Total hip replacement, lower limb blood flow and venous thrombogenesis

Effects of intermittent pneumatic compression on femoral vein peak venous velocity during active ankle exercise

INTRODUCTION

The risk of developing deep vein thrombosis (DVT) is high even after the period of bed rest following major general surgery including total joint arthroplasty (TJA). Mobile intermittent pneumatic compression (IPC) devices allow the application of IPC during postoperative exercise. Although ambulation included ankle movement, no reports have been made regarding the effects of IPC during exercise, including active ankle exercise (AAE), on venous flow. This study was performed to examine whether using a mobile IPC device can effectively augment the AAE-induced increase in peak velocity (PV).

METHODS

PV was measured by Doppler ultrasonography in the superficial femoral vein at rest, during AAE alone, during IPC alone, and during AAE with IPC in 20 healthy subjects in the sitting position. PV in AAE with IPC was measured with a mobile IPC device during AAE in the strong compression phase. AAE was interrupted from the end of the strong compression phase to minimize lower limb fatigue.

RESULTS

AAE with IPC (76.2 cm/s [95%CI, 69.0-83.4]) resulted in a significant increase in PV compared to either AAE or IPC alone (47.1 cm/s [95%CI, 38.7-55.6], p < 0.001 and 48.1 cm/s [95%CI, 43.7-52.4], p < 0.001, respectively).

DISCUSSION

Reduced calf muscle pump activity due to the decline in ambulation ability reduced venous flow. Therefore, use of a mobile IPC device during postoperative rehabilitation in hospital and activity including self-training in an inpatient ward may promote venous flow compared to postoperative exercise without IPC.

CONCLUSION

Use of a mobile IPC device significantly increased the PV during AAE, and simultaneous AAE with IPC could be useful evidence for the prevention of DVT in clinical settings, including after TJA.

The Role of Intraoperative Intermittent Pneumatic Compression Devices in Venous Thromboembolism Prophylaxis in Total Hip and Total Knee Arthroplasty

Venous thromboembolism (VTE) is a common complication after total hip arthroplasty (THA) and total knee arthroplasty (TKA), occurring in up to 85% of patients who are not treated with prophylaxis. The initiation of VTE development may occur intraoperatively. This study investigated whether this gap in VTE prophylaxis can be addressed by the use of intraoperative intermittent pneumatic compression devices (IPCDs) and if intraoperative IPCDs have a meaningful benefit in preventing symptomatic VTE. The authors defined symptomatic VTE as deep venous thrombosis in either lower extremity or a pulmonary embolism. The authors evaluated the medical records of 3379 patients who underwent THA or TKA at their institution in 2014 and 2015. Effects of various factors, including age, sex, body mass index, and smoking status, were compared between these 2 cohorts. Patients who experienced a symptomatic VTE were also matched by age, sex, and procedure type with randomly selected controls. In the patient sample, 47 patients (1.4%) developed VTE. Forty (1.2%) of these patients underwent TKA, whereas 7 (0.2%) underwent THA. Venous thromboembolism occurred less frequently in patients who received intraoperative IPCDs (0.8%) than in patients who did not receive them (1.5%); however, this difference did not reach statistical significance. Total knee arthroplasty was associated with increased odds of VTE compared with THA, as was female sex. These results did not show a statistically significant benefit to the intraoperative use of IPCDs. Pneumatic compression remains a fast, easy, low-cost, low-risk, intuitive intervention that can supplement the postoperative multimodal approach and is worthy of further study. Intraoperative IPCD use should be considered for patients with a higher risk of VTE. [Orthopedics. 2018; 41(1):e98-e103.].

Venous Hemodynamics After Total Hip Arthroplasty: A Comparison Between Portable vs Stationary Pneumatic Compression Devices and the Effect of Body Position

BACKGROUND

Improvements in device design have allowed for portable pneumatic compression devices (PPCDs). However, portability results in smaller pumps that move less blood. Additionally, although patients often stand when wearing PPCDs, few studies have evaluated the hemodynamic effects of PCDs while standing.

METHODS

A crossover study was performed to compare a PPCD (ActiveCare+S.F.T.; Medical Compression Systems, Or Akiva, Israel) to a stationary pneumatic compression device (SPCD) (VenaFlow; DJO Global, Carlsbad, CA) on hemodynamics in supine and standing positions among 2 cohorts composed of 10 controls and 10 total hip arthroplasty patients. Differences in baseline peak venous velocity (PVV), PVV with each PCD, and delta PVV with each PCD were assessed. A multivariate analysis was performed to examine differences between cohorts, devices, and position.

RESULTS

In both positions, the SPCD demonstrated a larger change in PVV when compared to the PPCD (P < .001). The total hip arthroplasty group had a greater delta PVV while standing when considering both PCDs together (P < .001). When considering both cohorts, delta PVV was greater while standing, only when the SPCD was used (P < .001). There was no difference between standing and supine positions when the PPCD was used.

CONCLUSION

The SPCD demonstrated a greater capacity to increase PPV in the supine and standing positions. The SPCD generated greater values of PVV and delta PVV in the standing position. Although these results demonstrate a difference between devices, it is important to establish the PVV necessary to prevent VTE before one is considered more effective.

