Low molecular weight heparin for prevention of venous thromboembolism in patients with lower-leg immobilization

  • Review
  • Intervention

Authors


Abstract

Background

Immobilization of the lower leg is associated with venous thromboembolism (VTE). Low molecular weight heparin (LMWH) is an anticoagulant treatment which might be used in adult patients with lower-leg immobilization to prevent deep venous thrombosis (DVT) and its complications. This is an update of the review first published in 2008.

Objectives

To assess the effectiveness of low molecular weight heparin for the prevention of venous thromboembolism in patients with lower-leg immobilization in an ambulant setting.

Search methods

For this update the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator searched the Specialised Register (last searched June 2013) and CENTRAL (2013, Issue 5).

Selection criteria

Randomized controlled trials (RCTs) and controlled clinical trials (CCTs) that described thromboprophylaxis by means of LMWH compared with no prophylaxis or placebo in adult patients with lower-leg immobilization. Immobilization was by means of a plaster cast or brace.

Data collection and analysis

Two authors independently assessed trial quality and extracted data. The review authors contacted the trial authors for additional information if required. Statistical analysis was carried out using Review Manager (RevMan 5).

Main results

We included six RCTs fulfilling the above criteria with a total of 1490 patients. We found an incidence of VTE ranging from 4.3% to 40% in patients who had a leg injury that had been immobilized in a plaster cast or a brace for at least one week and who received no prophylaxis, or placebo. This number was significantly lower in patients who received daily subcutaneous injections of LMWH during immobilization (event rates ranging from 0% to 37%; odds ratio (OR) 0.49; fixed 95% confidence interval (CI) 0.34 to 0.72; with minimal evidence of heterogeneity with an I2 of 20%, P = 0. 29). Comparable results were seen in the following subcategories: operated patients, conservatively treated patients, patients with fractures, patients with soft-tissue injuries, patients with proximal thrombosis, patients with distal thrombosis and patients with below-knee casts. Complications of major bleeding events were extremely rare (0.3%) and there were no reports of heparin-induced thrombocytopenia.

Authors' conclusions

Use of LMWH in outpatients significantly reduces VTE when immobilization of the lower leg is required.

Résumé scientifique

Héparine de bas poids moléculaire pour la prévention de la thromboembolie veineuse chez les patients ayant les jambes immobilisées

Contexte

L'immobilisation de la jambe est associée à la thromboembolie veineuse (TEV). L'héparine de bas poids moléculaire (HBPM) est un traitement anticoagulant qui pourrait être utilisé chez les patients adultes ayant les jambes immobilisées afin de prévenir la thrombose veineuse profonde (TVP) et ses complications. Ceci est une mise à jour de la revue publiée pour la première fois en 2008.

Objectifs

Évaluer l'efficacité de l'héparine de bas poids moléculaire dans la prévention de la thromboembolie veineuse chez les patients ayant les jambes immobilisées dans un cadre ambulatoire.

Stratégie de recherche documentaire

Pour cette mise à jour, le coordinateur de recherche d'essais du groupe Cochrane sur les maladies vasculaires périphériques a effectué des recherches dans ce registre spécialisé (dernière recherche en juin 2013) et dans CENTRAL (2013, numéro 5).

Critères de sélection

Les essais contrôlés randomisés (ECR) et les essais cliniques contrôlés (ECC) qui décrivaient une thromboprophylaxie au moyen de la HBPM comparé à l'absence de prophylaxie ou à un placebo chez des patients adultes ayant les jambes immobilisées. L'immobilisation se faisait à l'aide d'un plâtre ou d'une orthèse.

Recueil et analyse des données

Deux auteurs ont indépendamment évalué la qualité méthodologique des essais et extrait des données. Les auteurs de la revue ont contacté les auteurs des essais pour avoir des informations complémentaires en cas de besoin. Une analyse statistique a été réalisée au moyen de l’outil Review Manager (RevMan 5).

Résultats principaux

Nous avons inclus six ECR portant sur un total de 1 490 patients et remplissant les critères ci-dessus. Nous avons découvert une incidence de la TEV de 4,3 % à 40 % chez les patients qui avaient une lésion à la jambe ayant été immobilisée dans un plâtre ou une orthèse pendant au moins une semaine et qui ne recevaient aucune prophylaxie ou recevaient un placebo. Ce chiffre a été significativement plus faible chez les patients qui recevaient des injections sous-cutanées quotidiennes de HBPM au cours de l'immobilisation (taux d'événements de 0 % à 37 % ; rapport des cotes (RC) 0,49 ; intervalle de confiance (IC) à 95 % fixe 0,34 à 0,72) et peu de preuves d'hétérogénéité avec un I2 de 20 %, P = 0, 29). Des résultats comparables ont été observés dans les sous-catégories suivantes : les patients opérés, les patients traités de manière conservatrice, les patients présentant des fractures, les patients présentant des lésions des tissus mous, les patients ayant une thrombose proximale, les patients ayant une thrombose distale et les patients ayant des plâtres au-dessous du genou. Les complications d'événements hémorragiques majeurs ont été extrêmement rares (0,3 %) et il n'y a eu aucune notification de thrombocytopénie induite par l'héparine.

Conclusions des auteurs

L'utilisation de la HBPM chez les patients externes réduit de façon significative la TEV lorsque l'immobilisation de la jambe est nécessaire.

Plain language summary

Low molecular weight heparin for prevention of venous thromboembolism in adults with lower-leg immobilization in an outpatient setting

Immobilization of the lower limb with plaster cast or brace in adult patients is associated with deep venous thrombosis (DVT). In order to prevent this complication preventive treatment with anticoagulants is often used, most commonly low molecular weight heparin (LMWH). Different indications for the use of LMWH are given in existing national guidelines. Therefore we searched the literature for trials on this topic, in order to develop an evidence-based stand on this matter.

Six randomized controlled trials were found and judged to be of sufficient quality to use in a meta-analysis. The trials involved 1490 patients: 750 patients received LMWH subcutaneously once daily; 740 patients received no prophylaxis or placebo. Incidence rates of DVT ranging from 4.3% to 40% were found in the control groups and ranging from 0% to 37% in the LMWH groups. There was a significant difference (odds ratio 0.49, 95% confidence interval 0.34 to 0.72). Further analysis showed a significant reduction of the occurrence of DVT when using LMWH in the following subgroups: operated patients; conservatively treated patients; patients with fractures; patients with soft-tissue injuries; patients with below-knee casts; a group with proximal thrombosis and a group with distal thrombosis.

There were few reported adverse effects in the treated patients. Two patients in the treatment group and one in the placebo group had to discontinue the LMWH due to major bleeding events. In the treatment group minor bleeding events were reported in up to 8% of cases. One patient developed facial eczema.

We conclude that LMWH should be considered in adult patients with immobilization of the lower leg to prevent occurrence of venous thromboembolism. It should not only be considered in patients with an above-knee cast but also in patients with a below-knee cast. LMWH can safely be used for this indication.

Résumé simplifié

L'héparine de bas poids moléculaire pour la prévention de la thromboembolie veineuse chez l'adulte ayant les jambes immobilisées dans un cadre ambulatoire

L'immobilisation du membre inférieur avec un plâtre ou une orthèse chez le patient adulte est associée à une thrombose veineuse profonde (TVP). Afin de prévenir cette complication, un traitement préventif aux anticoagulants est souvent utilisé, le plus généralement avec de l'héparine de bas poids moléculaire (HBPM). Les directives nationales existantes donnent des indications diverses pour l'usage de la HBPM. Par conséquent, nous avons effectué des recherches dans la littérature pour trouver des essais sur ce sujet afin de développer une position fondée sur des preuves sur cette question.

