hematoma/bleeding121.88 (0.25–20.61).54
Heart attack100.37 (0.00–7.04).55
Gastrointestinal tract037.93 (0.77–>999.99).17
irritation
Urinary tract infection013.38 (0.18–494.36).46
Pulmonary embolism013.38 (0.18–494.36).46
Peptic ulcer013.38 (0.18–494.36).46
Hyperhidrosis013.38 (0.18–494.36).46

Venous Thromboembolic Disease Events

Patient No.LocationOperative ArmDays PostoperativeDetectionPulmonary EmbolismSymptomsRisk FactorsTreatment
1Right upper extremityYes8UltrasoundNoSwelling, painNAEnoxaparin sodium and warfarin sodium
2Right upper extremityYes9UltrasoundNoSwelling, edema70 years oldWarfarin sodium
3Right upper extremityYes17UltrasoundNoSwelling, edemaHistory of pulmonary embolismEnoxaparin sodium
4Left upper extremityYes18UltrasoundNoSwellingHigh blood pressure, high cholesterolRivaroxaban
5Right lower extremityNo43UltrasoundNoSwellingNARivaroxaban
6Right lower extremityNo10UltrasoundYesSwelling, shortness of breathNARivaroxaban
Authors

The authors are from the Department of Orthopaedic Surgery (EA, TG), Rowan University School of Osteopathic Medicine, Stratford; The Rothman Institute (LSA, CW, BC, GW), Egg Harbor Township; and the Department of Marketing (MP), Rowan University, Glassboro, New Jersey.

The authors have no relevant financial relationships to disclose.

Correspondence should be addressed to: Tara Gaston, DO, Department of Orthopaedic Surgery, Rowan University School of Osteopathic Medicine, One Medical Center Dr, Academic Center, Ste 162, Stratford, NJ 08084 ( tara.gaston88@gmail.com).

Received: April 18, 2018
Accepted: August 17, 2018

10.3928/01477447-20181227-05

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