Ultrasound-Guided Ischiogluteal Bursa & Hamstring Injection

Anatomy Overview

• Semimembranosus: originates on the superolateral ischial tuberosity; has the largest proximal tendon of the three
• Conjoint tendon (biceps femoris long head + semitendinosus): originates medially at the ischial tuberosity
• Sciatic nerve: travels superficial to the quadratus femoris, lateral to the ischial tuberosity - the most critical structure to identify and protect
• The bursa sits deep to gluteus maximus and superficial to the hamstring tendons

Indications

Patient Positioning

1. Prone position - standard, easy access; sciatic nerve sits closer to the ischial tuberosity
2. Lateral decubitus, hip flexed 90° (preferred by many) - the sciatic nerve migrates significantly laterally away from the ischial tuberosity compared to prone, reducing the risk of inadvertent nerve injection (Wisniewski et al., PM&R 2014)

Transducer Selection

• Linear-array (medium frequency): preferred for lean patients; better resolution
• Curvilinear (low frequency): needed in larger body habitus; provides wider field of view to see the ischial tuberosity, hamstring tendons, and sciatic nerve simultaneously

Scanning Protocol (Step-by-Step)

1. Place the transducer in the anatomic axial (transverse) plane over the posterior superior iliac spine (PSIS)
2. Slide inferiorly until the lateral sacrum is seen medially
3. Continue inferiorly; the ischial tuberosity becomes visible as a prominent bony hyperechoic surface
4. Move the transducer laterally to identify the sciatic nerve - it appears oval/round, superficial to the quadratus femoris muscle
5. Optimize position so all four structures are visible simultaneously in one image:
   • Gluteus maximus (superficial)
   • Hamstring tendon origins (deep to gluteus maximus)
   • Ischial tuberosity (bony backstop)
   • Sciatic nerve (lateral, superficial to quadratus femoris)

Injection Technique

Needle Approach

• In-plane technique: lateral to medial
• Needle: 22-gauge, 64-89 mm (2.5-3.5 inch) spinal needle
• Mark the skin at the lateral edge of the transducer, prep in standard sterile fashion
• Infiltrate superficial local anesthetic down to the plane of the bursa

Needle Trajectory

• Advance the needle in-plane, lateral to medial under real-time ultrasound visualization
• Target: deep to gluteus maximus, superficial to hamstring tendons (for bursa injection)
• For hamstring tendon injection: advance to the peritendinous space adjacent to the tendon origin at the ischial tuberosity
• The ischial tuberosity serves as a firm bony backstop - needle should not advance past it

Critical Safety Step

• Confirm sciatic nerve position before advancing - trace it clearly and ensure the needle trajectory is lateral to it
• Dynamic real-time guidance is mandatory; do not advance blindly

Injectate

Image: US-Guided Proximal Hamstring Injection Technique

Complications to Counsel

• Sciatic nerve injury - most feared; avoidable with careful nerve identification before injection
• Post-injection pain flare (especially corticosteroid, first 24-48 h)
• Tendon weakening/rupture with repeated corticosteroid injections (particularly intratendinous injection - avoid)
• Infection/hematoma
• Fat atrophy/skin depigmentation if superficial injection
• Hypopigmentation in darker skin types

Practical Tips

• Lateral decubitus with hip at 90° flexion is preferred to maximize sciatic nerve distance from needle path
• Always identify the sciatic nerve first before advancing the needle
• For bursitis: deliver corticosteroid into the bursal space, not into the tendon substance
• For tendinopathy: peritendinous injection (not intratendinous) for corticosteroid; for PRP, some advocate fenestration/needling of the tendon
• US guidance produces accurate ischial bursograms without overflow to adjacent structures compared to landmark-guided technique (cadaveric studies confirm accuracy)
• Feasibility studies (Wisniewski et al., PM&R 2014) confirm US-guided ischial bursa injections can be performed safely without damage to adjacent neurovascular structures

Recent Evidence