Six essais contrôlés randomisés ont été trouvés et jugés d'une qualité suffisante pour pouvoir être utilisés dans une méta-analyse. Les essais portaient sur 1 490 patients : 750 patients recevaient de la HBPM par voie sous-cutanée une fois par jour ; 740 patients ne recevaient aucune prophylaxie ou recevaient un placebo. Des taux d'incidence de la TVP de 4,3 % à 40 % ont été découverts dans les groupes témoins contre 0 % à 37 % dans les groupes sous HBPM. Il y avait une différence significative (rapport des cotes 0,49, intervalle de confiance à 95 % 0,34 à 0,72). Une analyse supplémentaire a montré une réduction significative de la survenue d'une TVP lors de l'utilisation de la HBPM dans les sous-groupes suivants : les patients opérés, les patients traités de manière conservatrice, les patients présentant des fractures, les patients présentant des lésions des tissus mous, les patients ayant des plâtres au-dessous du genou, un groupe ayant une thrombose proximale et un groupe ayant une thrombose distale.

Peu d'effets indésirables ont été signalés chez les patients traités. Deux patients dans le groupe de traitement et un dans le groupe sous placebo ont dû interrompre la HBPM en raison d'événements hémorragiques majeurs. Dans le groupe de traitement, des événements hémorragiques mineurs ont été rapportés dans une proportion pouvant atteindre 8 % des cas. Un patient a développé un eczéma facial.

Nous concluons que la HBPM doit être envisagée chez les patients adultes ayant une jambe immobilisée afin de prévenir la survenue d'une thromboembolie veineuse. Elle doit non seulement être envisagée chez les patients ayant un plâtre au-dessus du genou, mais également chez les patients ayant un plâtre au-dessous du genou. La HBPM peut être utilisée sans risque pour cette indication.

Notes de traduction

Traduit par: French Cochrane Centre 6th December, 2012
Traduction financée par: Minist�re des Affaires sociales et de la Sant�

Background

Lower-leg immobilization is associated with deep venous thrombosis (DVT) and pulmonary embolism (PE). Is there a role for low molecular weight heparin (LMWH) in patients with lower-leg immobilization to prevent venous thrombosis and its complications?

Pre-disposing risk factors for venous thromboembolism (VTE) can be divided into individual patient factors, trauma, or surgery-related factors. Patient-related factors include obesity; thrombophilia (a hereditary or acquired predisposition to thrombosis); a previous thrombosis; age over 40 years; cardiovascular insufficiency; or post-thrombotic syndrome (PTS) of the lower leg (Clagett 1995; Zagrodnick 1990). Immobilization is considered a significant risk factor for the development of DVT and PE (Knudson 1996; Kudsk 1989; Kujath 1991).

Other factors associated with an increased risk of VTE include: blood transfusion; surgery; fracture of the pelvis, femur or tibia; spinal cord injury; head injury; shock on hospital admission; venous injury; more than three days on ventilation; the time from injury to operation; or operation time (Abelseth 1996; Knudson 2004).

In a group of 102 patients with lower-limb fractures Abelseth found a rate of DVT of 28% (Abelseth 1996). All patients were operated on and mobilized without the use of a plaster cast. Proximal fractures were associated with a higher risk of DVT compared with more distal fractures (Abelseth 1996). Other reported incidences of venographically-proven DVT in patients with lower-limb fractures range from 27% to 78% (Breyer 1984; Geerts 1994; Hjelmstedt 1968; Kudsk 1989; Spieler 1972). The percentages in hospitalized patients are generally higher than in outpatients. In outpatients immobilized in plaster casts without LMWH, the incidence of DVT on ultrasonography ranges from 4.5% to 16.5% (Kock 1995; Kujath 1993; Reilmann 1993; Zagrodnick 1990). The incidence of PE in trauma patients with DVT without prophylaxis is 4.3%, with a high mortality rate (20% to 23.3%). In patients with DVT receiving thromboprophylaxis this incidence can be lowered to 0.3% to 2.0% (Hill 2002).

The primary goal of administering thromboprophylaxis is to prevent PE. Furthermore, prevention of DVT and its possible complications such as postphlebitic syndrome is of great importance. Oral anticoagulants, unfractionated heparin (UFH) and LMWH have been studied for this indication as treatment options. In clinical guidelines, the recommendations on preventing venous thrombosis in patients with isolated lower-leg injuries distal to the knee are sparse. In 2002, the Scottish Intercollegiate Guidelines Network recommended patients with lower-limb fractures for LMWH prophylaxis (SIGN 2002), but in their current version they recommend assessment for thrombosis and bleeding risks. Both the 2004 and 2012 ACCP Antithrombotic Guidelines suggest no prophylaxis rather than pharmacologic thromboprophylaxis (Geerts 2004; ACCP 2012). Their advice is based on the findings of a multicenter study that has remained published only in abstract form (Selby 2010), combined with the data from our own meta-analysis in the previous version of this review (Testroote 2008). In Selby's study (the D-KAF trial) consecutive patients with isolated fractures of the distal leg requiring surgery were randomized to dalteparin 5000 IU or placebo once daily SC. Patients were screened using proximal ultrasound (only of the upper leg, not the calf) at day 14. The researchers were interested in clinically important venous thromboembolism (CIVTE). The study authors found that the overall incidence of CIVTE was so low (1.9%; 95% CI 0.7 to 4.7%) with no observed differences between dalteparin and placebo, that recruitment was stopped early. For this reason, we did not include this study in our meta-analysis. The study demonstrates the large discrepancy between trials that utilize venographic outcomes (all DVTs) and CIVTE. However, the ACCP authors performed their own analysis of the combined data and found that the results did not establish the benefit of thromboprophylaxis in the patients enrolled. High-risk patients might still be considered for prophylaxis according to the ACCP. The latter is also advised by the British College of Standards in Haematology (BCSH 2006). A fourth guideline recommends LMWH prophylaxis in lower-limb injury where the leg is immobilized or full weight bearing is not possible (CBO 2006).

Therefore, national guidelines do not come to an evidence-based stand and there remains substantial practice variation amongst surgeons regarding the use of anticoagulation measures (Batra 2006). In daily clinical practice there remains a huge variation in the way thromboprophylaxis is used. A Dutch survey among surgeons shows 79% prescribe prophylaxis for above-knee casts and 30% for below-knee casts (Truijers 2005). In a survey among Italian orthopedic surgeons there was great heterogeneity in terms of timing and duration of prophylaxis since none of the answers were associated with greater than 75% consensus among the respondents (Ageno 2004). A survey performed by the author of this review confirms this view (Testroote 2011).

Objectives

To assess the effectiveness of low molecular weight heparin for the prevention of venous thromboembolism in patients with lower-leg immobilization in an ambulant setting.

Methods

Criteria for considering studies for this review

Types of studies

We considered all randomized controlled trials (RCTs) and controlled clinical trials (CCTs) that describe thromboprophylaxis by means of low molecular weight heparin (LMWH) in adults with lower-leg immobilization in an ambulant setting. Treatment with LMWH could have started in hospital before the patient was discharged.

Types of participants

Adults treated with a leg cast or brace in an ambulant setting. Weight bearing and duration of the leg cast were not considered as criteria for inclusion or exclusion. We performed subgroup analysis of surgically treated and conservatively managed patients.

Types of interventions

Studies comparing LMWH with no prophylaxis or placebo. If statistically feasible, subgroup analysis of different LMWHs will be performed at a later stage when the review is updated. Oral anticoagulants, UFH and aspirin were not considered in our review, and studies using these drugs, as a comparator were excluded.

Types of outcome measures

Primary outcomes
  • Morbidity - symptomatic or asymptomatic DVT (confirmed by venography or ultrasonography), PE (confirmed by ventilation-perfusion scan, CT scan or angiography), or any combination of these items, as a combined symptomatic venous thromboembolism (VTE) endpoint.

Secondary outcomes
  • Mortality - PE, confirmed at post mortem; other cause(s) of death.

  • Adverse outcomes of treatment: bleeding, heparin induced thrombocytopenia (HIT), allergy, others.

