Top Tweets for #Peripheralnerveblock
๐ง ๐๐๐๐๐๐๐๐ ๐๐ ๐๐๐๐๐๐๐๐๐๐ โ ๐๐๐๐๐ ๐๐๐๐๐๐
#RegionalAnesthesia #LocalAnesthetics #Neurotoxicity #Crystallization #Ultrasound #PeripheralNerveBlock #NerveInjury #InVitro #CriticalAppraisal #EvidenceBasedMedicine #RAPM
๐๐ฅ๐๐ง๐๐๐๐ ๐๐ฃ๐ฃ๐ฅ๐๐๐ฆ๐๐:
๐ต ๐. ๐๐๐๐ ๐๐๐ ๐๐๐ ๐๏ฟฝ๏ฟฝ๐๐๐ ๐๐๐๐๐๐๐๐ ๐๐๐๐?
โช๏ธ LA/adjuvant mixtures can form visible precipitates.
โช๏ธ 24โ33 MHz ultrasound can detect them in a clear liquid environment.
โช๏ธ A semiquantitative sonographic crystallisation score was proposed.
โช๏ธ This demonstrates visibility of precipitates, not biological toxicity.
๐ ๐. ๐๐๐๐๐๐ โ ๐๐๐๐๐ ๐๐๐๐๐๐
โช๏ธ Hyperechoic particles are easy to identify against an almost anechoic liquid background.
โช๏ธ Around nerves, fascia, fat, muscle, epineurium and connective tissue already create heterogeneous echogenicity.
โช๏ธ Distinguishing a tiny crystal from normal tissue echoes may therefore be extremely difficult.
โช๏ธ UHF imaging also has limited penetration - approximately 1โ2 cm in this setting.
โช๏ธ The authors themselves acknowledge that in-vivo visibility remains uncertain.
๐ด ๐. ๐๐๐๐๐๐๐๐๐๐๐๐๐๏ฟฝ๏ฟฝ๐ ๐๐ ๐๐๐ ๐๐๐ ๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐
โช๏ธ Mixing two solutions may alter pH, ionisation and solubility โ precipitation.
โช๏ธ The real question is what happens after injection.
โช๏ธ Do crystals remain undissolved at 37ยฐC and physiological pH?
โช๏ธ What happens after dilution by extracellular fluid, buffering, protein interaction and vascular clearance?
โช๏ธ Do they dissolve, fragment, aggregate or persist?
โช๏ธ Persistence was not studied.
โช๏ธ Temperature was not even controlled in this experiment.
๐ฃ ๐. ๐๐๐๐๐๐๐ โ ๐๐๐๐๐๐ ๐๐๐๐๐๐
โช๏ธ Axons are not lying freely exposed beside the needle tip.
โช๏ธ They are protected within endoneurial, perineurial and epineurial compartments.
โช๏ธ Therefore, direct access of relatively large particulate material to vulnerable neural structures cannot simply be assumed.
โช๏ธ The important question is not merely โDid crystals form?โ
โช๏ธ It is:
Formation โ Persistence โ Neural localisation โ Cellular interaction โ Structural injury โ Functional neurological deficit
โช๏ธ None of these downstream steps was demonstrated here.
โช๏ธ Importantly, nerve injury does not necessarily require direct crystal entry into an axon; vascular, inflammatory or perineural mechanisms are theoretically possible, but these also remain unproven.
โ ๏ธ ๐๐๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐๐๐๐๐๐๐ ๐๐๐๐๐๐๐๐
โช๏ธ Only n=1 preparation per formulation was reported.
โช๏ธ Multiple images from one sample โ independent experimental replication.
โช๏ธ Samples underwent gravitational settling and were subsequently stirred before later measurements.
โช๏ธ Stirring itself could have influenced the apparent increase in crystallisation grade.
โช๏ธ The proposed ultrasound grading score was not microscopically validated.
โช๏ธ Therefore, excellent observer agreement confirms agreement between readers, not necessarily biological validity of the grading system.
๏ฟฝ๏ฟฝ๏ฟฝ๏ฟฝ ๐๐๐ ๐๐๐๐๐๐๐๐๐
โช๏ธ Crystal formation โ crystal persistence.
โช๏ธ Crystal persistence โ neural exposure.
โช๏ธ Neural exposure โ neurotoxicity.
โช๏ธ Ultrasound visibility in liquid โ reliable identification in living tissue.
โช๏ธ A laboratory precipitate should not become a surrogate marker for nerve injury.
