Case Prep: Sacroiliac (SI) Joint Fusion

Case / Approach Snapshot

• Anatomy at risk: level localization, cord/cauda equina, exiting and traversing roots, dura, vertebral artery or segmental vessels, esophagus/trachea/pleura/viscera by approach, and fusion/instrumentation landmarks.
• Operative steps: position and pad carefully, confirm level, expose the planned corridor, decompress neural elements, reconstruct or instrument when indicated, verify alignment/hardware, and close with attention to hematoma and wound risk; use the detailed operative sequence and approach notes below as the step-by-step source.
• Rescue plans: wrong level, durotomy, neurologic change, vertebral artery/visceral/pleural injury, graft or hardware problem, epidural hematoma, dysphagia/airway issue, and infection prevention/escalation.
• Figures: review Figures, Imaging & Video and the Curated Image Set; embedded local figures should remain open-access, public-domain, or otherwise reusable with attribution.
• Papers: review High-Yield Literature for seminal sources, modern reviews, and outcome data specific to this page.

One-Liner

[Age]yo [M/F] with sacroiliac joint dysfunction (SI joint pain) refractory to conservative management planned for minimally invasive [lateral transiliac] SI joint fusion.

Figures, Imaging & Video

🎥 Operative video — search operative video on YouTube ▸ · The Neurosurgical Atlas ▸

Neurosurgical Atlas · AO Spine / Surgery Reference · Radiopaedia · PubMed Central — operative figures © linked; see media-sources.md

High-Yield Literature

• Sacroiliac Joint Interventions — Yang AJ. Physical medicine and rehabilitation clinics of North America 2022. PubMed
• Sacroiliac Joint Anatomy — Roberts SL. Physical medicine and rehabilitation clinics of North America 2021. PubMed
• Sacroiliac joint dysfunction: anatomy, pathophysiology, differential diagnosis, and treatment approaches — Waldman LE. Skeletal radiology 2025. PubMed
• Sacroiliac Joint Interventions — Soto Quijano DA. Physical medicine and rehabilitation clinics of North America 2018. PubMed
• The sacroiliac joint: an overview of its anatomy, function and potential clinical implications — Vleeming A. Journal of anatomy 2012. PubMed
• Sacroiliac Joint: Mimics and Pitfalls — Lowry MKJ. Seminars in musculoskeletal radiology 2025. PubMed
• Sacroiliac joint pain — Dreyfuss P. The Journal of the American Academy of Orthopaedic Surgeons 2004. PubMed
• The Sacroiliac Joint — Polly DW Jr. Neurosurgery clinics of North America 2017. PubMed
• Sacroiliac Joint Diagnostic Block and Radiofrequency Ablation Techniques — Loh E. Physical medicine and rehabilitation clinics of North America 2021. PubMed
• The Sacroiliac Joint: A Current State-of-the-Art Review — Polly DW Jr. JBJS reviews 2024. PubMed

Curated Image Set

Open-access figures are embedded from PubMed Central articles and kept unique to this guide.

Fig. 1. Patient flow. SIJA = sacroiliac joint arthrodesis, CM = conservative management, FU = follow-up, m = month, X-over = crossover, and LTFU = lost to FU. Source: Randomized Trial of Sacroiliac Joint Arthrodesis Compared with Conservative Management for Chronic Low Back Pain Attributed to the Sacroiliac Joint — The Journal of Bone and Joint Surgery. American Volume 2019; CC BY-NC-ND.

Fig. 2. Change in VAS low back (LB) pain, VAS leg pain, ODI, EQ-5D time trade-off (TTO), EQ-5D VAS, and Zung Depression Scale scores. Blue indicates the conservative management group, and green… Source: Randomized Trial of Sacroiliac Joint Arthrodesis Compared with Conservative Management for Chronic Low Back Pain Attributed to the Sacroiliac Joint — The Journal of Bone and Joint Surgery. American Volume 2019; CC BY-NC-ND.

Fig. 3. Change in functional test (active straight leg raise test) by treatment and time (left) and the number of positive physical examination signs (right). Blue indicates the conservative… Source: Randomized Trial of Sacroiliac Joint Arthrodesis Compared with Conservative Management for Chronic Low Back Pain Attributed to the Sacroiliac Joint — The Journal of Bone and Joint Surgery. American Volume 2019; CC BY-NC-ND.

Fig. 4. Proportion of subjects reporting opioid use in the past 2 weeks by treatment and study visit. Blue indicates the conservative management (CM) group, and green indicates the sacroiliac… Source: Randomized Trial of Sacroiliac Joint Arthrodesis Compared with Conservative Management for Chronic Low Back Pain Attributed to the Sacroiliac Joint — The Journal of Bone and Joint Surgery. American Volume 2019; CC BY-NC-ND.

Fig. 5-A. Change in walking distance and ambulatory status. Source: Randomized Trial of Sacroiliac Joint Arthrodesis Compared with Conservative Management for Chronic Low Back Pain Attributed to the Sacroiliac Joint — The Journal of Bone and Joint Surgery. American Volume 2019; CC BY-NC-ND.

