High Tibial Osteotomy

Clinical Indications

• Varus malalignment with:
  1. Medial compartment osteoarthritis (OA) and pain
  2. Instability
     • Alteration of the slope can compensate for anterior or posterior translation in ACL or PCL deficient knee
  3. Protection of chondral or meniscal surgery
     • Restoration of mechanical axis maintains longevity of the soft tissue procedure

Contraindications

1. Absolute:

   • Patellofemoral OA
   • Tricompartmental OA
   • Fixed flexion contracture >10 degrees
   • Fixed varus or valgus contracture >10 degrees
   • Lateral tibial subluxation >1cm

2. Relative:

   • Poor range of motion (ROM) (<90 degrees flexion)
   • Smoker
   • Inflammatory arthropathy
   • Varus thrust on walking

Ideal Patient

1. Young
2. Non-smoker
3. Correctible deformity
4. Isolated medial OA

Surgical Techniques

Traditionally Closing Lateral Wedge

• Disadvantages:
  1. Patella baja
  2. Altered slope
  3. More challenging total knee replacement (TKR)
  4. Peroneal nerve palsy
  5. Loss of bone stock

Medial Opening Wedge

• Disadvantages:
  1. Non-union
  2. Risk of collapse or fixation loss
• Advantages:
  1. Retention of slope and bone stock
  2. Easier TKR
  3. No patella baja
• Outcome:
  • No high-quality trials indicate superiority of one technique over the other.

Alternative Techniques

Dome Osteotomy

• Description: Done above the tibial tubercle.
• Indication: Useful for big, multiplanar correction.
• Advantages: Does not alter patella height.
• Disadvantages: Technically difficult.

Distraction Osteogenesis Technique

• Indication: For very large corrections using the Taylor Spatial Frame (TSF) for gradual distraction.

Pre-Operative Planning

History

• Determine if pain is acute or insidious.
• Rule out meniscal tear vs arthrosis.
• Assess symptoms like instability, locking, or catching.
• Consider smoking history.

Examination

• Overall alignment.
• Check for concurrent patella instability and consider tubercle transfer if necessary.
• Assess knee stability.
• Identify the point of pain.

Investigations

1. Simple AP, lateral, and skyline X-rays of the knee standing.
2. Long leg standing alignment X-rays.
3. MRI.
4. Arthroscopic evaluation pre-operatively.

Osteotomy Planning

1. Long leg AP views are essential for planning.

2. Mark the mechanical axis of the leg – from the center of the femoral head to the center of the ankle.

   • The axis should pass just lateral to the middle of the tibial plateau.
   • If the line passes more medially, the knee is in varus; if more laterally, the knee is in valgus.

3. Osteotomy Angle:

   • Aim for slight overcorrection to valgus.
   • Calculate the angle between the two lines (femoral head to the desired axis and ankle to the same point) for correction.

4. Opening Wedge Height:

   • Draw a line from 4cm distal to the medial joint line to just proximal to the fibula head (this is the osteotomy cut plane).
   • Measure the distance from the subtended line to the femoral mechanical axis line to determine how much the osteotomy needs to be opened for angular correction.

Post-Operative Management

• ROM exercises.
• Touch-weight bearing (TWB) for 6 weeks (6/52).

Outcomes

• Conversion to TKR vs Primary TKR:

  • High tibial osteotomy may have longer surgical time, less mean ROM, and is technically more demanding, but clinical outcomes do not correlate with these factors.

• Closing vs Opening Wedge:

  • No long-term outcome difference between closing and opening wedge techniques, though theoretical benefits of the opening wedge are widely accepted today.

• Overall:

  • High tibial osteotomy provides good long-term results, with a mean follow-up of 10 years in some studies, maintaining activity levels and pain relief.