The clinically meaningful question is therefore not:
โ๐๐๐ง ๐ฐ๐ ๐ฌ๐๐ ๐๐ ๐๐ซ๐ฒ๐ฌ๐ญ๐๐ฅ๐ฌ?โ
It is:
โ๐๐จ ๐ญ๐ก๐๐ฌ๐ ๐๐ซ๐ฒ๐ฌ๐ญ๐๐ฅ๐ฌ ๐ฌ๐ฎ๐ซ๐ฏ๐ข๐ฏ๐ ๐ข๐ง ๐ฏ๐ข๐ฏ๐จ, ๐ซ๐๐๐๐ก ๐ ๐๐ข๐จ๐ฅ๐จ๐ ๐ข๐๐๐ฅ๐ฅ๐ฒ ๐ฏ๐ฎ๐ฅ๐ง๐๐ซ๐๐๐ฅ๐ ๐ง๐๐ฎ๐ซ๐๐ฅ ๐๐จ๐ฆ๐ฉ๐๐ซ๐ญ๐ฆ๐๐ง๐ญ, ๐๐ง๐ ๐๐๐ฎ๐ฌ๐ ๐๐๐ฆ๐จ๐ง๐ฌ๐ญ๐ซ๐๐๐ฅ๐ ๐ข๐ง๐ฃ๐ฎ๐ซ๐ฒ?โ
Until that chain is demonstrated, this remains an interesting proof-of-concept imaging experiment, rather than evidence of clinically relevant nerve toxicity.
๐ฅ ๐๐ก๐๐๐ ๐๐๐ข๐๐: ๐๐งโ๐ฆ ๐ก๐ข๐ง ๐๐๐ข๐จ๐ง ๐ง๐๐ ๐ก๐จ๐ ๐๐๐ฅ
#RegionalAnesthesia #AnkleBlock #FITBlock #SciaticBlock #SaphenousBlock #MotorSparing #FootSurgery #PeripheralNerveBlock #RegionalAnaesthesia #CriticalAppraisal #EvidenceBasedPractice #ClinicalReasoning
๐๐ฅ๐๐ง๐๐๐๐ ๐๐ฃ๐ฃ๐ฅ๐๐๐ฆ๐๐:
๐ง ๐ฆ๐๐ข๐ฅ๐ง ๐๐ก๐๐ง๐ข๐ ๐ฌ
๐น Sciatic nerve โ Tibial nerve + Common peroneal/fibular nerve
๐น Distally โ Tibial, superficial & deep peroneal/fibular + sural nerves supply most of the foot
๐น Saphenous nerve adds the femoral contribution
๐ ๐๐ข๐ช ๐ ๐๐ก๐ฌ ๐ฃ๐ฅ๐๐๐๐ฆ?
๐น Conventional ankle block โ 5
๐น FIT ankle block โ 2
๐น Popliteal sciatic + saphenous block โ 2
๐น SPEDI block โ 1
๐น Neuraxial โ 1
๐ฏ ๐ฆ๐ข, ๐ช๐๐๐ง ๐ฅ๐๐๐๐๐ฌ ๐ ๐๐ง๐ง๐๐ฅ๐ฆ?
๐น Not merely how many times we prick
๐น But where we block, what we block and why we block
๐น Surgical anesthesia? Analgesia? Motor preservation? Early ambulation?
๐ ๐๐๐ฌ ๐ง๐๐๐๐๐ช๐๐ฌ๐ฆ
๐น Fewer pricks โ automatically better block
๐น Distal block โ completely motor-free block
๐น Ankle block mainly preserves proximal/extrinsic leg motor function, while intrinsic foot motor function may still be affected
๐น Choose the strategy according to the desired clinical outcome - not the needle count.
๐ง๐ต๐ฒ ๐ฏ๐ฒ๐๐ ๐ฏ๐น๐ผ๐ฐ๐ธ ๐ถ๐ ๐ป๐ผ๐ ๐๐ต๐ฒ ๐ผ๐ป๐ฒ ๐๐ถ๐๐ต ๐๐ต๐ฒ ๐ณ๐ฒ๐๐ฒ๐๐ ๐ฝ๐ฟ๐ถ๐ฐ๐ธ๐; ๐ถ๐ ๐ถ๐ ๐๐ต๐ฒ ๐ผ๐ป๐ฒ ๐๐ต๐ฎ๐ ๐ฏ๐ฒ๐๐ ๐บ๐ฎ๐๐ฐ๐ต๐ฒ๐ ๐๐ต๐ฒ ๐ฝ๐๐ฟ๐ฝ๐ผ๐๐ฒ.
