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Has lockdown influenced the incidence of VTE in total joint replacement during covid-19 pandemic?

1st March 2021

The pandemic has had a huge impact on the ability of healthcare professionals to deliver services to non-COVID-19 patients, such as elective operating in orthopaedics.

As the peak of the pandemic in the UK passed, the British Orthopaedic Association (BOA) and NHS England set out a phased return of elective orthopaedic services.1,2 Including a 14-day period of self-isolation prior to surgery, pre-operative C-19 testing, and surgery at a clean, ‘green’, non-COVID-19 site.1,2


Following the first lockdown, a retrospective UK study [Shehzaad et al] has looked at the risk effect of 14-day self-isolation, introduced to minimize the risk of transmission, on VTE incidence among 50 patients undergoing total joint replacement (TJR).

The study measured VTE incidence at two and four weeks post-surgery. Results show overall 8% of patients suffered a VTE complication, much higher than reported in the literature:

  • The team hypothesize that this rate relates to the 14-day self-isolation period and immobility prior to surgery,
  • And recommend that all patients undergoing TJR, that require a period of self-isolation, are VTE risk assessed prior to self-isolation and prescribed mechanical and/or chemical prophylaxis to reduce the likelihood of developing VTE.

All patients were administered VTE prophylaxis post-operatively, both chemical (low molecular weight heparin or aspirin, depending on surgeon preference) and mechanical (graduated compression stockings and intermittent pneumatic compression devices). All patients who developed a VTE were on low molecular weight heparin.


Results show the incidence of VTE was 8% (n = 4), clinical DVT was 2% (n = 1), and the incidence of non-fatal PE was 6% (n = 3) following TJR. Findings that are significantly higher than reported in the literature, namely:

O’Reilly et al3 reported an incidence of 1.9% for symptomatic non-fatal PE in 5,999 patients after orthopaedic elective surgery. Another group from Norway reported a cumulative incidence of 2.7% for symptomatic VTE, of which 1.1% developed a PE and 1.5% developed a DVT.4 A group in California looked at over 43,000 patients over a four-year period and reported a cumulative incidence of 2.1% and 2.8% of VTE after THA and TKA, respectively.5 Douketis et al6 performed a metanalysis of over 7,000 cases and reported an incidence of 3.2% for symptomatic VTE three months after TKA or THA.

The significant difference in incidence reporting favours the notion that the effect of self-isolation has an impact.

Prolonged immobility is a recognized risk factor for developing VTE, due to the venous stasis proposed by Rudolph Virchow.6 All patients had to undergo a 14-day period of self-isolation, which limited the amount of outdoor exposure and exercise they were able to do. In addition, the majority of these patients endured a significant deterioration in quality of life and pain as a result of cancelled and rescheduled operations due to the pandemic.7 This will have worsened their arthritis, made their immobility worse, and started a vicious cycle, further increasing their risk of developing VTE.

Patients awaiting TJR usually have problems mobilizing, with their arthritis pain reducing their mobility or patients requiring walking aids to mobilize. The majority of our patients were independently mobile. However, 38% required some form of walking aid to mobilize. Those using walking aids had a statistically significant increased risk of VTE in the study population (p = 0.016, chi-squared test).

All of the patients that developed VTE had some restricted mobility and required an aide. This suggests that reduced mobility is an additional risk factor for the development of VTE. This may be compounded by having to self-isolate, and therefore cause these patients to have a further reduction in their mobility in the self-isolation period. This further strengthens the hypothesis that immobility has had an influence.8

All patients who developed VTE were female. There has been research to suggest women are more prone to VTE due to pregnancy in the young patient, menopause, and hormone replacement therapy (HRT) in the older patient.9 Two of the patients were on HRT at some point prior to the surgery, but not in the run-up.

Obesity has been shown to be a risk factor for the development of VTE.10 The individuals who developed a VTE had a BMI > 29.9 kg/m2, classing them as obese. Studies show that women were more likely than men to change their weight prior to TJR, and younger patients were more likely to gain weight than older patients both before and after THA and TKA.11 The study hypothesizes this phenomenon to be much greater during self-isolation due to the immobility, as described above.