Venous and arterial thrombosis – pathogenesis and the rationale for anticoagulation

Thromboembolic disorders are major causes of morbidity and mortality. It is well-recognised that the pathogenesis is different for arterial and venous thrombosis; however, both involve coagulation activation. Anticoagulants are used for the prevention and treatment of a wide variety of thromboembolic and related conditions. Agents with anti-inflammatory properties in addition to anticoagulation may be particularly beneficial. Traditional anticoagulants, although effective, are associated with certain limitations. Understanding the pathological processes associated with thrombosis and the rational target for anticoagulation is essential, not only for the development of safer and more effective agents, but also for better clinical management of patients who require anticoagulation therapy. In recent years, new oral agents that target single enzymes of the coagulation cascade have been developed – some of those are in advanced stages of clinical development. Based on scientific rationale, both factor Xa and thrombin are viable targets for effective anticoagulation.

Intense Triceps Surae Contraction Increases Lower Extremity Venous Blood Flow

Objective

Venous thromboembolism can be prevented by physical prophylaxis, such as active ankle exercise (AAE), in addition to pharmacological treatment. However, the relationship between the intensity of triceps surae (TS) exercise and venous flow is unclear, and physical thromboprophylaxis has not been established for patients with leg cast immobilization. The goals of the current study were to clarify the degree of intensity of TS isotonic contraction required to increase peak blood velocity (PV) in the superficial femoral vein to higher than that at no resistance and to determine if TS isometric contraction can increase PV.

Methods

A prospective, nonrandomized, controlled trial was performed in 20 healthy young adult men. PVs at rest and during one TS isotonic or isometric contraction were measured using Doppler ultrasonography. Isotonic contraction intensity was defined as no resistance with contraction of maximum effort and 25%, 50%, 75%, and 100% of one repetition maximum (1RM). Isometric contraction intensity was defined as 15-35%, 40-60%, 65-85%, and 90-100% of the maximal voluntary contraction.

Results

Isotonic contraction at 75% 1RM (51.4 cm/s [95% CI, 40.1-62.6]) and 100% 1RM (54.9 cm/s [95% CI, 43.1-66.7]) significantly increased PV compared to that with no resistance (41.0 cm/s [95% CI, 32.2-49.8]) (P=0.005, 0.001, respectively). Isometric contraction increased PV significantly at all intensities (all P≤0.002).

Conclusions

Applying resistance at ≥75% 1RM increases venous flow and enhances the effect of AAE with TS isotonic contraction. TS isometric contraction may serve as thromboprophylaxis for patients undergoing leg cast immobilization.

Impact of Active Ankle Movement Frequency on Velocity of Lower Limb Venous Flow following Total Hip Arthroplasty

Background. Although active ankle movement plays a predominant role in mechanical thromboprophylaxis following total hip arthroplasty (THA), the most effective frequency of movement remains unclear. Materials and Methods. In 29 consecutive patients undergoing THA, the velocity of blood flow in the profunda femoris was measured after various frequencies of ankle movement two days after THA using a pulse wave Doppler ultrasound system. To test the interobserver reliabilities for the velocity measured with Doppler ultrasound system, the intraclass correlation coefficient was calculated based on the measurement in 10 limbs of healthy volunteers. Results. At 0, 1, and 2 minutes after ankle movement, the velocity after movement at 60 contractions per minute was significantly faster than that after movement at 40 or 80 contractions per minute (p = 0.0007, repeated-measures analysis of variance). The intraclass correlation coefficient score in two investigators was 0.849 (95% confidence interval, 0.428 to 0.962). Conclusions. Active ankle movement at 60 contractions per minute is recommended in patients receiving THA to obtain optimal venous blood flow.

Optimal Duration for Prophylaxis of Deep Vein Thrombosis: The New Focus?

It is usual to stop prophylaxis of most surgical patients at hospital discharge. However, there is increas ing evidence that some patients are at risk of thromboem bolism after treatment is stopped. Some evidence and several proposals from the literature are presented, but to date, the situation remains unclear.

Different types of intermittent pneumatic compression devices for preventing venous thromboembolism in patients after total hip replacement

BACKGROUND

Total hip replacement (THR) is an effective treatment for reducing pain and improving function and quality of life in patients with hip disorders. While this operation is very successful, deep vein thrombosis (DVT) and pulmonary embolism (PE) are significant complications after THR. Different types of intermittent pneumatic compression (IPC) devices have been used for thrombosis prophylaxis in patients following THR. Available devices differ in compression garments, location of air bladders, patterns of pump pressure cycles, compression profiles, cycle length, duration of inflation time and deflation time, or cycling mode such as automatic or constant cycling devices. Despite the widely accepted use of IPC for the treatment of arterial and venous diseases, the relative effectiveness of different types of IPC systems as prophylaxis against thrombosis after THR is still unclear.

OBJECTIVES

To assess the comparative effectiveness and safety of different IPC devices with respect to the prevention of venous thromboembolism in patients after THR.

SEARCH METHODS

For this update the Cochrane Peripheral Vascular Diseases Group Trials Search Coordinator searched the Specialised Register (November 2014), CENTRAL (2014, Issue 10). Clinical trial databases were searched for details of ongoing and unpublished studies. Reference lists of relevant articles were also screened. There were no limits imposed on language or publication status.

SELECTION CRITERIA

Randomized and quasi-randomized controlled studies were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, assessed trials for eligibility and methodological quality, and extracted data. Disagreement was resolved by discussion or, if necessary, referred to a third review author.

