Arthrocentesis & Intraarticular Glucocorticoid Injection
Overview
Needle insertion into joint ทำเพื่อ:
1.
Arthrocentesis (diagnostic/therapeutic
aspiration)
2.
Intraarticular injection
Most injections:
- glucocorticoid
± - local
anesthetic
INDICATIONS
1. Diagnostic Arthrocentesis
Most important indications
Suspected Septic Arthritis
ข้อสำคัญ:
septic arthritis ต้อง aspirate เสมอถ้าสงสัย
Especially important:
- diabetic
- immunocompromised
- poor
follow-up reliability
Important pearl
Septic arthritis:
coexist กับ gout/RA ได้
ดังนั้น:
- culture
- crystal
analysis
ควรทำพร้อมกัน
Timing
ควร aspirate:
BEFORE antibiotics
เพราะ antibiotics ทำให้:
- synovial
WBC ลดลง ~50%
2. Suspected Crystal Arthropathy
Gold standard diagnosis:
synovial crystal analysis
แม้:
- US
- DECT
(dual-energy CT)
ช่วยได้
แต่ aspiration ยัง preferred
Indications for Intraarticular Steroid Injection
Inflammatory arthritis
- RA
- PsA
- spondyloarthritis
- reactive
arthritis
Crystal arthritis
- gout
- CPPD
- BCP (Basic
calcium phosphate crystal) arthritis
Osteoarthritis
Especially:
- moderate-severe
knee OA
RELATIVE CONTRAINDICATIONS
1. Septic arthritis
Absolute practical contraindication to steroid injection
2. Overlying cellulitis/periarticular infection
Risk:
- inoculate
infection into joint
3. Periarticular fracture
Steroid may impair bone healing
4. Planned arthroplasty
Important:
avoid steroid injection within 3 months before arthroplasty
Associated with:
- ↑ PJI risk
5. Joint instability
Steroid may worsen:
- ligament
weakness
- capsular
laxity
6. Juxtaarticular osteoporosis
7. Repeated injections in OA
Repeated steroid injections:
- diminishing
benefit
- possible
cartilage toxicity
Important Point: Anticoagulation
Generally safe:
- warfarin
- DOACs
- antiplatelet
agents
Warfarin
Usually acceptable if:
- INR ≤3–3.5
Unless:
- septic
joint suspected →
proceed urgently
INFORMED CONSENT
Discuss:
- infection
- postinjection
flare
- facial
flushing
- bleeding
- leakage
- steroid
adverse effects
Important risks
Septic arthritis
Rare:
~1/1000–3000 procedures
Postinjection flare
~5%
Can mimic infection
Facial flushing
Up to 10%
Usually not allergy
EQUIPMENT
Needle size
Standard
22G ideal for most joints
Larger needle (18–20G)
Use for:
- large
knee effusion
- viscous
pus
- Baker
cyst
- thick
synovial fluid
Needle length
- small/medium
joints → 1 inch
- shoulder/knee
→ 1.5–2 inch
- obese
patient → longer
Syringe size
Preferred
5 mL often ideal
Large effusion
20–50 mL syringe
Important Pearl
Large syringe:
- more
resistance
- harder
to distinguish tendon injection
GENERAL PRINCIPLES OF NEEDLE ENTRY
Goals:
1.
easiest capsule access
2.
avoid neurovascular structures
3.
avoid skin lesions/infection
Needle:
bevel-up always
KNEE ARTHROCENTESIS (High-yield)
Preferred approaches
Suprapatellar approach
Best for:
- large
effusions
Parapatellar approach
Best for:
- smaller
effusions
Infrapatellar seated approach
Useful when:
- wheelchair
patient
- cannot
extend knee
Suboptimal for aspiration
Knee Position
Slight flexion:
15–20°
Key maneuver
Compression/manipulation:
increases aspiration success
HIP ASPIRATION
Usually:
image-guided only
Methods:
- fluoroscopy
- ultrasound
SHOULDER ASPIRATION
Anterior approach
Most commonly used
Posterior approach
Advantages:
- less
painful
- patient
doesn’t see needle
NO-TOUCH TECHNIQUE
Key principle:
avoid touching sterilized field
Sterile gloves not always necessary if proper no-touch
technique used
Infection risk
Can reduce septic joint risk to:
<1/2000
SKIN PREPARATION
Preferred:
- chlorhexidine
or - iodine
prep
Avoid:
alcohol alone
LOCAL ANESTHESIA
Lidocaine
- 0.5–2
mL
- along
needle track
Disadvantage:
- may
reduce culture sensitivity
Ethyl chloride spray
Provides:
~15 sec anesthesia
Useful for:
- quick
skin puncture
JOINT ASPIRATION
Before steroid injection
Always visually inspect fluid
If fluid:
- turbid
- purulent
- unexpectedly
viscous
→ send:
- Gram
stain
- culture
- cell
count
before steroid injection
Debulking Effusions
Benefits:
- pain
relief
- ↓ chondrocyte damage
- ↑ steroid effectiveness
Especially useful in:
- RA
knees
- large
tense effusions
Important Pearl
Aspiration before steroid injection:
lower relapse rate
SYNOVIAL FLUID STUDIES
Send when diagnosis uncertain:
- cell
count
- differential
- Gram
stain
- culture
- crystal
analysis
ULTRASOUND GUIDANCE
Indications
- deep
joints
- obesity
- difficult
anatomy
- failed
aspiration (“dry tap”)
- suspected
septic joint
Particularly useful for
- hip
- shoulder
- wrist
- prosthetic
joints
DRY TAP
Definition:
unable to aspirate fluid despite repositioning
Causes
1. Technical failure
Most common
2. Altered anatomy
- prior
surgery
- deformity
- trauma
3. Needle obstruction
- synovium
- plica
- debris
- viscous
fluid
4. Small effusion
5. No actual effusion
Important Knee Dry Tap Causes
- fat
pad
- plica
- obesity
Approach to Dry Tap
1.
Change approach
2.
Compression maneuvers
3.
Ultrasound/fluoroscopy
Prosthetic Joint Pearl
Suspected septic prosthetic joint:
failed blind tap →
urgent fluoroscopic-guided aspiration
Orthopedic emergency
JOINT LAVAGE
Usually:
NOT recommended
because:
- dilutes
sample
- complicates
interpretation
Possible role:
- prosthetic
joint infection
- sternoclavicular
septic arthritis
POST-PROCEDURE CARE
Advise:
- decrease
weightbearing 24–48 hr
- ice
- OTC
analgesics
- keep
site clean
FOLLOW-UP
Depends on disease:
- OA
injection → months
- inflammatory
arthritis flare →
shorter follow-up
ANTICOAGULATION PEARLS
Generally safe:
- warfarin
- DOACs
Bleeding complications:
very rare
High-yield Clinical Pearls
- Septic
arthritis and gout can coexist
- Aspirate
before antibiotics whenever possible
- Crystal
analysis remains gold standard for gout diagnosis
- Avoid
steroid injection if septic arthritis suspected
- Avoid
steroid injection within 3 months before arthroplasty
- Large
viscous effusions may require 18–20G needle
- Aspiration
before steroid injection improves outcomes
- Dry
tap does not exclude septic arthritis
- Ultrasound
greatly improves success in difficult joints
- Prosthetic
joint infection + failed blind tap = fluoroscopic-guided aspiration
urgently
- Debulking
tense effusions improves pain and may protect cartilage
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