๐ง ๐ฆ๐๐๐๐ง๐๐ โ๐ก๐๐ฅ๐ฉ๐โ: ๐๐ฆ โ๐๐ก๐ง๐ฅ๐๐ก๐๐จ๐ฅ๐๐โ ๐ฅ๐๏ฟฝ๏ฟฝ๏ฟฝ๐๐๐ฌ ๐๐ก๐ง๐ฅ๐๐ก๐๐จ๐ฅ๐๐?
#RegionalAnesthesia #SciaticNerve #SciaticNerveBlock #PoplitealBlock #PeripheralNerveBlock #NerveAnatomy #Sonoanatomy
#GrayZonesInRA #GrayAreasInRA
๐๐๐๐ ๐๐๐๐๐ ๐๐ ๐๐:
๐ฌ ๐. ๐๐๐ฅ๐ฆ๐ง ๐จ๐ก๐๐๐ฅ๐ฆ๐ง๐๐ก๐ ๐ง๐๐ ๐๐ก๐๐ง๐ข๐ ๐ฌ
โซ๏ธ Calling SCN, a nerve, is itself is MISNOMER.
โซ๏ธ It is a composite neural complex containing TN + CPN within a paraneural envelope.
โซ๏ธ TN & CPN are distinct nerves.
โซ๏ธ Each has its own epineurium, fascicles, perineurium.
โซ๏ธ Therefore:
SCN paraneural boundary โ TN/CPN epineurium.
๐ฏ ๐. ๐ฆ๐จ๐๐ฃ๐๐ฅ๐๐ก๐๐จ๐ฅ๐๐ โ ๐ง๐ฅ๐จ๐ ๐๐ก๐ง๐ฅ๐๐ก๐๐จ๐ฅ๐๐
โซ๏ธ Extraparaneural โ outside the SCN paraneural envelope.
โซ๏ธ Subparaneural โ inside that envelope.
โซ๏ธ Yet injectate may remain outside both TN & CPN epineuria.
๏ฟฝ๏ฟฝ๏ฟฝ๐ป๐๐ถ๐ฑ๐ฒ ๐ฆ๐๐ก ๐ฐ๐ผ๐บ๐ฝ๐น๐ฒ๐
โ ๐ถ๐ป๐๐ถ๐ฑ๐ฒ ๐ง๐ก/๐๐ฃ๐ก.
โซ๏ธ Thus, spread may look โintraneuralโ relative to the composite SCN while remaining extraneural to its component nerves.
โซ๏ธ Nerve swelling on ultrasound โ proof of intraepineurial TN/CPN injection.
โซ๏ธ Previous MRI/sonographic studies have already demonstrated this important terminologyโanatomy mismatch.
โIntraneuralโ means little unless we specify WHICH boundary has been crossed.
๐งฉ ๐. ๐ช๐๐๐ก ๐๐ข๐๐ฆ ๐๐ง ๐๐๐๐ข๐ ๐ ๐ง๐ฅ๐จ๐๐ฌ ๐๐ก๐ง๐ฅ๐๐ก๐๐จ๐ฅ๐๐?
โซ๏ธ Cross TN epineurium โ intraneural to TN.
โซ๏ธ Cross CPN epineurium โ intraneural to CPN.
โซ๏ธ Remain outside fascicles โ intraneuralโextrafascicular.
โซ๏ธ โSubepineurialโ therefore belongs within this broad extrafascicular domain.
โซ๏ธ Cross perineurium โ intrafascicular/endoneural.
Paraneural โ Subparaneural โ Subepineurial/Extrafascicular โ Intrafascicular
๐๐ก๐ง๐ฅ๐๐ก๐๐จ๐ฅ๐๐ โ ๐๐ก๐ง๐ฅ๐๐๐๐ฆ๐๐๐๐จ๐๐๐ฅ.
๐งช ๐. ๐ก๐๐ช ๐๐๐๐๐ฉ๐๐ฅ๐๐ ๐ฆ๐ง๐จ๐๐ฌ - ๐ช๐๐๐ง ๐๐ข๐๐ฆ ๐๐ง ๐ฅ๐๐๐๐๐ฌ ๐ฃ๐ฅ๐ข๐ฉ๐?
โซ๏ธ Paraneural/subparaneural spread was universal.
โซ๏ธ Deeper subepineurial and extrafascicular spread occurred variably.
โซ๏ธ No intrafascicular spread was demonstrated.
But important limitations remain:
โ ๏ธ No histology โ exact microscopic boundary crossing unconfirmed.