MAIN RESULTS

Only one quasi-randomized controlled study with 121 study participants comparing two types of IPC devices met the inclusion criteria. The authors found no cases of symptomatic DVT or PE in either the calf-thigh compression group or the plantar compression group during the first three weeks after the THR. The calf-thigh pneumatic compression was more effective than plantar compression for reducing thigh swelling during the early postoperative stage. The strength of the evidence in this review is weak as only one trial was included and it was classified as having a high risk of bias.

AUTHORS' CONCLUSIONS

There is a lack of evidence from randomized controlled trials to make an informed choice of IPC device for preventing venous thromboembolism (VTE) following total hip replacement. More research is urgently required, ideally a multicenter, properly designed RCT including a sufficient number of participants. Clinically relevant outcomes such as mortality, imaging-diagnosed asymptomatic VTE and major complications must be considered.

Effect of post-discharge venous thromboembolism on hospital quality comparisons following hip and knee arthroplasty

BACKGROUND

Symptomatic pre-discharge venous thromboembolism (VTE) rates after total or partial hip or knee arthroplasty have been proposed as patient safety indicators. However, assessing only pre-discharge VTE rates may be suboptimal for quality measurement as the duration of stay is relatively short and the VTE risk extends beyond the inpatient setting.

METHODS

Patients who underwent total or partial hip or knee arthroplasty were identified in the 2008 through 2010 American College of Surgeons (ACS) National Surgical Quality Improvement Program (NSQIP) database. Outcomes of interest were the deep venous thrombosis (DVT), pulmonary embolism (PE), and overall VTE rates within thirty days after surgery and the rates during the pre-discharge and post-discharge portions of this time period. Risk-adjusted hospital rankings based on only pre-discharge (inpatient) events were compared with those based on both pre-discharge and post-discharge events within thirty days of surgery.

RESULTS

A total of 23,924 patients underwent total or partial hip arthroplasty (8499) or knee arthroplasty (15,425) at ninety-five hospitals. For hip arthroplasty, the VTE rate was 0.9%, with 57.9% of the events occurring after discharge. For knee arthroplasty, the VTE rate was 1.9%, with 38.3% of the events occurring after discharge. The median time of VTE occurrence was eleven days postoperatively for hip arthroplasty and three days for knee arthroplasty. The median duration of stay was three days for both hip and knee arthroplasty. When hospitals were ranked according to VTE rates, hospital outlier status designations changed when post-discharge events were included (κ = 0.386; 44% false-positive rate for low outliers). The median change in hospital quality ranking was 7 (interquartile range, 2 to 17), with a rank correlation of r = 0.82.

CONCLUSIONS

Nearly twice as many VTE complications were captured if both pre-discharge and post-discharge events were considered, and inclusion of post-discharge events changed hospital quality rankings. These data suggest that inclusion of post-discharge events should be considered when comparing the quality of hospitals on the basis of postoperative VTE rates.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Review article: Venous thromboembolism after total joint replacement

Venous thromboembolism can occur in up to 84% of cases following total joint replacement. It can result in pain, swelling, chronic post-thrombotic syndrome, and pulmonary embolism. Its prevention is vital to the success of the surgery. To achieve a safe and effective prophylaxis, a combination of mechanical and pharmacologic agents should be used. New generation of thromboprophylactic agents target different factors of the coagulation pathway.

Symptomatic venous thromboembolism and mortality in orthopaedic surgery - an observational study of 45 968 consecutive procedures

Background

Little information exists on the presentation of symptomatic venous thromboembolism (VTE) in orthopaedic surgery when a defined protocol for thromboprophylaxis is used. The objective with this study was to establish the VTE rate and mortality rate in orthopaedic surgery.

Methods

We performed a prospective, single centre observational cohort study of 45 968 consecutive procedures in 36 388 patients over a 10 year period. Follow-up was successful in 99.3%. The primary study outcome was the incidence of symptomatic deep vein thrombosis (DVT), symptomatic pulmonary embolism (PE) and mortality at 6 weeks, specified for different surgical procedures. The secondary outcome was to describe the DVT distribution in proximal and distal veins and the proportion of VTEs diagnosed after hospital discharge. For validation purposes, a retrospective review of VTEs diagnosed 7–12 weeks postoperatively was also performed.

Results

In total, 514 VTEs were diagnosed (1.1%; 95% CI: 1.10-1.14), the majority (84%) after hospital discharge (432 out of 514).With thromboprophylaxis, high incidence of VTE was found after internal fixation (IF) of pelvic fracture (12%; 95% CI: 5–26), knee replacement surgery (3.7%; 95% CI: 2.8-5.0), after internal fixation (IF) of proximal tibia fracture (3.8%; 95% CI: 2.3-6.3) and after IF of ankle fracture (3.6%; 95% CI: 2.9-4.4). Without thromboprophylaxis, high incidence of VTE was found after Achilles tendon repair (7.2%; 95% CI: 5.5-9.4). In total 1094 patients deceased (2.4%; 95% confidence interval (CI): 2.33- 2.44) within 6 weeks of surgery. Highest mortality was seen after lower limb amputation (16.3%, CI: 13.8-19.1) and after hip hemiarthroplasty due to hip fracture (9.6%, CI; 7.6-12.1).

Conclusion

The overall incidence of VTE is low after orthopaedic surgery but our study highlights surgical procedures after which the risk for VTE remains high and improved thromboprophylaxis is needed.

