DEEP VEIN THROMBOSIS - DIAGNOSIS AND TREATMENT
Wells Score | D-dimer + Ultrasound | Anticoagulation 3-6 Months
WELLS SCORE FOR DVT
Critical Must-Knows
- Wells score stratifies pretest probability - guides D-dimer use
- D-dimer has HIGH sensitivity but LOW specificity - rules OUT if negative + low Wells
- Compression ultrasound is gold standard (95% sensitive for proximal DVT)
- Proximal DVT (popliteal and above) MUST be treated - high PE risk
- Anticoagulate 3 months if provoked (surgery), 3-6 months if unprovoked
Examiner's Pearls
- "D-dimer useless if high Wells score - go straight to ultrasound
- "Calf vein DVT (distal) controversial - some treat, some serial ultrasound
- "Postoperative DVT is PROVOKED - lower recurrence risk than unprovoked
- "Rivaroxaban and apixaban do NOT need LMWH lead-in (unlike warfarin)
Clinical Imaging
Imaging Gallery
Critical Exam Concepts
Wells Score is NOT Diagnostic
Wells score only estimates probability. You still need D-dimer or imaging to diagnose. High Wells = skip D-dimer, go to ultrasound.
D-dimer has Limited Specificity
Postoperative patients often have elevated D-dimer (trauma, surgery, inflammation). Only useful if LOW Wells AND negative D-dimer = excludes DVT.
Proximal vs Distal DVT
Proximal DVT (popliteal vein and above) MUST be treated - 10-30% PE risk. Distal (calf) DVT - controversial, some treat, some observe with serial ultrasound.
Treatment Duration is Risk-Based
Provoked (surgery): 3 months. Unprovoked: 3-6 months minimum, consider indefinite if high risk. Weigh recurrence risk vs bleeding risk.
Quick Decision Guide
| Clinical Scenario | Wells Score | Next Step | If Positive |
|---|---|---|---|
| Post-THA, calf swelling, low suspicion | 0-1 (Low) | D-dimer first | If D-dimer negative - stop. If positive - ultrasound |
| Post-trauma, unilateral leg swelling | 2 (Moderate) | D-dimer + ultrasound | Treat if ultrasound positive |
| Whole leg swelling, prior DVT, active cancer | 3+ (High) | Skip D-dimer, go to ultrasound | Anticoagulate immediately if positive |
| Bilateral leg swelling, no other features | Consider alternative diagnosis | Assess for heart failure, hypoalbuminemia | DVT is usually unilateral |
CAPSBEDWells Score for DVT
Memory Hook:Remember CAPSBED to calculate Wells score - Cancer, Active immobility, Prior DVT, Swelling, Bedridden, Enlarged calf, and Deduct 2 if alternative diagnosis!
3-3-IDVT Treatment Duration
Memory Hook:3-3-I: 3 months provoked, 3-6 months unprovoked, Indefinite if recurrent or cancer!
SEEVirchow's Triad for Thrombosis
Memory Hook:SEE why DVT occurs: Stasis, Endothelial injury, Excessive clotting!
Overview and Clinical Significance
Why Orthopaedic Surgery is High Risk
Orthopaedic surgery is VERY HIGH RISK for VTE due to: venous stasis (immobility, tourniquet), endothelial injury (surgical trauma), hypercoagulability (inflammatory response). THA and TKA have 40-60% DVT risk WITHOUT prophylaxis.
DVT Epidemiology
- Incidence: 1-2 per 1000 population annually
- Ortho surgery: 2-3% WITH prophylaxis
- Peak: Days 7-14 postoperatively
- Location: 80% lower limb, 20% upper limb
- Proximal vs distal: 60% proximal, 40% calf only
Consequences of Untreated DVT
- Pulmonary embolism: 10-30% risk
- Post-thrombotic syndrome: 20-50% at 2 years
- Recurrent VTE: 10-30% over 5 years
- Chronic venous insufficiency
- Death from massive PE: 1-5%
Pathophysiology and Virchow's Triad
Virchow's Triad
DVT results from the interplay of three factors (Virchow's Triad):
1. Venous Stasis:
- Immobility from surgery, anesthesia, bed rest
- Tourniquet use during surgery
- Cast immobilization
- Long-haul flights (economy class syndrome)
- Paralysis (stroke, spinal cord injury)
2. Endothelial Injury:
- Surgical trauma to vessels
- Positioning pressure during surgery
- Central venous catheters
- Previous DVT (vessel damage)
- Inflammatory conditions
3. Hypercoagulability:
- Surgical stress response (tissue factor release)
- Cancer (procoagulant factors)
- Inherited thrombophilias (Factor V Leiden, Prothrombin mutation)
- Acquired states (pregnancy, OCP, HRT)
- Dehydration
Orthopaedic Surgery Risk
Why orthopaedic surgery is highest risk:
- Prolonged immobility (pre-op, intra-op, post-op)
- Direct vascular trauma (hip, knee surgery)
- Cement polymerization (heat, emboli)
- Tourniquet ischemia-reperfusion
- Inflammatory response activating coagulation
Risk by Procedure (without prophylaxis):
- THA: 40-60% DVT, 2-5% PE
- TKA: 40-70% DVT, 2-5% PE
- Hip fracture surgery: 40-50% DVT
- Spine surgery: 15-40% DVT
- Arthroscopy: 2-5% DVT
Pathophysiology Exam Point
Orthopaedic surgery involves ALL THREE components of Virchow's triad - stasis (immobility), endothelial injury (surgery), and hypercoagulability (inflammatory response). This is why VTE prophylaxis is mandatory.
