Adductor Canal Block

Quick Answer

Adductor canal block (ACB) targets the saphenous nerve and potentially other nerves within the adductor canal (Hunter's canal), providing sensory anesthesia to the medial leg, medial ankle, and medial foot while preserving quadriceps motor function. Anatomy: Adductor canal extends from apex of femoral triangle to adductor hiatus (10-15 cm length), bounded by sartorius (superficial/medial), vastus medialis (lateral), and adductor longus/magnus (posterior/deep); contains saphenous nerve, femoral artery, femoral vein, and nerve to vastus medialis. Indications: Total knee replacement (TKR) analgesia with preserved mobilization, medial knee surgery, saphenous neuralgia, combined with popliteal block for complete foot coverage. Technique: Ultrasound-guided - mid-thigh level, identify sartorius muscle (superficial), vastus medialis (lateral), adductor muscles (deep); femoral vessels within canal; saphenous nerve adjacent to artery; in-plane approach, deposit 10-15 mL local anaesthetic within canal. Advantage: Motor-sparing (preserves quadriceps strength for mobilization) unlike femoral nerve block. Duration: 8-14 hours (ropivacaine 0.5%). Catheter: Suitable for continuous infusion post-TKR. [1-20]

Anatomy

Adductor Canal (Hunter's Canal, Sub-Sartorial Canal)

Definition and Boundaries: The adductor canal is a conical fascial tunnel in the mid-thigh extending from the apex of the femoral triangle proximally to the adductor hiatus distally. It is approximately 10-15 cm in length in adults.

Roof (Superficial Wall):

• Sartorius muscle: Forms the roof of the canal for most of its length
• Fascial thickening: Strong fascia covering sartorius contributes to canal formation
• Attachment: Fascia blends with fascia lata and vastus medialis fascia

Floor (Deep Wall):

• Adductor longus (proximal third): Deep to sartorius, lateral to gracilis
• Adductor magnus (distal two-thirds): Forms the floor distally
• Adductor hiatus: Opening in adductor magnus where femoral vessels pass to become popliteal vessels

Lateral Wall:

• Vastus medialis muscle: Medial component of quadriceps femoris
• Vastus medialis fascia: Forms lateral boundary of canal

Medial Wall:

• No distinct medial wall: Canal opens medially
• Gracilis muscle: Lies medial and posterior to canal

Contents of Adductor Canal:

1. Femoral artery: Continues from femoral triangle, exits at adductor hiatus to become popliteal artery
2. Femoral vein: Medial to artery within canal
3. Saphenous nerve: Terminal sensory branch of femoral nerve (L3-L4), enters canal at apex, exits at adductor hiatus with vessels
4. Nerve to vastus medialis: Motor branch from femoral nerve to vastus medialis muscle
5. Lymphatics: Superficial and deep lymphatic vessels

Saphenous Nerve Anatomy:

Origin:

• Femoral nerve branch (L3-L4)
• Formation: Within femoral triangle or at apex
• Course: Descends through adductor canal with femoral vessels

Relation to Femoral Vessels:

• Position: Lateral to femoral artery within canal (variable)
• Relation: May be anterior, posterior, or lateral to artery
• Exits canal: At adductor hiatus with vessels

Distribution:

• Medial leg: Skin and fascia over anteromedial tibia
• Medial ankle: Anteromedial ankle joint, medial malleolus
• Medial foot: Medial border of foot to first metatarsophalangeal joint
• Arch: Medial longitudinal arch of foot
• Patellar branches: Occasionally supply anterior knee (variable)

Sartorial Branch (Variable):

• Small branch to sartorius muscle (motor)
• Usually not clinically significant if blocked

Femoral Triangle to Adductor Canal Transition:

Femoral Triangle Boundaries:

• Superior: Inguinal ligament
• Lateral: Sartorius muscle
• Medial: Adductor longus muscle
• Floor: Iliopsoas (lateral), pectineus (medial)
• Roof: Fascia lata

Apex of Femoral Triangle:

• Definition: Point where sartorius crosses adductor longus
• Transition: Where femoral vessels enter adductor canal
• Clinical significance: Most distal extent of femoral nerve proper; saphenous nerve branches here

Adductor Hiatus:

• Definition: Tendinous opening in adductor magnus
• Location: Just above knee joint
• Contents: Femoral vessels pass through to become popliteal vessels
• Saphenous nerve: Exits here to become superficial

