VTE Prevention | DVT and PE | Orthopaedic Perioperative Care
- High Risk Procedures: THA, TKA, hip fracture surgery require extended prophylaxis 28-35 days
- Mechanical: TED stockings + IPC - ALWAYS use with chemical for high-risk procedures
- Chemical Options: LMWH (enoxaparin), DOACs (rivaroxaban, apixaban), aspirin
- Duration: 28-35 days for THA/TKA/hip fracture - NOT just in-hospital
- Timing: Start LMWH 6-12 hours post-op; rivaroxaban 6-10 hours post-op
- “Extended prophylaxis 28-35 days is MANDATORY
- “LMWH is gold standard but DOACs are equivalent
- “Aspirin is acceptable after initial anticoagulant
- “Mechanical prophylaxis ALWAYS - even if on chemical
28-35 days for THA/TKA/hip fracture. VTE risk persists beyond discharge. In-hospital only is INADEQUATE.
Always combine methods for high-risk. Mechanical reduces VTE by 50% alone. Adding chemical reduces further.
EPCAT II: Aspirin non-inferior after initial anticoagulant. Can use aspirin to complete extended course after LMWH/DOAC.
LMWH: 6-12 hours post-op. DOACs: 6-10 hours post-op. Too early = bleeding. Too late = VTE.
- VTE Risk
- Very High
- Prophylaxis
- Mechanical + LMWH/DOAC
- Duration
- 35 days
- VTE Risk
- Very High
- Prophylaxis
- Mechanical + LMWH/DOAC
- Duration
- 14-35 days
- VTE Risk
- Very High
- Prophylaxis
- Mechanical + LMWH
- Duration
- 35 days
- VTE Risk
- High
- Prophylaxis
- Mechanical + LMWH
- Duration
- Until ambulatory
- VTE Risk
- Moderate
- Prophylaxis
- Mechanical ± aspirin
- Duration
- Until ambulatory
MCEVTE Prophylaxis Approach
Hook:MCE = Mechanical, Chemical, Extended - the three pillars of VTE prophylaxis in orthopaedics!
LEADChemical Prophylaxis Options
Hook:LEAD with prophylaxis - LMWH leads as gold standard, DOACs and Aspirin are alternatives!
Overview and Epidemiology
VTE is the most common preventable cause of in-hospital death. After THA/TKA without prophylaxis, DVT rates are 40-60% and symptomatic PE 1-2%. This is a mandatory exam topic.
Venous Thromboembolism (VTE) includes deep vein thrombosis (DVT) and pulmonary embolism (PE).
- Stasis: Immobility, surgery, prolonged recumbency
- Endothelial injury: Surgical trauma, inflammation
- Hypercoagulability: Surgery-induced, thrombophilia
All three components are present in orthopaedic surgery.
- THA: DVT 42-57%, PE 0.9-28%
- TKA: DVT 41-85%, PE 1.5-10%
- Hip fracture: DVT 46-60%, fatal PE 3-12%
- Major trauma: DVT 40-80%
These figures demonstrate why prophylaxis is mandatory.
Pathophysiology and Mechanisms
Most clinically significant DVTs originate in the deep calf veins (soleal sinuses) and propagate proximally. Proximal DVT (popliteal, femoral, iliac) carry highest PE risk. Upper limb DVT is uncommon in orthopaedics.
- Calf veins: Posterior tibial, peroneal, soleal sinuses (origin of most DVT)
- Proximal veins: Popliteal, femoral, iliac (highest PE risk)
- Upper limb: Subclavian, axillary (rare in orthopaedics)
- Thrombus forms in calf veins during/after surgery
- May propagate proximally (20-30% if untreated)
- Proximal DVT can embolize to pulmonary circulation
- PE mortality depends on clot burden and cardiopulmonary reserve
Classification Systems
VTE Risk Stratification
- Procedures
- THA, TKA, hip fracture, pelvic trauma
- Prophylaxis
- Mechanical + LMWH/DOAC
- Duration
- 28-35 days
- Procedures
- Major trauma, spine fusion, cancer surgery
- Prophylaxis
- Mechanical + LMWH
- Duration
- Until ambulatory or 14 days
- Procedures
- Foot/ankle, upper limb, arthroscopy
- Prophylaxis
- Mechanical ± aspirin
- Duration
- Until ambulatory
- Procedures
- Minor procedures, outpatient
- Prophylaxis
- Early mobilization
- Duration
- None required
Risk stratification guides prophylaxis intensity and duration.
