Tibial Deformity Correction Planning

Overview

This lecture details the planning and execution steps for correcting frontal plane tibial deformities, focusing on measurement, axis identification, apex localization, and osteotomy techniques.

Planning Tibial Deformity Correction

• Start with the MAP approach: Measure, Axis, Point.
• Measurement begins by assessing joint orientation angles.
• For tibial deformity, measure the medial proximal tibial angle and lateral distal tibial angle.
• Draw the axes for the proximal and distal tibial segments.
• Identify and point out the apex (or apices) of the deformity.

Measurement Steps

• Medial proximal tibial angle is measured to detect varus deformities.
• Proximal tibial mechanical axis is set using normal reference angles (87° average or matching normal contralateral values).
• Distal tibial mid-diaphyseal line is drawn; anatomical and mechanical axes are parallel in the tibia.
• Remeasure the lateral distal tibial angle using the mid-diaphyseal line.
• Identify multiple apices if present by intersection of axes.

Execution: ABC Method

• Follow the ABC pathway: Apex, Bone, Correction.
• Mark the apex locations based on the intersection of axes.
• Plan two osteotomies for multiple deformity apices (proximal varus and distal valgus).
• C-level lines are drawn through obtuse angles at axis intersections.
• Select the osteotomy type and level; for proximal deformity, use oblique medial opening wedge high tibial osteotomy.
• Osteotomy at apex allows for lateral hinge correction at the deformity site.
• For distal deformity near the joint line, place osteotomy proximally with hinge at apex, causing translation measured by axis separation at osteotomy.
• Complete correction by realigning axes and correcting joint orientation angles.

Summary Steps

• Map deformity: Measure angles, draw axes, identify apices.
• Execute plan: Mark apex, plan bony cut, define correction and hinge point.
• Remeasure angles post-correction to verify success.

Key Terms & Definitions

• Frontal plane deformity — Deviation of bone alignment when viewed from the front.
• MAP (Measure, Axis, Point) — Planning sequence for deformity analysis.
• ABC (Apex, Bone, Correction) — Execution sequence for osteotomy correction.
• Osteotomy — Surgical cutting of bone to correct alignment.
• Apex — Point of maximum bony deformity where axes intersect.
• Varus/Valgus — Inward (varus) or outward (valgus) angulation of a bone segment.

Action Items / Next Steps

• Practice measuring joint orientation angles on radiographs.
• Review osteotomy techniques and hinge placement for tibial corrections.