## Introduction
The **Pedicle Screw** is the fundamental anchor of spinal stabilization. While all pedicle screws serve the same basic purpose, surgeons must choose between two head designs: **Polyaxial** and **Monoaxial**. Each has a specific role in the surgical toolkit.
## Polyaxial Screws: The Versatile Choice
The head of a polyaxial screw can tilt and rotate relative to the screw shaft.
* **The Advantage:** It is much easier to align the heads and insert the rod, even when the screws are placed at different angles.
* **Clinical Benefit:** Shorter surgical time, less stress on the bone-screw interface during rod reduction.
* **Status:** The “workhorse” for routine degenerative spine surgery.
## Monoaxial Screws: The Corrective Powerhouse
The head is fixed rigidly to the screw shaft.
* **The Advantage:** It provides direct mechanical leverage for the vertebra.
* **Clinical Benefit:** Essential for **Derotation** in scoliosis surgery. When the surgeon pulls on the rod, the monoaxial screw forces the entire vertebra to move with it.
* **Status:** Reserved for complex deformity correction and specific trauma cases.
## Reduction Screws: The Hybrid Solution
Ortholyx also provides **Reduction Screws**, which feature long, removable “tabs” on the head. These allow for gradual pulling of the vertebra toward the rod, particularly useful in treating spondylolisthesis (slipped vertebrae).
## Conclusion
The choice depends on the goals of the surgery: ease of assembly (Polyaxial) or powerful correction (Monoaxial). Ortholyx provides both options in a variety of diameters and lengths, ensuring surgeons have the right anchor for every patient.