The Caprini Risk-Assessment Model
The Controversies section notes that "Caprini and other scores are widely used but were not derived for arthroplasty", and the patient-factor table lists individual risks — but the actual model that turns those factors into a recommendation is never set out. The Caprini score is the most widely used weighted, cumulative VTE risk-assessment model, and examiners expect you to know how it works and why it behaves oddly in orthopaedics.
Each risk factor is assigned 1, 2, 3 or 5 points by severity, and the points are summed:
- Representative factors
- Age 41-60, minor surgery, BMI over 25, swollen legs/varicose veins, oestrogen therapy, pregnancy/postpartum, sepsis
- Theme
- Minor / additive
- Representative factors
- Age 61-74, major open or arthroscopic surgery, malignancy, confined to bed more than 72 hours, central venous line
- Theme
- Moderate
- Representative factors
- Age 75 or older, prior VTE, family history of VTE, thrombophilia (factor V Leiden, prothrombin gene, lupus anticoagulant), heparin-induced thrombocytopenia
- Theme
- Strong / heritable
- Representative factors
- Elective arthroplasty, hip/pelvis/leg fracture, stroke or acute spinal cord injury within a month, multiple trauma
- Theme
- Dominant
0 = very low (early ambulation); 1-2 = low (mechanical); 3-4 = moderate (chemical or mechanical); 5 or more = high (chemical plus mechanical, extended duration).
an elective arthroplasty and a hip/pelvis/leg fracture each score 5 on their own, so essentially every major orthopaedic patient is already "high risk" before a single individual factor is added. That ceiling effect is exactly why the score has only modest discrimination within the arthroplasty population — it cannot separate the high-risk arthroplasty patient from the very-high-risk one. Its real value here is the opposite direction: flagging the extra factors (prior VTE, active cancer, thrombophilia) that push toward longer or higher-intensity prophylaxis, and risk-assessing the lower-risk and mixed surgical patients for whom it was actually derived.
Q: Why is the Caprini score of limited value for elective joint replacement? A: Elective arthroplasty alone scores 5 points (high risk), so every patient is already at ceiling before individual factors are counted — it cannot discriminate within the arthroplasty population. Use it to surface the additional risk factors (prior VTE, cancer, thrombophilia) that justify extending or intensifying prophylaxis, not to decide whether to give it.
HIP HIPHigh-Risk VTE Procedures
Hook:HIP HIP hooray for prophylaxis! These procedures need extended 35-day prophylaxis.
Clinical Assessment
- Calf pain: Worse with dorsiflexion (Homan's sign)
- Swelling: Asymmetric leg swelling
- Warmth: Affected limb warmer
- Erythema: Subtle redness
- Palpable cord: Thrombosed vein
Clinical signs are unreliable - 50% DVTs are asymptomatic.
- Dyspnea: Most common symptom
- Pleuritic chest pain: Sharp, worse on inspiration
- Tachycardia: Heart rate greater than 100
- Hypoxia: SpO2 less than 92%
- Syncope: Massive PE
PE is a clinical emergency - act immediately if suspected.
Clinical signs miss 50% of DVTs. Screening is not recommended. Focus on PREVENTION with appropriate prophylaxis rather than detection.
Investigations
Investigation for Suspected VTE
Wells Score for DVT or PE probability. Guides further investigation.
Sensitive but not specific. Useful to rule OUT VTE if negative. Always elevated post-operatively (not useful post-op).
Gold standard for DVT. Non-compressible vein = thrombus. Sensitivity greater than 95% for proximal DVT.
Gold standard for PE. CT pulmonary angiography. V/Q scan if contrast contraindicated.
Note: D-dimer is NOT useful post-operatively as it is always elevated. Use clinical suspicion and imaging.
