Obturator Internus Injection

Other Names

• Obturator Internus Injection

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Background

Illustration of Obturator Internus

Key Points

• Needle: 22 gauge, 3.5 inch
• Transducer: linear array transducer
• Identify sciatic nerve prior to initiating the procedure

Anatomy of Obturator Internus

• Origin: Posterior surface of obturator membrane, obturator foramen
• Insertion: greater trochanter of the femur
• Actions: externally rotate thigh, abduct thigh, stabilize hip joint
• Bursa of obturator internus between tendon and ischium

Palpation vs Ultrasound Guided

• This procedure can not safely be performed with palpation guidance
• Ultrasound is required to identify the anatomy and properly place the needle

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Indications

• Obturator Internus tendonitis or bursitis

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Contraindications

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

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Procedure

(A) shows the obturator internus in long axis. (B) Shows the probe position to visualize in long axis

Ultrasound of injection with needle in plane. Note sciatic nerve is marked S.

Equipment

• Sterile prep (i.e. chloraprep, chlorhexidine, iodine, etc)
• Gloves
• Needle: typically 20-22 gauge, 3.5 inch
• Syringe: 5-10 mL
• Gauze
• Ethyl Chloride
• Bandage
• Injectate
  • Local anesthetic
  • Corticosteroid
• Sterile probe cover

Ultrasound Findings

• Due to small size and depth, can be difficult to find
  • Dependent on body habitus of patient
  • Best visualized in long axis
• Low frequency, linear transducer is typically sufficient
• How to identify obturator internus
  • First localize the piriformis muscle
  • Obturator internus can be seen emerging from pelvis, passing over ischium
  • Internally/externally rotating hip can help with visualization
• Sciatic nerve is usually just superficial to lateral aspect of tendon

Technique: Long Axis, In Plane

• Patient Position
  • Prone
• Transducer position
  • Long axis to obturator internus
• Needle Approach/ Orientation
  • In plane
  • Lateral to medial or medial to lateral
• Target
  • Obturator internus muscle, tendon sheath, or bursa
• Pearls and Pitfalls
  • Must identify sciatic nerve prior to procedure
  • Typically, just superior to lateral obturator internus muscle

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Aftercare

• No significant restrictions
• Can augment with ice, NSAIDS

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Complications

• Skin: Subcutaneous fat atrophy, skin atrophy, skin depigmentation
• Painful local reaction
• Infection
• Hyperglycemia
• Tendon, nerve or blood vessel injury

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See Also

Internal

• Procedures Main
• Ultrasound Main
• Hip Pain Main

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