Venous thromboembolism (VTE) is a collective term referring to the diagnosis of deep vein thrombosis (DVT) or pulmonary embolism (PE). VTE is a commonly encountered diagnosis that can result in serious morbidity and a reported mortality of 10.6% within 30 days and 23% at one year¹. VTE can present in numerous different ways. Classically a patient with DVT will present with pain and swelling of the leg. A patient with PE is likely to present with symptoms such as chest pain, tachycardia, dyspnoea and haemoptysis².

In 2005, the House of Commons Health Committee reported that 25,000 people in the UK die from preventable VTE each year³ and NICE guidelines were introduced to facilitate an early reproducible process, which would allow prompt diagnosis and management of these patients.⁴ The guidance is predominantly based around the 2 level Wells score for both DVT⁵ (Figure 1) and PE⁶ (Figure 2) with the outcome of the score determining which subsequent investigation is performed. Even with the use of scoring systems such as this, it is down to the clinician to have a high index of suspicion for VTE where appropriate.

Figure 1. Two level DVT Wells score

Figure 2. Two level PE Wells score

Previously established significant risk factors for VTE include trauma, cancer, advanced age, obesity, family/personal history, cardiovascular disease, race¹⁵ and surgery⁷. Within surgery, orthopaedic procedures carry the highest risk, (1 in 45 after hip or knee replacement) second only to oncology⁸. Prior to discharge from a surgical unit, the index of suspicion for VTE is high. It is known that certain orthopaedic operations such as arthroplasty, pelvic fracture fixation and lower limb casts following foot & ankle surgery carry an increased risk of developing a VTE; therefore these patients commonly receive prolonged post-operative VTE prophylaxis for 28 days following total knee arthroplasty and 35 following total hip arthroplasty; according to NICE guidance CG92 or local trust policy. Recent evidence has also shown that increased surgical time increases the likelihood of a VTE post-operatively⁹. This heightens the risk of VTE in some orthopaedic procedures due to the nature of surgery and length of operative time required. Despite following guidance it is well evidenced that some patients continue to present with VTE following the cessation of prophylaxis^{10, 11}

The objectives of this study were to determine: what risk factors for VTE were present in patients who underwent orthopaedic surgery in specialised trauma unit and to establish the length of time that a patient is at risk of sustaining a VTE post orthopaedic surgery including the interval between their initial operative procedure and the subsequent presentation of VTE.

A retrospective case series of patients who underwent an orthopaedic procedure at Sheffield Teaching Hospitals NHS Foundation Trust – (Northern General Hospital) and re-presented to the trust with a subsequent VTE within one year of their initial operation. The study period was from 1/1/2010 to 31/12/2014. In order to be included patients must:

Have undergone an orthopaedic opertation recorded on ORMIS within the study period

Have undergone any imaging with coded as positive for VTE on PACS (electronic imaging software)

Any patients whom did not meet the inclusion criteria above were excluded from the study.

All eligible patients were identified and matched using an electronic patient database. Paper notes were requested for each patient who fulfilled the inclusion criteria and a team of two orthopaedic trainees then examined the notes using a 24-question proforma.

The proforma was a 3 page, A4 document that included:

Patient demographics; age, height, weight, BMI and gender.

Operative and anaesthetic information: Name of procedure, length of surgery, site of surgery and type of anaesthesia

Post-operative information: Intensive care transfer, time to mobilise, physiotherapy, thromboprophylaxis used both immediate post operatively and extended VTE if indicated

Past Medical history: Significant co-morbidities, Family/Personal history of VTE

Biochemistry: Creatinine, Urea, INR

VTE information; PE, DVT, site of DVT, timing of DVT from operation

The data was converted from the proforma into a computerised spreadsheet and analysed to determine any trends within the study population. The study population was then split into sub-groups for further statistical analysis

Sheffield teaching hospitals VTE guidance

All patients included in this study received care based on local inpatient guidelines for extended VTE prophylaxis. All patients are risk assessed on admission to hospital using local clerking document to establish risk factors(Table 1). Subcutaneous Dalteparin is the low molecular weight heparin (LMWH) recommended for use in inpatients at Sheffield teaching hospitals for the prevention of VTE. The recommended dosing of Dalteparin is summarised in Table 2. According to local guidelines, a proportion of orthopaedic patients will be offered extended thromboprophylaxis post discharge from hospital as shown in Table 3.

