In the name of God

HTO (Pearls & Pitfalls) M. Mardani Kivi Guilan University of Medical Sciences

Correct HTO: Patient selection Correct diagnose of location ,directing and magnitude of deformity Angle of correction Surgical technique Over-correction vs. Under-correction

The most ideal candidate for HTO Younger than 60 years Wishes to maintain an active life style Purely medial OA knee Varus deformity of less than 15 degrees

Contra-indications of HTO Bi- or tri-compartmental joint destruction Lateral OA (clinical results are not predictable) Flexion contracture exceeding 10 degrees Overall ROM of less than 90 degrees Varus deformation of more than 15 degrees

Components of Malalignment Location Extra-articular Femur Tibia Intra-articular Joint line obliquity Ligamentous laxity Articular cartilage deficiency Osseous deficiencies

Components of Malalignment Direction Sagittal Flexion Extension Coronal Varus Valgus Rotational Magnitude Mild (<10 degrees) Moderate (10 to 20 degrees) Severe (>20 degrees)

Corrective Osteotomy Techniques Tibial Lateral closing wedge Medial closing wedge Medial opening wedge Graft Staple Distraction histogenesis Barrel vault (dome) osteotomy Oblique metaphyseal wedge

Corrective Osteotomy Techniques Femoral Medial closing wedge Medial fixation Lateral fixation Oblique metaphyseal wedge Lateral opening wedge Lateral closing wedge

Many combinations available Many procedures Closed wedge osteotomy Dome-shaped osteotomy Hemi-closed/Hemi-open wedge osteotomy Open wedge osteotomy Many fixation devices and implants Staples External fixator Blade plate and screws Plate and screws

What combination is the best? No definite answer to this question When you will consider it, you should take long-term benefits for patients into account Ease to precisely correct the FTA to the targeted angle Less invasiveness Lower rate of complications Comfortableness after surgery Early return to daily life Lower rate of delayed/non-union Economical treatment costs Ease of revision TKA for the worst case scenario

What procedure is the best for HTO? Many procedures and fixation devises to perform HTO Precise alignment correction Rigid fixation Ease of possible TKA

Is HTO a curative surgery, or a temporary surgery? HTO is commonly recommended for relatively younger patients with medial OA Currently, the average life expectancy is getting longer and longer in advanced nations Thus, HTO is a temporary surgery until TKA We should make effort in surgery to obtain good 10-year results

A problem in possible TKA These knees have remarkable deformation and bone stock loss of the proximal tibia due to HTO Revision TKA is difficult to be performed After closed wedge osteotomy After dome-shaped osteotomy

How to make preoperative planning FTA Precise physical examinations Standing full-length A-P radiogram Draw 3 lines, Mechanical axis Femoral axis Tibial axis Measure the FTA (femoro-tibial angle) Normal value: 173 to 175 degrees

Lower limb malalignment Coronal Sagittal Rotational

Orientation Alignment Position of each articular surface relative to axes of the individual limb Alignment Collinearity of the hip, knee ankle

Mechanical and anatomic bone axes

The mechanical axis, based on  a line connecting the centers of the femoral head and the tibiotalar joint, averages 1.2 degrees of varus, whereas  the femoral–tibial (anatomic) angle normally averages 5 degrees of valgus. 

Joint orientation angles & nomenclature mLDFA=85-90° mMPTA=85-90° JLCA=0-2° mLPFA=90° mLDTA=89°

Radiographic assessment of coronal deformities

Mechanical axes of the leg

MAD>15 mm medial Varus deformity mMPTA<85-90° mLDFA>85-90° Femoral varus deformity Tibial varus deformity

Valgus deformity MAD>10mm lateral mMPTA>85-90° mLDFA<85-90° Femoral valgus deformity Tibial valgus deformity

Intero-sseous

Condylar

Sagittal plane mechanical axes

Radiographic assessment of sagittal deformities

Femoral cause of sagittal malalingment

Tibial cause of malalignment

Knee subluxation source of sagittal malalignment

Rotation deformity

Femoral anteversion

Femoral anteversion 15.6±6.7°

Tibial tubercle-trochlear groove distance (TT-TG) TT-TG≤15mm

Tibial torsion TFA≤15

Tibial torsion Physiologic value 23.5±5.1° ext

What is appropriate limb alignment after HTO? 3-6 valgus 10-12 valgus 6-14 valgus.

Angular correction angle(ACA) The weight-bearing line method divides the tibial plateau from 0% to 100% (medial to lateral) to determine the desired intersection coordinate of the mechanical axis through the knee joint.   Wedge height is calculated by tracing the wedge on the radiograph with the desired angle of correction. The wedge height measurement on the radiograph is then normalized by the radiographic magnification present.  

Angular correction angle(ACA) Fujisawa point

Pre-Op Planning Full length film of the leg is ideal to assure the restoration or overcorrection of the mechanical axis The simplest method for determining the angle of correction involves drawing a line from the center of the femoral head to the lateral margin of the tibial spine and then a line from the lateral tibial spine to the center of the ankle. The angle from these 2 lines represents your angle of correction

Center of rotation of angulation (CORA) Paley method In a femur with pathologic femoral varus or valgus, the femoral deformity is determined at the center of angulation of rotation (CORA) located at the intersection of the proximal and distal anatomical axes of the femur.

The CORA method of planning has revealed the relationships between the ACA, CORA, and osteotomy level. These are summarized as osteotomy rules 1 and 2 and a corollary to these rules. Osteotomy rule 1 states that angular correction with the ACA and the osteotomy passing through the CORA leads to complete colinear realignment of the proximal and distal axes of the bone, without displacement of the bone ends.

Osteotomy rule 2 states that when the ACA passes through the CORA but the osteotomy is at a different level, complete colinear realignment of the proximal and distal axis lines occurs, with displacement of the bone ends. Finally, the corollary to these osteotomy rules is that when the ACA and osteotomy do not pass through a CORA, a secondary translation deformity of the proximal and distal axis lines results.

Take home message In malalignment evaluation consider hip, knee and ankle joints. Insist on proper radiologic assessment. Consider malalignment in sagittal, coronal and rotational plane. Be careful of tibial slope in HTO. HTO is a temporary surgery until TKA Surgeons should make effort in surgery so that the good results maintain 10 years or more

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