Fig. 5-B. Change in work status and comparison with baseline. Source: Randomized Trial of Sacroiliac Joint Arthrodesis Compared with Conservative Management for Chronic Low Back Pain Attributed to the Sacroiliac Joint — The Journal of Bone and Joint Surgery. American Volume 2019; CC BY-NC-ND.

Fig. 5-C. Change in satisfaction and desirability of having a surgical procedure again by treatment and follow-up visit. Source: Randomized Trial of Sacroiliac Joint Arthrodesis Compared with Conservative Management for Chronic Low Back Pain Attributed to the Sacroiliac Joint — The Journal of Bone and Joint Surgery. American Volume 2019; CC BY-NC-ND.

Fig. 6. Change in VAS low back (LB) pain, VAS leg pain, ODI, Zung Depression Scale, EQ-5D time trade-off (TTO), and EQ-5D VAS scores including subjects who crossed over from conservative… Source: Randomized Trial of Sacroiliac Joint Arthrodesis Compared with Conservative Management for Chronic Low Back Pain Attributed to the Sacroiliac Joint — The Journal of Bone and Joint Surgery. American Volume 2019; CC BY-NC-ND.

Fig. 7. Imaging of typical configuration of implants. Fig. 7-A Inlet-view pelvic radiograph. Fig. 7-B A 12-month CT image from a different subject showing no radiolucencies around the first… Source: Randomized Trial of Sacroiliac Joint Arthrodesis Compared with Conservative Management for Chronic Low Back Pain Attributed to the Sacroiliac Joint — The Journal of Bone and Joint Surgery. American Volume 2019; CC BY-NC-ND.

Fig. 8. A 12-month CT image depicting bilateral implants with bone apposition along the entire length of the superior and inferior sides of both implants. Also, there is bone overgrowth at the… Source: Randomized Trial of Sacroiliac Joint Arthrodesis Compared with Conservative Management for Chronic Low Back Pain Attributed to the Sacroiliac Joint — The Journal of Bone and Joint Surgery. American Volume 2019; CC BY-NC-ND.

History of Present Illness

• Chief complaint: Unilateral low back/buttock pain below L5, often radiating to posterior thigh/groin, worse with sitting-to-standing, stairs, single-leg loading
• Fortin finger sign (points to PSIS), pain over the SI joint
• Failed conservative management (PT, NSAIDs, SI joint injections)
• Etiology: degenerative, post-lumbar fusion (adjacent SI stress), post-partum, trauma

Past Medical History

• Prior lumbar fusion (accelerates SI degeneration), inflammatory arthropathy (sacroiliitis — different management), prior pelvic trauma
• Standard PMH

Imaging Review

Diagnostic Workup (key — confirm the SI joint is the pain source)

• Image-guided SI joint anesthetic injection(s) providing significant temporary relief (>50-75%) — strongly supports diagnosis and surgical candidacy
• Physical exam provocative tests (≥3 positive: thigh thrust, FABER, distraction, compression, Gaenslen)

  CT / X-ray

• SI joint degeneration, anatomy for implant trajectory, exclude other pathology, sacral dysmorphism

  MRI lumbar

• Exclude lumbar source (rule out concurrent stenosis/radiculopathy mimicking)

Labs

• CBC, BMP, Coags, type and screen

Neurological Examination

• Lower extremity exam (typically normal — distinguishes from radiculopathy), SI provocative tests, gait

Surgical Planning

Case Logistics, OR Needs & Orders

• OR table/bed: Jackson/Allen/open-frame radiolucent table, or ProAxis/hinged table when sagittal alignment adjustment is useful; keep abdomen free for venous decompression.
• OR setup: radiolucent/Jackson table, fluoroscopy or O-arm/navigation, microscope/loupes for decompression, implant trays/graft ready for fusion, neuromonitoring for myelopathy/cord-risk cases, and postop brace plan confirmed.
• Special needs: arterial line/Foley/type-screen for long fusion/corpectomy, no long paralytic when MEPs are used, MAP/normotension for myelopathy or cord-risk cases, antibiotic redosing, and anticoagulation/DVT plan.
• Immediate postop orders: neuro checks by myotome/sensory level, airway/dysphagia watch for anterior cervical cases, CT/X-rays per construct, drain care, brace/activity orders, DVT prophylaxis timing, bowel regimen, and PT/OT mobilization.