โ ๏ธ Needle-tip position uncertain โ deeper dye cannot automatically prove sequential inward migration.
โ ๏ธ No pressure monitoring โ mechanism of tissue separation remains unknown.
โ ๏ธ Latex + cadaver โ LA + living nerve.
โ ๏ธ Very small sample โ TNโCPN differences remain hypothesis-generating.
โ ๏ธ โSubepineurialโ & โextrafascicular intraneuralโ may represent different depths of the same continuum, not completely separate compartments.
โ ๏ธ Absence of fascicular dye โ proof of clinical safety.
Most importantly:
The study demonstrates DISTRIBUTION, not necessarily TRAJECTORY.
๐ ๐. ๐ช๐๐ฌ ๐ข๐๐ โ๐๐ก๐ง๐ฅ๐๐ก๐๐จ๐ฅ๐๐ ๐ฆ๐๐กโ ๐ฆ๐ง๐จ๐๐๐๐ฆ ๐ก๐๐๐ ๐ฅ๐๐๐ก๐ง๐๐ฅ๐ฃ๐ฅ๐๐ง๐๐ง๐๐ข๐ก
โซ๏ธ Much of the reassuring โintraneuralโ literature comes from the popliteal SCN.
โซ๏ธ Prior clinical, MRI, sonographic & cadaveric studies have shown that:
apparent SCN intraneural spread may actually be subparaneural or extrafascicular.
โซ๏ธ Their findings therefore cannot be automatically extrapolated to ordinary single-epineurial peripheral nerves.
The โsafe intraneural SCNโ narrative may partly be an ANATOMICAL NOMENCLATURE problem.
๐ก ๐๐๐ฌ ๐ง๐๐๐๐๐ช๐๐ฌ๐ฆ
โซ๏ธ Popliteal SCN โ simple single-epineurial nerve.
โซ๏ธ Think TN + CPN within a specialised paraneural complex.
โซ๏ธ Extraparaneural โ subparaneural.
โซ๏ธ Subparaneural โ intraepineurial TN/CPN.
โซ๏ธ SCN spread may appear โintraneuralโ while remaining extraneural to TN & CPN.
โซ๏ธ Subepineurial = intraneuralโextrafascicular to the individual nerve.
โซ๏ธ Intraneural โ intrafascicular.
๐ฏ ๐๐๐๐ข๐ฅ๐ ๐๐๐๐๐๐ก๏ฟฝ๏ฟฝ ๐๐ก ๐๐ก๐๐๐๐ง๐๐ข๐ก โ๐๐ก๐ง๐ฅ๐๐ก๐๐จ๐ฅ๐๐โ, ๐๐ฆ๐:
Which boundary was crossed : PARANEURIUM, EPINEURIUM or PERINEURIUM?
Anatomy should define the terminology, not ultrasound appearance alone.
๐ฅ RA & ANS: A. Knowing the Sympathetic System Before Blocking It
#RegionalAnesthesia #SympatheticNervousSystem #AnesthesiaEducation #NeuraxialAnesthesia #PeripheralNerveBlock #PainMedicine #RAandANS
#PerioperativeMedicine #StressResponse #AdrenalMedulla #AnatomyMatters
#TipOfTheDay #MyRATips
Tip of the Day:
Why regional anesthesia does more than just numb pain?
The sympathetic nervous system quietly travels alongside our nerves and vessels and when we perform RA, we often block it without even trying.
๐ง The Sympathetic Highway
๐น ๐ฆ Origin: Starts in the spinal cord from T1โL2 (thoracolumbar outflow)
๐น ๐ฃ๏ธ Exit route: Leaves via ventral root โ spinal nerve โ white ramus
๐น ๐ Relay station: Enters the sympathetic chain. May synapse at the same level, go up/down, or pass through as splanchnic nerves
๐น ๐ฟ Final journey: Returns via gray ramus. Travels with peripheral nerves and blood vessels to skin, muscles, joints, and organs
๐ฏ One-line rule๐
White ramus = exit from spinal nerve (T1โL2 only)
Gray ramus = entry into spinal nerve (all levels)