Clinical Assessment - Wells Score
Clinical Assessment Alone is Unreliable
Clinical features (pain, swelling, warmth) have LOW specificity - many mimics exist. Wells score improves pretest probability estimation but imaging is required for diagnosis.
Wells Score Calculation
| Clinical Feature | Points | Clinical Notes |
|---|---|---|
| Active cancer | +1 | Treatment within 6 months or palliative |
| Paralysis or recent immobilization | +1 | Plaster cast or bedridden with lower limb paresis |
| Bedridden greater than 3 days OR major surgery less than 12 weeks | +1 | Most ortho patients score this |
| Tenderness along deep venous system | +1 | Palpation of deep veins |
| Entire leg swollen | +1 | Thigh and calf both swollen |
| Calf swelling greater than 3cm vs other leg | +1 | Measure 10cm below tibial tuberosity |
| Pitting edema (symptomatic leg) | +1 | Confined to symptomatic leg |
| Collateral superficial veins | +1 | Non-varicose |
| Previously documented DVT | +1 | Prior confirmed DVT |
| Alternative diagnosis as likely or more likely | -2 | Cellulitis, Baker cyst, muscle strain |
Wells Score Interpretation
| Score | Probability | DVT Prevalence | Next Step |
|---|---|---|---|
| 0-1 | Low (unlikely) | 5% | D-dimer - if negative, stop; if positive, ultrasound |
| 2 | Moderate | 17% | D-dimer AND ultrasound |
| 3 or more | High (likely) | 53% | Proceed directly to ultrasound (skip D-dimer) |
Diagnostic Investigations
DVT Diagnostic Algorithm
Use clinical features to calculate Wells score (0-1 Low, 2 Moderate, 3+ High). This determines next step.
If Wells 0-1 (Low), check D-dimer. If NEGATIVE - DVT excluded (99% NPV). If POSITIVE - proceed to ultrasound.
If Wells 3+ (High), D-dimer has low utility - go directly to compression ultrasound. Start empiric anticoagulation if delay expected.
Proximal leg vein ultrasound (femoral and popliteal veins). If negative but high suspicion, repeat at 7 days. If positive, treat.
D-dimer Testing
Principle: D-dimer is a fibrin degradation product elevated in VTE. High sensitivity (95-98%) but low specificity (40-60%).
When D-dimer is Useful
- Low Wells score (0-1)
- Negative D-dimer = DVT excluded
- High negative predictive value (99%)
- Avoids unnecessary imaging
When D-dimer is NOT Useful
- High Wells score (3+) - go to imaging
- Postoperative patients - often elevated
- Cancer, pregnancy, elderly - often elevated
- Positive D-dimer does NOT diagnose DVT
Interpretation:
- Negative D-dimer + Low Wells: DVT excluded, no further testing
- Positive D-dimer: Proceed to ultrasound (does NOT confirm DVT)
- In postop ortho patients: Often falsely elevated - limited utility
The key point is that D-dimer is a rule-out test only, not a diagnostic test.
Ultrasound Imaging
Treatment - Anticoagulation
Start Anticoagulation Immediately if DVT Confirmed
Once DVT is diagnosed, start anticoagulation immediately (same day). Delays increase PE risk. Choice of anticoagulant depends on patient factors, renal function, and bleeding risk.