Different types of intermittent pneumatic compression devices for preventing venous thromboembolism in patients after total hip replacement

BACKGROUND

Total hip replacement (THR) is an effective treatment for reducing pain and improving function and quality of life in patients with hip disorders. While this operation is very successful, deep vein thrombosis (DVT) and pulmonary embolism (PE) are significant complications after THR. Different types of intermittent pneumatic compression (IPC) devices have been used for thrombosis prophylaxis in patients following THR. Available devices differ in compression garments, location of air bladders, patterns of pump pressure cycles, compression profiles, cycle length, duration of inflation time and deflation time, or cycling mode such as automatic or constant cycling devices. Despite the widely accepted use of IPC for the treatment of arterial and venous diseases, the relative effectiveness of different types of IPC systems as prophylaxis against thrombosis after THR is still unclear.

OBJECTIVES

To assess the comparative effectiveness and safety of different IPC devices with respect to the prevention of venous thromboembolism in patients after THR.

SEARCH METHODS

The Cochrane Peripheral Vascular Diseases Group Trials Search Coordinator searched the Specialised Register (May 2012), CENTRAL (2012, Issue 4), MEDLINE (April Week 3 2012) and EMBASE (Week 17 2012). Clinical trial databases were searched for details of ongoing and unpublished studies. Reference lists of obtained articles were also screened. There were no limits imposed on language or publication status.

SELECTION CRITERIA

Randomized and quasi-randomized controlled studies were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, assessed trials for eligibility and methodological quality, and extracted data. Disagreement was resolved by discussion or, if necessary, referred to a third review author.

MAIN RESULTS

Only one quasi-randomized controlled study with 121 study participants comparing two types of IPC devices met the inclusion criteria. The authors found no cases of symptomatic DVT or PE in either the calf-thigh compression group or the plantar compression group during the first three weeks after the THR. The calf-thigh pneumatic compression was more effective than plantar compression for reducing thigh swelling during the early postoperative stage. The strength of the evidence in this review is weak as only one trial was included and it was classified as having a high risk of bias.

AUTHORS' CONCLUSIONS

There is a lack of evidence from randomized controlled trials to make an informed choice of IPC device for preventing venous thromboembolism (VTE) following total hip replacement. More research is urgently required, ideally a multicenter, properly designed RCT including a sufficient number of participants. Clinically relevant outcomes such as mortality, imaging-diagnosed asymptomatic VTE and major complications must be considered.

Impact of venous thromboembolism on clinical management and therapy after hip and knee arthroplasty

Postoperative deep vein thrombosis (DVT) occurs most often in the large veins of the legs in patients undergoing major joint arthroplasty and major surgical procedures. These patients remain at high risk for venous thromboembolic events. In patients undergoing total hip or total knee arthroplasty (THA or TKA, respectively), different patterns of altered venous hemodynamics and hypercoagulability have been found, thus the rate of distal DVT is higher than that of proximal DVT after TKA. In addition, symptomatic venous thromboembolism (VTE) occurs earlier after TKA than THA; however, most of those events occur after hospital discharge. Consequently, extended thromboprophylaxis after discharge should be considered and is particularly important after THA owing to the prolonged risk period for VTE. Evidence-based guideline recommendations for the prevention of VTE in these patients have not been fully implemented. This is partly owing to the limitations of traditional anticoagulants, such as the parenteral route of administration or frequent coagulation monitoring and dose adjustment, as well as concerns about bleeding risks. The introduction of new oral agents (e.g., dabigatran etexilate and rivaroxaban) may facilitate guideline adherence, particularly in the outpatient setting, owing to their oral administration without the need for routine coagulation monitoring. Furthermore, the direct Factor Xa inhibitor rivaroxaban has been shown to be more effective than enoxaparin in preventing VTE.

The ''critical thrombosis period'' in major orthopedic surgery: when to start and when to stop prophylaxis

Patients undergoing major orthopedic surgery are at high venous thromboembolism (VTE) risk, with morbid and potentially fatal consequences. Anticoagulant VTE prophylaxis reduces rates of postoperative deep vein thrombosis by up to 60% to 70% in these patients. Therefore, pharmacological prophylaxis with low-molecular-weight heparins (LMWHs), vitamin K antagonists, or fondaparinux is recommended by current guidelines. However, there remains an ongoing debate regarding when to initiate and the optimal duration for prophylaxis. Here, we discuss the mechanisms underlying thrombus formation in patients undergoing major orthopedic surgery, and we review the current literature on the benefit-to-risk ratio associated with preoperative and postoperative initiation of thromboprophylaxis and also the benefit-to-risk ratio in cases of neuraxial anesthesia. We also discuss the duration of postoperative VTE risk following major orthopedic surgery and assess the ''critical thrombosis period'' when prophylaxis should be provided. Current literature reflects the need to balance the improved efficacy of initiating prophylaxis close to the surgery with increased risk of perioperative bleeding. Evidence from pathology, epidemiology, and clinical studies suggests the risk period for VTE begins at surgery and extends well beyond hospitalization-a crucial issue when considering how long to give prophylaxis-and, in the case of total hip arthroplasty, for at least 3 months after surgery. Literature supports the greater use of ''just-in-time'' thromboprophylaxis initiation and after-discharge continuation of optimal prophylaxis in orthopedic surgery patients. Providing optimal thromboprophylaxis throughout the critical thrombosis period where a patient is at VTE risk will ensure the best reductions in VTE-related morbidity and mortality.