Search methods for identification of studies

 

Electronic searches

For this update the Cochrane Peripheral Vascular Diseases Group Trials Search Co-ordinator (TSC) searched the Specialised Register (last searched June 2013) and the Cochrane Central Register of Controlled Trials (CENTRAL) 2013, Issue 5, part of The Cochrane Library, (www.thecochranelibrary.com). See Appendix 1 for details of the search strategy used to search CENTRAL. The Specialised Register is maintained by the TSC and is constructed from weekly electronic searches of MEDLINE, EMBASE, CINAHL, AMED, and through handsearching relevant journals. The full list of the databases, journals and conference proceedings which have been searched, as well as the search strategies used are described in the Specialised Register section of the Cochrane Peripheral Vascular Diseases Group module in The Cochrane Library (www.thecochranelibrary.com).

Searching other resources

The review authors searched the reference lists of relevant studies.

Data collection and analysis

Selection of studies

Two review authors (MT and WS) independently assessed all studies that met the selection criteria. Disagreements were resolved by discussion.

Data extraction and management

Two review authors (WS and MT) independently extracted data to ensure the objectivity and validity of findings. A third review author (HJ) cross checked the information and disagreements were resolved by discussion. The review authors contacted trial authors for additional information if required.

Quality of trials

The quality of all relevant studies was assessed according to the guidelines for quality of trials from the Dutch Cochrane Centre, using a scoring scheme designed by representatives of the Dutch Cochrane Centre; the Quality Institute for Healthcare CBO; the Dutch General Practitioners Order; the Institute for Medical Technology Assessment; the Workgroup Investigation Quality; the College for Medical Assurances; Health Investigation in the Netherlands (ZonMw); and the Order of Medical Specialists (www.cochrane.nl).

Statistical analyses

Statistical analysis was carried out using RevMan 5. The fourth author (LJ) co-ordinated and advised on the statistical methods used. We searched for statistical heterogeneity by 'eyeballing'. We quantified heterogeneity by means of an I2 test.

Results

Description of studies

Results of the search

See Figure 1.

Figure 1.

Study flow diagram.

Included studies

We included six studies (Jorgensen 2002; Kock 1995; Kujath 1993; Lapidus 2007a; Lapidus 2007b; Lassen 2002). The characteristics of these six studies are summarized in the Characteristics of included studies table. All six studies were reported as full papers and included a total of 1490 participants (range 105 to 371). All studies were prospective with quite similar exclusion criteria. The most common exclusion criteria were: pregnancy; allergy to heparin or contrast media; uncontrolled hypertension; pre-existing bleeding disorders; presence of malignancies; recent brain or gastrointestinal bleeding; previous DVT; and chronic venous insufficiency. Each study used a different LMWH as choice of treatment. Nadroparin (Kujath 1993), Mono-Embolex (Kock 1995), tinzaparin (Jorgensen 2002), dalteparin (Lapidus 2007a; Lapidus 2007b) and reviparin (Lassen 2002), were administered once daily until removal of the plaster cast. There were no relevant differences between treatment and control groups regarding demographics or risk factors.

In two studies (Kock 1995; Kujath 1993), plaster cast fitted after surgery was used as an exclusion criterion. In one study (Lassen 2002), patients who underwent surgery before randomization might have had heparin treatment for up to four days before randomization. Another study treated all patients one week with LMWH before randomization (Lapidus 2007b). The included studies differed in the types of plaster cast (upper leg, lower leg, cylinder, or brace). Furthermore, there was a variation in the duration of immobilization: ranging from 15 days (Kujath 1993), up to 43 days (Lapidus 2007a).

In the included studies the primary outcome parameter was VTE. Deep venous thrombosis, both symptomatic and asymptomatic, was diagnosed by means of ascending venography (Jorgensen 2002; Lapidus 2007b; Lassen 2002) or ultrasound (Kock 1995; Kujath 1993; Lapidus 2007a). If ultrasound was used suspect findings had to be confirmed by venography. Clinically suspected PE had to be confirmed by ventilation-perfusion scintigraphy, angiography or spiral CT-scanning. Information concerning the number of patients with symptomatic and asymptomatic VTE and the extent of the DVT was collected. Secondary outcome parameters were mortality and side effects in both treatment and control groups.

Excluded studies

For this update we excluded an additional five studies (Ahmad 2003; Goel 2009; Marlovits 2007; NCT00843492; Selby 2010) making a total of 39 excluded articles. The reasons for exclusion are stated in the Characteristics of excluded studies table. The previous version of this review (Testroote 2008) reported that 74 articles were excluded. This number included guidelines, multiple study reports of included studies and cohort studies therefore, where appropriate, these articles have now been removed from as excluded studies.

Risk of bias in included studies

We used the scoring scheme provided on the website of the Dutch Cochrane Centre to assess the validity and 'quality' of the included randomized controlled trials (www.cochrane.nl). Although we found the general quality of the six included studies good, some remarks should be added.

The true thromboembolic rate in unprotected patients was not really obtained because in all six studies the high-risk patients were excluded from participation. Therefore the incidence in unprotected patients and the effect of LMWHs might be underestimated.

In four studies the included patients had a wide variety of different traumas, ranging from fractures to soft tissue injuries and tendon ruptures (Jorgensen 2002; Kock 1995; Kujath 1993; Lassen 2002). Since the risk of DVT is found to be related to the presence and type of fracture, as well as the extent of soft tissue injury and type and duration of surgery, heterogeneity might be introduced. However, by randomization this effect should be minimized. Two studies focused on a specific group of trauma patients (Lapidus 2007a, Lapidus 2007b). Furthermore, the drop-out rate in the studies was on the high side.

Three studies used ultrasound (Kock 1995; Kujath 1993, Lapidus 2007a), and three used venography (Jorgensen 2002; Lapidus 2007b; Lassen 2002), for diagnosis of DVT. The latter is considered the 'Gold Standard', but in routine practice is rarely used as first line investigation for DVT. Duplex ultrasonography and compression ultrasonography have a lower sensitivity and specificity compared to venography, especially for diagnosing calf vein thrombosis (CBO 2008; Lensing 1989). This might be the reason for the differences in the results between Kock 1995 and the studies that used venography (Jorgensen 2002; Lapidus 2007b; Lassen 2002), since there were no other major differences in patient characteristics and interventions. However, it does not explain the differences between the results of Kock, Kujath and Lapidus (Kock 1995; Kujath 1993, Lapidus 2007a). Also, investigations with different sensitivities and specificities were used to diagnose potential PE .

Lassen 2002 included patients who received up to four days of LMWH (32% of patients). Another study treated all patients with LMWH for one week prior to randomization (Lapidus 2007b). This might equalize the effects in the two groups and lead to an underestimation of the treatment effect. The study of Lapidus therefore merely focused on duration of treatment and not on the indication of treatment itself (Lapidus 2007b).

The dose of 3500 anti-Xa IU of tinzaparin that Jorgensen 2002 used might be too low, since another study showed equal antithrombotic effect using 4500 anti-Xa IU of tinzaparin compared with 40 mg of enoxaparin, which is the standard dose in orthopedic surgery (Eriksson 2001). This possibly creates an underestimation of the effect of prophylaxis.

Effects of interventions

1. Morbidity

Kujath et al included 253 participants in their study, of whom 126 received a subcutaneous injection of Fraxiparin daily, and 127 patients received no prophylaxis (Kujath 1993). Incidences of VTE were 16.5% (n = 21) in the control group and 4.8% (n = 6) in the LMWH group (odds ratio (OR) 0.25; 95% confidence interval (CI) 0.10 to 0.65) (Kujath 1993). Kock et al included 163 patients in the control group (no treatment), and 176 patients were assigned to receive LMWH once daily (Kock 1995). The incidence of DVT in the prophylaxis group was 0% versus 4.3% (n = 7) in the control group (OR 0.06; 95% CI 0.00 to 1.04). In 2002, Jorgensen et al published the results of their venographic-controlled study, and diagnosed DVT in 10 out of 99 patients in the treatment group and in 18 out of 106 patients in the control group (Jorgensen 2002). This difference was not significant (OR 0.55; 95% CI 0.24 to 1.26). Finally, in 2002 Lassen et al found an incidence of 35 of 188 patients randomly assigned to receive placebo (18.6%) and in 17 of 183 patients (9%) in the LMWH group (OR 0.45; 95% CI 0.24 to 0.83) (Lassen 2002). Lapidus et al published two studies in 2007 (Lapidus 2007a; Lapidus 2007b). The study on thromboprophylaxis after surgical treatment of Achilles tendon rupture revealed a high incidence of thromboembolic events: 37% in the treatment group versus 40% in the placebo group. The results were not significant (P = 0.8) (Lapidus 2007a). The study on prolonged thromboprophylaxis during immobilization after ankle surgery also did not reveal a significant difference: 21% in the treatment group versus 31% in the placebo group (P = 0.07) (Lapidus 2007b).