Anticoagulant Options for DVT Treatment
| Agent | Advantages | Disadvantages | Australian Context |
|---|---|---|---|
| Rivaroxaban/Apixaban (DOACs) | Oral from day 1, no monitoring, no LMWH lead-in | Cost, renal impairment, no reversal (limited) | PBS approved, first-line |
| LMWH + Warfarin | Cheap, reversible, familiar | LMWH injections, INR monitoring, drug interactions | Traditional approach, still used |
| LMWH alone | No monitoring, safe in cancer | Injections daily, expensive long-term | Cancer-associated VTE |
| Dabigatran | Oral, predictable | Needs 5-10d LMWH lead-in, renal clearance | Less used than rivaroxaban/apixaban |
Direct Oral Anticoagulants (First-Line)
Rivaroxaban:
- 15mg BD for 21 days, then 20mg daily
- No LMWH lead-in needed
- Reduce to 15mg daily if CrCl 30-50
Apixaban:
- 10mg BD for 7 days, then 5mg BD
- No LMWH lead-in needed
- Reduce to 2.5mg BD if 2 of: age greater than 80, weight less than 60kg, creatinine greater than 133
Advantages: Oral from day 1, predictable, no monitoring, easier than warfarin.
Contraindications: CrCl less than 30, active bleeding, mechanical valve, antiphospholipid syndrome.
Treatment Duration
| VTE Type | Duration | Rationale | Recurrence Risk |
|---|---|---|---|
| Provoked (surgery) | 3 months | Transient risk factor removed | 1-3% annual recurrence |
| Unprovoked first | 3-6 months minimum | Assess bleeding vs recurrence risk | 10% first year, 5% annual after |
| Recurrent unprovoked | Indefinite | High recurrence risk (15% annual) | 15% annual if stopped |
| Active cancer | Indefinite (while cancer active) | Ongoing hypercoagulable state | High recurrence |
| Thrombophilia (inherited) | Variable, often indefinite | Persistent increased risk | Depends on thrombophilia type |
Post-Surgical DVT is Provoked
DVT occurring after orthopaedic surgery is PROVOKED (transient risk factor). Treat for 3 months only. Lower recurrence risk (1-3% annually) vs unprovoked DVT (10% first year). Do NOT automatically anticoagulate indefinitely.
D-dimer to Guide Extended Therapy
In unprovoked DVT, positive D-dimer 1 month after stopping anticoagulation predicts higher recurrence risk. May guide decision for extended anticoagulation.
Special Situations
Calf Vein DVT - Controversial Management
Two Approaches:
| Strategy | Rationale | Recommendation |
|---|---|---|
| Anticoagulate for 6 weeks | Prevent propagation (20-30% propagate to proximal veins) | If symptomatic, high risk patients |
| Serial ultrasound (days 7, 14) | Treat only if propagates to proximal veins | If asymptomatic, low bleeding risk |
Current trend: Serial ultrasound unless high-risk features (extensive thrombus, severe symptoms, active cancer, prior VTE).
Complications of DVT and Anticoagulation
DVT Complications
| Complication | Incidence | Prevention/Management |
|---|---|---|
| Pulmonary embolism | 10-30% untreated | Anticoagulation prevents PE |
| Post-thrombotic syndrome | 20-50% at 2 years | Compression stockings (debated), early ambulation |
| Recurrent VTE | 10% first year (unprovoked) | Extended anticoagulation if high risk |
| Chronic venous insufficiency | Variable | Compression, elevation |
| Phlegmasia cerulea dolens | Rare | Emergency surgical thrombectomy |
Anticoagulation Complications
| Complication | Risk | Management |
|---|---|---|
| Major bleeding | 1-3% annually | Reversal agents, hold anticoagulant |
| Intracranial hemorrhage | 0.5-1% annually | Stop anticoagulation, reversal agent, neurosurgical review |
| GI bleeding | 2-4% annually | Endoscopy, reversal, PPI |
| Heparin-induced thrombocytopenia | 1-5% with UFH | Stop heparin, use alternative (argatroban, fondaparinux) |
| Warfarin skin necrosis | Rare (Protein C deficient) | Bridge with heparin when initiating warfarin |
Phlegmasia Cerulea Dolens
Phlegmasia cerulea dolens is massive iliofemoral DVT causing limb-threatening ischemia. Features: severely swollen, blue, painful leg with absent pulses. Emergency treatment: anticoagulation +/- surgical thrombectomy or catheter-directed thrombolysis. Fasciotomy if compartment syndrome develops.
