128 – Is routine VTE prophylaxis needed for patients placed in walker boot immobilization?

William Fishley, Allison L. Boden, Rajesh Kakwani, Amiethab Aiyer.

Response/Recommendation: Patients in walker boot immobilization may be at increased risk of development of venous thromboembolism (VTE). Patients should be risk assessed and VTE prophylaxis offered on an individual basis.

Strength of Recommendation: Limited.

Rationale: Immobilization of the lower limb in a walker boot can provide an alternative to a cast for post-operative and non-operative management of many foot and ankle-related conditions. Potential benefits include the removal for hygiene purposes, the ability to perform range of motion exercises, and the potential to adjust the fit with resolution of swelling. Furthermore, a boot does not require a clinic visit for definitive removal.

A 2017 Cochrane Review which included eight randomized controlled trials (RCT), assessed the effectiveness of low-molecular-weight heparin (LMWH) for the prevention of VTE in patients with lower limb immobilization1. In patients who received no prophylaxis, the incidence of deep venous thrombosis (DVT) ranged from 4.3% to 40% but was reduced in patients who received prophylaxis. Most of the trials included in this review utilized only cast immobilization, while three studies also included patients immobilized in a brace. The authors concluded there was moderate-quality evidence that LMWH reduced the number of venous thromboembolic events. Another systematic review performed in 2019 found a lower risk of VTE when patients with temporary immobilization of the lower extremity received VTE prophylaxis2.

For this recommendation, RCT investigating VTE prophylaxis regimens in patients in boot or brace immobilization were identified. In addition, RCT were also included if they reported the incidence of VTE in patients immobilized in a boot, orthosis, or brace in comparison to a control group in any other form of immobilization, or no immobilization.

Four RCT of VTE prophylaxis regimens including patients in orthoses or braces were identified. All of them were included in the previously mentioned systematic review2. In patients requiring immobilization after fracture or achilles tendon rupture, Lassen et al., reported the incidence of DVT identified by venography as 19% in a placebo group compared to 9% in those receiving reviparin (p=0.01)3. Lapidus et al., reported no significant difference in the incidence of DVT identified by phlebography between patients receiving dalteparin or placebo following immobilization after ankle fractures4 or surgery for achilles tendon rupture (ATR)5. Finally, Samama et al., reported an incidence of VTE of 2.3% in patients receiving fondaparinux compared to 7.9% in those receiving nadroparin6. None of the studies presented sub-group data or analysis of those patients in boot or orthosis immobilization, and in all trials, most patients were immobilized in a cast.

Six additional RCT reporting the incidence of VTE during immobilization in a boot, brace, or orthosis compared to another form of immobilization were identified. Kortekangas et al., investigated patients with ankle fractures treated with an orthosis versus a cast7. There were no symptomatic DVT in the 80 patients treated in an orthosis for three weeks. There were 3 (3.6%) DVT recorded in the 83 patients treated in a cast, although this difference was not statistically significant. Lehtonen et al., randomized patients with ankle fractures to post-operative immobilization in a cast or early mobilization in a functional ankle brace8. Of the fifty patients treated in a cast, symptomatic DVT was identified in two patients (4%) compared to no DVT in the 50 patients in a brace.

In ATR, Groetelaers et al., investigated 60 patients randomized to either a cast or an Achillotrain flexible brace following minimally invasive repair9. Symptomatic DVT occurred in two (8%) of patients in the cast group compared to none in the Achillotrain group. Patients in the Achillotrain group were allowed to weight-bear and began mobilization earlier than the cast group. The United Kindom Study of tendo Achilles Rehabilitation (UKSTAR) RCT compared a brace against cast immobilization in ATR managed conservatively in 540 patients10. Symptomatic DVT was recorded in 2% of patients in a functional brace compared to 1% in a plaster (p = 0.51). Aufwerber et al., reported the incidence of asymptomatic DVT on ultrasound imaging in 150 patients following ATR surgery11. DVT was recorded in 29% of patients in a dynamic orthosis, compared to 31% of patients immobilized for two weeks in cast and then transferred into an Aircast boot. Patients in the dynamic orthosis group were permitted to begin weight bearing and mobilization earlier following surgery. The clinical importance of asymptomatic DVT remains uncertain12–14.

In an RCT by Lamb et al., 584 patients with ankle sprains were randomized to receive a below-knee cast, Aircast brace, Bledsoe boot, or tubular compression bandage. DVT was identified in one patient in every treatment group except for the compression bandage15.

None of these six studies identified a statistically significant difference in the incidence of VTE between forms of immobilization. With the exception of the study by Aufwerber et al.11, the incidence of VTE was a secondary outcome. As the search strategy was focused on VTE, it is acknowledged that other trials investigating the use of a brace or orthosis and reporting VTE only as a secondary outcome may not have been captured in the search. However, it is expected that such studies are likely to be similarly underpowered to detect a difference in the incidence of symptomatic DVT.