Ultrasound Anatomy

Probe Position:

• Level: Mid-thigh (approximately 10-15 cm proximal to knee)
• Orientation: Transverse, perpendicular to limb
• Probe type: High-frequency linear (10-15 MHz) standard
• Position: Medial aspect of thigh, sartorius muscle visible

Layer-by-Layer Sonographic Appearance:

Superficial:

1. Skin and subcutaneous tissue: Hyperechoic line (skin), hypoechoic subcutaneous fat
2. Sartorius muscle:
   • Shape: Flattened, ribbon-like, hypoechoic muscle
   • Position: Most superficial structure in view
   • Characteristics: Often appears as thin muscle belly with characteristic striations

Intermediate (Canal Contents): 3. Femoral artery:

• Shape: Round or oval, anechoic (black)
• Characteristics: Pulsatile, non-compressible, thick walls
• Position: Central within canal

4. Femoral vein:
   • Shape: Oval or round, anechoic
   • Position: Medial or deep to artery (variable)
   • Characteristics: Thin-walled, easily compressible
5. Saphenous nerve:
   • Shape: Small (2-3 mm), round or oval, hyperechoic
   • Position: Adjacent to artery (variable: lateral, anterior, or posterior)
   • Identification: Often difficult to visualize (may require nerve stimulator or tracing from proximal)

Deep: 6. Adductor longus/magnus:

• Shape: Large, hypoechoic muscle bulk
• Position: Deep to vessels
• Characteristics: Triangular or oval appearance, deep to canal

7. Vastus medialis:
   • Shape: Hypoechoic muscle
   • Position: Lateral to canal
   • Characteristics: Part of quadriceps group

Fascial Planes:

• Vastoadductor membrane: Fascia between vastus medialis and adductor muscles; defines canal floor
• Sartorial fascia: Superficial fascia over sartorius; contributes to canal roof

Key Ultrasound Identification Tips:

1. Find sartorius first: Most superficial muscle, characteristic ribbon shape
2. Locate vessels: Artery is pulsatile landmark
3. Saphenous nerve: Often difficult to see; look for small hyperechoic structure adjacent to artery
4. Trace proximally: Saphenous nerve can sometimes be traced from femoral triangle to canal
5. Dynamic assessment: Slight probe pressure compresses vein, improves visualization
6. Nerve stimulator: May help identify saphenous nerve (sensory - no motor response expected)

Variation in Saphenous Nerve Location:

• Lateral to artery (most common): 60%
• Posterior to artery: 25%
• Anterior to artery: 10%
• Not visible within canal: 5% (may be outside canal or too small)

Sensory and Motor Distribution

Saphenous Nerve Distribution:

Sensory (Primary Function):

• Medial leg: Anteromedial tibia, over medial tibial flare
• Medial ankle: Anteromedial ankle, medial malleolus
• Medial foot: Medial border of foot to first metatarsophalangeal joint
• Arch: Medial longitudinal arch
• Patellar branches: Variable supply to anterior knee (inconsistent)

Additional Structures in Canal:

• Nerve to vastus medialis: Motor to vastus medialis (part of quadriceps)
  • Blocking this nerve causes minimal quadriceps weakness (vastus medialis only)
  • Less significant than complete femoral nerve block

Clinical Coverage:

Complete Block with 10-20 mL:

• Medial leg sensation
• Medial ankle and foot
• Variable anterior knee coverage

Incomplete Coverage:

• Anterior knee: Femoral nerve branches (partial, variable)
• Lateral leg: Lateral femoral cutaneous nerve
• Posterior leg: Sciatic nerve

Motor Effects:

Saphenous Nerve:

• Purely sensory (no motor deficit from blocking saphenous alone)

Nerve to Vastus Medialis:

• Small motor component to vastus medialis
• May cause slight quadriceps weakness if blocked
• Less than 10-20% of total quadriceps strength

Femoral Triangle Block vs Adductor Canal Block:

• Femoral triangle: Blocks femoral nerve proper → complete quadriceps paralysis (vastus lateralis, intermedius, medialis, rectus femoris)
• Adductor canal: Blocks saphenous + minimal vastus medialis → preserved quadriceps function (85-95% preserved)

Preserved Motor Function:

• Knee extension: Largely preserved (minimal impact)
• Straight leg raise: Maintained
• Standing and ambulation: Possible with assistance
• Weight-bearing: Possible if pain controlled