Meta-analysis

We conducted a meta-analysis to establish whether there was evidence of a thromboprophylactic effect of LMWH, estimated the size of this effect, and investigated whether it was consistent across the included studies. We analyzed all patients together and subsequently the effect for different subcategories: surgically treated patients; patients with conservative treatment; patients with below-knee casts; patients with cylinder or above-knee casts; patients with fractures; patients with soft tissue injuries; PE; distal or proximal DVT; and finally the number of patients with symptomatic VTE.

All patients: Analysis 1.1

Six studies (Jorgensen 2002; Kock 1995; Kujath 1993; Lapidus 2007a; Lapidus 2007b; Lassen 2002) with a total of 1490 patients had incidences of injuries of the lower limb immobilized by a plaster cast or brace. The control group (n = 740) received no prophylaxis or placebo, the prophylaxis group received LMWH once daily (n = 750). The incidence of thromboembolic events in the control group ranged from 4.3% to 40% (134/740) and from 0% to 37% (75/750) in the prophylaxis group (OR 0.49:, 95% CI = 0.34 to 0.72), P = 0.00020.

Only patients with below-knee casts: Analysis 1.2

It was possible to obtain data on specific analyses of DVT in below-knee casts or braces from five studies (Jorgensen 2002; Kock 1995; Lapidus 2007a; Lapidus 2007b; Lassen 2002). In the studies of Lassen 2002 and Kujath 1993 the relation between the type of cast and occurrence of thrombosis was not part of the study design. However, from the study of Lassen 2002 the subgroup with rupture of the Achilles tendon could still be added. The incidence in the LMWH group of DVT ranged from 0% to 37%% and from 3.6% to 40% in controls (OR 0.54; 95% CI 0.37 to 0.80).

Only one study provided data on patients with cylinder or above-knee casts only (Kock 1995), with an incidence of 0% in the LMWH group and 2/24 (8.3%) in the control group.

Pulmonary embolism: Analysis 1.3

In the studies under review, PE was a rare complication in immobilization of the lower extremity. Lassen 2002 reported on four symptomatic patients in the control group; in two of them PE was confirmed by ventilation-perfusion scan. Kujath 1993 reported that in one patient in the group without prophylaxis there were clinical signs of a PE, but this diagnosis could not be proven by scintigraphic imaging.

Only patients with conservative treatment: Analysis 1.4

Four included studies provided incidences of DVT in conservatively treated patients (Jorgensen 2002; Kock 1995; Kujath 1993; Lassen 2002). When analyzed without consideration of type of cast or brace, the incidence ranged from 0% to 11.8% in the LMWH group and from 4.3% to 17.3% for the controls (OR 0.35; 95% CI 0.19 to 0.62), P = 0.00039.

Only surgically treated patients: Analysis 1.5

Information about surgically treated patients could be obtained from four studies (Jorgensen 2002; Lapidus 2007a; Lapidus 2007b; Lassen 2002). Both Kujath 1993 and Kock 1995 only analyzed conservatively treated patients. The incidence of DVT ranged from 7.2% to 37% in the LMWH group and from 18.0% to 40% in the control group (OR 0.54; 95% CI 0.37 and 0.80), P = 0.0018.

Fractures or soft tissue injuries: Analyses 1.6 and 1.7

Five studies provided information on patients with fractures (Jorgensen 2002; Kock 1995; Kujath 1993; Lapidus 2007b; Lassen 2002). These groups of patients contain both operated and conservatively treated patients. Results were significant (OR 0.53; 95% CI 0.36% to 0.78%), P = 0.0012. When analyzing the results from the patients with soft tissue injuries (Jorgensen 2002; Kock 1995; Kujath 1993; Lapidus 2007a; Lassen 2002), there is a significant difference as well (OR 0.39; 95% CI 0.22% to 0.68%), P = 0.00091.

Distal or proximal deep vein thrombosis: Analyses 1.8 and 1.9

Five studies provided information on the segment in which the thrombus was located (Jorgensen 2002; Kock 1995; Lapidus 2007a; Lapidus 2007b; Lassen 2002). The incidence of distal segment DVT, defined as below-knee DVT, ranged from 0% to 34.7% in participants who received LMWH and from 2.5% to 34.0% in the control group (OR 0.61; 95% CI 0.42 to 0.89), P = 0.0091. Proximal DVT (above knee) was rare; there were eight events in a total of 614 patients who received LMWH (incidences ranging from 0% to 4.0%) versus 20/603 (incidences ranging from 0.9% to 6.4%) in the controls (OR 0.41; 95% CI 0.19 to 0.91), P = 0.027.

Patients with symptomatic VTE: Analysis 1.10

All studies but one reported on patients with symptomatic VTE (Jorgensen 2002; Kock 1995; Kujath 1993; Lapidus 2007b; Lassen 2002). Lapidus 2007a did not report on patients with a symptomatic DVT due to fact that it was clinically not possible to differentiate symptoms of a possible DVT from those of normal postoperative findings. Lapidus 2007b reported on two events in the LMWH group and six events in the placebo group. Lassen 2002 mentioned two patients with PE and four with symptomatic DVT, all of them in the placebo group. Kujath 1993 reported on nine symptomatic patients, however, it is not clear whether they were in the treatment group or not. For that reason, this study is not included in analysis 1.10. Kock 1995 did not report on symptomatic patients in the Lancet publication, but additional information from five of the seven patients with thrombosis was found in a former publication. Jorgensen 2002 did not find any symptomatic VTE.

Symptomatic VTE was observed in two of 658 (0.3%) patients receiving LMWH versus 16 out of 645 (2.5%) patients in the control group (OR 0.16; 95% CI 0.05 to 0.56). If full information were available percentages might have been higher.

Heterogeneity

The results of the six eligible RCTs were fairly consistent (Jorgensen 2002; Kock 1995; Kujath 1993; Lapidus 2007a; Lapidus 2007b; Lassen 2002). When quantifying the results, there was some evidence of heterogeneity: I2 = 20%, P = 0.29. When performing a sensitivity analysis, the main results remained unchanged. For subgroup analysis the number of studies and patients included was considered to be too low to perform a sensitivity analysis.

2. Mortality

No mortality was reported in the six included studies (Jorgensen 2002; Kock 1995; Kujath 1993; Lapidus 2007a, Lapidus 2007b; Lassen 2002).

3. Adverse outcomes of treatment

Major side effects, such as hematoma, acute bleeding, allergy and thrombocytopenia were rare. Major bleeding did occur in two of 750 patients. Lassen reported major bleeding in two patients in the LMWH group (retroperitoneal bleeding in one and permanent discontinuation of LMWH due to minor bleeding in another) and in one patient in the placebo group (permanent discontinuation of LMWH due to minor bleeding). Fourteen patients in the LMWH group and twelve in the placebo group had a minor bleeding event (Lassen 2002).