Differential Diagnosis
The swollen, painful post-operative limb and the breathless post-operative patient both have important mimics. Anchoring on VTE risks missing a treatable alternative — and treating a mimic as VTE exposes a fresh surgical wound to unnecessary anticoagulation.
- Distinguishing features
- Unilateral whole-leg swelling, warmth, calf tenderness
- Key test
- Compression ultrasound (non-compressible vein)
- Why it matters
- Therapeutic anticoagulation needed
- Distinguishing features
- Pleuritic pain, dyspnoea, tachycardia, hypoxia
- Key test
- CTPA
- Why it matters
- Life-threatening; treat empirically if unstable
- Distinguishing features
- Tense swelling, bruising, falling haemoglobin
- Key test
- Clinical, ultrasound, FBC
- Why it matters
- Anticoagulation would worsen it — opposite treatment
- Distinguishing features
- Erythema with defined border, fever, raised CRP
- Key test
- Clinical, inflammatory markers
- Why it matters
- Needs antibiotics, not anticoagulation
- Distinguishing features
- Sudden calf pain, crescent bruise at ankle
- Key test
- Ultrasound
- Why it matters
- Mimics DVT closely; conservative management
- Distinguishing features
- Bilateral or chronic, painless, pitting
- Key test
- Clinical
- Why it matters
- No acute intervention
- Distinguishing features
- Hypoxia, petechiae, confusion 24–72h post long-bone fracture
- Key test
- Clinical (Gurd criteria), CXR
- Why it matters
- Supportive care, not anticoagulation
Management Algorithm
Mechanical Prophylaxis
Mechanical Methods
Graduated compression stockings. Below-knee or thigh-high. Reduces DVT by 50% alone. Proper fit essential.
Sequential calf compression. Apply in OR, continue post-op. More effective than TED alone. Combine with TED for best effect.
Venous foot pump. Alternative to IPC. May be used if calf access limited.
Mechanical prophylaxis is ALWAYS indicated for high-risk procedures, even with chemical prophylaxis.
Surgical Technique
Surgical Strategies to Reduce VTE
- Minimize tourniquet time: Longer tourniquet = higher risk
- Gentle tissue handling: Reduce endothelial injury
- Regional anesthesia: May reduce VTE vs general
- Intraoperative IPC: Start before induction
- Adequate hydration: Avoid hypovolemia
- Avoid hypotension: Maintain perfusion
These strategies complement mechanical and chemical prophylaxis.
Complications
- Incidence
- 1-3%
- Management
- Hold anticoagulant, reverse if severe, mechanical only
- Incidence
- 2-5%
- Management
- May require washout, balance VTE and bleeding risk
- Incidence
- 0.5-1%
- Management
- Stop heparin, use fondaparinux or argatroban
- Incidence
- Rare
- Management
- Neurological emergency - decompress urgently
- Incidence
- 1-2%
- Management
- PPI cover, balance benefits vs risks
HIT is a serious complication of heparin products. Check platelets day 5-10 if using LMWH. If suspected, stop heparin and use alternative (fondaparinux, argatroban).
Heparin-Induced Thrombocytopenia and the 4T Score
The complications table names HIT, "check platelets day 5-10" and the "4T score", but never explains the entity or the score — yet HIT is the one prophylaxis complication where the intuitive response is wrong, so it is heavily examined.
The paradox: immune (type II) HIT is caused by IgG antibodies against complexes of heparin and platelet factor 4 (PF4). The antibody-PF4-heparin immune complex activates platelets, so despite a falling platelet count the patient becomes intensely prothrombotic — venous and arterial "white clots", not bleeding. (Type I is a mild, early, non-immune, self-limiting dip and is benign.) HIT is commoner with unfractionated heparin than LMWH, and commoner after surgery; the platelet fall is classically days 5-14, or within a day if heparin was given in the preceding ~100 days (rapid-onset HIT).