Indications and Contraindications

Indications

Primary Indications:

Total Knee Replacement (TKR):

• Most common indication: Postoperative analgesia with preserved mobilization
• Advantage over femoral block: Motor-sparing allows early mobilization, reduces fall risk
• Evidence: Equivalent analgesia to femoral nerve block for TKR with significantly less quadriceps weakness [21-30]
• Enhanced recovery: Facilitates ERAS (Enhanced Recovery After Surgery) protocols
• Physiotherapy: Allows active participation in postoperative rehabilitation

Medial Knee Surgery:

• Arthroscopy: Diagnostic and therapeutic procedures
• Meniscal surgery: Medial meniscectomy or repair
• Medial ligament repair: MCL injuries
• Medial patellofemoral ligament reconstruction: MPFL repair

Combined Blocks:

• With popliteal block: Complete foot and ankle coverage for foot surgery
• With obturator block: More complete medial knee coverage
• With sciatic block: Complete lower limb below knee

Saphenous Neuralgia:

• Diagnosis: Diagnostic block for medial knee/leg pain
• Treatment: Therapeutic block for saphenous neuralgia
• Post-surgical pain: Medial knee pain after surgery

Acute Pain Management:

• Knee fractures: Analgesia with preserved function
• Soft tissue injuries: Medial knee trauma
• Chronic pain: CRPS affecting medial lower limb

Specific Advantages:

• Motor preservation: 85-95% quadriceps strength maintained
• Fall prevention: Reduced fall risk compared to femoral block
• Early mobilization: Walking with assistance within hours of surgery
• Ambulatory surgery: Suitable for outpatient procedures
• Catheter suitability: Excellent site for continuous infusion

Contraindications

Absolute Contraindications:

• Infection at site: Cellulitis, abscess over medial thigh
• Patient refusal: Unable to consent
• True local anaesthetic allergy: Rare
• Local anaesthetic toxicity: Current or recent
• Compartment syndrome risk: Relative contraindication in high-risk cases

Relative Contraindications:

Anticoagulation (ASRA Guidelines):

• Adductor canal is considered intermediate risk (similar to femoral)
• Warfarin: INR <1.5
• Therapeutic LMWH: Delay 12-24 hours
• DOACs: Hold 2-3 days
• Antiplatelets: Generally safe
• Consideration: Vessels are smaller than femoral at canal level, but still significant bleeding risk

Anatomical Concerns:

• Previous femoral vascular surgery: Grafts, stents in femoral region
• Significant adductor muscle atrophy: May alter anatomy
• Peripheral vascular disease: Risk of vascular injury
• Severe obesity: Deep block (>8 cm), technical difficulty
• Pre-existing saphenous neuropathy: Document baseline function

Medical Concerns:

• Severe quadriceps weakness pre-existing: Risk of exacerbation
• Inability to ambulate safely: Even with preserved quadriceps
• Confusion/delirium: Risk of unprotected mobilization and falls

Surgical Concerns:

• Lateral knee procedures: ACB provides minimal lateral coverage
• Tourniquet pain: Does not prevent thigh tourniquet pain

Technique

Pre-Block Assessment

Mandatory Checks:

1. Informed consent:

   • Procedure explanation (ultrasound-guided injection in mid-thigh)
   • Benefits (pain relief, preserved movement)
   • Risks (vascular puncture, nerve injury, LAST, failure)
   • Document consent

2. Medical history:

   • Previous blocks and outcomes
   • Neuropathy (diabetes, vascular disease)
   • Bleeding disorders, anticoagulation status
   • Allergies (local anaesthetics, skin prep)

3. Physical examination:

   • Baseline quadriceps strength: Straight leg raise, knee extension against resistance
   • Baseline sensation: Medial leg, ankle, foot
   • Vascular assessment: Femoral, popliteal, pedal pulses
   • Skin examination: No infection at planned site

4. Medication review:

   • Anticoagulants: Check INR, aPTT if indicated
   • Last dose of DOACs
   • Antiplatelet therapy

5. Monitoring setup:

   • Continuous ECG, NIBP, SpO2
   • Minimum monitoring duration

6. Intravenous access:

   • Patent IV cannula (20G or larger)

7. Resuscitation preparedness:

   • Lipid emulsion 20% available
   • Emergency equipment ready

Patient Positioning

Position:

• Supine: Standard position
• Leg position: Slightly externally rotated (15-30°), knee slightly flexed (pillow under knee optional)
• Exposure: Medial thigh from mid-thigh to knee

Alternative:

• Lateral decubitus: Operative side up (less common, used if supine positioning difficult)

Ultrasound-Guided Technique

Equipment:

• Ultrasound: High-frequency linear probe (10-15 MHz)
• Needle: 50-80 mm, 22G, echogenic
• Local anaesthetic: 10-15 mL (see dosing section)
• Extension tubing: For aspiration
• Sterile prep: Chlorhexidine 2% in alcohol, sterile drapes, sterile probe cover

Scanning Protocol:

1. Initial identification:

   • Place probe transverse on medial mid-thigh
   • Identify sartorius muscle (superficial, ribbon-like)
   • Locate femoral artery (pulsatile, within canal)
   • Identify saphenous nerve (adjacent to artery if visible)

2. Optimize image:

   • Adjust depth (typically 3-6 cm)
   • Adjust gain and focus
   • Apply gentle pressure to compress vein
   • Trace nerve proximally if needed for confirmation

3. Confirm anatomy:

   • Sartorius superficial
   • Vessels within canal
   • Adductor muscles deep
   • Vastus medialis lateral

Needle Insertion:

In-Plane Approach (Recommended):

• Entry point: Medial thigh, superficial to sartorius or through sartorius
• Direction: Lateral toward canal
• Visualisation: Entire needle shaft visible
• Target: Within adductor canal, adjacent to saphenous nerve (or perivascular spread)
• Advantages: Excellent visualization, safe trajectory away from vessels

Out-of-Plane Approach:

• Entry point: Superior to probe
• Direction: Caudal
• Target: Canal contents
• Disadvantages: Less control, vascular proximity

Injection Technique:

1. Advance to target:

   • Advance needle under ultrasound guidance
   • Target: Within adductor canal, adjacent to saphenous nerve or femoral artery
   • Avoid vessel penetration

2. Aspiration test:

   • Before injection, aspirate to check for blood
   • If blood return: Withdraw, reposition

3. Test dose:

   • Inject 2-3 mL local anaesthetic
   • Observe for spread within canal
   • Look for separation of fascial layers
   • Confirm no vascular uptake

4. Full injection:

   • Incremental injection: 3-5 mL aliquots
   • Aspiration between aliquots
   • Total volume: 10-15 mL
   • End point: Spread within canal, around saphenous nerve, between fascial layers

Optimal Spread:

• Circumferential: Around saphenous nerve
• Canal filling: Spread within adductor canal along vessel sheath
• Distal-proximal: Spread along length of canal (10-15 cm)

Alternative Techniques

Perifemoral Approach:

• Injection at apex of femoral triangle or just distal
• Higher volume required (20 mL)
• Risk of femoral nerve spread (motor block)
• Less precise than true adductor canal approach

Distal Approach (Above Knee):

• Injection near adductor hiatus
• Smaller canal, more difficult anatomy
• Vessels becoming popliteal (deeper)
• Less commonly used

Landmark-Based (Historical):

• Location: 4-6 cm superior to medial femoral condyle
• Approach: Perpendicular to skin, advance until bone (femur) then withdraw slightly
• Injection: 10-15 mL in fanwise distribution
• Status: Replaced by ultrasound (more reliable, safer)

Catheter Techniques

Indications:

• Total knee replacement (primary indication)
• Major knee surgery requiring prolonged analgesia
• Enhanced recovery protocols

Technique:

• Catheter: 18-20G multi-orifice, 40-50 cm
• Insertion: Through-needle or over-needle
• Position: 3-5 cm within adductor canal beyond needle tip
• Confirmation: Test dose 3-5 mL, ultrasound visualization if possible
• Securement: Adhesive dressings, tunneling (3-5 cm subcutaneous)

Infusion Regimens:

Duration:

• Typical: 2-5 days
• Maximum: 7 days with good care
• Infection risk increases after day 3-4

Local Anaesthetic Selection and Dosing

Single-Shot Block

Standard Regimens:

Volume Considerations:

• 10 mL: Minimum effective volume, limited spread
• 15 mL: Optimal volume, reliable spread within canal
• 20 mL: Risk of spread to femoral nerve (motor block)
• Avoid: >20 mL (increased motor block risk without analgesic benefit)

Additives:

Maximum Doses:

• Ropivacaine: 3 mg/kg
• Bupivacaine: 2 mg/kg
• Calculate on lean body weight in obesity

Continuous Infusion

Infusion Solutions:

PCRA (Patient-Controlled Regional Analgesia):

• Basal: Ropivacaine 0.2% at 5 mL/h
• Bolus: 3-5 mL
• Lockout: 20-30 minutes
• 4-hour limit: 60-80 mL

Clinical Scenarios:

Total Knee Replacement:

• Preoperative: Ropivacaine 0.5%, 15 mL
• Postoperative: Ropivacaine 0.2% at 8 mL/h with PCRA
• Duration: 48-72 hours
• Advantages: Early mobilization, reduced opioid use

Day Surgery Knee Arthroscopy:

• Ropivacaine 0.375%, 15 mL
• Duration: 6-10 hours
• Discharge when ambulating safely

Complications and Management

Local Anaesthetic Systemic Toxicity (LAST)

Risk Factors:

• Vascular injection (femoral vessels in canal)
• Large volume (>20 mL)
• Absence of ultrasound guidance
• Rapid injection

Prevention:

• Ultrasound visualization
• Incremental injection with aspiration
• Epinephrine-containing solution
• Volume 10-15 mL (not excessive)

Management:

• Follow ASRA LAST protocol
• Lipid emulsion 20%: 1.5 mL/kg bolus, 0.25 mL/kg/min infusion
• Seizure control with benzodiazepines
• Cardiovascular support

Vascular Puncture

Incidence: 1-3% with ultrasound [31-35]

Management:

• Firm pressure 5-10 minutes
• Compression dressing
• Monitor for hematoma
• Hold anticoagulation if significant

Prevention:

• Ultrasound visualization
• Avoid vessel penetration
• Short-bevel needles

Motor Block (Quadriceps Weakness)

Incidence: 5-15% (dose-dependent) [36-40]

Mechanisms:

• Spread to femoral nerve proper
• Block of nerve to vastus medialis
• Excessive volume (>20 mL)
• Proximal needle placement (too close to femoral triangle)

Prevention:

• Limit volume to 10-15 mL
• Inject in mid-thigh (not proximal)
• Avoid femoral triangle apex
• Use lower concentrations for less spread

Management:

• Usually self-limiting (block duration)
• Protect from falls
• Consider assistance for mobilization
• Reassurance

Nerve Injury

Incidence: <0.1% [41-45]

Prevention:

• Avoid intraneural injection
• Low pressure injection
• Ultrasound guidance
• Limit attempts

Management:

• Document deficit
• Observation (most resolve)
• Neurology referral if persistent
• Physical therapy

Other Complications

Infection:

• Incidence: <0.1% single shot, 1-3% catheters
• Prevention: Aseptic technique
• Management: Antibiotics, catheter removal

Failed Block:

• Incidence: 5-10%
• Causes: Technical failure, anatomical variation, inadequate volume
• Management: Repeat block, alternative analgesia

Compartment Syndrome:

• Risk: Block masks pain
• Contraindication: High-risk cases
• Monitoring: If performed, monitor compartment pressures

Clinical Scenarios and SAQs

SAQ 1: Adductor Canal Anatomy (10 marks)

Question: A 65-year-old patient requires adductor canal block for total knee replacement.

a) Describe the anatomical boundaries of the adductor canal (4 marks)

b) Which structures pass through the adductor canal? (3 marks)

c) Describe the sensory distribution of the saphenous nerve (2 marks)

d) Why does adductor canal block preserve quadriceps function compared to femoral nerve block? (1 mark)

Model Answer:

a) Boundaries (4 marks):

• Roof: Sartorius muscle and fascia (1 mark)
• Floor: Adductor longus (proximal) and adductor magnus (distal) (1 mark)
• Lateral wall: Vastus medialis muscle and fascia (1 mark)
• Extends from apex of femoral triangle to adductor hiatus (1 mark)

b) Canal contents (3 marks):

• Femoral artery and vein (1 mark)
• Saphenous nerve (1 mark)
• Nerve to vastus medialis (motor branch) (1 mark)

c) Saphenous distribution (2 marks):

• Medial leg, medial ankle, medial foot and arch (1 mark)
• Variable contribution to anterior knee (1 mark)

d) Quadriceps preservation (1 mark):

• Saphenous is purely sensory; femoral nerve at femoral triangle blocks all quadriceps motor branches

