Piriformis Injection

Other Names

• Piriformis Injection
• Piriformis Bursa Injection
• Piriformis Muscle Injection
• Piriformis Muscle Sheath Injection

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Background

Illustration of the piriformis anatomy

• This page refers to injections in or around the piriformis muscle
  • This procedure should be performed with ultrasound guidance

Key Points

• Transducer will be linear or curvilinear depending on patients body habitus
• Best visualized in axial oblique plane from superomedial to inferolateral
• Identify sciatic nerve prior to procedure

Anatomy

• Piriformis Muscle
  • Lies deep to gluteus maximus
  • External rotator of the hip
  • Originates on anterolatral sacrum, passes through greater sciatic foramen, inserts on superior greater trochanter
• Sciatic Nerve
  • Typically found deep to the piriformis muscle
  • Rarely, may pierce the muscle belly or be found superficial to it

Palpation vs Ultrasound Guidance

• A cadaveric study showed ultrasound is significantly more accurate than fluoroscopy

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Indications

• Piriformis Syndrome

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Contraindications

• Absolute
  • Anaphylaxis to injectates
  • Overlying cellulitis, skin lesion or systemic infection
  • Septic Bursitis
• Relative
  • Can be treated with less invasive means
  • Muscle tear or rupture
  • Hyperglycemia or poorly controlled diabetes
  • Lack of symptom improvement with previous injection

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Procedure

Demonstration of probe and needle position

Demonstration of internal and external rotation position to help confirm identification of piriformis

Needle tip is seen injecting into piriformis muscle a safe distance from the sciatic nerve

Equipment

• Sterile including chloraprep, chlorhexadine, iodine
• Ultrasound with sterile probe cover
• Gloves
• Needle: typically 21-22 gauge, 3.5 inch
• Syringe: 5-10 mL
• Gauze
• Bandage
• Injectate
  • Local anesthetic
  • Corticosteroid/ injectate

Ultrasound Findings

• Piriformis is best visualized in long axis
  • Low frequency curvilinear probe is typically required
  • In patients with a smaller body habitus, a linear medium frequency probe may suffice
• Identify piriformis
  • Identify the posterior superior iliac spine
  • Slide the probe caudally, the ilium will disappear and the probe will be over the great sciatic notch
  • Maintain the medial side of the probe while inferiorly rotating the lateral probe over the piriformis muscle
  • The piriformis can be seen originating from the sacrum extending inferolaterally to the greater trochanter
  • Flex the knee, internally/externally rotate hip to help identify piriformis
  • Final probe position: axial oblique from superomedial to inferolateral

Technique

• Patient Position
  • The patient is prone
• Transducer position
  • Axial oblique from superomedial to inferolateral
• Needle orientation/ approach
  • In plane
  • Lateral to medial or medial to lateral
• Target
  • Piriformis muscle sheath and/or muscle
• Pearls and Pitfalls
  • Identify sciatic nerve during pre-procedural sonography
  • Sciatic nerve is typically deep but can run through or above piriformis
  • Passive internal/external rotation of hip is very useful to identify muscle

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Aftercare

• No major restrictions in most cases
• Can augment with ice, NSAIDS

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Complications

• Sciatic Nerve Injury
  • May inadvertently regionally block the sciatic nerve which will resolve as anesthetic wears off
  • Can also fenestrate sciatic nerve if not careful during procedure

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See Also

Internal

• Procedures Main
• Ultrasound Main
• Hip Pain Main

External

• https://www.sportsmedreview.com/blog/performing-a-piriformis-muscle-injection/

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