๐ What Happens During Regional Anesthesia?
๐ข Sympathetic fibers are small, superficial, and highly sensitive to local anesthetics
โก๏ธ They get blocked earlier and more easily than motor fibers
๐ก๏ธ Clinical Signs
โจ ๐ฅ Warm limb after block โ sympathetic vasodilation
โจ ๐ง Dry skin โ sudomotor block
โจ ๐ Drop in BP after spinal/epidural โ sympathetic blockade
โจ ๐๏ธ Ptosis, miosis, warm arm โ Hornerโs syndrome (after stellate spread)
โ But Important Reality Check
โ ๏ธ Not all pain is sympathetic pain
โ Tourniquet pain
โ Ischemic pain
โ Compartment syndrome pain
๐ These persist because they involve:
๐น Deep C-fibers & A-delta fibers ๐งฌ
๐น Central sensitization๐ง
๐น Multi-segmental spinal input ๐
๐น Ischemic chemical mediators ๐งช
๐น Blocking sympathetic efferents โ blocking all pain afferents๐น
๐ฏ Why This Matters to Us (RA Perspective):
๐งฉ Perfect block โ pain-free tourniquet
๐งฉ Large-volume proximal blocks feel โbetterโ
๐งฉ Vasodilation happens before sensory loss
๐งฉ Sympathetic block is a feature, not a complication
๐ Take-home
RA always blocks the sympathetic system but pain relief depends on much more than just sympathetic blockade.
๐ฅ
The Great Regional Anesthesia โSelf-Goalโ: Blaming the Protector ๐ช
#RegionalAnaesthesia #PeripheralNerveBlock
#ReboundPain #MultimodalAnalgesia
#OpioidSparing #AcutePainManagement
#Anaesthesia #EvidenceBasedPractice
#TipOfTheDay #MyRATips
Tip of the Day:
๐๏ธImagine Thisโฆ
๐Your home is under constant attack (the nonstop barrage of postoperative nociception).
๐At the front gate stands one brave soldier (your Peripheral Nerve Block (PNB).
๐ช One Soldierโฆ Fighting for You
He:
๐ก๏ธ Blocks every strike
๐ฅ Absorbs every hit
๐คซ Keeps your home quiet
โณ Protects you for hours
He fights aloneโฆ but he fights brilliantly.
๐When the Soldier Fallsโฆ
Every warrior has limits.
When exhaustion takes him down (the block wears off):
๐ฅ The attackers surge
๐๏ธ Damage occurs
๐ฑ Chaos breaks loose
And what happens?
You turn around and say: โThe destruction started when he fell - so he must be responsible.โ
That, right there, is the SELF GOAL.
Blaming the only thing that protected you.
๐ฏ The Correct Logic
The soldier saved you for hours.
The real problem is that the walls were never reinforced.
You never sent in:
๐ Paracetamol
๐ NSAIDs / COX-2 inhibitors
๐ Pre-emptive dosing
๐ Scheduled MMA
When the soldier fell, the unprepared system collapsed.
๐ The enemy didnโt get stronger.
Your defenses were incomplete.
๐ What Is Rebound Pain?
โญRebound pain = the normal return of surgical nociception once a single-shot PNB wears off.
โญIt is:
๐ง Physiological, not pathological
๐ Transient, not persistent
๐ Preventable, not inevitable
โ
Rebound pain only becomes dramatic when block offset meets weak MMA.
โ
If the systemic analgesia is poor, the rebound looks like a โcomplication.โ
โ
But it's really a system-created phenomenon.
๐ฅRebound Pain Doesnโt Increase Opioids - Bad MMA Does
Many claim:
โ PNB โ Rebound Pain โ More Opioids
But the true sequence is:
๐ก๏ธ PNB provides exceptional early analgesia
๐ Block wears off
โ ๏ธ Weak MMA creates an analgesic gap
๐ Rescue opioids shoot up
So the correct chain is:
โ PNB โ Opioids
โ Poor MMA โ Opioids
๐จThe Real Problem in the BMJ Paper
๐ โRebound painโ was a label, not an outcome - the 0.17/10 NRS difference is clinically negligible.
๐ Raw data show PNB patients used fewer opioids; the โ22.7% increaseโ appears only after heavy modelling.
๐ PNB patients received more pre-op opioids and weaker MMA - yet the block was blamed instead of the analgesic plan.
๐ Pain spikes after block regression only when MMA is inadequate - thatโs a system failure, not a block failure.
๐ฉบ The same study shows lower chronic pain at 12 months in PNB patients - clear proof that PNB is the protector.
โญFinal Take-Home Message
PNBs are NOT the problem - poor perioperative analgesia is.
โ PNBs reduce early pain and early opioid use
โ PNBs reduce chronic post-surgical pain
โ PNBs improve recovery & shorten hospital stay
โ Rebound pain is fully preventable with good MMA
โ PNBs do NOT inherently increase opioids
โ Rebound pain is NOT a block complication
โ Blaming RA is a clinical self-goal
๐กPNB is the protector โ not the culprit.