---

SAQ 2: Clinical Application in Total Knee Replacement (12 marks)

Question: A 70-year-old woman is undergoing total knee replacement. The surgical team wishes to facilitate early mobilization.

a) Compare the advantages and disadvantages of adductor canal block versus femoral nerve block for this patient (6 marks)

b) What volume and concentration of local anaesthetic would you use to optimize analgesia while minimizing motor block? (3 marks)

c) Describe the ultrasound landmarks for performing an adductor canal block (3 marks)

Model Answer:

a) ACB vs femoral block (6 marks):

• ACB advantages: Preserves quadriceps function (85-95%), allows early mobilization, reduced fall risk, enables active physiotherapy participation (3 marks)
• ACB disadvantages: May provide slightly less complete anterior knee analgesia compared to femoral block, does not cover posterior knee (sciatic needed) (2 marks)
• Femoral block: Complete anterior knee analgesia but causes quadriceps paralysis, increased fall risk (1 mark)

b) Local anaesthetic selection (3 marks):

• Ropivacaine 0.5% or bupivacaine 0.375%, 10-15 mL (1 mark)
• Rationale: Effective analgesia with minimal motor block at this volume (1 mark)
• Avoid >20 mL to prevent spread to femoral nerve (1 mark)

c) Ultrasound landmarks (3 marks):

• Mid-thigh level, medial aspect (1 mark)
• Sartorius muscle superficial (ribbon-like), femoral artery pulsatile within canal, saphenous nerve adjacent to artery (1 mark)
• Adductor muscles deep, vastus medialis lateral (1 mark)

---

SAQ 3: Complications and Safety (8 marks)

Question: During performance of an adductor canal block, you aspirate blood through the needle.

a) What is your immediate management? (2 marks)

b) What measures can be taken to prevent vascular complications during adductor canal block? (3 marks)

c) A patient develops quadriceps weakness after an adductor canal block. What are the possible causes, and how would you manage this? (3 marks)

Model Answer:

a) Immediate management (2 marks):

• Withdraw needle immediately, apply firm pressure for 5-10 minutes (1 mark)
• Reposition and reassess with ultrasound before attempting again (1 mark)

b) Prevention measures (3 marks):

• Use ultrasound guidance to visualize vessels (1 mark)
• Incremental injection with frequent aspiration (1 mark)
• Consider using epinephrine-containing solution for early intravascular warning (1 mark)

c) Quadriceps weakness causes and management (3 marks):

• Causes: Excessive volume (>20 mL) causing spread to femoral nerve, proximal injection near femoral triangle, nerve to vastus medialis block (2 marks)
• Management: Protect patient from falls, assistance with mobilization, usually self-limiting (block duration), lower volume for future blocks (1 mark)

ANZCA Exam Focus

Key Examination Topics

1. Anatomy: Canal boundaries, contents, saphenous nerve course
2. Motor preservation: Mechanism of quadriceps sparing
3. Indications: TKR analgesia, combined blocks
4. Technique: Ultrasound anatomy, probe position
5. Pharmacology: Volume limitations to prevent motor block
6. Evidence: ACB vs femoral block literature
7. Complications: Vascular puncture, motor block, LAST

Common Viva Questions

• "Describe the anatomy of the adductor canal and its clinical relevance for knee surgery"
• "Compare adductor canal block to femoral nerve block for total knee replacement"
• "How would you perform an ultrasound-guided adductor canal block?"
• "What are the advantages of motor-sparing blocks in lower limb surgery?"

Indigenous Health Considerations

Aboriginal and Torres Strait Islander Health

Aboriginal Australians experience higher rates of knee osteoarthritis and total knee replacement due to increased prevalence of obesity, diabetes, and occupational factors. Adductor canal block offers particular advantages for this population by enabling early mobilization, which supports return to remote communities where prolonged rehabilitation may not be readily available.

Chronic Disease Considerations: Diabetes and renal disease impact local anaesthetic pharmacokinetics, requiring careful dosing and monitoring. Pre-existing peripheral neuropathy must be documented to avoid misattribution of chronic deficits to the block.

Access and Follow-up: Regional anaesthesia facilitating early discharge aligns with patient preferences to return to community promptly. Clear instructions regarding mobilization and fall prevention are essential when follow-up care requires RFDS or telephone consultation.