Deep vein thrombosis prevention in joint arthroplasties: continuous enhanced circulation therapy vs low molecular weight heparin

Deep vein thrombosis prevention efficacy using a new, miniature, mobile, battery-operated pneumatic system (continuous enhanced circulation therapy [CECT] system) combined with low-dose aspirin was compared to enoxaparin. One hundred twenty-one patients who underwent total hip or knee arthroplasty were prospectively randomized into 2 groups. The study group was treated by the CECT system starting immediately after the induction of anesthesia. Postoperatively, a daily 100-mg aspirin tablet was added. The control group received 40 mg of enoxaparin per day. Bilateral venography was performed at the fifth to eight postoperative day. In the CECT group, as compared to the enoxaparin group, there was a significantly lower overall rate of DVT and proximal DVT. Safety profiles were similar in both groups. The combination of the CECT device with low-dose aspirin is more effective than enoxaparin in preventing deep-vein thrombosis after lower limb arthroplasties.

Prevention of Venous Thromboembolism Following Orthopaedic Surgery

Patients undergoing total hip or total knee replacement are at high risk of venous thromboembolism (VTE), and are therefore considered to be populations well suited for the evaluation and dose optimisation of new anticoagulants. Deep vein thrombosis may lead to life-threatening pulmonary embolism, disabling morbidity in the form of the post-thrombotic syndrome, and risk of recurrent thrombotic events. There is increasing evidence that anticoagulant treatment for the prevention of VTE should be extended from 1 to at least 4 weeks after surgery. Anticoagulation with vitamin K antagonists (such as warfarin), low molecular weight heparin or unfractionated heparin effectively lowers the risk of VTE, but these anticoagulants have limitations such as the need for coagulation monitoring and subsequent dose adjustment (vitamin K antagonists), difficulty of continuing prophylaxis out of hospital because of the requirement for parenteral administration, and risk of heparin-induced thrombocytopenia. The development of new anticoagulants has been pursued with the aim of finding more effective, safer and/or more convenient therapies. Thrombin is a central regulator in the coagulation and inflammation process and several direct thrombin inhibitors (DTIs) with distinct pharmacological profiles, as well as pharmacological differences from the conventional anticoagulants, are currently in clinical use for certain indications or are under development. Clinical experience with parenterally administered DTIs has accumulated since the mid 1990s, although only desirudin (a recombinant hirudin) is currently approved for use in patients undergoing orthopaedic surgery. Two oral DTIs, ximelagatran and dabigatran etexilate, are in clinical development. Dabigatran etexilate has recently been evaluated in phase II clinical trials in patients undergoing total hip replacement. Several large phase III trials have now demonstrated the efficacy and safety of ximelagatran in the prevention of VTE following total hip or knee replacement. Ximelagatran can be used with an oral fixed dose without the need for coagulation monitoring or dose adjustment. Hence, it offers significant potential to facilitate the management of anticoagulation in or out of hospital.

Comprehensive deep venous thrombosis prevention strategy after total-knee arthroplasty

OBJECTIVE

Venous thromboembolism after total-knee arthroplasty represents a common early postoperative complication resulting in significant morbidity. Despite this, the optimal prophylactic regimen is controversial. The prevalence of venous thromboembolism has been cited as high as 35% in patients receiving pharmacologic prevention alone. We investigated the efficacy of a comprehensive prevention protocol encompassing the use of epidural anesthesia, aspirin, venous foot compression pumps, and early mobilization in a series of consecutive total-knee arthroplasties.

DESIGN

A series of 100 consecutive total-knee arthroplasty patients were enrolled into the prospective trial. All patients were allowed full weight bearing on the first postoperative day and ambulation as tolerated. Venous foot compression pumps and aspirin were used immediately after surgery in the totality of subjects. Seventy-five percent of the patients were transferred to an acute rehabilitation service during the first postoperative week. The presence of deep-vein thrombosis was subsequently determined with the routine use of venous duplex scans.

RESULTS

Three patients (3%) demonstrated evidence of distal deep-vein thrombosis. No patient had symptomatic pulmonary embolism.

CONCLUSION

The combination of epidural anesthesia, aspirin, immediate postoperative venous foot compression pumps, and early ambulation together seem to be a more effective approach to prevent the occurrence of thromboembolic events after knee replacements than pharmacologic prevention alone.

Current controversies in deep vein thrombosis prophylaxis after orthopaedic surgery

As a result of easy measurable perioperative bleeding and a high number of subclinical deep vein thromboses after surgery, total hip replacement has become a benchmark for antithrombotic drug development. Today, a nonscientific evidence-based transatlantic view on thromboprophylaxis in orthopaedic surgery exists. Efforts should be taken to bridge these divergent opinions. We need to standardize study designs that allow unbiased comparison and aggregation of data to get insight in rare complications like the cauda equina syndrome associated with spinal analgesic techniques and anticoagulation and to optimize thromboprophylaxis in homogeneous groups of patients. Dosage, timing of initiation in relation to surgery, and duration of prophylaxis seems a crucial and open question for all homogeneous groups of orthopaedic patients. A definition on surgical bleeding, which allows practical measurement procedures and quantification, is lacking. Clinical studies on vascular endpoints are warranted to achieve relevant basic data for health economic analyses, which also lack scientific standardized procedures. An intercontinental close cooperation is needed to solve these issues.