Altogether, there were no significant differences between the treatment and control groups. Kock reported on five patients with minor complications (four small local hematomas, one facial eczema) (Kock 1995). Jorgensen saw four patients in the treatment group with a wound infection compared with one in the control group (Jorgensen 2002). Kujath did not observe any side effects (Kujath 1993). Lapidus did not report any major bleeding. In one study he mentioned one patient with a nosebleed after two days of dalteparin (Lapidus 2007b) and in the other he reported on two patients (one in the dalteparin group and one in the placebo group) who discontinued medication due to minor bleeding (Lapidus 2007a).

Discussion

As early as 1944 the first study on deep venous thrombosis (DVT) following leg injuries was published reporting incidences of 7% to 18% (Bauer 1944). Nonfatal and fatal pulmonary embolism (PE) complicate DVT of the lower extremities. Fatal PE used to be a common cause of death in hospitals because of the often clinically occult nature of DVT.

By meta-analysis of the data obtained from the six included studies (Jorgensen 2002; Kock 1995; Kujath 1993; Lapidus 2007a, Lapidus 2007b; Lassen 2002), we found an incidence of venous thromboembolism (VTE) ranging from 4.3% to 40% diagnosed by means of compression ultrasound and/or venography in patients who had a leg injury that had been immobilized in a plaster cast or a brace for at least one week and who received no prophylaxis, or placebo. This number was significantly lower (ranging from 0% to 37%) in patients who received daily subcutaneous injections of LMWH during the entire period of immobilization.

Comparable results were seen in the following subcategories: patients with a below-knee cast; surgically treated patients; conservatively treated patients; patients with fractures; patients with soft-tissue injuries; and patients with proximal or distal DVT. The odds ratios (OR) between the individual subgroups were rather similar, with an overlap of the confidence intervals (CI). Therefore it is not possible to indicate a subgroup where prophylaxis is not indicated. Numbers were too small for statistically significant results in the subgroups of only cylinder or above-knee casts, and for PE.

The discussion on the use of LMWH in immobilization of the lower leg focuses on two issues: the reduction of symptomatic VTE and the relevance of distal DVT. By meta-analysis we were able to show that in the treatment group a significant difference was obtained. The incidence of symptomatic VTE was reduced from 2.5% to 0.3% (OR 0.16; 95% CI 0.05 to 0.56).

Over eighty percent of DVTs diagnosed were located distally. Calf vein thrombosis propagates and becomes proximal in between 0% and 25% of patients, accounting for a mean of 10%. Up to 10% of proximal DVTs embolize massively and are potentially fatal, so this disorder can be very dangerous (Anonymous 1986; Schellong 2007). Opinions differ about the risk of post-thrombotic syndrome (PTS) after distal DVT. It is stated that the risk is considerably lower than in proximal DVT. Results are inconsistent on the relationship between the location of the initial thrombus and the subsequent development of PTS. Some prospective studies reported rates of PTS after distal DVT that were as high as 20% to 80% (McLafferty 1998; Schulman 1986). Hence, distal DVT appears to be associated with a substantial risk of subsequent PTS. Further research is indicated to elicit the exact role of distal DVT in the development of PTS (Kahn 2006).

The incidence of complications in the review seemed to be low compared with data in the literature. Major bleeding was reported in 0.27% (two out of 750 patients) and minor bleeding in up to 5.5% of patients (Lassen 2002). In contrast Reilmann reported up to 14% of patients with hematomas due to injections (Reilmann 1993). Another study even described it up to 28%, although part of the patients were not treated with LMWH but with unfractionated heparin (Zagrodnick 1990). In our six included studies no cases of heparin-induced thrombocytopenia were described, which is in concordance with the observation that this condition is seldom seen in combination with LMWH.

The six studies used different types of LMWH. The total number of patients was insufficient to evaluate which type of LMWH to choose. Evidence published so far indicates that any differences between LMWH preparations, if they exist, must be extremely small (Geerts 2004). It is unlikely that a properly sized and designed study comparing the various LMWHs will ever take place. Sample size calculations quickly reach over 10,000 if one considers appropriate definitions of 'non inferiority' when comparing the various antithrombotic regimens (Vaitkus 2004).

Venography is considered the most accurate method of diagnosing DVT (Abelseth 1996; Bergqvist 2002). It is an invasive procedure and there is a reported incidence of serious adverse reactions to the contrast media in the range of 0.4% to 2% (Lensing 1990). Duplex ultrasound is the most common non-invasive test used to diagnose venous thrombosis of the extremities. Compared with venography, ultrasound has been shown to be reliable in the diagnosis of proximal symptomatic DVT, with a sensitivity and specificity of over 90%. However, for distal thrombosis a sensitivity of 73% can be reached when combining compression ultrasound with color-doppler ultrasound (CBO 2008). Considering the properties of the imaging methods used to diagnose PE, a recent systematic review showed a sensitivity of 86% for the ventilation-perfusion scintigraphy and a specificity of 46% compared with pulmonary angiography. For the CT scan the percentages were respectively 85% and 94% (Hayashino 2005). Consequently, the number of instances of DVT and PE missed seems to be acceptable when including studies with different diagnostic procedures and should not influence our conclusions to a major extent. However, an underestimation of the incidence of VTE can occur when using ultrasound, CT-scan or ventilation-perfusion scanning.

Among surgeons there is a consensus that prophylaxis should be prescribed to moderate and high risk patients. Opinions differ, however, on the definitions of moderate and high risk. Several attempts have been made to stratify the risk for VTE of immobilized patients (Gearhart 2000; Zagrodnick 1990). Knudson developed a scheme, based on analysis of 1602 episodes of VTE using the National Trauma Data Bank, to identify trauma patients with a high risk of thrombosis (Knudson 2004). Fracture of the lower limb and an age of over 40 years were among the factors used for selection. However, she also stated that in this way 90% of cases of patients with VTE would be identified and 10% would be missed (Knudson 2004). By contrast, in another study patients under 40 years of age with soft tissue injuries also sustained DVT (Kock 1995). Up to now no stratification method has proven its superiority or has gained general acceptance.

In most cases where prophylaxis was prescribed, it was administered throughout the period of immobilization. Only Lapidus randomized patients after administration of LMWH for one week. No significant result was obtained between the treatment and the placebo group (Lapidus 2007b). Although it is clear that the former strategy works, there are no data on the optimal period of administration of LMWH.

The finding of an increased incidence of DVT in an untreated population calls for measures and thromboprophylaxis seems necessary if immobilization in a cast or brace is needed. Post-traumatic DVT can lead to PE or long-term damage in the form of PTS (Kakkar 1994). Low molecular weight heparin has not shown to be effective in reducing the incidence of VTE. The possible complications of major bleeding events (2/750 patients or 0.3%) and heparin-induced thrombopenia (none in this review) have shown to be extremely rare, and do not outweigh the beneficial effect of reduction of thromboses.

Authors' conclusions

Implications for practice

Use of low molecular weight heparin (LMWH) in outpatients significantly reduces the number of venous thromboembolic events when a plaster cast or brace is required. Because DVT venous thrombosis can lead to serious morbidity, we advise administration of LMWH during the entire period of immobilization of the lower extremity. This advice accounts for both lower and above-knee casts or braces.

Implications for research

Even with LMWH as a prophylactic measure, incidences of DVT ranging from 0% to 10% mean a very high absolute rate of morbidity in the population, given the enormous frequency of trauma to the leg. Immobilization should be avoided as much as possible, and treatment requiring less immobilization should always be considered. In order to further reduce the number of venous thromboembolic events we encourage all research to develop less immobilizing treatment options, and to develop even more effective and safe thromboprophylactic drugs.

Development of even more effective LMWHs might be a challenge. At this moment it remains difficult to prove superiority of a specific LMWH since the research needed will require a huge number of patients. Of interest is the development of new groups of drugs.

This review did not focus on the ongoing discussion on the clinical relevance of calf vein thrombosis. It simply confirmed its more frequent occurrence in immobilized patients. Future research might bring more clarity in the discussion on the significance of calf vein thrombosis.

Since the optimal period of treatment is unclear, further research should be performed to get more insight into this matter.

In this analysis we did not focus on scoring systems and individual risk factors. Future research might give more directives on specific advice for the different subgroups based on patient and trauma characteristics.