The 4T score estimates pre-test probability — each item scores 0, 1 or 2:
- 2 points
- Fall over 50% AND nadir 20 or higher
- 1 point
- Fall 30-50% or nadir 10-19
- 0 points
- Fall under 30% or nadir under 10
- 2 points
- Clear onset days 5-10 (or day 1 if heparin within 30 days)
- 1 point
- Onset after day 10, unclear, or day 1 with heparin 30-100 days ago
- 0 points
- Fall before day 4 with no recent heparin
- 2 points
- New confirmed thrombosis, skin necrosis, or systemic reaction post IV bolus
- 1 point
- Progressive/recurrent or silent thrombosis, erythematous skin lesions
- 0 points
- None
- 2 points
- None apparent
- 1 point
- Possible
- 0 points
- Definite
0-3 = low probability (HIT effectively excluded clinically), 4-5 = intermediate, 6-8 = high. An intermediate or high score triggers treatment and laboratory confirmation.
- Stop ALL heparin immediately — including LMWH, heparin flushes and heparin-bonded lines.
- Start a non-heparin anticoagulant at therapeutic dose (the patient is clotting, not bleeding): a direct thrombin inhibitor such as argatroban, or danaparoid or fondaparinux.
- Do NOT transfuse platelets prophylactically — it fuels the thrombosis.
- Do NOT start warfarin until the platelet count recovers (over 150) — early warfarin precipitates venous limb gangrene / skin necrosis through protein C depletion; overlap and bridge instead.
- Confirm the diagnosis: an anti-PF4/heparin immunoassay (ELISA) (sensitive, not specific) plus a functional assay — the serotonin-release assay (SRA), the gold standard (specific). Document a heparin allergy and avoid heparin thereafter.
Q: Platelets fall to 70 on day 7 of LMWH after hip fracture surgery — what do you do? A: Suspect HIT, score the 4Ts. If intermediate/high: stop all heparin, start a non-heparin anticoagulant (argatroban/danaparoid/fondaparinux), do not transfuse platelets, do not start warfarin until platelets recover, and confirm with anti-PF4 ELISA plus the serotonin-release assay. The danger is thrombosis, not bleeding.
Postoperative Care
Post-Discharge VTE Prevention
Educate on VTE symptoms. Calf pain, swelling, shortness of breath. Seek immediate help if suspected.
Continue LMWH or DOAC as prescribed. Ensure patient understands regimen. Self-injection teaching for LMWH.
May switch to aspirin for completion. Based on EPCAT II evidence. Continue until 35 days total.
Review at follow-up. Stop prophylaxis at 35 days if fully mobile. Continue longer if high-risk or immobile.
Patient compliance with home prophylaxis is essential. Simplify regimens where possible.
Outcomes and Prognosis
With Prophylaxis:
- DVT: Reduced to 2-5%
- Symptomatic PE: Less than 0.5%
- Fatal PE: Less than 0.2%
Prognostic Factors for VTE:
- Higher Risk
- 5-10x baseline
- Implication
- Consider extended prophylaxis beyond 35 days
- Higher Risk
- 3-5x baseline
- Implication
- LMWH preferred over aspirin
- Higher Risk
- 2-5x baseline
- Implication
- Hematology input
- Higher Risk
- 2x
- Implication
- Higher dose or longer duration
- Higher Risk
- 1.5x
- Implication
- Adequate prophylaxis
Appropriate prophylaxis makes VTE a rare event after modern arthroplasty.
Guidelines, Registries & Global Practice
Global epidemiology: Without prophylaxis, venographic DVT occurs in roughly 40–60% after major lower-limb arthroplasty or hip fracture. Modern prophylaxis plus early mobilisation has driven symptomatic VTE after elective THA/TKA to roughly 1% or less at 90 days, with fatal PE now well under 0.5%. The greatest residual burden of fatal PE is in hip-fracture and polytrauma patients.