๐กRebound pain reflects a gap in MMA, not a flaw in RA.
๐ฏ ๐ Forward Flow Forward: Mastering the Popliteal Pathway via Smart ACB Strategies ๐
#RegionalAnesthesia #NerveBlocks #UltrasoundGuided #PeripheralNerveBlock #AnesthesiaEducation #AdductorCanalBlock #PoplitealPlexus #AnteriorApproach #DSB #HiPAC #4in1Block #KneeAnalgesia #MotorSparing #TipOfTheDay #MyRATips
Tip of the Day:
๐ง The Adductor Canal: Natureโs Passageway to the Popliteal Fossa
๐The AC is a musculoaponeurotic tunnel, bounded by two muscles (VMM & ALM/AMM) and one aponeurosis (VAM).
๐It naturally connects the anterior thigh to the posterior thigh through the adductor hiatus.
๐ Using this anatomical passageway, local anesthetic can be directed from an anterior approach to reach posterior targets like the popliteal plexus and even sciatic nerve branches.
๐ขVolume Dynamics & Direction in ACB-Based Techniques
๐ When performing ACBs for knee or below-knee surgeries, understanding how LA moves and how we can guide that movement is critical for:
๐ฆตTargeting the popliteal plexus (for knee analgesia),
๐ฆตOr reaching the sciatic nerve trunks (for foot/ankle surgery).
๐ก Popliteal Plexus = Enough for Knee Surgery
โจLA spread to posterior capsule & intra-articular branches (tibial & obturator articular twigs) is usually sufficient for TKA and arthroscopy.
โจAchievable with 15โ20โฏmL when injected in the PURPLE perivascular zone at the proximal AC (just distal to FT apex).
๐ก Sciatic Trunk Coverage = Needed for Below-Knee Surgery
โจFull coverage of the TN & CPN requires: High-volume LA (30โ40โฏmL) in the AC.
โจThe drug follows the femoral artery through the adductor hiatus into the popliteal fossa and around the sciatic nerve.
๐ข๐ What Did Dye Studies Show?
๐Multiple dye and contrast studies have confirmed spread to the popliteal plexus when large volumes (20โ30 mL) are injected perivascularly in the distal AC.
๐In the landmark Gautier et al. series, 20 mL of contrast injected into the AC showed dye around the sciatic nerve in all cases, with limited sensory or motor impact.
๐Similarly, Runge et al. and Goffin et al. (cadaveric work) demonstrated consistent spread into the popliteal fossa, especially when dye was injected 1โ2 cm above the adductor hiatus.
๐Most importantly, Johnston et al. confirmed that dye injected into the distal AC could spread to the popliteal plexus, while distal FT injections did not.
๐Hi-PAC and 4-in-1 innovated further by extending the anterior spread to the sciatic trunk.
๏ฟฝ๏ฟฝThe only contradictory claim (RAPM, 2023) lacks dissection and underreports its own positive data.
๐ Where to Inject? The โPurple Zoneโ
๐ฏ Optimal target = deep to sartorius, lateral to femoral artery, and under the VAM.
๐ฃ This is the perivascular PURPLE zone, a conduit that sends LA through the adductor hiatus โ popliteal fossa.
๐ How Much? Volume Matters
๐<10โฏmL: Often insufficient to reach the popliteal plexus or include major articular branches.
๐15-20 mL: Ideal for proximal AC โ to achieve popliteal spread without sciatic involvement.
๐โฅ20โฏmL: Increases likelihood of sciatic spread, especially if injected distally in the AC.
โ๏ธ DSB Technique = Dual Injection for Strategic Spread
๐Volume Efficiency + Direction Control
๐น 1st injection: 10-20 mL in distal FT pre-fills the proximal tract, restricting retrograde spread of the second injection.
๐น 2nd injection: 10โ20 mL in AC moves distally, pushing the drug toward the popliteal plexus
โ
Key Advantage: DSB achieves popliteal plexus involvement with less total volume than needed in a single-shot ACB alone.
๐ง Concept: Blocking the Backdoor, Opening the Front - By โsealing offโ the proximal path with the first bolus, DSB converts the second bolus into a distally driven column, minimizing leakage and maximizing effect.
๐Why the RAPM (Smulders et al.) Study Missed the Mark?
๐งCadaveric study, but no dissectionโ.
๐CT after 30 min - not real-time, no vascular flow, potential underestimation.