Acknowledgements

We are indebted to Mrs S Morrenhof-Atkinson for carefully reviewing the text of the review on its grammatical content.

Data and analyses

Download statistical data

Comparison 1. Low molecular weight heparin versus no prophylaxis/placebo
Outcome or subgroup titleNo. of studiesNo. of participantsStatistical methodEffect size
1 DVT: irrespective of type of plaster, whether operated or not61490Odds Ratio (M-H, Random, 95% CI)0.49 [0.34, 0.72]
2 DVT: in below-knee cast, whether operated or not5894Odds Ratio (M-H, Fixed, 95% CI)0.54 [0.37, 0.80]
3 PE3896Odds Ratio (M-H, Fixed, 95% CI)0.20 [0.01, 4.23]
4 DVT: only non-operated patients4788Odds Ratio (M-H, Fixed, 95% CI)0.35 [0.19, 0.62]
5 DVT: operated patients4699Odds Ratio (M-H, Fixed, 95% CI)0.54 [0.37, 0.80]
6 DVT: fractures5817Odds Ratio (M-H, Fixed, 95% CI)0.53 [0.36, 0.78]
7 DVT: soft-tissue injuries5658Odds Ratio (M-H, Fixed, 95% CI)0.39 [0.22, 0.68]
8 DVT: distal segment51208Odds Ratio (M-H, Fixed, 95% CI)0.61 [0.42, 0.89]
9 DVT: proximal segment51217Odds Ratio (M-H, Fixed, 95% CI)0.41 [0.19, 0.91]
10 Symptomatic VTE41303Odds Ratio (M-H, Fixed, 95% CI)0.16 [0.05, 0.56]
Analysis 1.1.

Comparison 1 Low molecular weight heparin versus no prophylaxis/placebo, Outcome 1 DVT: irrespective of type of plaster, whether operated or not.

Analysis 1.2.

Comparison 1 Low molecular weight heparin versus no prophylaxis/placebo, Outcome 2 DVT: in below-knee cast, whether operated or not.

Analysis 1.3.

Comparison 1 Low molecular weight heparin versus no prophylaxis/placebo, Outcome 3 PE.

Analysis 1.4.

Comparison 1 Low molecular weight heparin versus no prophylaxis/placebo, Outcome 4 DVT: only non-operated patients.

Analysis 1.5.

Comparison 1 Low molecular weight heparin versus no prophylaxis/placebo, Outcome 5 DVT: operated patients.

Analysis 1.6.

Comparison 1 Low molecular weight heparin versus no prophylaxis/placebo, Outcome 6 DVT: fractures.

Analysis 1.7.

Comparison 1 Low molecular weight heparin versus no prophylaxis/placebo, Outcome 7 DVT: soft-tissue injuries.

Analysis 1.8.

Comparison 1 Low molecular weight heparin versus no prophylaxis/placebo, Outcome 8 DVT: distal segment.

Analysis 1.9.

Comparison 1 Low molecular weight heparin versus no prophylaxis/placebo, Outcome 9 DVT: proximal segment.

Analysis 1.10.

Comparison 1 Low molecular weight heparin versus no prophylaxis/placebo, Outcome 10 Symptomatic VTE.

Appendices

Appendix 1. CENTRAL search strategy

#1MeSH descriptor: [Thrombosis] this term only1177
#2MeSH descriptor: [Thromboembolism] this term only992
#3MeSH descriptor: [Venous Thromboembolism] this term only275
#4MeSH descriptor: [Venous Thrombosis] explode all trees2164
#5(thromboprophyla* or thrombus* or thrombotic* or thrombolic* or thromboemboli* or thrombos* or embol*):ti,ab,kw 11702
#6MeSH descriptor: [Pulmonary Embolism] explode all trees858
#7PE or DVT or VTE:ti,ab,kw 2160
#8((vein* or ven*) near thromb*):ti,ab,kw 4969
#9#1 or #2 or #3 or #4 or #5 or #6 or #7 or #8 13394
#10MeSH descriptor: [Immobilization] explode all trees553
#11MeSH descriptor: [Mobility Limitation] explode all trees139
#12MeSH descriptor: [Splints] this term only342
#13MeSH descriptor: [Braces] this term only288
#14MeSH descriptor: [Casts, Surgical] explode all trees377
#15immobili* 1598
#16brace* 793
#17splint* 1348
#18plaster* 709
#19cast 1738
#20#10 or #11 or #12 or #13 or #15 or #16 or #17 or #18 or #19 5169
#21MeSH descriptor: [Heparin, Low-Molecular-Weight] explode all trees1632
#22*heparin* or LMWH or nadroparin* or fraxiparin* or enoxaparin or Clexane or klexane or lovenox or dalteparin or Fragmin or ardeparin or normiflo or tinzaparin or logiparin or Innohep or certoparin or sandoparin or reviparin or clivarin* or danaproid or danaparoid or bemiparin or bioparin or Alphaparin or Troparin 8494
#23antixarin or ardeparin* or bemiparin* or Zibor or cy 222 or embolex or monoembolex or Mono-embolex or parnaparin* or "rd 11885" or tedelparin or Kabi-2165 or Kabi 2165 196
#24emt-966 or emt-967 or pk-10169 or pk10169 20
#25cy-216 or cy216 or seleparin* or tedegliparin or seleparin* or tedegliparin* or tedelparin or Boxol or Liquemine 85
#26fr-860 14
#27wy90493 or wy-90493 10
#28kb-101 or kb101 or lomoparan or orgaran 65
#29parnaparin or fluxum or lohepa or lowhepa or "op 2123" or parvoparin 52
#30AVE5026 or M118 or RO-14 44
#31#21 or #22 or #23 or #24 or #25 or #26 or #27 or #28 or #29 or #30 8561
#32#9 and #20 and #31 in Trials68

Feedback

Anticoagulant feedback, 14 February 2011

Summary

Feedback received on this review, and other reviews and protocols on anticoagulants, is available on the Cochrane Editorial Unit website at http://www.editorial-unit.cochrane.org/anticoagulants-feedback.

What's new

DateEventDescription
4 September 2013New citation required but conclusions have not changedSearches were rerun. No new studies were included. Five additional studies were excluded. One ongoing study added. Minor edits made. One new author joined review team. Conclusions not changed.
4 September 2013New search has been performedSearches were re-run. No new studies were included. Five additional studies were excluded. One ongoing study added.

History

DateEventDescription
14 February 2011AmendedLink to anticoagulant feedback added
10 November 2008AmendedAmendment to Plain language summary at the request of the authors. Amendments to contact details of two authors.
18 July 2008AmendedConverted to new review format.

Contributions of authors

MT assessed trial quality, extracted data.
WS assessed trial quality, extracted data.
HJ crosschecked information.
LJ coordinated and advised on statistical methods.

Declarations of interest

None known

Sources of support

Internal sources

  • No sources of support supplied

External sources

  • Chief Scientist Office, Scottish Government Health Directorates, The Scottish Government, UK.

    The PVD Group editorial base is supported by the Chief Scientist Office.

Characteristics of studies

Characteristics of included studies [ordered by study ID]

Jorgensen 2002

Methods

Study design: randomized, controlled, assessor-blinded, open, multicenter trial.

Method of randomization: random numbers.

Concealment of allocation: sealed envelopes.

Losses to follow up: 95; treatment group 49; control group 46.

Intention-to-treat analysis: no.

Participants

Country: Denmark.

Number: 300 (treatment group 148; control group 152).

Age: adult patients > 18 years (range 18 to 93).

Sex (male/female): treatment group 79/69; control group 93/59.

Inclusion criteria: planned plaster immobilization of the lower leg for at least 3 weeks.

Exclusion criteria: pregnancy; allergy to heparin or contrast media; known liver or renal impairment; uncontrolled hypertension; bleeding disorders; recent GI bleeding; or inability to perform self injection.