Altered venous function and deep venous thrombosis following proximal femoral fracture

The effect of surgery for femoral neck fracture on lower limb venous blood flow and its relationship to deep vein thrombosis was investigated in 179 patients. Blood flow was measured using strain gauge plethysmography before surgery, in the 1st week after surgery, and at 6 week review. There was a significant reduction in both venous outflow and venous capacitance, affecting both fractured and non-fractured legs but significantly greater in the fractured leg. Venous function remained significantly impaired in both lower limbs 6 weeks after surgery. There was a significant correlation between the reduction in venous function and the development of deep vein thrombosis.

Symptomatic and asymptomatic deep vein thrombosis after total hip replacement. Differences in phlebographic pattern, described by a scoring of the thrombotic burden

The aim was to describe the phlebographic pattern of asymptomatic and symptomatic deep vein thrombosis (DVT) after total hip replacement by the use of a scoring system in 102 consecutive patients (54 asymptomatic, 48 symptomatic). The DVTs were scored from 1 to 3, and registered in a scoring system dividing the deep veins into 12 separate segments. The asymptomatic patients had a significantly lower total mean DVT score of 3.7 compared to 9.1 in the symptomatic group of patients. The mean ratio of the DVT scores in the deep muscle veins in conjunction with the superficial femoral vein in relation to the total mean score was significantly higher in the asymptomatic patients (74.9%) compared to the symptomatic group (62.4%). A direct sign of DVT, displayed as a filling defect, was seen on the phlebogram in 116 of the 119 legs, and concomitant nonfilling in other vein segments was noted in 6% of the asymptomatic patients, while in the symptomatic group this was the case to a significantly higher level, namely, 46%. A subgroup of asymptomatic patients operated unilaterally, with bilateral DVT had a significantly higher total mean DVT score on the operated side (4. 6) compared to the unoperated side (3.4). The total mean DVT score increased with time after surgery in the group of symptomatic patients. A low total mean DVT score with a predominance of DVT in, or in the connection to, the deep muscle veins is displayed among the asymptomatic patients. This is significantly different from the symptomatic patients who have more extensive DVTs, especially when diagnosed several weeks postoperatively, and frequently with edema and occlusive DVT.

Numerical model of deep venous thrombosis detection using venous occlusion strain gauge plethysmography

Strain gauge plethysmography (SGP) is a non-invasive method used in the detection of deep venous thrombosis (DVT). The technique is based on the measurement of calf volume changes in response to venous occlusion by a thigh cuff, the volume changes reflecting the rates of arterial inflow and venous outflow. A numerical model of the blood circulation within the limb and the response of this to a SGP test has been derived, based on treating the different parts of the circulatory system in the leg as resistance and capacitance elements. The simulation results were compared with clinical studies and support the ability of SGP to detect non-occlusive clots of more than 50-60% of the lumen, as well detecting calf vein occlusion. The non-linear behaviour of the venous compliance with intra-luminal pressure appears to be a particularly important factor within the model. In addition, increases in venous tone due to post-operative venospasm were shown to be a potential source of false positive results.

Pneumatic compression hemodynamics in total hip arthroplasty

A crossover study was performed to evaluate the effect of several pneumatic compression devices and active dorsoplantar flexion in 10 patients who underwent total hip arthroplasty. Using the Acuson 128XP/10 duplex ultrasound unit with a 5-MHz linear array probe, peak venous velocity and venous volume were assessed above and below the greater saphenous vein and common femoral vein junction. A computer generated randomization table was used to determine the order of the test conditions. The pneumatic compression devices evaluated included two foot pumps, one foot and calf pump, one calf pump, and three calf and thigh pumps. Statistical analyses included analysis of variance and analysis of variance with covariance between devices and patients. The covariates tested were the baseline measurements and the order in which the devices were tested. Differences between devices relate in part to the frequency and rate of inflation and the location and type of compression. Pulsatile calf and foot and calf pneumatic compression with a rapid inflation time produced the greatest increase in peak venous velocity, whereas compression of the calf and thigh showed the greatest increase in venous volume. Because patient and nursing compliance is essential to the success of mechanical prophylaxis for thromboembolic disease, the more simple, yet efficacious, devices that are easier to apply and less cumbersome appear to have a greater likelihood of success. In the active and alert patient, active dorsoplantar flexion should be encouraged.

Late occurring clinical deep vein thrombosis in joint-operated patients

In a prospective study of 4,840 patients, we determined the annual incidence of clinical deep vein thrombosis (DVT) in mobilized, discharged orthopedic-operated "high-risk" patients (hip replacement surgery, knee replacement surgery, nailed hip fracture) and assumed "low-risk" patients (diagnostic knee arthroscopy). In addition, the time from the operation to the time when the patients were readmitted with clinically suspected DVT and the distribution of radiologically-confirmed DVT were recorded. Thromboprophylaxis was routinely given for about 10 days to the high-risk groups during the hospital stay but not to patients undergoing knee arthroscopy. During 9 years, the annual incidence of DVT following major procedures was 2.1% (95% CI 1.6-2.6) vs. 0.6% (95% CI 0.2-1.1) after diagnostic knee arthroscopy. Symptoms appeared, on average, 27 (3-150) days after total hip replacement surgery, 36 (3-150) days after nailed hip fracture, 17 (6-30) days after total knee replacement and 1 (1-6) day after knee arthroscopy. In hip-operated patients, 50% of the DVTs were found in the proximal veins vs. 40% following knee arthroplasty.