Communication: Working with Aboriginal Health Workers facilitates culturally safe informed consent. Visual aids and family involvement support comprehension where English may not be the first language.

Māori Health Considerations

Māori populations have higher rates of knee osteoarthritis and obesity, making adductor canal block particularly valuable for total knee replacement. The motor-sparing nature facilitates participation in physiotherapy and early mobilization, supporting return to whānau and community.

Cultural Safety: Whānau involvement in decision-making is important. Communication with Māori Health Workers or Kaiawhina supports effective education about the block and postoperative expectations.

Chronic Disease Impact: Higher rates of diabetes and metabolic syndrome require careful assessment of pre-existing neuropathy and consideration of local anaesthetic pharmacokinetics in renal/hepatic impairment.

Regional Anaesthesia Benefits: Motor-sparing blocks allow earlier safe discharge, which is culturally preferred for care close to family. However, reliable analgesia is essential, and catheter techniques should be considered for major surgery to ensure adequate pain control in rural settings.

Key References

[1] Jæger P, Zaric D, Fomsgaard JS, et al. Adductor canal block versus femoral nerve block for analgesia after total knee arthroplasty: a randomized, double-blind, placebo-controlled study. Reg Anesth Pain Med. 2013;38(6):526-532. PMID: 24121611

[2] Kim DH, Lin Y, Goytizolo EA, et al. Adductor canal block versus femoral nerve block for total knee arthroplasty: a prospective, randomized, controlled trial. Anesthesiology. 2014;120(3):540-550. PMID: 24343288

[3] Lund J, Jenstrup MT, Jæger P, et al. Continuous adductor-canal-blockade for adjuvant post-operative analgesia after major knee surgery: preliminary results from 180 catheterisations. Acta Anaesthesiol Scand. 2011;55(10):1224-1229. PMID: 21999526

[4] Jæger P, Nielsen ZJK, Henningsen MH, et al. Adductor canal block versus femoral nerve block and quadriceps strength: a randomized, double-blind, placebo-controlled, crossover study in healthy volunteers. Anesthesiology. 2013;118(2):409-415. PMID: 23249926

[5] Kwofie MK, Shastri UD, Gadsden JC, et al. The effects of ultrasound-guided adductor canal block versus femoral nerve block on quadriceps strength and fall risk: a blinded, randomized trial of volunteers. Reg Anesth Pain Med. 2013;38(4):321-325. PMID: 23783082

[6] Grevstad U, Baas D, Borchgrevink PC, et al. Comparison of the analgesic effect of an adductor canal block and a femoral triangle block after total knee arthroplasty: a randomized clinical trial. Reg Anesth Pain Med. 2020;45(7):508-514. PMID: 32235130

[7] Elkassabany NM, Antosh S, Ahmed M, et al. The risk of falls after total knee arthroplasty with the use of a femoral nerve block versus an adductor canal block: a double-blinded randomized controlled study. Anesth Analg. 2016;122(5):1696-1703. PMID: 27089000

[8] Li D, Yang Z, Xie X, et al. Adductor canal block provides better performance after total knee arthroplasty compared with femoral nerve block: a systematic review and meta-analysis. Int Orthop. 2016;40(5):925-933. PMID: 26705195

[9] Seidel R, Wijayathunga C, Rangelova G, et al. Adductor canal block provides better pain control compared to femoral nerve block in simultaneous bilateral total knee arthroplasty: a randomized controlled trial. J Arthroplasty. 2021;36(7S):S271-S277. PMID: 33483268

[10] Mariano ER, Kim TE, Wagner MJ, et al. A randomized comparison of proximal and distal ultrasound-guided adductor canal catheter insertion sites for knee arthroplasty. J Ultrasound Med. 2014;33(9):1653-1662. PMID: 25125515

[11] Bendtsen TF, Moriggl B, Chan V, et al. Anatomical description of the saphenous nerve block at the adductor canal region: a cadaver study. Acta Anaesthesiol Scand. 2014;58(7):867-872. PMID: 24862819

[12] Horn JL, Pitsch T, Salinas F, et al. Anatomic basis to the ultrasound-guided approach for saphenous nerve blockade. Reg Anesth Pain Med. 2009;34(2):177-181. PMID: 19282727

[13] Wong WY, Bjørn S, Strid JM, et al. Defining the location of the adductor canal using ultrasound. Reg Anesth Pain Med. 2017;42(2):241-245. PMID: 28002295

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