Using the LBL Tool for Precision Levelling Osteotomy Planning

Using the LBL Tool for Precision Levelling Osteotomy Planning

  1. Cranial Closing Wedge Osteotomies (CCWO)
  2. CBLO procedures
  3. Eccentric TPLO procedures

The LBL tool helps you achieve your desired postoperative tibial plateau angle (TPA) while simultaneously predicting:

  1. Changes in tibial length
  2. Mechanical axis shift (induced procurvatum)
  3. Levelling CORA magnitude

Unlike traditional planning methods, the LBL tool is based on Paley’s Longitudinal Bisector Line concept, allowing you to make informed decisions about osteotomy positioning and its mechanical consequences.

Before You Begin:


Ensure you have:

  1. A calibrated mediolateral radiograph
  2. The tibia positioned in a true sagittal projection
  3. Completed image calibration

 Opening the LBL Tool

  1. Open the Toolbox.
  2. Select Crescentic Saw.
  3. Choose LBL Tool.

The tool will appear centred on your image together with the information panel.

 Step 1 – Define the Tibial Mechanical Axis

The mechanical axis (green line) forms the foundation of the entire plan.

Distal landmark

Position the distal endpoint at the:

  1. Centre of the talus

Proximal landmark

Position the proximal endpoint at the:

  1. Centre of the tibial plateau beneath the intercondylar eminences

Important: If you move the mechanical axis after completing the plan, the joint orientation line will reset and must be redefined.

 Step 2 – Define the Joint Orientation Line

Position the blue joint orientation line as a best-fit tangent to the tibial plateau.

Once this has been placed, VPOP® PRO automatically calculates:

  1. Preoperative TPA
  2. Mechanical caudal proximal tibial angle (mCrPTA)
  3. Target mechanical axis

 Step 3 – Set Your Target TPA

The target TPA defaults to 5°, but can be adjusted in three ways:
  1. Edit the Target TPA value
  2. Edit the target mCrPTA
  3. Drag the purple target mechanical axis directly on the image

All measurements update dynamically as changes are made.

Understanding the Information Panel

The information panel provides live planning data including:

  1. Preoperative TPA
  2. Target TPA
  3. Target mechanical caudal proximal tibial angle
  4. Levelling CORA magnitude
  5. Tibial length change
  6. Mechanical axis shift

These values update automatically throughout planning.

Planning a Cranial Closing Wedge Osteotomy

The wedge apex is typically positioned near the distal end of the tibial crest while leaving adequate space proximally for implant placement.

The LBL allows you to position the levelling CORA precisely and immediately predicts the mechanical consequences of that position.

ACA CORA Position

Positioning the CORA relative to the Longitudinal Bisector Line determines tibial length changes.

CORA Position

Result

On the LBL

Tibial length preserved

Cranial to the LBL

Tibial length increases

Caudal to the LBL

Tibial length decreases

The information panel continuously displays the predicted change in tibial length. 

Optimising Wedge Geometry

VPOP® PRO automatically generates an isosceles wedge that corresponds to the required levelling CORA magnitude.

This helps optimise cortical load sharing while maintaining the planned correction.

After confirming the wedge position:

  1. Note the wedge dimensions.
  2. Record D1 and D3 measurements if required.
  3. Create the ostectomy.
  4. Define the proximal fragment.
  5. Complete the reduction.

The postoperative plan updates automatically to display the achieved correction.

Planning a CBLO

The LBL tool also integrates directly with the Crescentic Saw tool.

  1. Delete any existing wedge.
  2. Add a Crescentic Saw.
  3. Select the LBL tool.
  4. Position the levelling CORA along the target mechanical axis.
  5. Adjust the cranial–caudal position to control tibial length changes.

The information panel updates continuously to display:

  1. Levelling CORA magnitude
  2. Mechanical axis shift
  3. Predicted tibial length change

Completing the Plan

Once satisfied with the CORA position:

  1. Select the Crescentic Saw tool.
  2. Perform the osteotomy.
  3. Define the proximal fragment.
  4. Rotate by the displayed levelling CORA magnitude.
  5. Record D1 and D3 measurements as required.
  6. Complete implant templating.

Key Points

  1. Always define the mechanical axis before any other measurements.
  2. Repositioning the mechanical axis resets the joint orientation line.
  3. The LBL predicts tibial length changes before performing the osteotomy.
  4. Positioning the CORA directly on the LBL preserves tibial length.
  5. The information panel updates in real time throughout planning.

Video Tutorial

For a complete demonstration of the LBL workflow, watch the accompanying tutorial video below:



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