High Tibial Osteotomy - Recon

Summary
- High Tibial Osteotomy (HTO) is a surgical procedure that is performed to correct angular deformities of the knee to prevent development or progression of unicompartmental osteoarthritis.
- It is predominately done to correct for varus deformities in young patients but can also be done to correct valgus deformities.
- Contraindications include inflammatory arthritis, flexion contracture > 15 degrees, bicompartmental osteoarthritis, and ligamentous instability.

Etiology
- Use
  - predominately done for varus deformities
  - less common for valgus deformities
- Angular deformity in the knee leads to abnormal distribution of weight bearing stresses
  - can accelerate wear in medial or lateral compartments of the knee and lead to degeneration
  - HTO is commonly combined with cartilage restoration procedures to provide better mechanical environment for biologic repair

Indications
- Indications
  - young, active patient (<50 years) in whom an arthroplasty would fail due to excessive wear
  - healthy patient with good vascular status
  - non-obese patients
  - pain and disability interfering with daily life
  - only one knee compartment is affected
  - compliant patient that will be able to follow postop protocol
- General contraindications
  - inflammatory arthritis
  - obese patient BMI>35
  - flexion contracture >15 degrees
  - knee flexion <90 degrees
  - procedure will need >20 degrees of correction
  - patellofemoral arthritis
  - ligament instability
  - varus thrust during gait

Anatomy
- Mechanical axis of lower extremity
  - can be assessed by drawing straight line from center of femoral head to the center of the ankle joint
  - line axis should pass just medial to the medial tibial spine

Presentation
- Symptoms
  - pain on medial or lateral side of knee
- Exam
  - knee malalignment

Imaging
- Radiographs
  - show knee malalignment using mechanical axis line

Varus-producing tibial osteotomy
- Surgical goals
  - unload the involved joint compartment by correcting tibial malalignment
  - maintain the joint line perpendicular to mechanical axis of the leg
- Indications
  - can be done for valgus knee with lateral compartment degeneration
    
    deformity should be <12 degrees or else the joint line will become oblique
  - specific contraindications
    
    medial compartment arthritis
    
    loss of medial meniscus
    
    distal femoral osteotomy better if lateral femoral condyle hypoplasia present

Valgus-producing tibial osteotomy
- Goals
  - unload the involved joint compartment by correcting tibial malalignment
    
    A medial unloader brace can be used for therapeutic and diagnostic purposes. If a patient benefits from the brace, they are likely to benefit from surgery.
  - maintain the joint line perpendicular to mechanical axis of the leg
- Indications
  - can be done for varus knee with medial compartment degeneration (more common)
  - best results achieved by overcorrection of the anatomical axis to 8-10 degrees of valgus
  - specific contraindications
    
    narrow lateral compartment cartilage space with stress radiographs
    
    loss of lateral meniscus
    
    lateral tibial subluxation >1cm
    
    medial compartment bone loss >2-3mm
    
    varus deformity >10 degrees
- Technique
  - lateral closing wedge technique
    
    most common technique
    
    wedge of bone removed with tibia via an anterolateral approach
    
    ORIF of wedge
    
    has advantages
    
    more inherent stability allows for faster rehab and weight bearing
    
    no required bone grafting
  - medial opening wedge technique
    
    transverse bone cut made in proximal tibia, and wedged open on medial side
    
    ORIF of wedge
    
    has advantages
    
    of maintaining posterior slope
    
    avoids proximal tibiofibular joint
    
    avoids peroneal nerve in anterior compartment
  - focal dome osteotomy (concavity proximal)
    
    the center of the dome is located at the center of rotation of angulation (CORA)
    
    has advantages
    
    corrects limb alignment with the least translation of bone ends
    
    least translation of anatomical axis
    
    minimal shortening

Complications
- Recurrence of deformity
  - 60% failure rate after 3 years when
    
    failure to overcorrect
    
    patients are overweight
- Loss of posterior slope
- Patella baja
  - refers to a shortened patellar tendon which decreases the distance of the patellar tendon from the inferior joint line
    
    can be caused by raising tibiofemoral joint line in opening wedge osteotomies
    
    can be caused by retropatellar scarring and tendon contracture
    
    can cause bony impingement of patella on tibia
- Compartment syndrome
- Peroneal nerve palsy
  - more common in lateral opening wedge osteotomy and lateral closing wedge osteotomy
  - minimal risk in medial opening wedge osteotomy
- Malunion or nonunion

Prognosis
- Varus-producing high tibial osteotomy
  - success rate is 87% in 10 years
- Valgus-producing high tibial osteotomy
  - success rate is 50-85% in 10 years