Level of difficulty

Intermediate. The bony landmarks are easy to see, but the sacrum is a curved, uneven surface and the target plane lies right on the bone. The name and the best injection point are still being worked out.

Anatomy

The back of the sacrum has three bony ridges on each side of the midline: the median sacral crest (fused spinous processes), the intermediate crest (fused articular processes) and the lateral crest. The dorsal sacral foramina lie just outside the intermediate crest.

The multifidus muscle fills the groove beside the median crest, covered by the tendinous aponeurosis of erector spinae. Local anaesthetic placed between these muscles and the bone is in the same plane as the lumbar and thoracic erector spinae plane.

From here it reaches the dorsal rami of the sacral nerves, which supply the skin over the sacrum and buttock. Spread through the dorsal foramina may also reach the ventral rami and the sacral epidural space. This probably explains the perineal and genital analgesia, but the exact mechanism is still debated.

Contrast studies show spread up to the lumbar levels, which explains reports of analgesia for hip and lumbar spine surgery.

Because the injection is deep to multifidus, some authors call it the sacral multifidus plane block. The target is the same.

Drawing of a probe on the lower back next to a drawing of the back of the sacrum with erector spinae and multifidus, the sacral crests, the dorsal foramina and the dorsal sacral nerves — Left: probe placed over the sacrum. Right: the back of the sacrum. Multifidus and erector spinae lie over the median and intermediate crests, and the dorsal sacral nerves leave through the dorsal foramina beside them.

Drawing of the inside of the pelvis showing the sacral plexus from L4 to S4, the sciatic, pudendal and posterior femoral cutaneous nerves, and the dorsal sacral rami behind the sacrum — The sacral plexus seen from inside the pelvis (front, ventral rami) and the dorsal sacral rami S1–S4 behind the sacrum. The pudendal nerve (S2–S4) supplies the perineum.

Surface anatomy

Posterior superior iliac spines (PSIS): a line between them crosses S2.
Median sacral crest in the midline.
Sacral hiatus and cornua at the lower end (for orientation).
Natal cleft.

Indications

Anorectal surgery: haemorrhoidectomy, fistula, fissure and pilonidal sinus surgery.
Children's genital and urological surgery: circumcision and hypospadias repair, as an alternative to a caudal block.
Transurethral and other perineal surgery.
Lumbar spine surgery, and hip surgery (single-sided block; case reports and small trials).
Coccygectomy and coccyx pain.

Nerves blocked

Dorsal rami of S1–S4 (skin over the sacrum and buttock)
Often the sacral ventral rami and pudendal nerve territory through the dorsal foramina
Variable lumbar spread (L2–L5 in some imaging studies)

Landmark technique

Surface anatomy, relevant structures and landmarks

Not recommended without ultrasound. The plane lies on the bone and the dorsal foramina are close.

Positioning

Prone with a pillow under the pelvis, or lateral with the hips flexed (usual for children under general anaesthesia).

Block technique

Ultrasound guided: see below.

Needle choice

22 G short-bevel block needle, 50 mm in children and 80 mm in adults.

Neurostimulation technique

Not used.

Choice of local anaesthetic (including volume)

Children: 0.5–1 mL/kg in total of 0.2% ropivacaine or 0.25% bupivacaine or levobupivacaine, split between the two sides for a midline operation.
Adults: 20–30 mL of 0.2–0.375% ropivacaine or 0.25% levobupivacaine, split between the two sides if bilateral.
Check the total dose against weight: use the dose calculator.

Ultrasound technique

Sacral erector spinae plane block, transverse view at S2: labelled schematic ultrasound illustration — Transverse view at S2 (paramedian approach). Median crest in the middle, intermediate crests on each side; the gaps lateral to them are the dorsal foramina.

MSC
median sacral crest (midline)
ISC
intermediate sacral crest on each side: the needle target
DSF
dorsal sacral foramen: a gap in the bone line, avoid
Multifidus
multifidus filling the groove beside the median crest
ESA
erector spinae aponeurosis and thoracolumbar fascia
PSIS
posterior superior iliac spine (ilium)
Needle
in plane from lateral onto the intermediate crest

Original schematic illustration © **Nerve Blocks**. Not to scale.

Ultrasound image: Figure 3B from Dost et al. 2026 (see the acknowledgement at the end of the page). Hover over the picture, or press Show scan, to switch between the scan and the illustration.