In summary, limited evidence was identified to establish if routine VTE prophylaxis reduces the risk of VTE in walker boot immobilization. All four RCT of VTE prophylaxis combined data for patients in a boot or orthosis with patients in cast immobilization. In six RCT comparing patients immobilized in a boot or orthosis versus those in cast immobilization, there were no statistically significant differences in the incidence of VTE. These studies displayed heterogeneity in the type of injury, operative versus non-operative intervention, and the type of orthosis. Additional variation, even within individual studies, in weight-bearing status and mobilization of the ankle and foot are also likely to affect the incidence of VTE. However, the literature demonstrates that VTE may occur in patients placed in boot or brace immobilization, when the patients are instructed to weight-bear at < 50% early after surgery11.

In view of the limitations, future research specifically investigating VTE in patients immobilized in a walker boot is needed. We recommend that patients should be assessed and VTE prophylaxis offered on an individual basis according to patient factors, weight-bearing status, and mobilization status.


1.         Zee AA, van Lieshout K, van der Heide M, Janssen L, Janzing HM. Low molecular weight heparin for prevention of venous thromboembolism in patients with lower-limb immobilization. Cochrane Database Syst Rev. 2017;8:CD006681. doi:10.1002/14651858.CD006681.pub4

2.         Horner D, Stevens JW, Pandor A, et al. Pharmacological thromboprophylaxis to prevent venous thromboembolism in patients with temporary lower limb immobilization after injury: systematic review and network meta-analysis. J Thromb Haemost. 2020;18(2):422-438. doi:10.1111/jth.14666

3.         Lassen MR, Borris LC, Nakov RL. Use of the low-molecular-weight heparin reviparin to prevent deep-vein thrombosis after leg injury requiring immobilization. N Engl J Med. 2002;347(10):726-730. doi:10.1056/NEJMoa011327

4.         Lapidus LJ, Ponzer S, Elvin A, et al. Prolonged thromboprophylaxis with Dalteparin during immobilization after ankle fracture surgery: a randomized placebo-controlled, double-blind study. Acta Orthop. 2007;78(4):528-535. doi:10.1080/17453670710014185

5.         Lapidus LJ, Rosfors S, Ponzer S, et al. Prolonged thromboprophylaxis with dalteparin after surgical treatment of achilles tendon rupture: a randomized, placebo-controlled study. J Orthop Trauma. 2007;21(1):52-57. doi:10.1097/01.bot.0000250741.65003.14

6.         Samama CM, Lecoules N, Kierzek G, et al. Comparison of fondaparinux with low molecular weight heparin for venous thromboembolism prevention in patients requiring rigid or semi-rigid immobilization for isolated non-surgical below-knee injury. J Thromb Haemost. 2013;11(10):1833-1843. doi:10.1111/jth.12395

7.         Kortekangas T, Haapasalo H, Flinkkilä T, et al. Three week versus six week immobilisation for stable Weber B type ankle fractures: randomised, multicentre, non-inferiority clinical trial. BMJ. 2019;364:k5432. doi:10.1136/bmj.k5432

8.         Lehtonen H, Järvinen TLN, Honkonen S, Nyman M, Vihtonen K, Järvinen M. Use of a cast compared with a functional ankle brace after operative treatment of an ankle fracture. A prospective, randomized study. J Bone Joint Surg Am. 2003;85(2):205-211. doi:10.2106/00004623-200302000-00004

9.         Groetelaers RPTGC, Janssen L, van der Velden J, et al. Functional Treatment or Cast Immobilization After Minimally Invasive Repair of an Acute Achilles Tendon Rupture: Prospective, Randomized Trial. Foot Ankle Int. 2014;35(8):771-778. doi:10.1177/1071100714536167

10.       Costa ML, Achten J, Marian IR, et al. Plaster cast versus functional brace for non-surgical treatment of Achilles tendon rupture (UKSTAR): a multicentre randomised controlled trial and economic evaluation. Lancet. 2020;395(10222):441-448. doi:10.1016/S0140-6736(19)32942-3

11.       Aufwerber S, Heijne A, Edman G, Grävare Silbernagel K, Ackermann PW. Early mobilization does not reduce the risk of deep venous thrombosis after Achilles tendon rupture: a randomized controlled trial. Knee Surg Sports Traumatol Arthrosc. 2020;28(1):312-319. doi:10.1007/s00167-019-05767-x

12.       Raskob GE, Spyropoulos AC, Cohen AT, et al. Association Between Asymptomatic Proximal Deep Vein Thrombosis and Mortality in Acutely Ill Medical Patients. J Am Heart Assoc. 2021;10(5):e019459. doi:10.1161/JAHA.120.019459

13.       Warwick D, Samama MM. The contrast between venographic and clinical endpoints in trials of thromboprophylaxis in hip replacement. J Bone Joint Surg Br. 2000;82(4):480-482. doi:10.1302/0301-620x.82b4.9876

14.       Horner D, Hogg K, Body R. Should we be looking for and treating isolated calf vein thrombosis? Emerg Med J. 2016;33(6):431-437. doi:10.1136/emermed-2014-204230

15.       Lamb SE, Marsh JL, Hutton JL, Nakash R, Cooke MW, Collaborative Ankle Support Trial (CAST Group). Mechanical supports for acute, severe ankle sprain: a pragmatic, multicentre, randomised controlled trial. Lancet. 2009;373(9663):575-581. doi:10.1016/S0140-6736(09)60206-3