๐งชUsed 2โฏmL groups (!), only 30โฏmL showed popliteal spread in 3 cases - yet still concluded โno sciatic spread.โ
โ No comparison with prior positive studies
โ Ignored key findings in 30 mL group
๐Titled with a strong claim despite contradictory findings: misleading, non-neutral, and goal-directed bias.
๐Contrast in CT can resemble soft tissue = interpretation bias.
๐ Why Modify ACB Instead of Adding Blocks?
๐ซ You donโt always need iPACK or posterior sciatic blocks.
โ
A single smart ACB (or DSB) can:
๐ณCover posterior capsule of the knee
๐ณReach articular sciatic branches
๐ณSometimes even spread to sciatic trunk (if needed, with higher volume)
๐ Minimizes motor block, preserves function, reduces number of injections.
๐ฅAchieve foot analgesia from the front in below-knee surgeries when using Hi-PAC or 4-in-1.
๏ฟฝ๏ฟฝ๏ฟฝ๐ Final Take-Home Message
โ
Site trumps name: Where and how you inject matters more than the block label
โ
15โ20 mL in the purple zone = safe & effective posterior knee coverage
โ
DSB enhances forward flow, limiting volume while boosting effectiveness
โ
30โ40 mL directed distally (Hi-PAC/4-in-1) can reach sciatic trunk from anterior thigh
โ
One modified ACB can replace multiple blocks -if you respect anatomy and guide your volume!
โ
Popliteal-plexus spread rarely weakens ankle; Hi-PAC/4-in-1 almost certainly will factor this into rehab plans. So, always use diluted LA for selective sensory blockade.
โ
Document your plan - write โPopliteal-plexus target (20 mL)โ or โHi-PAC (35 mL) for below-knee surgeryโ so PACU and physio teams know what to expect.
๐ One clever anterior injection can replace multiple blocks - if you know what you're doing.๐ก
"๐งฌ Vastoadductor Membrane (VAM): Gateway to Smart Analgesia in TKA ๐ก"
#VastoadductorMembrane #VAM #DualSubsartorialBlock
#MotorSparingAnesthesia #RegionalAnesthesia #AdductorCanalBlock #UltrasoundGuidedBlock #AnatomyMatters #FascialPlanes #PeripheralNerveBlock
#AnesthesiaEducation #SmartBlocking #AnatomicalPrecision #TKAPainManagement #EnhancedRecoveryAfterSurgery #FastTrackSurgery
#KneeSurgeryCare #TipoftheDay #MyRATips
Tip of the Day:
๐ง Anatomical Role of the VAM
๐งตThe VAM is a dense, collagen-rich fascial septum forming the anteromedial boundary of the adductor canal.
๐It lies deep to the sartorius, separating the vastus medialis muscle (VMM) from the adductor longus and magnus muscles.
๐งฑIt acts as a physical barrier and anatomical tunnel wall, crucial for directing local anesthetic (LA) flow.
๐Attachments and Boundaries
๐นLaterally: Attaches to the posteromedial border of vastus medialis.
๐นPosteromedially: Anchors to the anterior surfaces of adductor longus (proximal) and adductor magnus (distal).
๐งฉForms the anteromedial fascial boundary of the adductor canal, opposite the posteromedial muscle wall.
๐Extent and Dimensions
๐Length: Approximately 7.6 cm from the apex of the femoral triangle to the adductor hiatus.
๐Width: Varies - about 2.2 cm proximally, 1.7 cm midsection, and 0.5 cm distally.
๐Proximal origin: Around 28 cm distal to ASIS.
๐Distal termination: About 10 cm above the adductor tubercle.
๐ฌ๏ธFenestrations in the VAM
๐Present in ~75% of cadaveric specimens.
๐Allow limited cross-compartment communication between the STMโVMM plane and the adductor canal.
๐ขFenestrations are physiological gaps in the VAM that allow passage of:
๐ฉNerve to vastus medialis (NVM)
๐ฆSaphenous nerve branches (31%)
๐งObturator nerve branches (12.5%)
๐ชPerforating veins (22%)
๐งLocal Anesthetic Flow Dynamics
๐ฅWhen LA is injected in the STMโVMM interfascial plane, it prefers to spread:
๐ฝBeneath the VAM into the adductor canal - the path of least resistance.
๐Along the natural musculoaponeurotic tunnel, facilitating broader spread and nerve coverage.
โ ๏ธWhile fenestrations exist, they offer greater fascial resistance than the canal tunnel, hence most LA flows under the VAM, not through it.