Interventions

Treatment group: LMWH 3500 IU anti-Xa of tinzaparin (Innohep) once daily.

Control group: no prophylaxis.

OutcomesAt cast removal unilateral venography was performed.
NotesDose of tinzaparin relatively low; contains both operated and non-operated patients; previous DVT is not excluded; 205/300 were included in final assessment.
Risk of bias
BiasAuthors' judgementSupport for judgement
Allocation concealment (selection bias)Low riskSealed envelopes.

Kock 1995

Methods

Study design: randomized, controlled, open trial.

Method of randomization: randomization list stratified for varicose veins and obesity.

Concealment of allocation: not reported.

Losses to follow up: 5 refused to take part; 32 excluded due to exclusion criteria; data not evaluated on 52; treatment group 21; control group 31.

Intention-to-treat analysis: yes.

Participants

Country: Germany.

Number: 428 recruited; 5 refused to take part; 32 excluded due to exclusion criteria; 339 (treatment group 176; control group 163).

Age mean + (range): treatment group 34.1 years (18 to 63); control group 33.5 years (range 18 to 64).

Sex (male/female): treatment group 104/72; control group 104/59.

Inclusion criteria: age 18 to 65; conservative treatment of injury with below-knee cast or cylinder cast.

Exclusion criteria: previous DVT; pregnancy; clotting disorders or anticoagulation medication; bleeding; chronic venous insufficiency; contraindications for heparin prophylaxis; plaster cast after surgery.

Interventions

Treatment group: LMWH 32 mg (Mono-embolex NM) once daily.

Control group: no prophylaxis.

OutcomesAt randomization and at plaster removal compression ultrasound and duplex scanning was performed; suspected positive findings were confirmed by phlebography.
Notes 
Risk of bias
BiasAuthors' judgementSupport for judgement
Allocation concealment (selection bias)Unclear riskNot reported.

Kujath 1993

Methods

Study design: randomized, controlled, open trial.

Method of randomization: randomization plan "after Sachs".

Concealment of allocation: not reported.

Losses to follow up: 53 excluded post randomization.

Intention-to-treat analysis: no.

Participants

Country: Germany.

Number: 253; treatment group 126; control group 127 (306 admitted to the study; 53 excluded).

Age mean + (range): treatment group 32.9 years (16 to 70); control group 35.6 years (range 16 to 76).

Sex (male/female): treatment group 69/57; control group 77/50.

Inclusion criteria: age over 16 years; injury of the lower limb being treated conservatively; immobilization by a plaster cast applied for at least 7 days.

Exclusion criteria: known thrombopathy; oral anticoagulation; recent brain or GI bleeding; acute pancreatitis; inflammatory heart disease.

Interventions

Treatment group: LMWH 36 mg heparin fraction calcium (Fraxiparin ) once daily.

Control group: no prophylaxis.

OutcomesAfter plaster removal or at occurrence of symptoms compression ultrasound to diagnose DVT; in case of doubtful or positive findings a phlebography was carried out. In case of suspected PE scintigraphic analysis was performed.
NotesNone of the patients were operated on.
Risk of bias
BiasAuthors' judgementSupport for judgement
Allocation concealment (selection bias)Unclear riskNot reported.

Lapidus 2007a

Methods

Study design: randomized, controlled, double blind trial.

Method of randomization: by computer.

Concealment of allocation: not specifically reported but states identical syringes were prefilled with either dalteparin or sodium chloride.

Losses to follow up: 4.

Intention-to-treat analysis: no.

Participants

Country: Sweden.

Number: 105; treatment group 52; control group 53.

Age mean (SD): treatment group 37 years (8); control group 42 years (9).

Sex (male/female): treatment group 41/11; control group 42/11.

Inclusion criteria: age 18 to 75 years; admitted for an acute (0 to 72 hours) Achilles tendon rupture accepted for surgery.

Exclusion criteria: inability or refusal to give informed consent; ongoing treatment with anticoagulant therapy; known allergy for contrast media; kidney disorder; recent thromboembolic event; recent surgery; known malignancy; current bleeding disorder; pregnancy; treatment with platelet inhibitors.

Interventions

Treatment group: LMWH dalteparin 5000 units sc once daily until removal of the plaster cast.

Control group: placebo.

OutcomesDiagnosis of DVT by means of ultrasound and confirmation by venography.
Notes 
Risk of bias
BiasAuthors' judgementSupport for judgement
Allocation concealment (selection bias)Low riskIdentical syringes were prefilled with either dalteparin or sodium chloride.

Lapidus 2007b

Methods

Study design: randomized, controlled, double blind trial.

Method of randomization: not reported.

Concealment of allocation: not specifically reported but states identical syringes were prefilled with either dalteparin or sodium chloride.

Losses to follow up: 75.

Intention-to-treat analysis: no.

Participants

Country: Sweden.

Number: 272; treatment group 136; control group 136.

Age mean (SD): treatment group 49 years (14); control group 48 years (14).

Sex (male/female): treatment group 62/74; control group 62/74.

Inclusion criteria: age 18 to 75 years; admitted for an acute (0 to 72 hours) ankle fracture and accepted for surgery.

Exclusion criteria: inability or refusal to give informed consent; ongoing treatment with anticoagulant therapy; known allergy for contrast media; kidney disorder; recent thromboembolic event; recent surgery; known malignancy; current bleeding disorder; pregnancy; treatment with platelet inhibitors; multi-trauma.

Interventions

Treatment group: LMWH dalteparin 5000 units sc once daily until removal of the plaster cast.

Control group: placebo.

OutcomesDiagnosis of DVT by means of ascending venography.
NotesAll patients treated with LMWH one week before randomization.
Risk of bias
BiasAuthors' judgementSupport for judgement
Allocation concealment (selection bias)Low riskIdentical syringes were prefilled with either dalteparin or sodium chloride.

Lassen 2002

  1. a

    BP: blood pressure
    DVT: deep vein thrombosis
    GI: gastrointestinal
    Hg: mercury
    IU: international units
    LMWH: low molecular weight heparin
    MI: myocardial infarction
    PE: pulmonary embolism
    sc: subcutaneous
    UFH: unfractionated heparin
    VTE: venous thromboembolism

Methods

Study design: randomized, controlled, double blind trial.

Method of randomization: computer (blocks of four).

Concealment of allocation: not specifically reported but states identical syringes were prefilled with either reviparin or placebo.

Losses to follow up: 69 excluded.

Intention-to-treat analysis: no.

Participants

Country: Denmark.

Number: 440; treatment group 217; control group 223.

Age median (interquartile range): treatment group 47 years (37 to 55); control group 47 years (37 to 56).

Sex (male/female): treatment group 112/105; control group 114/108.

Inclusion criteria: age 18 years or older; fracture of the leg or rupture of the Achilles tendon requiring at least 5 weeks of immobilization in a plaster cast or brace within 4 days of the injury.

Exclusion criteria: body weight < 35 kg; pre-existing VTE; systolic BP > 200 mm Hg or diastolic BP > 110 mm Hg; cerebral vascular aneurysm; cerebral vascular accident within the preceding 3 weeks; active gastroduodenal ulcer; bacterial endocarditis; platelet count 1000,000/cu mm; previous treatment with UFH or LMWH, fibrinolytic agents or oral anticoagulants; known hypersensitivity to contrast media; kidney disorder; MI within the preceding 3 months; multiple myeloma; pregnancy; history of drug or alcohol abuse.

Interventions

Treatment group: LMWH reviparin (1750 anti-Xa units) once daily.

Control group: placebo.

OutcomesVenography was performed within one week after removal of the plaster to diagnose DVT. In cases of suspected PE, ventilation-perfusion lung scanning or pulmonary angiography was performed.
NotesStudy contains both operated and non-operated patients; up to four days of LMWH prophylaxis was allowed before randomization.
Risk of bias
BiasAuthors' judgementSupport for judgement
Allocation concealment (selection bias)Low riskIdentical syringes were prefilled with either reviparin or placebo.

