Study Design: Fair Test of Anchor Strength

• Materials:

• iFuse (7 mm × 45 mm; 3 samples)

• Sacrix® TS (8 mm × 40 mm; 6 samples)

• Method: Uniform polyurethane foam blocks (ASTM F1839, Grade 15) were used to simulate bone—eliminating anatomical variability. Each implant was inserted 20 mm deep and subjected to controlled axial pull‑out testing using an INSTRON 8874 system until failure KIC Ventures.

• Controlled geometry: Effective surface areas were nearly identical—iFuse at 294 mm² vs. Sacrix at 290 mm²—ensuring a fair comparison KIC Ventures.

Interpretations: Anchoring Matters

• Threefold stronger pull‑out suggests threaded implants substantially improve mechanical fixation. This is essential in compromised or osteoporotic bone, where stability is precarious.

• Consistent failure mode: Both implants failed at the foam interface, underlining that design, not surface area, drives anchorage strength

Clinical Implications

• Enhanced stability with fewer implants: Threaded Sacrix® may reduce the number of implants needed per procedure, potentially shortening surgery time.

• Altered surgical approach: Strong anchorage may allow for simplified fixation strategies in lower bone densities.

• Design direction: Data support future SIJ device development to favor fully threaded designs for anchoring efficacy.

• Revision considerations: Stronger fixation may necessitate specialized removal tools during revision if the implant is well-seated.

In a standardized axial pull‑out test, the Sacrix® fully threaded screw demonstrated 3× greater anchoring strength compared to the non‑threaded iFuse implant—highlighting the mechanical advantage of threaded designs in SIJ fusion. These findings suggest threaded fixation should be a key consideration in both device selection and future development.