Overview

The Posteromedial to Ventrolateral (PML) technique is a recently described surgical approach for sacroiliac joint (SIJ) fusion. It was developed to address certain anatomic and procedural challenges associated with existing fusion trajectories, such as lateral-to-medial or posterolateral methods. The PML trajectory originates on the dorsal aspect of the sacrum and extends toward the ventrolateral ilium along a sacro-alar-iliac path.

Background

Traditional SIJ fusion methods generally use a lateral-to-medial implant trajectory, which passes across three cortices of bone. While this trajectory has been well studied and demonstrates consistent outcomes, there are concerns regarding potential injury to branches of the superior gluteal artery (SGA) and the need to pass through significant soft tissue, particularly in heavier patients.

The posterolateral trajectory has been used as an alternative to reduce the amount of lateral dissection, but published reports have noted potential differences in biomechanical stability and patient outcomes compared with the standard lateral-to-medial approach.

The PML trajectory was developed as a means to avoid the vascular structures of the lateral ilium and reduce the amount of tissue exposure required for implant placement, while maintaining transfixing engagement of the SIJ through three cortices.

Technique Description

The paper by Ogunseinde (2025) describes the PML method through a case video and stepwise operative report. The key procedural elements are as follows:

1. Incision and Access
   A single midline incision is made over the dorsal sacrum. This position allows for bilateral access to the sacroiliac joints without separate lateral incisions.

2. Trajectory Planning
   Using fluoroscopic guidance, a posteromedial entry point is selected on the sacrum. The guidewire is advanced toward the ventrolateral ilium, aligning along the sacro-alar-iliac direction. Inlet and outlet fluoroscopic views confirm the appropriate trajectory.

3. Implant Placement
   The SIJ is transfixed through three bone cortices. Fluoroscopic imaging confirms the implant’s position relative to the sacral and iliac anatomy.

4. Bilateral Application
   The same incision can be used to access and treat both joints sequentially, reducing the need for additional surgical entry points.

Reported Findings

The technique was applied in four clinical cases described in the publication. Observations included:

• No vascular complications or injury to the superior gluteal artery branches.

• No neural injury or hardware malposition reported.

• Stable implant placement achieved through fluoroscopic confirmation.

• The approach provided bilateral joint access through a single incision.

The author concluded that the PML trajectory offers a feasible alternative for SIJ fusion that avoids the lateral ilium vasculature and minimizes the amount of soft tissue dissection required.

Comparison with Existing Trajectories

Lateral-to-Medial Trajectory

• Entry Point: Lateral ilium

• Main Concerns: Superior gluteal artery branches; larger soft-tissue exposure

• PML Distinctions: Avoids lateral iliac entry

Posterolateral Trajectory

• Entry Point: Posterior ilium

• Main Concerns: Potentially reduced stability in prior studies

• PML Distinctions: Uses dorsal sacral entry, transfixing through sacro-alar-iliac path

PML Trajectory

• Entry Point: Dorsal sacrum

• Main Concerns: Not yet extensively studied

• PML Distinctions: Single incision, dorsal to ventrolateral trajectory

Summary

The Posteromedial to Ventrolateral (PML) technique represents a new transfixing implant trajectory for sacroiliac joint fusion. It begins on the dorsal surface of the sacrum and proceeds toward the ventrolateral ilium. The reported cases demonstrate that this trajectory can achieve bilateral SIJ fixation through a single incision while avoiding key vascular structures.

Further research and comparative outcome data will be necessary to evaluate its biomechanical characteristics and long-term clinical performance relative to established fusion methods.

References

Ogunseinde B. Single Incision Posteromedial to Ventrolateral (PML) Surgical Technique for Minimally Invasive Sacroiliac Joint Fusion. Clin Spine Surg. 2025 Aug 1;38(7):319-325. doi: 10.1097/BSD.0000000000001867. Epub 2025 Jun 20. PMID: 40539626; PMCID: PMC12278755.