Comparison of the use of a foot pump with the use of low-molecular-weight heparin for the prevention of deep-vein thrombosis after total hip replacement. A prospective, randomized trial

We conducted a prospective, randomized trial to compare the safety and effectiveness of the A-V Impulse System foot pump with that of low-molecular-weight heparin for reducing the prevalence of deep-vein thrombosis after total hip replacement. Of 290 patients who were to have a primary total hip replacement, 143 were randomized to receive enoxaparin (forty milligrams daily) for seven days after the operation and 147, to use the foot pump for seven days. The primary outcome measure was the prevalence of deep-vein thrombosis, as determined by venography on the sixth, seventh, or eighth postoperative day. Secondary outcome measures included transfusion requirements, intraoperative blood loss, postoperative drainage, blood-loss index, appearance of the site of the wound according to a subjective visual-analog scale, and swelling of the thigh. The patients' compliance with the regimen for use of the foot pump was monitored with an internal timing device, and their acceptance of the device was assessed with a questionnaire. Symptoms consistent with pulmonary embolism were investigated with ventilation-perfusion scanning. The patients were contacted later for detection of symptoms of venous thromboembolism that may have occurred during the first three months after discharge from the hospital. Venography was performed on 274 patients: 136 who used the foot pump and 138 who received enoxaparin. Deep-vein thrombosis was detected in twenty-four (18 per cent) of the patients who used the foot pump compared with eighteen patients (13 per cent) who received enoxaparin (95 per cent confidence interval for the difference in proportions, -3.9 to +13.0 per cent). Thrombosis in the calf was found in seven patients (5 per cent) in the former group compared with six patients (4 per cent) in the latter (95 per cent confidence interval for the difference, -4.2 to +5.8 per cent), and proximal thrombosis was observed in seventeen patients (13 per cent) in the former group compared with twelve patients (9 per cent) in the latter (95 per cent confidence interval for the difference, -3.5 to +11.1 per cent). None of these differences was significant. No patient in either group had major proximal deep-vein thrombosis; all proximal thrombi were isolated entities involving the femoral valve cusp and were of unknown importance. One patient who used the foot pump had a non-fatal pulmonary embolism. One patient who received enoxaparin had a symptomatic deep-vein thrombosis during hospitalization. Two patients (one from each group [0.7 per cent]) were readmitted to the hospital because of a symptomatic deep-vein thrombosis despite normal venographic findings at the time of discharge. There was no difference in the transfusion requirements or the intraoperative blood loss between the two groups. There were more soft-tissue side effects in the patients who received enoxaparin than in those who used the foot pump: there was more bruising of the thigh and oozing of the wound (p < 0.001 for each), postoperative drainage (578 compared with 492 milliliters; p = 0.014), and swelling of the thigh (twenty compared with ten millimeters; p = 0.03). Of 124 patients who used the foot pump and were asked about the acceptability of the device, fourteen (11 per cent) said that it was uncomfortable, twenty-one (17 per cent) reported sleep disturbance, and four (3 per cent) stated that they had stopped using the device. Conversely, ten (8 per cent) found it relaxing. We concluded that the foot pump is a suitable alternative to low-molecular-weight heparin for prophylaxis against thromboembolism after total hip replacement and that it produces fewer soft-tissue side effects. Tolerance of the device is a problem for some patients.

Thromboprophylaxis in hip arthroplasty. New frontiers and future strategy

Coagulation-related complications are a frequent cause of death following hip replacement surgery. Venographically-proven deep vein thrombosis (DVT) is found in a high frequency. Most cases have no symptoms. Fatal pulmonary embolism (PE) may develop from subclinical thrombi. In addition, arterial thromboses may induce serious cardiovascular events and an unknown number of patients may develop cardiorespiratory insufficiency, due to non-fatal venous PE. Finally, several patients may develop venous insufficiency. Recent prospective double-blind studies have shown that the frequency of deep vein thrombosis increased after hospital discharge in patients undergoing hip replacement surgery. Prolonged thrombo-prophylaxis with low-molecular-weight heparin (dalteparin or enoxaparin) is recommended for at least 5 weeks after the operation.

The effect of active movement of the foot on venous blood flow after total hip replacement

Surgeons often encourage patients to move their feet in an attempt to prevent venous stasis, but there is little evidence that this measure is beneficial. We investigated the effect of active movement of one foot on the venous blood flow four days after total hip replacement. The actual venous outflow at rest was measured with use of venous occlusion strain-gauge plethysmography in thirty-eight patients. The patients were randomly allocated to the control group (eighteen patients) or the exercise group (twenty patients). A baseline measurement was followed by a one-minute period of rest (control group) or of maximum plantar flexion and dorsiflexion of the foot, ankle, and toes at a rate of thirty cycles per minute (exercise group). The venous outflow was measured again at two, seven, twelve, and thirty minutes in both groups. Movement of the foot for one minute produced a significant and sustained increase (p < 0.002) in the venous outflow (mean maximum increase, 22 per cent). The value remained greater than the baseline level for thirty minutes (mean increase, 6.5 per cent) (p < 0.2). The increase was gradual, reaching a maximum twelve minutes after the completion of exercise. Our results confirm the beneficial hemodynamic effects of active movement of the foot in the postoperative period and suggest that patients should move the feet and ankles postoperatively as part of a prophylactic regimen directed at decreasing the risk of venous thrombosis.