Ultrasound scan of the same view, without labels — Transverse view at S2 (paramedian approach). Median crest in the middle, intermediate crests on each side; the gaps lateral to them are the dorsal foramina.

MSC
median sacral crest (midline)
ISC
intermediate sacral crest on each side: the needle target
DSF
dorsal sacral foramen: a gap in the bone line, avoid
Multifidus
multifidus filling the groove beside the median crest
ESA
erector spinae aponeurosis and thoracolumbar fascia
PSIS
posterior superior iliac spine (ilium)
Needle
in plane from lateral onto the intermediate crest

Original schematic illustration © **Nerve Blocks**. Not to scale.

Ultrasound image: Figure 3B from Dost et al. 2026 (see the acknowledgement at the end of the page). Hover over the picture, or press Show scan, to switch between the scan and the illustration.

Sacral erector spinae plane block, midline sagittal view: labelled schematic ultrasound illustration — Midline sagittal view over the median crests S1 to S4. The needle comes from above onto S4; one injection spreads to both sides.

S1–S4
median sacral crests (fused spinous processes), getting deeper towards the tail
ESA
erector spinae aponeurosis over the crests
Multifidus
thin multifidus and soft tissue in the midline
Needle
in plane from cranial to caudal, onto the S4 crest

Original schematic illustration © **Nerve Blocks**. Not to scale.

Ultrasound image: Figure 4B from Dost et al. 2026 (see the acknowledgement at the end of the page). Hover over the picture, or press Show scan, to switch between the scan and the illustration.

Labelled transverse ultrasound image of the sacrum showing the median and intermediate sacral crests, erector spinae and multifidus, the needle path and the spread of local anaesthetic on the bone — Paramedian approach, transverse view. The local anaesthetic (blue) spreads under multifidus, on the bone between the median and intermediate sacral crests.

Yellow dots
Needle path (added by the authors)
Blue
Spread of local anaesthetic (added by the authors)

Labelled midline sagittal ultrasound image of the sacrum showing S2, S3 and S4, erector spinae and multifidus, the needle path from cranial to caudal and the spread of local anaesthetic — Midline approach, sagittal view. The needle comes in plane from the head end towards S4. The local anaesthetic (blue) spreads under the erector spinae aponeurosis over S2–S4.

Yellow dots
Needle path (added by the authors)
Blue
Spread of local anaesthetic (added by the authors)

Positioning

Prone or lateral. Operator on the side of the needle; screen opposite.

Scanning technique

Find the sacral hiatus and cornua, then slide up in the midline to the median sacral crest.
Midline approach: turn the probe longitudinal (sagittal) over the median crests S1–S4 and insert the needle in plane from above (cranial to caudal) until it touches the S4 crest. Inject deep to the erector spinae aponeurosis; one injection spreads to both sides and may pool towards the sacral hiatus. This approach works best in younger children.
Paramedian approach: turn the probe transverse at S2, find the intermediate crest about 1.5–2 cm from the midline, and insert the needle in plane from lateral (or from below with a longitudinal probe) onto the crest.
Watch the drug lift multifidus and erector spinae off the bone and spread up and down the sacrum.

Structures to identify

Median sacral crest
Intermediate sacral crest
Dorsal sacral foramina (gaps in the bone line)
Multifidus
Erector spinae aponeurosis and thoracolumbar fascia
Posterior superior iliac spine

Block performance

Patient lying on the side with a sterile-covered linear probe across the sacrum and a block needle entering beside it — Paramedian approach: transverse probe over the sacrum, needle in plane.

Patient lying on the side with a sterile-covered linear probe along the midline of the sacrum and a block needle entering from the head end — Midline approach: probe along the midline of the sacrum, needle in plane from the head end (cranial to caudal).

Position / ergonomics

Stand beside the patient at the level of the pelvis, screen on the other side.

Probe

Linear high-frequency; curvilinear in larger adults.

Settings

Musculoskeletal preset, depth 3–6 cm.

Depth

1–2 cm in children; 3–5 cm in adults.

Needle size

22 G, 50–80 mm.

Needling technique

Paramedian: in plane from lateral (transverse probe) or along the crest (parasagittal probe). Midline: in plane from cranial to caudal onto the S4 crest.

Optimal needle-tip position

On the bone of the median or intermediate crest, deep to multifidus. Not into a dorsal foramen.

Drug choice

See above.

Volume

0.5–1 mL/kg in children; 20–30 mL in adults.