Characteristics of excluded studies [ordered by study ID]

StudyReason for exclusion
  1. a

    DVT: deep vein thrombosis
    LMWH: low molecular weight heparin
    PE: pulmonary embolism
    SC: subcutaneous
    UFH: unfractionated heparin
    VTE: venous thromboembolism

Abelseth 1996Prospective incidence study, not a randomized or controlled clinical trial; operated patients without plaster immobilization and LMWH. Clinical and not outpatients.
Ageno 2004Survey on thrombosis prophylaxis by Italian orthopedic surgeons.
Ahmad 2003This study focuses on pathophysiology of heparin-induced thrombocytopenia (HIT) syndrome. The object was to determine the relative generation and functionality of AHPF4 antibodies in patients who were immobilized with plaster casts receiving 1750 IU of clivarin (reviparin) or a placebo. It is a substudy of the included study Lassen 2002.
Anonymous 1991Not a randomized or controlled clinical trial.
Anonymous 1995Not a randomized or controlled clinical trial.
Armbrecht 1993Patients operated for tendon rupture, one group treated with plaster and LMWH; the other group with early functional mobilization without prophylaxis. No clinical DVTs seen.
Bauer 1944Not a randomized or controlled clinical trial.
Breyer 1984Not a randomized or controlled clinical trial.
Bridges 2003LEAP-study (LMWH expedited Anticoagulation Program) to decrease number of inpatient days on warfarin and total hospital days for trauma patients requiring DVT. Case-control study.
Eriksson 2001Randomized controlled trial. Comparison of fondaparinux and enoxaparin after hip-fracture surgery.
Freeark 1967Not a randomized or controlled clinical trial.
Geerts 1994Prospective study of VTE after major trauma. No prophylaxis against VTE.
Geerts 1996Randomized controlled clinical trial of LMWH and low-dose heparin. Focus on major trauma, not outpatients.
Gehling 1994Prospective clinical study to determine incidence of DVT, no antithrombotic treatment.
Gehling 1998Randomized controlled clinical trial. Comparison of acetylsalicylic acid with LMWH in plaster immobilized trauma patients.
Giannadakis 2000Prospective clinical study to determine incidence of DVT in selected patients, no antithrombotic treatment.
Goel 2009A prospective randomized double-blind controlled trial using LMWH with saline injection as placebo in adults who had sustained an isolated fracture below the knee that required operative fixation. Study authors did not focus on immobilization of the lower leg in plaster-cast, so this study does not meet our inclusion criteria. The study authors included 238 patients and all underwent bilateral venography for diagnosis of DVT. There was no statistically significant difference in the incidence of DVT between the patients treated with LMWH or placebo (P = 0.22). However, owing to a cessation of funding, recruitment had to be ended before the necessary sample size was established (another reason for exclusion). The study results could not categorically exclude a potentially beneficial role of LMWH-treatment, and the authors recommend a further randomized controlled trial is undertaken.
Greenfield 1997Randomized controlled clinical trial. Clinical trauma patients randomized to low-dose UFH, LMWH, pneumatic compression devices, or foot pumps with or without vena caval filters.
Haas 1989Observational study on the use and tolerance of LMWH in ambulant patients. Not focused on trauma.
Harenberg 1998Prospective cohort study to determine the clinical incidence of VTE and the tolerance to LMWH in operated and not operated surgical and orthopedic patients.
Hjelmstedt 1968Not a randomized or controlled clinical trial.
Kannus 1991Review on treatment for acute tears of the lateral ligaments of the ankle. Not focused on subject of thrombosis prophylaxis.
Knudson 1996Randomized controlled clinical trial; LMWH in high-risk trauma patients, compared with mechanical methods of prophylaxis.
Knudson 2004Retrospective study to identify VTE incidence and risk factors in trauma patients using the American College of Surgeons National Trauma Data Bank.
Kudsk 1989Not a randomized or controlled clinical trial. Focuses on multi trauma patients.
Lassen 2000Not a randomized or controlled clinical trial.
Lippert 1995Not a randomized or controlled clinical trial.
Marlovits 2007This study focused on prolonged thrombosis prophylaxis after arthroscopic surgery rather than immobilization of the lower leg after trauma and was excluded for that reason.
Martinole 2003Not a randomized or controlled clinical trial.
Micheli 1975Case report, expert opinion.
NCT00843492The purpose of this ongoing study sponsored by GlaxoSmithKline is to evaluate the efficacy and safety of fondaparinux in comparison with a LMWH (nadroparin) in preventing VTE in patients with leg injuries below the knee that require a cast or other type of immobilization but not surgery. This study does not meet our inclusion criteria (LMWH versus placebo or no prophylaxis),
Nesheiwat 1996Case report and literature review.
Reilmann 1988Not a randomized or controlled clinical trial. Prospective study in which patients received LMWH plus dihydroergotamine (DHE) versus heparin alone or low-dose continuous intravenous heparin.
Reilmann 1993Not a randomized or controlled clinical trial. Study of 97 trauma patients who received heparin fragment calcium during admission and continued afterwards throughout cast period, compared with two groups without prophylaxis: Achilles tendon ruptures and talofibular ruptures.
Schultz 2004Focus on multi trauma patients.
Selby 2010In this study (known as the D-KAF trial) consecutive patients with isolated fractures of the distal leg requiring surgery were randomized to dalteparin 5000 IU or placebo once daily SC. Patients were screened using proximal ultrasound (only of the upper leg, not the calf) at day 14. The researchers were interested in clinically important venous thromboembolism (CIVTE). The study authors found that the overall incidence of CIVTE was so low (1.9%; 95% CI 0.7 to 4.7%) with no observed differences between dalteparin and placebo, that recruitment was stopped early. For this reason, we did not include this study in our meta-analysis. However, the study demonstrates the large discrepancy between trials that utilize venographic outcomes (all DVTs) and CIVTE.
Spieler 1972Not a randomized or controlled clinical trial.
Wolf 1992Cohort of 515 patients with plaster immobilization of the lower leg treated with LMWH; no comparison.
Zagrodnick 1990Retrospective data and prospective study to evaluate self-injection of UFH and LMWH .

Characteristics of ongoing studies [ordered by study ID]

NCT00881088

  1. a

    DVT: deep vein thrombosis
    PE: pulmonary embolism

Trial name or titlePROTECT: Prophylaxis of thromboembolic complications trial
MethodsA prospective, randomized, controlled, single blinded, multi-center trial. The purpose of this study is to determine the need for thromboprophylaxis in patients with a fracture of the lower extremity being treated conservatively in a below-knee plaster cast and to assess if both of the two tested prophylactic treatments are effective for this indication.
ParticipantsPatients of at least 18 years with a nonsurgical fracture of the lower extremity requiring immobilization in a below-knee plaster cast for a minimum of 4 weeks.
InterventionsPatients will be randomly assigned to one of three groups: one receiving nadroparin (2850 IE anti-Xa = 0.3 ml, given once daily), one receiving fondaparinux (2.5 mg = 0.5 ml, given once daily) and one receiving no prophylaxis.
OutcomesAt the time of removal of the plaster cast symptoms or signs suggestive of DVT or PE will be noted and a color duplex ultrasonography of the treated limb will be performed in all patients by an experienced technician according to a strict diagnostic test protocol. When there is incompressibility of a vein or lack of flow the diagnosis of DVT is made. The technician will be blinded to treatment.
In case of a suspected pulmonary embolism pulmonary angiography will be performed.
Starting dateMay 2009
Contact informationDepartment of Surgery
VU Medisch Centrum
P.O. Box 7057
1007 MB Amsterdam
The Netherlands
Phone: +31(0)20-4444444 (pager *7310)
E-mail: marlieke.bruntink@gmail.com
NotesA study from the Netherlands, investigating the need for thromboprophylaxis in patients with a fracture of the lower extremity being treated conservatively in a below-knee plaster cast. Both fondaparinux and nadroparin are analysed for this indication, versus no prophylaxis.

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