Performing an Ischial Bursa Injection
Introduction
The ischial bursa is also known as the ischiogluteal bursa. The ischial bursa is found just superficial to the origin of the hamstring (3). Patients will typically complain of buttocks pain with prolonged sitting (3). Ischial bursitis can occur due to chronic repetitive microtrauma and acute injury (5). Ischial bursitis can be confused with ischiofemoral impingement syndrome, which is the entrapment of the quadratus femoris muscle between the ischium and lesser trochanter (2).
Location of the ischial bursa
Diagnosis of ischial bursitis can be aided with an MRI, which can show enhancement of fluid posteroinferior to the ischial tuberosity and at the inferior tip of the gluteus maximus (4). An ultrasound evaluation may show hypoechoic fluid overlying the hamstring tendon origin.
Injection Technique
An injection of the ischial bursa can be done with the patient placed in prone or lateral decubitus position (3). A curvilinear-array transducer should be used for the procedure (6). Prior to any injection, the sciatic nerve should be identified. The sciatic nerve can sometimes be found just lateral to the ischial tuberosity obstructing the path of the needle towards the ischial bursa (3). If a clear route to the bursa cannot be found, the patient can be placed in the lateral decubitus position (3). In the lateral decubitus position with the hips placed in 90 degrees of flexion, the sciatic nerve can move more lateral (3). A study showed that the nerve can move 13.5mm on average laterally with this position (7). The sciatic nerve is found superficial to the quadratus femoris (7).
Lateral injection approach (1)
A 22 gauge three and a half inch spinal needle is typically used for the injection. The injection is typically directed from a lateral to medial approach. The ultrasound image should show the ischial tuberosity, gluteus maximus muscle, hamstring tendons, and sciatic nerve (6). The needle will be guided to the superficial portion of the hamstring origin (3).
Ultrasound guided ischial bursa injection
Conclusion
An ischial bursa injection can help aid in diagnosis and potentially in treatment of ischial bursitis. The injection can potentially be hindered by the position of the sciatic nerve, so placing the patient in a lateral decubitus position with hip flexed can move the sciatic nerve laterally.
By Gregory Rubin, DO
rubinsportsmed.com
– More Hip Pain @ Sports Medicine Review: https://www.sportsmedreview.com/by-joint/hip/
– Ischial Bursitis @ Wiki Sports Medicine: https://wikism.org/Ischial_Bursitis
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