1. In the name of God

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

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

4. 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

5. 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

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

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

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

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

10. 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

11. 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

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

13. 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

14. 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

15. 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

16. Lower limb malalignment
Coronal
Sagittal
Rotational

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

18. Mechanical and anatomic bone axes

19. 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. 

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

21. Radiographic assessment of coronal deformities

22. Mechanical axes of the leg

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

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

25. Intero-sseous

26. Condylar

27. Sagittal plane mechanical axes

28. Radiographic assessment of sagittal deformities

29. Femoral cause of sagittal malalingment

30. Tibial cause of malalignment

31. Knee subluxation source of sagittal malalignment

33. Rotation deformity

34. Femoral anteversion

35. Femoral anteversion 15.6±6.7°

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

37. Tibial torsion
TFA≤15

38. Tibial torsion
Physiologic value 23.5±5.1° ext

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

40. 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.  

41. Angular correction angle(ACA)
Fujisawa point

42. 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

43. 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.

45. 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.

46. 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.

55. 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

56. Thank you for Your Attention