Evidence-Based VTE Prophylaxis Protocol After Elective Total Hip / Knee Replacement

Major lower limb arthroplasty is among the highest-risk settings for venous thromboembolism, because it combines all three elements of Virchow’s triad — venous stasis from immobilisation, endothelial injury from surgical trauma, and a post-operative hypercoagulable state.

Venous thrombosis is primarily a disease of old age, and hip, knee and pelvic surgery are the classic predisposing factors, with obesity and malignancy as accessory factors.

In up to 50% of cases of venous thrombosis an additional underlying genetic predisposition becomes manifest under these circumstances.

Without prophylaxis, DVT rates after arthroplasty historically reached 40–60%; thromboprophylaxis of surgical and medical patients at medium and high risk is now firmly established practice.

Risk is highest in the first 2 weeks but remains elevated for up to 3 months, which is why extended prophylaxis matters.

Assess every patient pre-operatively for VTE risk (prior VTE, cancer, thrombophilia, obesity, immobility, hormone therapy) and bleeding risk (active bleeding, thrombocytopenia, severe renal or hepatic impairment, recent intracranial haemorrhage).

Older age, frailty, and renal impairment shift the balance and demand dose adjustment rather than omission.

Intermittent pneumatic compression devices (IPC) should be applied from admission and continued while the patient is in bed.

IPC alone is used when the bleeding risk is unacceptable or the patient refuses pharmacological prophylaxis.

Graduated compression stockings may be added, but are contraindicated in peripheral arterial disease and severe neuropathy.

Early mobilisation and adequate hydration are essential adjuncts and are the cheapest interventions available.

All of the following are supported as prophylactic agents after arthroplasty: LMWH; fondaparinux; dabigatran, apixaban or rivaroxaban (for THA/TKA but not hip fracture surgery); low-dose unfractionated heparin; adjusted-dose vitamin K antagonist; or aspirin.

LMWH (enoxaparin 40 mg once daily subcutaneously) remains the reference standard against which all other agents are compared.

DOACs are used at reduced thromboprophylactic doses and have been used specifically for extended out-of-hospital thromboprophylaxis in high-risk orthopaedic surgery such as hip and knee replacement.

Fondaparinux 2.5 mg once daily is an alternative; avoid if creatinine clearance is below 30 ml/min.

Aspirin is an option, but see the current evidence below — it is not equivalent to LMWH.

Treatment should be for at least 10 to 14 days and ideally up to 35 days.

In practice: up to 35 days after total hip replacement and about 14 days after total knee replacement, reflecting the different risk profiles of the two operations.

Start LMWH 12 hours before or 12 hours after surgery, or at least 6–8 hours post-operatively once haemostasis is secure.

With neuraxial (spinal or epidural) anaesthesia, observe strict intervals to avoid spinal haematoma: at least 12 hours after a prophylactic LMWH dose before needle placement or catheter removal, and at least 4 hours after catheter removal before the next dose.

The current standard of care in hip fracture is to stabilise comorbid conditions, repair the hip (ideally under spinal anaesthesia), and encourage early ambulation with aggressive rehabilitation, with prophylactic anticoagulation throughout.

Reduce the dose or extend the dosing interval of LMWH in renal impairment; tinzaparin is least renally dependent.

DOAC prophylactic doses require renal-function-based adjustment, and DOACs are not recommended for hip fracture surgery (as opposed to elective arthroplasty).

Do not routinely screen asymptomatic patients with ultrasound before discharge — it does not improve outcomes.

Educate the patient and family about the symptoms of DVT and PE before discharge, and ensure a clear plan for who supervises injections at home.