This retrospective study investigated patients who re-presented with a VTE following discharge post orthopaedic surgery at Sheffield Teaching Hospital NHS Foundation Trust (NGH). The study supports the current literature regarding specific risk factors for developing PE such as obesity, arthroplasty surgery and personal or family history of VTE¹³. Over 85% of the study sample had one or more co-morbidities. The most predominant risk factors identified in this cohort were hypertension and IHD, or commonly both.

It could be hypothesised that due to their impaired cardiovascular function, these patients are less mobile and thus at a higher risk of developing a VTE. It should also be considered that vessel wall damage due to hypertension is more likely to lead to thrombus formation and thus a thromboembolic event. This could suggest the need for extended VTE prophylaxis in an already at risk population, with recognised risk factors, compared to patients without risk factors.

This study supports previously established data that VTE can occur despite prophylaxis¹⁴ with one third of re-presentations with were receiving on-going pharmacological prophylaxis at the time of VTE diagnosis.

Up to 6 months post-surgery, the data showed that 76% of DVTs presented on the ipsilateral side following lower limb or hip operations, however following the initial 6 month period, the trend reversed and the contralateral leg was more frequently affected.

It seems likely from study, that in the short term, immobility of the affected leg coupled with local inflammatory factors and probable post-operative vascular disruption increases the likelihood of a DVT occurring on the ipsilateral side. As time passes however, it could be suggested that such local factors have less impact and pre-existing and established risk factors influence the likelihood of a patient having equal chance of developing a DVT in both legs respectively.

When using the Wells score a patient gains one point for ‘surgery within 4 weeks’ for PE, or 12 weeks for DVT. Within this current cohort, 46% of DVTs and 79% of patients presenting with PE presented after this window and would not have scored a point. It may be the case that later presenting VTE are unrelated to the initial surgery although we feel this may highlight the need for clinical suspicion in patients with risk factors and an orthopaedic surgical history outside the 4 week timeframe.

This study shows that the majority of patients present with VTE following the cessation of the recommended post-operative pharmacological prophylaxis, according to local guidelines. This could suggest that current guidance for thromboprophylaxis is not extensive enough and that patients should be offered prophylaxis for a longer duration if appropriate when considering additional risks and complications.

This study only reviewed patients who re-presented locally. NGH is the regional centre for orthopaedics and patients who were admitted to other hospitals are not included in this study.

No formal imaging took place prior to operating in any of the patients in this study and it may be the case that they had an undiagnosed VTE before their operation.

It may be the case that patients who re-presented did not have a VTE confirmed on imaging due to empirical treatment or operator skill and will have therefore not been included in this study.

A proportion of patients may have developed an asymptomatic VTE and thus not re-presented.

As this is a retrospective study using patient notes, co-morbidities, family history and personal history of VTE may not have been recorded and it is likely that this study underestimates the prevalence of these factors

This study supports that previously evidenced risk factors such as obesity, personal and family history of DVT, cardiovascular disease, long operative time and arthroplasty may increase a patient’s risk of developing a VTE despite the administration of post-operative VTE prophylaxis.

Current guidance on VTE prophylaxis in arthroplasty, pelvic surgery and patients in lower limb casts suggest extended thromboprophylaxis post-operatively. However this study suggests that patients presenting with risk factors, as outlined in this study, may be at an increased risk of developing VTE for a prolonged period of time. This study has several limiting factors including: only including patients from a single trust and a lack of demographic data available for patients undergoing surgery and not representing with a VTE resulting in an inability to conduct a true cohort study.

Community physicians, Emergency Department clinicians and orthopaedic surgeons should approach VTE with a high index of suspicion in any patient following an orthopaedic operation. We feel further research into this area is required to compare risk factors following orthopaedic surgery in patients who either did, or did not, develop a VTE after an extended period.