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Quantifying the risk of venous thromboembolism for temporary lower limb immobilisation in ambulatory patients

Three Part Question

In [non surgical ambulatory patients with lower limb injury] does [temporary immobilisation] increase the three month risk of [venous thromboembolic disease or sudden death]

Clinical Scenario

A 30 year old patient attends your department 2 weeks following a lateral malleolar ankle fracture. They complain of increased pain and cramping up the calf. The toes are swollen but there are no clinical signs of compartment syndrome.

You are concerned about the possibility of DVT and arrange an ultrasound scan to investigate further. A junior doctor asks you what the incidence /pretest probability of venous thromboembolism is within this cohort of immobilised ambulatory patients.

You tell them that is an excellent question. And that you will give them one week to find out the answer for you.

Search Strategy

MEDLINE was searched using the OVID Interface from 1948 to July Week 1 2011. EMBASE was searched using the OVID Interface from 1980 to 2011 Week 27. The Cochrane Database of Systematic Reviews was also searched using direct terminology applicable to the three part question.

(exp IMMOBILIZATION/) OR (exp CASTS, SURGICAL/) OR (exp SPLINTS/) OR (immobilisation.ti,ab) OR ( OR (plaster AND of AND OR (plaster AND of AND paris.ti,ab) OR (plaster AND cast.ti,ab) OR (backslab.ti,ab) OR exp Splints/] AND [(lower AND limb.ti,ab) OR (lower AND OR exp LEG/ OR exp Lower extremity/] AND [(exp VENOUS THROMBOEMBOLISM/) OR (exp THROMBOEMBOLISM/) OR exp Deep Vein Thrombosis/ OR (exp PULMONARY EMBOLISM/) OR (deep AND vein AND OR (pulmonary AND OR (VTE.ti,ab) OR (exp DEATH, SUDDEN)]

Search Outcome

One hundred and twenty-four papers were retrieved, of which five were directly relevant to the three-part question. One systematic review was discounted due to substantial heterogeneity within subjects, inclusion of partly treated patients within the conservative arm and further methodological concerns (Schade and Roukis).

Relevant Paper(s)

Author, date and country Patient group Study type (level of evidence) Outcomes Key results Study Weaknesses
Patil et al
100 Ambulatory patients immobilised in lower limb cast for conservatively treated ankle fracturesProspective observational cohort (level of evidence 2b)Incidence of DVT on cast removal 5/100 = 5% (95% CI 1 to 9%) 72% patients were fully weight bearing within the plaster. Duration of time in cast ranged from 3 to 7 weeks.
Testroote et al
388 ambulatory non-surgical patients in temporary immobilisation following isolated lower limb injuryPrespecified subgroup analysis within systematic review (level of evidence 2a)Incidence of deep vein thrombosis in conservatively treated patients44/388 = 11.3% (no confidence intervals provided)Included studies which excluded those patients at high risk of VTE - likely underestimating incidence. No distinction made between proximal/distal and symptomatic/asymptomatic DVT.
Nilsson-Helander et al
100 consecutive patients with acute achilles tendon rupture, of which half were randomised to conservative non-surgical treatmentProspective observational cohort (level of evidence 2b)Colour duplex sonography verified thrombosis in all patients32/95 = 33.7%Small numbers. Underpowered. Initial thromboprophylaxis for operative patients and then based on surgical preference.
Colour duplex sonography verified thrombosis in non surgical patients18/46 = 39.1%
PIOPED verified pulmonary embolism in non surgical patients3/46 = 6.5%
Healey et al
New Zealand
208 patients with an injury to the tendo achilles requiring immobilisation in a cast, treated for >1/52 as an outpatient. Retrospective audit to identify patients with achilles injury, followed by cross reference with VTE database and retrospective medical record review to identify VTE events. Cumulative symptomatic VTE events within the cohort6.3% (95% CI 3.4 to 10.5)Patients with follow up outside district excluded. 20% cohort underwent some form of surgical intervention throughout the study period.
Confirmed Pulmonary Embolism within the study period1.4%
Proximal DVT within the study period1.9%
Distal DVT within the study period2.9%
Thomas and van Kampen
381 Orthopaedic patients in temporary lower limb immobilisation managed on an outpatient basis. Retrospective case series. All patients diagnosed with DVT over a 1 year period were cross checked against a plaster register to determine immobilisation statusIncidence of DVT7/381 (1.84%)Mixture of surgical and conservative patients. Retrospective - only accounts for patients presenting at their institution with acute symptoms and appropriately investigated for suspected DVT. Isolated PE ignored. No structured follow up No adjudication comittee No confidence intervals or estimation of variability.
Incidence of PE within DVT cases4/7 (57%)