Side-by-side major guidelines:
- Stance on agent
- No single agent mandated; pharmacological and/or mechanical
- Duration (THA / TKA)
- Surgeon discretion
- Distinctive feature
- Discourages duplex screening of asymptomatic patients
- Stance on agent
- LMWH, DOAC, fondaparinux, VKA, UFH or aspirin all acceptable
- Duration (THA / TKA)
- Min 10–14 days, extend to 35
- Distinctive feature
- Suggests adding IPC to drug prophylaxis
- Stance on agent
- Explicitly endorses aspirin protocols and DOACs
- Duration (THA / TKA)
- THA up to 28–35 days / TKA 14 days
- Distinctive feature
- LMWH-then-aspirin sequence written into guideline
- Stance on agent
- LMWH or DOAC for major lower-limb surgery
- Duration (THA / TKA)
- Extended after THA, shorter after TKA
- Distinctive feature
- Emphasises early mobilisation and individualised bleeding-risk assessment
Joint registries (NJR, AJRR, AOANJRR, SHAR) report symptomatic VTE and 90-day mortality as quality metrics rather than mandating one agent. Pragmatic trials embedded in trauma networks (PREVENT CLOT) and arthroplasty cohorts (EPCAT II) have shifted high-resource practice toward aspirin-based regimens after an initial anticoagulant.
- High-resource: ready access to DOACs, LMWH, mechanical IPC devices and outpatient anticoagulation clinics; cost and patient-satisfaction data increasingly favour aspirin where appropriate.
- Limited-resource: LMWH and DOACs may be unaffordable or cold-chain–limited; aspirin plus aggressive early mobilisation and, where available, graduated compression stockings is a pragmatic, evidence-supported strategy. Mechanical IPC pumps are often scarce, raising the relative importance of chemical prophylaxis and mobilisation.
every surgical patient should have a documented VTE and bleeding-risk assessment, mechanical prophylaxis where pharmacological agents are contraindicated, and a clear discharge plan for extended prophylaxis. Failure to risk-assess and to prescribe extended prophylaxis is a recurrent medicolegal theme worldwide.
Controversies & Areas of Uncertainty
EPCAT II and PREVENT CLOT show aspirin is non-inferior for clinically important outcomes, yet PREVENT CLOT found a small excess of (mostly distal, often asymptomatic) DVT with aspirin. Whether this matters clinically — and in which patients — remains debated.
Guidelines diverge from 10–14 days (NICE TKA, some ACCP options) up to 35 days. The lower thrombotic burden after TKA versus THA means the marginal benefit of prolonged prophylaxis after knee replacement is uncertain.
For low-risk arthroplasty with rapid mobilisation, some advocate mechanical methods plus aspirin alone. Robust trials isolating the independent contribution of stockings versus IPC versus chemical agents are lacking.
Caprini and other scores are widely used but were not derived for arthroplasty and have modest discrimination. There is no universally validated tool to individualise agent and duration in elective joint replacement.
AAOS recommends against duplex screening of asymptomatic patients, yet some units still screen high-risk groups. Treating asymptomatic distal DVT of uncertain significance risks over-anticoagulation.
Isolated distal (calf) DVT detected on surveillance has a low embolic risk. Whether to anticoagulate, surveil, or ignore it is unresolved and varies by guideline and bleeding risk.
MCQ Practice Points
Q: How long should VTE prophylaxis continue after THA? A: 28-35 days. VTE risk persists beyond hospital discharge. In-hospital only prophylaxis is inadequate.
Q: When should enoxaparin be started after THA? A: 6-12 hours post-operatively. Too early increases bleeding risk. Too late may allow thrombus formation.
Q: What trial supports aspirin for VTE prophylaxis after arthroplasty? A: EPCAT II (NEJM 2018) showed aspirin is non-inferior to rivaroxaban when used to complete extended prophylaxis after initial anticoagulant.
Q: What is the DVT rate after THA without prophylaxis? A: 40-60% DVT, 1-2% symptomatic PE. This demonstrates why prophylaxis is mandatory.
Q: What is the role of mechanical prophylaxis in VTE prevention? A: Always use mechanical prophylaxis (TED + IPC) as adjunct. Essential for patients with bleeding contraindications. Start IPC intraoperatively.
Q: How do you manage suspected HIT in a post-arthroplasty patient? A: Stop all heparin immediately. Use non-heparin anticoagulant (fondaparinux, argatroban). Check platelet count and 4T score.