Diagnosis & Indication

• Indication: SI joint pain confirmed by exam + diagnostic injection relief, refractory to ≥6 months conservative care
• Goals: fuse/stabilize the SI joint with implants placed across the joint

Position

• OR table/bed: Jackson/Allen/open-frame radiolucent table, or ProAxis/hinged table when sagittal alignment adjustment is useful; keep abdomen free for venous decompression.
• Lateral or prone (per system), fluoroscopy (inlet/outlet/lateral pelvis), padded

Key Surgical Steps (MIS Lateral Transiliac)

1. Fluoroscopic localization (true lateral, inlet, outlet pelvic views)
2. Small lateral buttock incision over the ilium
3. Guide pin across the ilium, through the SI joint, into the sacrum under fluoroscopy — stay within bone, avoid the sacral foramina/canal and the sciatic notch; confirm trajectory on all views
4. Sequential drilling/broaching across the joint
5. Place implants (triangular titanium rods / screws / threaded implants) across the SI joint (typically 2-3) for stabilization/fusion
6. Confirm implant position on inlet/outlet/lateral fluoroscopy (within sacral bone, not in foramina/canal)
7. Closure

Critical Anatomy & Structures at Risk

1. Sacral nerve roots (S1, S2) in the foramina — implant too anterior/medial breaches foramen
2. L5 nerve root (anterior to sacral ala)
3. Sacral canal / cauda (too medial), sciatic notch / superior gluteal vessels (too inferior/posterior)
4. SI joint, iliac vessels (anterior breach)

Equipment

• SI fusion implant system (triangular implants/screws + instruments), fluoroscopy (essential) ± navigation/robotics
• Neuromonitoring (selected)

Monitoring

• Triggered EMG (selected — confirm implants not breaching foramina)

Anesthesia

• General; fluoroscopy; standard

Potential Complications

1. Sacral nerve root injury (foraminal breach), L5 injury
2. Implant malposition, vascular injury (notch/anterior breach)
3. Nonunion/persistent pain (patient selection critical), implant loosening
4. Wound issues, nerve irritation

Operative Note Template

Preoperative Diagnosis: [Right/Left] sacroiliac joint dysfunction (confirmed by diagnostic injection), refractory to conservative care

Postoperative Diagnosis: Same

Procedure: Minimally invasive [right/left] sacroiliac joint fusion with [N] [triangular titanium] implants

Surgeon / Assistant: Anesthesia: General endotracheal EBL / Fluids: Adjuncts: Fluoroscopy (inlet/outlet/lateral) [± navigation]; [triggered EMG] Implants: [N] SI fusion implants [triangular titanium] Complications: None

Indications: [Age]yo [M/F] with SI joint pain confirmed by exam and >[50–75]% relief from image-guided SI injection, refractory to ≥6 months of conservative care. Risks (sacral nerve injury, malposition) discussed.

Description of Procedure: After consent and time-out, general anesthesia was induced and the patient positioned [lateral/prone] with fluoroscopy. True lateral, inlet, and outlet pelvic views were obtained. A small lateral buttock incision was made over the ilium, and a guide pin advanced across the ilium, through the SI joint, into the sacrum — staying within bone and avoiding the sacral foramina, canal, and sciatic notch, confirmed on all views.

The trajectory was drilled/broached and [N] implants placed across the joint for stabilization/fusion. Final inlet/outlet/lateral fluoroscopy confirmed the implants were within sacral bone and clear of the foramina/canal. [Triggered EMG confirmed no foraminal breach.]

Closure was performed. The patient was discharged [same day] with protected weight-bearing on the operative side.

Postoperative Plan

• Outpatient/short stay, neuro checks (sacral roots)
• Protected weight-bearing per surgeon (often partial on operative side x weeks)
• X-ray/CT postop (implant position), pain assessment
• Activity progression, PT; follow-up for fusion
• Counsel: outcomes depend on correct patient selection (confirmed SI source)

Chief-Level Case Review

Use these as the senior-level mental model for Sacroiliac (SI) Joint Fusion:

• Decision point: Localize twice and instrument once: numbering, transitional anatomy, prior hardware, rib count, navigation dataset, and fluoroscopic level confirmation are mandatory.
• Technical lever: Positioning is treatment: table choice, abdomen-free prone setup, alignment goals, shoulders/hips, eyes/plexus pressure, neuromonitoring baselines, and fluoroscopic access all change the case.
• Bailout: Protect neural elements by sequence: decompression before correction when needed, MAP support for cord risk, no long paralytic with MEPs, and immediate response to signal change.
• Postop watch: Finish with construct logic: decompression adequacy, screw purchase, alignment, fusion bed/graft, drain plan, brace/activity orders, postop CT/X-rays, and DVT timing.

Common Pimp Questions

Use these to pressure-test preparation for Sacroiliac (SI) Joint Fusion:

1. What neurologic level and root are responsible for the presenting deficit?
2. What is the decompression target and how will you know it is adequately decompressed?
3. What instability, deformity, bone-quality, or fusion variable changes the construct?
4. What vascular, visceral, dural, or neural structure is the main structure at risk?
5. What postop brace, drain, mobilization, MAP, antibiotic, and DVT plan should be ordered?

Attending Preference Variables

Items that commonly vary by surgeon or institution:

• Positioning frame, arms, traction, and localization workflow: [attending-specific]
• Navigation/robot/fluoro use, screw system, graft/biologic choice, and drain threshold: [attending-specific]
• Neuromonitoring modality and MAP goal for myelopathy, deformity, or cord-risk cases: [attending-specific]
• Brace, Foley, antibiotics, mobilization, and DVT prophylaxis timing: [attending-specific]