Temporary immobilisation in non-surgical isolated limb trauma within the preceding 2 months has been recently associated with 2% of all venous thromboembolisms (Bertoletti et al). These events can be potentially fatal. Limb immobilisation has also recently been highlighted as provoking the highest risk of venous thromboembolism among all causes of immobilisation (Beam et al). National guidance promotes clear advice regarding thromboprophylaxis in hospital inpatients. There is little advice regarding ambulatory patients seen in the emergency department who are exposed to similar risk. To address the issue properly we must first understand the scale of the problem, by identifying the incidence of disease in order to quantify risk. There are several common issues regarding the majority of studies generating data within the designated cohort. First, the use of venous thromboembolism as an outcome generates controversy: an event can range from an isolated asymptomatic distal deep vein thrombosis to a life-threatening pulmonary embolism. Some would argue that these events have profoundly differing morbidity/mortality rates and as such should not be collated as an outcome. Second, many studies group post-surgical ambulatory together with conservatively treated patients. This can confound the emergency department cohort and should be carefully avoided when addressing epidemiological data through contemporary research.

Editor Comment

The incidence of venous thromboembolism following temporary immobilisation for isolated lower limb trauma in ambulatory patients is approximately 11%.

Clinical Bottom Line

The incidence of venous thromboembolism following temporary immobilisation for isolated lower limb trauma in ambulatory patients is approximately 11%. This rate can vary in different ambulatory cohorts from 2% to 30%, depending on the type of injury and immobilisation used. Although the majority of these events will be distal deep vein thrombosis, pulmonary emboli do occur in this cohort and contribute to cumulative incidence.

Level of Evidence

Level 2 - Studies considered were neither 1 or 3.


  1. Patil S, Gandhi J, Curzon I, et al. Incidence of deep-vein thrombosis in patients with fractures of the ankle treated in a plaster cast J Bone Joint Surg (Br) 2007;89-B:1340-3
  2. Testroote M, Stiger W, de Visser DC, et al. Low molecular weight heparin for prevention of venous thromboembolism in patients with lower-leg immobilization Cochrane Database of Systematic Reviews 2008, Issue 4
  3. Bertoletti L, Rhigini M, Bounameaux H, et al; Acute venous thromboembolism after non major orthopaedic surgery or post-traumatic limb immobilisation Thrombosis and Haemostasis 2011;105:739-741
  4. Nilsson-Helander K, Thurin A, Karlsson J, et al. High incidence of deep vein thrombosis after Achilles tendon rupture: a prospective study Knee surgery, Sports traumatology, Arthroscopy. 2009;17(10):1234-1238
  5. Beam DM, Courtney DM, Kabrehl C, et al. Risk of thromboembolism varies, depending on category of immobility in outpatients Annals of Emergency Medicine 2009;54(2):147-152
  6. Healey B, Beasley R, Weatherall M. Venous thromboembolism following prolonged cast immobilisation for injury to the tendo achillis. The Journal of Bone and Joint Surgery (Br) 2010;92-B:646-650
  7. Thomas S, van Kampen M. Should orthopedic outpatients with lower limb casts be given deep vein thrombosis prophylaxis? Clinical & Applied Thrombosis/Hemostasis 17(4):405-7
  8. Schade VL, Roukis TS. Antithrombotic pharmacologic prophylaxis use during conservative and surgical management of foot and ankle disorders: a systematic review. Clin Podiatr Med Surg 2011;28:571–88.