Chris dowding pgy1 university of ottawa orthopedics
1 / 31

Alignment Principals in TKA - PowerPoint PPT Presentation

  • Uploaded on

Chris Dowding, PGY1 University of Ottawa Orthopedics. Alignment Principals in TKA. Previous Presentations by Scott McGuffin and Seyon Sathiaseelan. Objectives. Review “Normal” Knee Biomechanics Review “Normal” Knee Alignment Discuss How Alignment is Restored/Maintained in TKA

I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
Download Presentation

PowerPoint Slideshow about 'Alignment Principals in TKA' - turner

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Chris dowding pgy1 university of ottawa orthopedics

Chris Dowding, PGY1

University of Ottawa Orthopedics

Alignment Principals in TKA

  • Previous Presentations by Scott McGuffin andSeyonSathiaseelan


  • Review “Normal” Knee Biomechanics

  • Review “Normal” Knee Alignment

  • Discuss How Alignment is Restored/Maintained in TKA

  • Identify the Consequences of Poor Alignment in TKA

  • Brief review of New Literature

Knee biomechanics
Knee Biomechanics

  • Knee moves in several planes:

    • hinge joint (ginglymus)

    • sliding joint (arthrodial)

  • Change in alignment during ROM:

    • Femoral rollback

    • Internal Rotation of Tibia

Ginglymus hinge joint
Ginglymus (hinge) Joint

  • ROM – 3 Axes

    • Sagittal

      • Extension to -10°, Flexion to 150°

    • Coronal

      • Varus/Valgus play of <5°

    • Axial

      • IR 10°, ER 30°

Arthrodial gliding joint
Arthrodial (gliding) Joint

  • Translations

    • Anteroposterior 5-10mm

    • Mediolateral 1-2mm

  • Compression/Distraction

    • 2-5mm

Knee biomechanics1
Knee Biomechanics

  • Posterior translation of femoral condyles on the tibia during flexion

    • Medial 2mm

    • Lateral 20mm

  • Thus, internal rotation of tibia occurs during flexion

  • Alignment

    • Axes:

      • Coronal

      • Axial

      • Sagittal

    Coronal alignment
    Coronal Alignment

    • Proximal tibia in 3° of varus from AAT/MAT

    • Distal femur in 9° of valgus from AAF

    • Thus, anatomical and mechanical axes of the femur diverge at 6° (femorotibial angle of 174°)



    Axial alignment of femur
    Axial Alignment of Femur

    • Whiteside’s line

      • AP intercondylar line

    • Transepicondylar axis

    • Posterior condylar axis



    Sagittal alignment
    Sagittal Alignment

    • Normal radiographic posterior slope of tibial = plateau ~7-10°

    • Menisci correct this to about 3° of posterior slope

    Q angle
    Q Angle

    • The angle between the extensor mechanism axis and a line joining the centre of the patella with the tibialtuberosity

      • Divergence = poor tracking of patella

    Goals of tka
    Goals of TKA

    • Restore overall mechanical axis (180°)

    • Balance ligaments

    • Maintain normal Q angle

    • Restore joint line

    Goals of tka1
    Goals of TKA

    • However:

      • If implants are placed in varus or valgus subsidence occurs:

    Goals of tka2
    Goals of TKA

    • Subsidence is bad because it defeats the purpose of TKA in the first place

    • How to prevent subsidence but retain overall joint alignment in order to maintain balanced ligament tension and proper gait mechanics?

    Native alignment
    Native Alignment

    • Recall:

      • 6 degrees of valgus

      • 3 degrees of posterior tibial slope

      • Internal rotation of tibia relative to femur during flexion

      • Q-angle 14 deg for males and 17 deg for females


    Tibial cut
    Tibial Cut

    • Goal is to have the joint line perpendicular to the mechanical axis

    • By placing implants perpendicular to mechanical axis of each bone, it ensures that mechanical axis of limb goes through center of new joint

    Tibial cut1
    Tibial Cut

    • Tibial cut made perpendicular to mechanical axis to prevent varus subsidence of tibial component



    Tibial cut2
    Tibial Cut

    • Posterior slope 3°

    • Ensures adequate flexion space

    • Prevents anterior subsidence of tibial component

    Distal femoral cut
    Distal Femoral Cut

    • Increased lateral joint space with a perpendicular tibial cut

    • This is corrected by making a distal femoral valgus cut angle of 6° relative to the AAF, instead of the anatomic 9°

    • Distal femur now perpendicular to mechanical axis





    Posterior femoral cut
    Posterior Femoral Cut

    • Recall the axial alignment of the distal femur



    Posterior femoral cut1
    Posterior Femoral Cut

    • Externally rotating the femoral component by 3° creates a symmetrical flexion gap

    Patellofemoral tracking
    Patellofemoral Tracking

    • Increased Q angle:

      • IR of femoral component

      • Valgus knee

      • Medialization of femoral component

      • IR of tibial component (medial 1/3 of TT)

      • Lateralization of the patellar dome

    Alignment in tka
    Alignment in TKA

    • Malalignment may lead to:

      • Femorotibial instability

      • Patellofemoral instability

      • Patellar fracture

      • Stiffness

      • Accelerated polyethylene wear

      • Implant subsidence/loosening

    Research in knee alignment
    Research in Knee Alignment

    • Most new publications evaluate methods of obtaining and maintaining what we think is ideal alignment, rather than challenging or testing what ideal alignment is

    • Many publications deal with the use of navigation

      • Due to the importance of alignment with respect to positive outcomes navigation may become more and more popular

      • However it is expensive and potentially time consuming, so research is being done to determine whether it can be used to provide a significantly better outcome over traditional methods

    Research in knee alignment1
    Research in Knee Alignment

    • The advantages of computer assistance in total knee arthroplasty, Bar et. Al, AOTT 2011.

      • Retrospective case review 175 cases

      • Coronal alignment, incision length, hospital stay all favoured computer assisted TKA

    Research in knee alignment2
    Research in Knee Alignment

    • A computed tomography based study on rotational alignment accuracy of the femoral component in total knee arthroplasty using computer-assisted orthopaedic surgery, van der Linden-van der Zwaag et al, SICOT 2011

      • Prospective analysis of 20 TKA using navigation

        • Significant difference in rotation of femoral implant when measured by navigation vs. post op CT

    Research in knee alignment3
    Research in Knee Alignment

    • Anterolateral approach with tibial tubercle osteotomy versus standard medial approach for primary total knee arthroplasty: does it matter?, Hirschmann et al, Muskoloskeletal Disorders 2011.

      • Prospective multicenter study

      • Medial parapatellar vs. lateral patellar with tibial tubercle ostetomy

      • Comparison

        • Flexion and pain at two years

          • Lateral patellar gave more flexion (4 degrees), less pain (using scale)

        • However Medial parapatellar shorter OR time and less post-op complications