๐กClinical Relevance in Regional Anesthesia
โACB targets the saphenous nerve, but often misses the NVM and other terminal femoral branches.
โ
DSB uses:
๐ฉบA proximal injection in the STMโVMM plane to directly block NVM and SN.
๐A second injection into the adductor canal to reinforce distal coverage.
๐Why ACB Alone is Not Enough for TKA?
โACB only targets the saphenous nerve in the adductor canal.
โ It misses:
๐กNVM (often outside the canal in the STMโVMM plane)
๐กPeripatellar plexus and Subsartorial plexus branches
๐กObturator nerve contributions and
๐กPosterior knee nerves (if volume <15ml)
๐ While fenestrations help some spread, they are not sufficient alone to ensure full knee coverage.
๐ง Take-Home Messages
๐ ๏ธThe VAM is not the roof of the AC - thatโs the sartorius. Instead, VAM forms the medial fascial wall that governs how LA spreads.
โ
The VAM is not just a fascial boundary - itโs an anatomical gateway that determines the success or failure of motor-sparing regional anesthesia techniques.
๐ฆLA injected beneath the VAM into the adductor canal flows easily along the low-resistance tunnel, not primarily through fenestrations.
๐Its fenestrations allow cross-compartmental spread.
โACB alone, despite VAM fenestrations, is not sufficient for TKA.
๐งฉMastering the VAM's anatomy and spread mechanics is essential for maximizing regional block efficacy while preserving quadriceps strength.
๐ทใClickใhttps://t.co/kbYr7P6bGV
#Postoperativepainmanagement;#Peripheralnerveblock;#Kneearthroplasty;#Epiduralanalgesia;#Rehabilitation;#Rehabilitation;
Data suggest periph nerve blocks provide analgesic benefit when intrathecal morphine can't be used or as rescue technique for refract pain. ASRA Pain Medicine News: https://t.co/RrcC497j4Z @MKwesiKwofie @DElmofty @NarouzeMD @ruthi_landau #Cesarean #Analgesia #PeripheralNerveBlock
Delivered today! A #SAFIRA evaluation pack to @JoanaMMagalhae๐ Looking forward to hearing the results of the evaluation!
#regionalanaesthesia #innovation #UGRA #nerveblock #anesthesiology #nerveblocks #anaesthesia #USGRA #peripheralnerveblock
#Fascia plays an essential role in #PeripheralNerveBlock. Check our newest video here to learn the tricks to make your practice safer and more successful. https://t.co/olisHOBaiE
@NaveenEipe @Jerryblocksthat @Nadia_Hdz_MD @docmatter @OttAnesthesia @OttawaHospital @OttawaTrauma Many thanks @Jerryblocksthat for organizing this opportunity to discuss #RibFracture management with #PeripheralNerveBlock Catheters.
See how SAFIRAยฎ can be integrated into #peripheralnerveblock procedures such as this #ankleblock
Watch the 2 minute video https://t.co/pZ7aS2HJWX
#regionalanaesthesia #anaesthetist #SAFIRA #footsurgery
What challenges face #anaesthetists when carrying out a #peripheralnerveblock & how can #SAFIRAยฎ help overcome them?
Dr Peter Merjavy shares his thoughts in this short video https://t.co/glSZki1QOY
#regionalanaesthesia #anaesthesia
#regionalanesthesia #jedi #peripheralnerveblock Is Jedi Grip efficient and effective in ultrasound-guided peripheral n... https://t.co/TaxYg8OO3r
@NarouzeMD That block was so beautiful it inspired me to do a Regional Anesthesia Fellowship. #peripheralNerveBlock
#morningglory !!! one of @PennAnesthesia residents who rotated through #regionalanesthesia made the #peripheralnerveblock a primary anesthetic @PennMedicine #HUP #culturalshift #heretheycome @nelkassabany @VeenaGraffMD @jochrochmd @shuang821 @ibadiolamd @James22kim
Are you joining us in #Asheville? It's going to be beautiful that time of year! This is our last #PeripheralNerveBlock course for 2018! Check it out and grab your seat now.
@terasonUS
Editorial: What are the risks and benefits of intraneural local anesthesia injection? #RegionalAnesthesia #PeripheralNerveBlock #Anaesthesia #Anesthesia #RegionalAnaesthesia #localAnesthesia https://t.co/yyX8iooyjU
Images in #Anesthesiology: Ultrasound-guided #regionalAnesthesia micro air bubble contrast to visualize the needle. #peripheralNerveBlock #anesthesia #anaesthesia https://t.co/DO5lTAmoRB
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