> ## Documentation Index
> Fetch the complete documentation index at: https://docs.navnx.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Tunnels

> Planning femoral and tibial tunnels with coordinates, angles, and 3D visualisation.

## Tunnel Planning

Tunnel placement is a critical step in ligament reconstruction planning. NavNX provides tools to define, visualise, and validate tunnel parameters for both femoral and tibial tunnels.

## Adding a Tunnel

<Steps>
  <Step title="Open the tunnel tool">
    Click the **Add Tunnel** button in the toolbar and select the tunnel type: **Femoral** or **Tibial**.
  </Step>

  <Step title="Define the entry point">
    Click on the viewport (in any 2D view mode) to place the tunnel entry point on the bone surface.
  </Step>

  <Step title="Define the exit point">
    Click again to place the exit point. The tunnel trajectory is drawn as a line between these two points.
  </Step>

  <Step title="Review in the properties panel">
    The properties panel on the right displays the calculated tunnel parameters.
  </Step>
</Steps>

## Tunnel Parameters

The properties panel displays and allows editing of:

| Parameter             | Description                                                  |
| --------------------- | ------------------------------------------------------------ |
| **Entry coordinates** | X, Y, Z position of the entry point (mm)                     |
| **Exit coordinates**  | X, Y, Z position of the exit point (mm)                      |
| **Inclination angle** | Angle in the coronal plane (degrees)                         |
| **Anteversion angle** | Angle in the sagittal plane (degrees)                        |
| **Diameter**          | Tunnel diameter (mm) — adjustable via slider or direct input |
| **Depth**             | Tunnel length from entry to exit (mm) — auto-calculated      |

You can edit coordinates and angles directly in the properties panel. Changes are reflected in real time across all views.

## Validation Warnings

NavNX validates tunnel parameters and displays warnings when values fall outside recommended ranges:

* Tunnel length too short or too long for the selected implant
* Diameter mismatch with the selected implant
* Tunnel trajectory intersects the opposite cortex at an extreme angle

<Warning>
  Validation warnings are advisory. Clinical judgement should always take precedence over automated checks.
</Warning>

## 3D Visualisation

Tunnels are rendered as semi-transparent cylinders in the 3D and Bone views using VTK.js. The cylinder colour indicates the tunnel type:

* **Blue** — femoral tunnel
* **Green** — tibial tunnel

Orbit, pan, and zoom to inspect the tunnel trajectory from any angle. Tunnels update in real time as you adjust parameters.

<Tip>
  Switch to the Bone 3D view after placing tunnels to verify that the trajectory avoids critical structures and that entry/exit points are correctly positioned on the cortical surface.
</Tip>