Exam Viva Scenarios
Practise clinical reasoning and management decisions out loud
“You are planning a primary THA on a 65-year-old man with no prior VTE history. What is your VTE prophylaxis protocol?”
“A 70-year-old woman is undergoing TKA. She has a history of GI bleeding and is on aspirin for coronary artery disease. How do you manage VTE prophylaxis?”
“Post-operative day 3 after TKA, the patient develops sudden dyspnea and pleuritic chest pain. HR 120, SpO2 88% on room air. What is your approach?”
VTE Risk
- THA/TKA/Hip fracture = very high
- 40-60% DVT without prophylaxis
- 1-2% symptomatic PE
- Risk persists 35 days post-op
Prophylaxis Approach
- MCE: Mechanical + Chemical + Extended
- TED + IPC for ALL high-risk
- LMWH is gold standard
- DOACs are equivalent alternatives
Duration
- THA: 35 days
- TKA: 14-35 days
- Hip Fracture: 35 days
- NOT just in-hospital
Timing
- LMWH: 6-12 hrs post-op
- Rivaroxaban: 6-10 hrs post-op
- Start IPC in OR
- TED immediately post-op
Complications
- HIT: Stop heparin, use alternative
- Major bleeding: 1-3%
- Balance VTE vs bleeding risk
- Spinal epidural haematoma with neuraxial anaesthesia
Evidence Base
- 4541 elective THA patients; rivaroxaban 10mg OD vs enoxaparin 40mg SC OD for 36 days
- Primary composite (DVT, non-fatal PE, all-cause death): 1.1% rivaroxaban vs 3.7% enoxaparin (ARR 2.6%, P less than 0.001)
- Major VTE: 0.2% vs 2.0% (P less than 0.001)
- Major bleeding similar: 0.3% vs 0.1% (P=0.18)
- 3148 TKA patients; rivaroxaban 10mg OD vs enoxaparin 30mg BD for 10–14 days
- Primary composite VTE/death: 6.9% rivaroxaban vs 10.1% enoxaparin (ARR 3.19%, P=0.012)
- Major bleeding 0.7% vs 0.3% (P=0.11, not significant)
- Companion knee-arthroplasty trial to RECORD1
- 778 THA patients; all received dalteparin for 10 days, then randomised to aspirin or dalteparin for a further 28 days
- Symptomatic VTE: 0.3% aspirin vs 1.3% dalteparin — aspirin non-inferior (P less than 0.001)
- Clinically significant bleeding 0.5% aspirin vs 1.3% dalteparin
- Stopped early for slow recruitment but established the lead-in-then-aspirin concept
- 3424 THA/TKA patients; all received rivaroxaban for 5 days, then randomised to aspirin 81mg OD or continued rivaroxaban (30 days THA, 9 days TKA)
- Symptomatic VTE: 0.64% aspirin vs 0.70% rivaroxaban (P less than 0.001 for non-inferiority)
- Major bleeding: 0.47% vs 0.29% (NS); clinically important bleeding 1.29% vs 0.99% (NS)
- Aspirin is a cheap, oral, well-tolerated agent to complete extended prophylaxis
- 12211 patients with operative extremity fractures or any pelvic/acetabular fracture
- Aspirin 81mg BD vs enoxaparin 30mg BD; primary outcome 90-day all-cause death
- Death 0.78% aspirin vs 0.73% LMWH — aspirin non-inferior
- DVT slightly higher with aspirin (2.51% vs 1.71%); PE identical (1.49% each)
- Extended prophylaxis (minimum 10–14 days, up to 35 days) recommended after THA/TKA/hip fracture
- LMWH, fondaparinux, DOACs, adjusted-dose VKA, low-dose UFH or aspirin all acceptable agents
- Add intermittent pneumatic compression to pharmacological prophylaxis where feasible
- Mechanical-only prophylaxis if high bleeding risk; switch to drug once risk falls
- All elective THA/TKA patients should receive pharmacological and/or mechanical prophylaxis
- No single agent mandated — surgeon discretion balancing VTE and bleeding risk
- Routine post-operative duplex screening of asymptomatic patients NOT recommended
- Assess for prior VTE which increases risk