Evidence Base
EINSTEIN DVT Trial - Rivaroxaban vs Warfarin
- RCT of 3449 patients with acute DVT
- Rivaroxaban (15mg BD x21d then 20mg daily) vs LMWH + warfarin
- Non-inferior for recurrent VTE (2.1% vs 3.0%)
- Similar major bleeding (0.8% vs 1.2%)
AMPLIFY Trial - Apixaban for VTE
- RCT of 5395 patients with VTE
- Apixaban vs LMWH + warfarin
- Non-inferior for VTE recurrence (2.3% vs 2.7%)
- Lower major bleeding (0.6% vs 1.8%, p less than 0.001)
ACCP Guidelines - Antithrombotic Therapy for VTE
- DOACs recommended over warfarin for non-cancer DVT (Grade 2B)
- Provoked DVT: 3 months anticoagulation
- Unprovoked DVT: Extended treatment if low bleeding risk
- Compression stockings no longer routinely recommended (Grade 2B)
PREVENT Trial - Extended VTE Prophylaxis After Hip/Knee Arthroplasty
- Extended thromboprophylaxis (5 weeks) reduces VTE after hip arthroplasty
- ASA non-inferior to rivaroxaban for extended prophylaxis after initial LMWH
- Chemical prophylaxis duration: 28-35 days post THA, 10-14 days post TKA
- Risk of VTE highest in first 2 weeks postoperatively
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Post-TKA Suspected DVT (~2-3 min)
"A 65-year-old woman presents 10 days after total knee arthroplasty with new onset left calf pain and swelling. Her right leg (operated) is also swollen but that is unchanged. Wells score is 2 (surgery less than 12 weeks, calf swelling). How would you investigate and manage?"
Scenario 2: High Wells Score DVT (~2-3 min)
"A 72-year-old man with known metastatic prostate cancer presents with entire left leg swelling and pain. He had a previous DVT 2 years ago. Wells score is 5. What is your diagnostic and management approach?"
MCQ Practice Points
Wells Score Interpretation
Q: A patient has Wells score of 1. What is the next appropriate step? A: D-dimer. Low Wells (0-1) = check D-dimer. If negative, DVT excluded. If positive, proceed to ultrasound.
Proximal vs Distal DVT
Q: What is the main difference in management between proximal and distal DVT? A: Proximal DVT (popliteal and above) MUST be treated due to 10-30% PE risk. Distal (calf) DVT can be managed with serial ultrasound OR anticoagulation depending on symptoms and risk factors.
DOAC Advantages
Q: What is the main advantage of rivaroxaban and apixaban over warfarin for DVT treatment? A: No LMWH lead-in needed. Rivaroxaban and apixaban can be started orally from day 1, whereas warfarin requires 5-10 days of LMWH bridging.
Treatment Duration
Q: How long should a post-surgical (provoked) DVT be anticoagulated? A: 3 months. Provoked VTE has low recurrence risk (1-3% annually) after transient risk factor removed.
Australian Context
VTE Prophylaxis Guidelines: The National Health and Medical Research Council (NHMRC) and Australian Commission on Safety and Quality in Health Care (ACSQHC) provide guidance on VTE prevention in hospitalized patients. All major orthopaedic procedures require mechanical and pharmacological prophylaxis.
Anticoagulant Access: Rivaroxaban, apixaban, and dabigatran are PBS-listed for treatment and secondary prevention of VTE. LMWH (enoxaparin, dalteparin) widely available for initial treatment and prophylaxis.
Therapeutic Guidelines: eTG (Therapeutic Guidelines) provides Australian-specific recommendations for VTE prevention and treatment in orthopaedic surgery, aligning with international best practice.
Compression Stockings: Graduated compression stockings and intermittent pneumatic compression devices are standard of care in Australian hospitals for VTE prevention during and after major orthopaedic surgery.
DEEP VEIN THROMBOSIS - DIAGNOSIS AND TREATMENT
High-Yield Exam Summary
Wells Score (CAPSBED)
- •Cancer active +1, Paralysis +1, Prior DVT +1
- •Swelling entire leg +1, Bedridden greater than 3d/surgery less than 12wks +1
- •Enlarged calf greater than 3cm +1, Differential diagnosis unlikely -2
- •Score 0-1 Low, 2 Moderate, 3+ High
Diagnostic Algorithm
- •Low Wells (0-1): D-dimer - if negative stop, if positive ultrasound
- •High Wells (3+): Skip D-dimer, go to ultrasound
- •Ultrasound: Non-compressible vein = DVT
- •D-dimer: High sensitivity, low specificity (useless if postop)
Treatment - Anticoagulation
- •First-line: DOACs (rivaroxaban 15mg BD x21d then 20mg, OR apixaban 10mg BD x7d then 5mg BD)
- •No LMWH lead-in with rivaroxaban/apixaban
- •Alternative: LMWH + warfarin (5-10d overlap until INR 2-3)
- •Cancer VTE: LMWH preferred (CLOT trial)
Duration of Treatment
- •Provoked (surgery): 3 months
- •Unprovoked first: 3-6 months minimum
- •Recurrent unprovoked: Indefinite
- •Active cancer: Indefinite while cancer active
Special Situations
- •Distal (calf) DVT: Serial ultrasound OR treat (controversial)
- •CrCl less than 30: Cannot use DOACs - use LMWH + warfarin
- •Proximal DVT MUST be treated (10-30% PE risk)
- •IVC filter: Only if anticoagulation contraindicated