Ageing has another negative effect on endothelial dysfunction and venous insufficiency, leading to increased incidence of VTE.12 Patients over the age of 40 are at significantly increased risk compared with younger patients. This risk is estimated to be double with each subsequent decade.8 These patients become more immobile as they age, adding another major risk factor to their predisposition of developing VTE. All study patients who developed a VTE event were greater than 40, increasing their risk for VTE.

Another variable, not measured in the study, is pre-operative level of hydration of the patients. Hydration has played an important role in preventing VTE prior to major surgery, due to the increased blood viscosity.13 Many of study cohort had not had any oral fluids for almost 12 hours prior to admission, and a few patients had to wait longer to go down to theatre. The dehydration was, occasionally, exacerbated by lack of intravenous fluid prescription.

From the data, the study showed a significant increase in VTE events, with the only altered variable being immobility during the 14-day self-isolation following TJR.

Patients are encouraged to mobilize after their operation as much as possible which is guided by physiotherapy. Unfortunately, this service is not available at home for patients, and there may be a higher tendency toward sedentary activities rather than active mobilization.

Research has shown that standardized home therapy programmes significantly reduce the likelihood of VTE complications.14 Simple active ankle movements have been shown to increase maximum venous outflow and reduce blood rheology, which may reduce the development of VTE.15 In addition, initiation of mechanical prophylaxis (in the form of graduated compression stockings and intermittent pneumatic compression devices) have been shown to greatly reduce VTE development in patients > 70 years old with a hip fracture.16 The study therefore proposes initiating a home physiotherapy pre-hab programme with mechanical prophylaxis, which will be given to patients when they are informed of a date for their procedure.

There is some debate as to whether starting pre-operative chemical prophylaxis can reduce the risk of developing VTE. Many authors have reported no advantage initiating chemical prophylaxis preoperatively, with the incidence of VTE being equally distributed in both groups.17,18 In fact, Borgen et al18 and Wein et al19 reported a higher bleeding risk intra- and postoperatively. However, neither of the authors used low-dose aspirin as an anticoagulant, which has been shown to have a lower bleeding risk compared to other aggressive anticoagulants.20

Though this study offers some valuable data during the COVID-19 pandemic, it does not provide conclusive evidence that self-isolation has directly increased the incidence of VTE and calls for further large randomized controlled trials to determine this correlation and to assess the effectiveness of pre-operative administration of chemical and mechanical thromboprophylaxis.

The sample size was lower than other studies investigating VTE incidence, due to the slow restart of elective services in a smaller green site hospital. Many patients have also declined to continue with their planned surgeries due to the risk of COVID-19.7

From the study population, immobile females who use a walking aid carry the greatest risk of developing a VTE. The study advocates that all patients undergoing TJR, who require a period of self-isolation, are pre-assessed prior to self-isolation for their risk of VTE. If they are in a moderate to high-risk group, the study recommend they be offered a minimum of mechanical prophylaxis during self-isolation, advised on general measures of hydration, and maintain their usual levels of mobility. Those in the highest risk group should also be considered for mechanical and chemical prophylaxis in combination to further reduce their relative VTE risk.


  1. No authors listed. Re-starting non-urgent trauma and orthopaedic care: full guidance. British Orthopaedic Association. 2020. https://www.boa.ac.uk/uploads/ assets/9383a53f-36d8-4782-8fe264c691b39b15/BOA-Guidance-for-restart-full-docfinal2-v11.pdf (date last accessed 4 August 2020).
  2. British Orthopaedic Association. Evidence based suggestions for the return to elective orthopaedic surgery following the COVID-19 pandemic. https://www. boa.ac.uk/policy-engagement/journal-of-trauma-orthopaedics/journal-of-traumaorthopaedics-and-coronavirus/evidence-based-suggestions-for-the-return.html (date last accessed Last accessed 4th August, 2020).
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Sue Davenport-VP Marketing Communications
1st March 2021