Optimal current if nerve stimulation is used

Not used.

Muscle responses acceptable

Not applicable.

Testing block success

Loss of cold sensation over the sacrum, perineum or buttock (awake patients)
No heart rate or blood pressure response to skin incision

Continuous techniques

Not usually used. Catheters have been placed in this plane in a few case reports.

Contraindications to the block

Absolute

Patient refusal
Infection over the sacrum (including an infected pilonidal sinus at the needle site)
Allergy to the drugs used

Relative

Sacral anomalies such as spina bifida or sacral agenesis
Coagulopathy or anticoagulants (drug can reach the sacral foramina and epidural space: follow the deep block guidance)
Local anaesthetic dose limits in small children for bilateral blocks

Side effects and complications

Side effects

Numb buttock and perineum
Possible temporary leg weakness or urinary retention if the drug spreads to the sacral roots or epidural space (uncommon)

Complications

Local anaesthetic toxicity (large volumes, especially bilateral in children)
Injection into a dorsal foramen or the sacral canal
Bruising or infection at the site (rare)

Pearls of wisdom

Start at the sacral hiatus and count upwards: the PSIS line marks S2.
Keep the needle tip on bone over a crest, not over a gap in the bone line (a foramen).
For a midline operation, give the volume in the midline or on both sides.
In children it is an option when parents or surgeons wish to avoid leg weakness after a caudal block.

Review of literature

Dost, Narayanan and colleagues (2026) reviewed the anatomy, techniques and 14 randomised trials. The block reduced pain and opioid use in adults, and lengthened analgesia compared with caudal or penile blocks in most children's trials. The evidence is still small and varied.
Rinaldi and Garo (2026) pooled 14 trials (1041 patients): fewer patients needed rescue analgesia and the first rescue came about 5 hours later, but the certainty of evidence was low.
Kozanhan and colleagues (2026) pooled six children's trials (437 children): longer time to first rescue analgesia and less paracetamol at 24 hours.
Nair and colleagues (2025) pooled 12 trials of the sacral multifidus plane block (768 patients) and found longer analgesia and less opioid use, with no serious complications.
Marrone and colleagues (2025) showed on CT spread from S1 up to L2 and to the S2–S3 roots after a single-sided injection.

Comparison with other blocks

Block	Coverage	Leg weakness	Notes
Sacral ESP / multifidus plane	Sacral dermatomes, perineum; variable lumbar	Rare	Plane block on bone; evidence growing
Caudal epidural	Sacral and lower lumbar	Possible	Well established in children
Pudendal	Perineum, anus, genitals	Possible (sciatic spread)	Deeper; one nerve each side
Dorsal penile	Penis only	None	Circumcision and distal hypospadias

References

Dost B, Narayanan M, Marrone F, et al. The sacral erector spinae plane block: a narrative review. Pain Ther 2026;15:131–147. PubMed
Rinaldi P, Garo ML. Efficacy and safety of sacral erector spinae plane (S-ESP) block in adult and pediatric patients during surgical procedures: a comprehensive systematic review and meta-analysis. J Clin Anesth 2026;111:112181. PubMed
Kozanhan B, Satici MH, Yildiz M, Tutar MS. Analgesic efficacy of sacral erector spinae plane block in pediatric infraumbilical surgeries: a systematic review and meta-analysis of randomized controlled trials. Minerva Anestesiol 2026;92:209–220. PubMed
Nair AS, Mistry T, Garg R. Ultrasound-guided sacral multifidus plane block for perioperative analgesia: a comprehensive systematic review, meta-analysis, and trial sequential analysis. Indian J Anaesth 2025;69:1341–1358. PubMed
Marrone F, Sorrentino T, Megna B, Fusco P, Diwan S. Sacral erector spinae plane block: computed tomography imaging in a hip fracture patient. A A Pract 2025;19:e02105. PubMed

Acknowledgement

Figures 1, 2, 3A, 3B, 4A and 4B on this page are from Dost B, Narayanan M, Marrone F, De Cassai A, Tulgar S, Aksu C, Merjavy P, Chin KJ. The sacral erector spinae plane block: a narrative review. Pain Ther 2026;15:131–147. © The Author(s) 2025. Used under CC BY-NC 4.0. No changes made, except that panels A and B of Figures 3 and 4 are shown separately, and 3B and 4B also appear behind the schematic illustrations.

SELF-ASSESSMENT

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Sacral erector spinae plane block (sacral multifidus plane block)