# Polyaxial Pedicle Screw Demo

An interactive product demo of a polyaxial pedicle screw and 5\.5 mm rod construct: parts, exploded view, pedicle insertion, tulip angulation, rod seating, locking and a quiz

By James Levin

Topic: Human Body & Medicine

[Open the interactive Jig](https://ask.jig.com/j/wVSg2dbJh7Nk)

## Guide

### 1. Polyaxial pedicle screw system

Four parts make one fixation point: a threaded pedicle screw shank, a polyaxial tulip head, a 5\.5 mm spinal rod and a locking set screw\. Click a part to pick it out; drag empty space to turn the construct\.

Scroll or pinch to look closer\.

### 2. Exploded view

The shank ends in a ball that sits inside the base of the tulip\. The rod drops into the tulip's U\-shaped saddle, and the set screw threads into the top of the tulip to close it\.

The parts are typically titanium alloy; anodised colours help identify parts\.

### 3. Into the pedicle

The screw is driven through the pedicle, the short bony bridge between the back of the vertebra and its body, angled slightly toward the midline\. The cutaway shows the thread inside the bone\.

Lumbar screws are commonly 40 to 50 mm long and roughly 6\.5 to 7\.5 mm in diameter\.

### 4. Tulip angulation

Because the head rides on a ball, the tulip can tilt in any direction while the screw stays put\. This lets the saddle line up with the rod even when screws enter at different angles\.

Angulation range varies by system; about 25 degrees to each side is a common figure\.

### 5. Seat the rod

With the saddle aligned, the 5\.5 mm rod is lowered straight down into the tulip until it rests on the base of the U\.

In surgery the rod is usually contoured to the spine's curve first\.

### 6. Lock the construct

The set screw is started straight to avoid cross\-threading, then tightened\. It presses the rod down onto the head, locking the rod and the tulip angle in one action\.

Final tightening uses a torque\-limiting driver with counter\-torque\.

### 7. Quiz 1 of 3

Which part locks both the rod and the tulip angle at the same time?

### 8. Quiz 2 of 3

Why is the tulip head polyaxial?

### 9. Quiz 3 of 3

Which part of the vertebra does the screw pass through on its way into the vertebral body?