The post-hospital discharge venous thrombosis risk of the orthopedic patient

ABSTRACTA prospective, randomized, double-blind trial was performed in total hip replacement patients to document the risk of deep vein thrombosis (DVT) after hospital discharge, and to assess the efficacy of sustained antithrombotic prophylaxis. In a total of 179 patients receiving enoxaparin 40 mg/day during hospitalization, those without venogram-proven DVT at discharge were randomly assigned to continue prophylaxis with enoxaparin (N=90) or receive placebo (N=89). At the end of 21 days' treatment, intention-to-treat analysis in 173 evaluable patients demonstrated a significantly lower incidence (P=0.018) of DVT in the enoxaparin group (7.1%; N=6) compared with the placebo group (19.3%; N=17). These findings were confirmed by perprotocol analysis in 155 patients. Minor bleeding episodes occurred in three patients in the enoxaparin group and one in the placebo group. Thus, total hip replacement patients have a significant risk of developing DVT after hospital discharge. Continued prophylaxis with enoxaparin is effective in reducing this risk.

Low-molecular-weight heparin (enoxaparin) as prophylaxis against venous thromboembolism after total hip replacement

BACKGROUND

The risk of venous thromboembolism in patients undergoing total hip replacement is known to be high. However, the optimal duration of prophylaxis with anticoagulant agents after this procedure is unknown. We sought to determine whether one month of anticoagulant therapy with the low-molecular-weight heparin enoxaparin is more effective than enoxaparin therapy given only during the hospitalization for surgery.

METHODS

Two hundred sixty-two patients undergoing total hip replacement received enoxaparin during their hospitalizations (average stay, 10 to 11 days). They were then randomly assigned to receive enoxaparin or placebo (131 patients each). Blinded outpatient therapy (or placebo) was continued long enough that the total treatment period, inpatient plus outpatient, was one month for each patient. Bilateral ascending phlebography was performed 19 to 23 days after discharge, with deep-vein thrombosis as the primary end point. Distal and proximal thrombosis, pulmonary embolism, and hemorrhage were also recorded, as were deaths.

RESULTS

Venography was adequate in 116 patients in the placebo group and 117 in the enoxaparin group. We observed 43 episodes of deep-vein thrombosis and 2 episodes of pulmonary embolism in the placebo group, but only 21 episodes of deep-vein thrombosis and no episodes of pulmonary embolism in the enoxaparin group (incidence of thromboembolism, 39 percent and 18 percent, respectively; P<0.001). The difference in the incidence of proximal deep-vein thrombosis was also significant (24 percent and 7 percent in the placebo and enoxaparin groups, respectively; P<0.001). Six enoxaparin groups, respectively; P<0.001). Six patients in the enoxaparin group and one patient in the placebo group had hematomas at their injection sites. No patients died or had major complications.

CONCLUSIONS

There were significantly fewer venous thromboembolic complications in patients undergoing elective hip replacement when prophylaxis with enoxaparin was given for a total of one month, rather than only during the hospitalization.

Risk of deep-venous thrombosis after hospital discharge in patients having undergone total hip replacement: double-blind randomised comparison of enoxaparin versus placebo

BACKGROUND

The risk of deep-vein thrombosis (DVT) and pulmonary embolism after total hip replacement (THR) surgery may persist after hospital discharge, but the extent of the risk is not known. We carried out a single-centre, prospective, randomised, double-blind trial with the aims of quantifying this risk and assessing the efficacy of continued prophylactic treatment.

METHODS

At hospital discharge 13-15 days after surgery, we recruited 179 consecutive THR patients who had no DVT visible on bilateral ascending venography of the legs. The patients were randomly assigned subcutaneous enoxaparin (40 mg, once daily; n = 90) or placebo (n = 89) for 21 (19-23) days. The primary endpoint was the occurrence of DVT or pulmonary embolism. Venography was repeated at the end of 21 days' treatment or earlier if necessary.

FINDINGS

There were no deaths and no symptomatic pulmonary embolisms during the study or follow-up periods. Of 173 patients with evaluable venograms, intention-to-treat analysis of efficacy showed that the rate of DVT at day 21 after discharge was significantly lower in the enoxaparin group than in the placebo group (6 [7.1%] vs 17 [19.3%], p = 0.018). Distal DVT was detected in one (1.2%) patient in the enoxaparin group and in ten (11.4%) patients in the placebo group (p = 0.006). Proximal DVT was observed in five (5.9%) patients in the enoxaparin group and in seven (7.9%) patients in the placebo group (p = 0.592). A perprotocol analysis of efficacy in 155 patients confirmed these findings. Safety was good; three minor bleeding episodes occurred in the enoxaparin group and one in the placebo group, but none of these episodes necessitated withdrawal from the study.

INTERPRETATION

In patients who have undergone THR surgery, are without venogram-proven DVT at hospital discharge, and do not receive antithrombotic prophylaxis after discharge, the risk of late-occurring DVT remains high at least until day 35 after surgery. Continued prophylaxis with enoxaparin is effective and safe in reducing this risk.